[ladybug83]

‘85S ROW 5.4L stroker running LH2.3

Been having hot start issues lately. Car won’t start after sitting for 20-30min. Cranks, but won’t start. Has almost stranded me a few times, but it eventually starts right up if I let it sit long enough, which seems to vary.

- Swapped fuel pump relay for new, no change
- Jumped fuel pump, can hear it running, but no start
- Fuel injectors are original to car, tested and cleaned by witch-hunter about 9k miles ago. (I suspect they may be dribbly)

I’ve read a couple threads that point to the fuel pump check valve, mine is original to the car. A easy $25 possible fix, but it seems that it may be NLA. Has anyone found a work-around? Or a way to test if mine is working properly?

I found that the air hose between the fuel pump check valve and the other little metal control valve is cracked at the bend. If I recall correctly, this hose was NLA also when I last checked. I’ll try to repair with some adhesive-lined shrink tube for now. Wondering if this is leaking vacuum and my fuel is boiling.

Thanks for listening.

Josh

[ladybug83]

Can’t figure why I wouldn’t have spark when it’s hot. But it runs great. I’ll get it figured out one of these days. To be continued. Have a good work week everyone.

When you have no spark on LH 2.2/2.3 you always start with: CPS and ECU grounds. If the EZK/EZF doesn’t get a speed signal from the flywheel, or if the EZF/K isn’t operating (e.g. power, ground) then there will be no spark.

I didn’t re-absorb this thread, so I apologize in advance if this question has been answered: what is the history of the CPS and EZK and LH?

When was the last time you checked if ECU (two) and engine ground (one) bolts (three total) are clean and tight?

And yes, the failure modes can be heat dependent.

What’s the history of the LH harness? Bad shielding and/or a break or frayed wires on the CPS branch of the harness can cause these symptoms also.

Ok great, some more things to look into.

I checked, cleaned, retightened all of the grounds, front to back, a couple weeks ago. But I’ll re-inspect for any damage to the wires and looms. LH2.3 units and CPSs were installed when the engine was rebuilt about 5-6k miles ago. Swapping them out for fresh rebuilds might be easy though, easier than refreshing the CE panel. The harness itself is original to the car, with fresh plugs and shielding, also done when the motor was rebuilt. Greg had to modify the harness to make it work with the 2.3 and the added CPSs and hall sensor. I assume the sensors were new when installed.

Thank you for the continued support

[ladybug83]

Pics of the possible offenders

IMG_5545.jpeg

IMG_5546.jpeg

IMG_5547.jpeg

[jschiller]

The check valve should be easy to find. According to this chart I found, a lot of contemporaneous cars used the same one:
MERCEDES-BENZ 190E 1984-1993
MERCEDES-BENZ 230 1977-1978
MERCEDES-BENZ 240D 1977-1983
MERCEDES-BENZ 260E 1987-1989
MERCEDES-BENZ 280CE 1978-1981
MERCEDES-BENZ 280E 1977-1981
MERCEDES-BENZ 280S 1975-1976
MERCEDES-BENZ 280SE 1977-1980
MERCEDES-BENZ 300CD 1978-1985
MERCEDES-BENZ 300D 1977-1985
MERCEDES-BENZ 300E 1986-1992
MERCEDES-BENZ 300SD 1978-1980
MERCEDES-BENZ 300SE 1988-1991
MERCEDES-BENZ 300SEL 1988-1991
MERCEDES-BENZ 300TD 1979-1985
MERCEDES-BENZ 350SL 1972
MERCEDES-BENZ 380SE 1984-1985
MERCEDES-BENZ 380SEC 1982-1983
MERCEDES-BENZ 380SEL 1981-1983
MERCEDES-BENZ 380SL 1981-1985
MERCEDES-BENZ 380SLC 1981
MERCEDES-BENZ 450SE 1973-1976
MERCEDES-BENZ 450SEL 1973-1980
MERCEDES-BENZ 450SL 1973-1980
MERCEDES-BENZ 450SLC 1973-1980
MERCEDES-BENZ 500SEC 1984-1985
MERCEDES-BENZ 500SEL 1984-1985
PORSCHE 911 1973-1994
PORSCHE 924 1981-1982
PORSCHE 928 1978-1995
PORSCHE 930 1978-1979

You could get a Uro version here:
https://www.rockauto.com/en/moreinfo.ph ... qdICiVtK9P

[ladybug83]

Thanks! That URO valve looks different than the one I was targeting. The black plastic check valve 928-110-429-06

[jschiller]

Thanks! That URO valve looks different than the one I was targeting. The black plastic check valve 928-110-429-06

Check with Roger, he shows it on his site and it looks like it was used every year with one part number or the other.

[SeanR]

Hot start issues are typically fuel related, specifically the Temp II sensor. A quick test would be to floor the accelerator so the throttle body is wide open allowing all of the air to enter the engine when cranking. If the car starts when you do this it's over fueling so either a bad temp II or the wires under the boot are touching. I'd start by checking the wires and if that's not it, then swap the sensor.

[worf]

‘85S ROW 5.4L stroker running LH2.3

Been having hot start issues lately. Car won’t start after sitting for 20-30min. Cranks, but won’t start. Has almost stranded me a few times, but it eventually starts right up if I let it sit long enough, which seems to vary.

- Swapped fuel pump relay for new, no change
- Jumped fuel pump, can hear it running, but no start
- Fuel injectors are original to car, tested and cleaned by witch-hunter about 9k miles ago. (I suspect they may be dribbly)

I’ve read a couple threads that point to the fuel pump check valve, mine is original to the car. A easy $25 possible fix, but it seems that it may be NLA. Has anyone found a work-around? Or a way to test if mine is working properly?

Your symptoms are consistent with vapor lock and/or loose grounds for the engine / engine harness.

In the first case you need to perform a fuel pressure leak down test. IIRC the WSM and/or LH-EZF troubleshooting guide provides directions. In short: if your liquid fuel system looses pressure after shut down, the fuel will turn to high-pressure vapor inside the lines and the pump can’t pump liquid against the high-pressure vapor in the liquid lines.

Once temperature falls and the fuel vapor looses vapor pressure then the pump can pump liquid fuel back into the rails.

For the latter case, when was the last time you disturbed the engine ground strap, battery ground strap, and engine harness grounds at the back of the block?

I found that the air hose between the fuel pump check valve and the other little metal control valve is cracked at the bend. If I recall correctly, this hose was NLA also when I last checked. I’ll try to repair with some adhesive-lined shrink tube for now. Wondering if this is leaking vacuum and my fuel is boiling.

You are confused here -^. You’ll need to backup a couple of steps a review what those bits actually are.

None of the stuff you describe or point to has anything to do with the fuel pump or *liquid fuel* system. All the stuff you point to has to due with the tank vapor system that returns air to the tank to replace the volume of fuel used by the engine.

The fuel pump check valve is ON the pump at the pump outlet. The fuel pressure regulator on the engine also has a check valve. Loss of liquid fuel pressure after shutdown means that one or both of those check valves is leaking pressure and/or your injectors are leaking.

[worf]

@SeanR’s guidance is also on target and easier to check than doing a pressure leak down and isolation test.

[ladybug83]

Thanks! That URO valve looks different than the one I was targeting. The black plastic check valve 928-110-429-06

Check with Roger, he shows it on his site and it looks like it was used every year with one part number or the other.

Got it. Thank you. I was targeting the wrong check valve. Got the right one from 928intl. Will try to install this weekend.

Hot start issues are typically fuel related, specifically the Temp II sensor. A quick test would be to floor the accelerator so the throttle body is wide open allowing all of the air to enter the engine when cranking. If the car starts when you do this it's over fueling so either a bad temp II or the wires under the boot are touching. I'd start by checking the wires and if that's not it, then swap the sensor.

Thanks Sean. I have done the pedal test when trying to start, and holding the pedal down while cranking didn’t change anything. I picked up a new temp2 anyways and will install this weekend and also check the wires.

‘85S ROW 5.4L stroker running LH2.3

Been having hot start issues lately. Car won’t start after sitting for 20-30min. Cranks, but won’t start. Has almost stranded me a few times, but it eventually starts right up if I let it sit long enough, which seems to vary.

- Swapped fuel pump relay for new, no change
- Jumped fuel pump, can hear it running, but no start
- Fuel injectors are original to car, tested and cleaned by witch-hunter about 9k miles ago. (I suspect they may be dribbly)

I’ve read a couple threads that point to the fuel pump check valve, mine is original to the car. A easy $25 possible fix, but it seems that it may be NLA. Has anyone found a work-around? Or a way to test if mine is working properly?

Your symptoms are consistent with vapor lock and/or loose grounds for the engine / engine harness.

In the first case you need to perform a fuel pressure leak down test. IIRC the WSM and/or LH-EZF troubleshooting guide provides directions. In short: if your liquid fuel system looses pressure after shut down, the fuel will turn to high-pressure vapor inside the lines and the pump can’t pump liquid against the high-pressure vapor in the liquid lines.

Once temperature falls and the fuel vapor looses vapor pressure then the pump can pump liquid fuel back into the rails.

For the latter case, when was the last time you disturbed the engine ground strap, battery ground strap, and engine harness grounds at the back of the block?

I found that the air hose between the fuel pump check valve and the other little metal control valve is cracked at the bend. If I recall correctly, this hose was NLA also when I last checked. I’ll try to repair with some adhesive-lined shrink tube for now. Wondering if this is leaking vacuum and my fuel is boiling.

You are confused here -^. You’ll need to backup a couple of steps a review what those bits actually are.

None of the stuff you describe or point to has anything to do with the fuel pump or *liquid fuel* system. All the stuff you point to has to due with the tank vapor system that returns air to the tank to replace the volume of fuel used by the engine.

The fuel pump check valve is ON the pump at the pump outlet. The fuel pressure regulator on the engine also has a check valve. Loss of liquid fuel pressure after shutdown means that one or both of those check valves is leaking pressure and/or your injectors are leaking.

Thank you for clarifying for me. I’ll check the fpr for gas smell, and check all of the grounds. I did have the battery ground strap off and on just prior to this last no start episode. I’ll inspect and clean all of the grounds you mentioned as well as install the new valve and sensor. I’ll also read the wsm and see what tools I need to do a pressure test.

Thank you again gentlemen. Your help is invaluable. I’ll update as we go. Have a great weekend.

[ladybug83]

Checked the fuel pressure regulator for fuel odor, none.

Replaced the temp II sensor and the connector boot, the wires and tyco plug look ok.

Replaced the check valve on the fuel pump.

Also cleaned all grounds on car, front to back. Ground cables at engine and battery look ok. Cleaned the battery ground terminal also just for the hell of it, no corrosion there.

Some oil is seeping on the passenger side valve cover, I suspect a few of the covers’ plugs. It had wetted the grounds there a little so I dried them and cleaned them. Also checked the torque on the valve cover plugs up to the service manual torque spec. They didn’t budge. Didn’t want to go past that without asking Greg first since he built the engine. Over tightening these would be a bad move and right up my skill-set-alley.

Haven’t had a chance to test it yet but hopefully this weekend. Will update again. Thanks again for the guidance.

[Sazerac]

When the dampers start to go and the car is hot starting, it seems that one often appearing symptom is that the cars will "cough" or stumble a lot before the intake clears and the right fuel/air mixture is reestablished.

The Bosch crank positions sensors on several different cars have a strange failure mode where they stop working well-enough when hot to start the car. However, the car will run when hot without a problem. It just needs to be cool to start.

I have had the first case happen on the 91 GT. And the second case happen on a SAAB convertible and a BMW. I don't know anything about the pre-S4 928s and if case 2 could apply to you, though.

[Alan]

Possible ICV malfunction when hot (I had this on my GTS) took a long time to diagnose because it worked fine on the bench (cold'ish).

[ladybug83]

Thank you both Sazerac and Alan. A couple more things I can look into. Also planning on getting a gauge set to test for fuel pressure.

I also thought I might put the IR camera up to the CE panel after driving for a while and see if anything is extraordinarily hot. Based on another thread I was reading. I think Stan mentioned failures at the relay plug on the board.

Still not starting when hot. Went for a 15min drive last Friday. It started up perfect and ran great. Stopped at the grocery store, was in there for 5mins, came out and no start. Waited 30-40mins, started right up and home I went.

[ladybug83]

Possible ICV malfunction when hot (I had this on my GTS) took a long time to diagnose because it worked fine on the bench (cold'ish).

Alan,
Are you referring to #37/37A. Im not sure I have the ICV your referring to on your GTS.

image.png

[ladybug83]

Got some time to tinker this weekend. Went for a 15 min drive. When I got back home, I checked spark at plug 1. No spark. Tried to check spark at each distributor wire, but I couldn’t see from the driver seat. I’ll have to figure out a better way to do this so I can see. An extension plug light perhaps, if that’s a thing.

I put an FLIR camera on the CE panel.
No fuses were hot.

Relays that were hot included:
LH-jet
Fuel pump
Ignition
Window winder(?) (maybe from having the door open for a while while checking the fuses and relays, don’t know)

Swapped out the first three relays, one at a time, in the order listed. No start until after I swapped out the ignition relay, then it started. I shut it down, locked up the house to go for another drive, and then no start again. Grrrrr

Short of any better advise, next on my list is pulling CE panel for inspection, cleaning and swapping out all the running relays and all fuses with new. I also have a new ignition switch I can swap in. CPSs should be easy to swap out too.

Can’t figure why I wouldn’t have spark when it’s hot. But it runs great. I’ll get it figured out one of these days. To be continued. Have a good work week everyone.

[worf]

Can’t figure why I wouldn’t have spark when it’s hot. But it runs great. I’ll get it figured out one of these days. To be continued. Have a good work week everyone.

When you have no spark on LH 2.2/2.3 you always start with: CPS and ECU grounds. If the EZK/EZF doesn’t get a speed signal from the flywheel, or if the EZF/K isn’t operating (e.g. power, ground) then there will be no spark.

I didn’t re-absorb this thread, so I apologize in advance if this question has been answered: what is the history of the CPS and EZK and LH?

When was the last time you checked if ECU (two) and engine ground (one) bolts (three total) are clean and tight?

And yes, the failure modes can be heat dependent.

What’s the history of the LH harness? Bad shielding and/or a break or frayed wires on the CPS branch of the harness can cause these symptoms also.

[ladybug83]

Can’t figure why I wouldn’t have spark when it’s hot. But it runs great. I’ll get it figured out one of these days. To be continued. Have a good work week everyone.

When you have no spark on LH 2.2/2.3 you always start with: CPS and ECU grounds. If the EZK/EZF doesn’t get a speed signal from the flywheel, or if the EZF/K isn’t operating (e.g. power, ground) then there will be no spark.

I didn’t re-absorb this thread, so I apologize in advance if this question has been answered: what is the history of the CPS and EZK and LH?

When was the last time you checked if ECU (two) and engine ground (one) bolts (three total) are clean and tight?

And yes, the failure modes can be heat dependent.

What’s the history of the LH harness? Bad shielding and/or a break or frayed wires on the CPS branch of the harness can cause these symptoms also.

Ok great, some more things to look into.

I checked, cleaned, retightened all of the grounds, front to back, a couple weeks ago. But I’ll re-inspect for any damage to the wires and looms. LH2.3 units and CPSs were installed when the engine was rebuilt about 5-6k miles ago. Swapping them out for fresh rebuilds might be easy though, easier than refreshing the CE panel. The harness itself is original to the car, with fresh plugs and shielding, also done when the motor was rebuilt. Greg had to modify the harness to make it work with the 2.3 and the added CPSs and hall sensor. I assume the sensors were new when installed.

Thank you for the continued support

[worf]

LH2.3 units and CPSs were installed when the engine was rebuilt about 5-6k miles ago.

How many years?

Also, why are you using plural to describe the engine speed sensor? Is there something else we need to know here?

Swapping them out for fresh rebuilds might be easy though, easier than refreshing the CE panel.

I’m an advocate for diagnosis before buying buying parts.

The harness itself is original to the car, with fresh plugs and shielding, also done when the motor was rebuilt. Greg had to modify the harness to make it work with the 2.3 and the added CPSs and hall sensor. I assume the sensors were new when installed.

Well… that’s interesting. So…Greg built it. Your profile says “SoCal.” Greg’s in SoCal. Why don’t you take it back to Greg?

Thing is… your 2.2 harness didn’t require modification for the single CPS/impulse/speed sender. It did require adding a Hall sender for cam position and, I would think, branches for two knock sensors. But, the S3 air guide “uses” one of the knock sensor holes. Doc Brown may also have done something “completely different.”

The next step in diagnosis involves the position/speed/impulse sender and some mechanics’ wire.

Post a picture of the CPS so that I know you’ve found it. (Since it has the same connector as knock and hall sensors, I want to be sure you’ve found it.)

[ladybug83]

LH2.3 units and CPSs were installed when the engine was rebuilt about 5-6k miles ago.

How many years?
5ish

Also, why are you using plural to describe the engine speed sensor? Is there something else we need to know here?
Because I’m confusing them with knock sensors

Swapping them out for fresh rebuilds might be easy though, easier than refreshing the CE panel.

I’m an advocate for diagnosis before buying buying parts.
Parts are sometimes borrowable

The harness itself is original to the car, with fresh plugs and shielding, also done when the motor was rebuilt. Greg had to modify the harness to make it work with the 2.3 and the added CPSs and hall sensor. I assume the sensors were new when installed.

Well… that’s interesting. So…Greg built it. Your profile says “SoCal.” Greg’s in SoCal. Why don’t you take it back to Greg?
I like working on the car when I can manage it, Greg has always been there when I can’t.

Thing is… your 2.2 harness didn’t require modification for the single CPS/impulse/speed sender. It did require adding a Hall sender for cam position and, I would think, branches for two knock sensors. But, the S3 air guide “uses” one of the knock sensor holes. Doc Brown may also have done something “completely different.”
Yes, hall sensor and knock sensors were added. My mistake for mixing it up with the CPS. It’s an S2

The next step in diagnosis involves the position/speed/impulse sender and some mechanics’ wire.

Post a picture of the CPS so that I know you’ve found it. (Since it has the same connector as knock and hall sensors, I want to be sure you’ve found it.) Will do, thanks. CPS is the one at the back of the block, beneath the air cleaner right? (A couple weeks ago, when I was routing around, I found that it was not fully tightened down. I added a washer beneath the mounting screw so it would fully tighten down, not too tight, but snugged down. Didn’t change the hot start issue.) I’ll check it out again, but I didn’t notice anything off with the wiring or the sensor itself, it had some anti-seize (I presume) on it, but otherwise was looking good

[Addlight]

Hi Ladybug,
I think I talked to you at a C&C in San Clemente last November. I was the guy from Colorado with an 86.5 (not there) who admired how clean and well put together your car was.

For those who have not seen this car, it's pretty spectacular. Champagne interior, Greg Brown stroker, very tasteful and cleanly done mods.

Matt

[ladybug83]

Hi Ladybug,
I think I talked to you at a C&C in San Clemente last November. I was the guy from Colorado with an 86.5 (not there) who admired how clean and well put together your car was.

For those who have not seen this car, it's pretty spectacular. Champagne interior, Greg Brown stroker, very tasteful and cleanly done mods.

Matt

Hi Matt! Thanks for the kind words. That’s a heck of a C&C huh? We love the variety of cars there every week. And usually some transaxles which is nice.

I’ve been having this hot start issue since before we met, but it’s been getting progressively worse. Use to happen once in a while, then sometimes, now all the time when it’s hot. Maybe that’ll be a blessing being able to target it. I’ll keep plugging away till I get it. Or, until I give up and take it to Greg lol!

[Zirconocene]

You're getting the best possible support from Sean and Worf, but one thing you wrote sort of stood out to me. Did you put a washer between the CPS and the bellhousing, in order to tighten things down, or between the bolt and the top of the sensor? If it's between the sensor and the bellhousing, that's not doing you any favors. It might not be the root cause of what you're experiencing, but the gapping for that sensor to the flywheel teeth is pretty important. It's a sort of Goldilocks thing: too close and it will hit, too far and it won't read quite right. I don't know if it will work for your car, but there are 3D printed tools you can get for the 944 to set the gap correctly.

As you might guess, this is coming from my experience with the 944, so apologies if it's not applicable to the 928; I haven't (yet) had issues with this part of my S4.

Good luck

[ladybug83]

Makes sense. I put the washer between the bolt and the top of the sensor. So the gap is the same. The sensor; however, sits atop of an aluminum spacer, the spacer atop the engine block. The spacer looks like it could be handmade, I figured GB made it perhaps to accommodate the gap your describing. Or maybe it's borrowed from another model, don't know for sure. Thing is, everything worked perfectly for a lot of miles, then gradually became a constant issue with these hot starts.

I know some are probably frustrated because Im not following the proper protocols. I just dont have the tools for it, so my fallback is replacing parts. Not recommended, I know. Its not that Im not listening, its just not all in my wheelhouse. I reached out to Greg to see when I could bring it to him. I'll keep everyone posted as to the outcome, and any more tinkering I do in the meantime.

Thanks again.

[worf]

Will do, thanks. CPS is the one at the back of the block, beneath the air cleaner right? (A couple weeks ago, when I was routing around, I found that it was not fully tightened down. I added a washer beneath the mounting screw so it would fully tighten down, not too tight, but snugged down. Didn’t change the hot start issue.) I’ll check it out again, but I didn’t notice anything off with the wiring or the sensor itself, it had some anti-seize (I presume) on it, but otherwise was looking good

Whatever GB did vis-a-vis the CPS when he did the LH2.3 conversion worked when he was done. A physical mod - I'm not sure what he did, I've never thought about this conversion - won't degrade or "change dimensions" over time. Why the mounting bolt was loose... dunno.

For clarity, shown below is the CPS on an S4 motor (Note that it is 'loose' as I don't bolt it down until the engine is installed so as to mitigate any risk of damage when the flywheel and clutch are installed.)



Based upon your symptoms this is my recommendation for further diagnosis:

- Trace the lead from the CPS to its 3-pin connector.
- Get a length of mechanics' wire or brass safety wire (something flexible, not too thick, somewhat easy to bend but stiff enough that you can push and pull) about 2 feet long.
- Twist one end of the wire around the LH harness just after the harness-side connector to the CPS
- Reassemble everything so that you can start, idle, and warmup (if required) the engine.

The purpose of this 'device' is to allow you to 'wiggle' the CPS branch of the LH harness while the engine is running to see if wiggling the harness causes the engine to stumble or die. It is a diagnostic for a break in the CPS branch of the harness. And yes, it can be heat dependent.

So, install the 'device' and then start the car. Once it's running see if "wiggling" the wire will change how the engine runs. If not, let the engine get warm and try again. If it still runs, then secure the wire, go for a drive (i.e. replicate you test procedure that results in a no start) and then when it doesn't start, wiggle the wire while trying to start the engine (two folks might be best or you'll need a longer wire.)

If this diagnostic 'passes' then it doesn't mean that you don't have a harness issue. It means that *if* you have a harness issue its deeper in the harness. On the other hand if the diagnostic results in the engine dying then you have your answer. In the former case the next step is to get an oscilloscope or start throwing random parts at it.

The thing is: most of the random parts you'd throw at it are duplicated (e.g. coils, caps, coil amps) and thus unlikely to kill ALL of the motor. The 'singular' items in the Spark system are: EZK, CPS, harness, EZK relay.

And then whatever GB did to the harness during the conversion.

Given that the harness is original and a billionty years old at this point and that the CPS is new (enough) I'd be concentrating on the harness after 'scoping signals during a no-start event.

HTH.

[ladybug83]

Whatever GB did vis-a-vis the CPS when he did the LH2.3 conversion worked when he was done. A physical mod - I'm not sure what he did, I've never thought about this conversion - won't degrade or "change dimensions" over time. Agree.

Why the mounting bolt was loose... dunno. me either, doesn’t seem to matter, didn’t change anything. It’s not like it was spinning in there either, just without the washer, it was a little rotationally wiggleable

For clarity, shown below is the CPS on an S4 motor (Note that it is 'loose' as I don't bolt it down until the engine is installed so as to mitigate any risk of damage when the flywheel and clutch are installed.) Got it. Looks like mine, without the spacer.



Based upon your symptoms this is my recommendation for further diagnosis:

- Trace the lead from the CPS to its 3-pin connector.
- Get a length of mechanics' wire or brass safety wire (something flexible, not too thick, somewhat easy to bend but stiff enough that you can push and pull) about 2 feet long.
- Twist one end of the wire around the LH harness just after the harness-side connector to the CPS
- Reassemble everything so that you can start, idle, and warmup (if required) the engine.

The purpose of this 'device' is to allow you to 'wiggle' the CPS branch of the LH harness while the engine is running to see if wiggling the harness causes the engine to stumble or die. It is a diagnostic for a break in the CPS branch of the harness. And yes, it can be heat dependent.

So, install the 'device' and then start the car. Once it's running see if "wiggling" the wire will change how the engine runs. If not, let the engine get warm and try again. If it still runs, then secure the wire, go for a drive (i.e. replicate you test procedure that results in a no start) and then when it doesn't start, wiggle the wire while trying to start the engine (two folks might be best or you'll need a longer wire.)I can do all of the above

If this diagnostic 'passes' then it doesn't mean that you don't have a harness issue. It means that *if* you have a harness issue its deeper in the harness. On the other hand if the diagnostic results in the engine dying then you have your answer. In the former case the next step is to get an oscilloscope or start throwing random parts at it.ok got it. This is the 2nd issue I had that an oscilloscope would be useful, have a recommendation?

The thing is: most of the random parts you'd throw at it are duplicated (e.g. coils, caps, coil amps) and thus unlikely to kill ALL of the motor. The 'singular' items in the Spark system are: EZK, CPS, harness, EZK relay. ok, these are all doable jobs for me. The harness being the most tedious, but doable, and on my to-do list anyways, just been stalling because I didn’t want to take the car off the road, I like driving it

And then whatever GB did to the harness during the conversion. Not exactly sure, but I don’t think it was an extensive harness mod.

Given that the harness is original and a billionty years old at this point and that the CPS is new (enough) I'd be concentrating on the harness after 'scoping signals during a no-start event. Sigh. Ive been stalling on making a new harness for a while now. Talked to GB, 6months ago, and again a year ago. He even offered me to borrow his peg board and supply me with wire. I’ve just been lazy about it, enjoying driving it, after building it for so long. But it may be time to stop putting it off. When I rebuilt the car, I stripped the harnesses, installed new plugs, insulation, etc. They cleaned up nice, but at the end of the day, 39 year old wire probably doesn’t perform as designed. Double sigh, LOL

HTH. it does, greatly, thank you for taking the time out of your day

[worf]

…When I rebuilt the car, I stripped the harnesses, installed new plugs, insulation, etc. They cleaned up nice, but at the end of the day, 39 year old wire probably doesn’t perform as designed. Double sigh, LOL

Ok. So, it’s not *exactly* the original harness. Is it? How far “down” did you go when you stripped it? All the way to the colored insulation layer for every wire from end connector to ECU/CEL connector? If you did then you have a good idea of the condition from stem to stern. Much better than do I.

“Old” wire isn’t necessarily a problem. Wire where the layers are stiff or where copper is exposed is a problem. Corrosion on contacts is a problem.

You can always just throw a CPS at it. I have had one be ‘bad’ after 5 years but, not with a no-start-when-hot.

[ladybug83]

Yup, I removed the outside layers of insulation so I could evaluate the condition of the colored wires, change the plugs, etc. I don’t believe I messed with anything past the firewall grommet, so the harnesses on the interior side of the firewall are as they were originally, sans any changes GB made, like the re-pin for example.

[ladybug83]

Well, this hot start thing may be solved. Or maybe masked, not sure.

Yesterday morning, before I got a chance to do any more diagnostics , I already had on hand a bunch of new 53 relays and blade fuses. Because the CE panel was such a hodgepodge of relays and fuses of various ages and histories, I thought why not change them out, just to hopefully also rule them out. I had swapped them up and around before with no change in the hot start problem, but the heck with it. All new fuses in the board and all new (10) 53 Bosch relays.

While I was in there, I poked around to see what I could see, nothing looked amiss. I checked on the grounds above the CE panel. Although I had cleaned them a few weeks back, I took them apart again and this time rubbed some deoxit on them all plus the mounting surfaces.

I also had to get into the pod for an unrelated gauge adjustment, and I had a new ignition switch so I figured why not, I put it in also since I was going to be in there.

I went for a 10 mile test drive, ready to test the harnesses and the fuel injectors upon my return. loop back to the house. Car is full hot. And it starts. Try a couple more times. Started every time

Then

Today I went for a 10mi drive and home. Hot starts three times over a ten minute period.

Went right back out for a 30mi drive and come home. Starts three times over a twenty minute period.

Fixed? Not sure.

Does relay function deteriorate over time? Or at once? Maybe one had been giving up the ghost slowly. Grounds? Ignition switch?

Could there be something more sinister at play and I’ve only reset the deteriorating condition?

Weird

Will keep driving and be ready to test harnesses and fuel injector function if it acts up again.

Thanks for everyone’s help so far.

[worf]

Good luck!

[ladybug83]

Thanks! Any ideas on what changed? Fixed or masked the issue?

[worf]

Thanks! Any ideas on what changed? Fixed or masked the issue?

You changed the ignition switch. That’s not usually a ‘stops-when-hot’ part. But, I suppose it could be.

You did a lot of messing with the CEL panel. And the formerly consistent failure mode has stopped.

Occam’s Razor points to the fuse panel. Loose CEL terminal for switching pin (85,86) on EZK relay. Or oxidation. Maybe loose pin *inside* EZK relay. Or maybe ground lugs above CEL.

Have you ever ‘bench cleaned’ the CEL panel? That’s a 15-year schedule maintenance item IMO. As is throwing away all the fuses and cheap relays that work hard (LH, EZK, FP.)

[ladybug83]

Bench inspected and cleaned the CE panel when the car was rebuilt, about 5 years ago now. Should’ve replaced all the fuses and relays then, but just getting around to it now. It was recommended not to replace things that are working and to focus on the stuff that doesn’t work. In hind sight, the fuses and relays (relatively cheap) should’ve been replaced given the scale of the rebuild.

[ladybug83]

Don’t know if it means anything, but upon removing the old ignition switch, it had seeped out some kind of oil. Maybe a centimeter-size drop on the bottom side of it, brownish in color. Can’t imagine what that’s about.

[worf]

Don’t know if it means anything, but upon removing the old ignition switch, it had seeped out some kind of oil. Maybe a centimeter-size drop on the bottom side of it, brownish in color. Can’t imagine what that’s about.

Whadit taste like?

Just kidding.

No fucking idea.

[worf]

Bench inspected and cleaned the CE panel when the car was rebuilt, about 5 years ago now.

Hmmm.. m’kay. So, not corrosion. Maybe terminal issues.

If you want more certainty, put back just the old EZK relay (if you labeled it) and see if the problem comes back.

It was recommended not to replace things that are working and to focus on the stuff that doesn’t work.

That recommendation usually comes from people that have never pondered the question: “Would you fly on an airplane that was only fixed when it broke?”

In hind sight, the fuses and relays (relatively cheap) should’ve been replaced given the scale of the rebuild.

Figuring out what WYAIT things to do or parts to replace is a multi-dimensional problem with dimensions of: money, time, and risk management.

[ladybug83]

I appreciate all the time you’ve spent on this. I feel like I should send you a banana bread or something. Seriously though, thank you. I’ll keep testing and update if anything changes.

[linderpat]

my money is on the relays. Remember the old Jim Bailey mantra - relay, relay relay! Whatever it is, hope you solved it once and for all.

[ladybug83]

Just an update on this hot start problem.

Since replacing all the “53” relays and the ignition switch, car hasn’t missed a beat.

Thanks again for everyone’s help on this, cheers.

[worf]