Fires then dies. HELP

[Ozruss90]

This situation happened months ago after I removed the cam angle sensor to replace the Oring due to an oil leak. After the sensor was replaced, the engine would fire and then dies within a few seconds. At the time it was suggested to be the fuel pump at fault. So without confirming I ordered a new fuel pump/sender assembly.
Still have the Fire up and die within seconds scenario. Fuel pump is operating and pumping fuel as it should.
Need help as to where to look next. Unfortunately I don?t have an OBD1 scanner. I have read that the engine should run even without input from the cam angle sensor, so ruling that part of it out.
Very much a coincidence though that this start/stop situation happened immediately after I replaced the c/a sensor.
HELP from the brains trust on here appreciated.

Cheers, Russell. 🇦🇺 AUSTRALIA

[scorp508]

Does this happen even if the car is cold, or only if the coolant is warm and around 175* (F) or higher?

[secondchance]

Does this happen even if the car is cold, or only if the coolant is warm and around 175* (F) or higher?

You are thinking primary fuel pump may be bad. Arn't you? I was wondering the same. Car may be starting on pressure generated by the secondary pump but secondary pump shutting off and with primary pump not working resulting in fuel pressure drop.

[scorp508]

You are thinking primary fuel pump may be bad. Arn't you?

More to rule something in/out before pointing fingers at any one root cause yet. :)

Below 176'ish (F) coolant temp both pumps run. Once above that only the primary runs unless the ECM commands the secondary to provide fuel as well.

So, if this is happening when the car is cold or at least well under that coolant temp, then either BOTH pumps aren't providing fuel as it'll idle on one easily, or there's something else going on.

I thought my primary pump had failed as it would die once over 176* when the secondary pump stopped. Long story short... the pump was fine and a harness connection inside the car had come loose where the primary pump gets its 12V from. I already had swapped both pumps out by the time I found it, so now I have a pair of perfectly good spare used pumps on a shelf. :eek:

The secondary pump can be forced to remain on >176* by depinning light green wire at C21 of the ECM as this wire is the signal from the ECM is used to turn the pump off. Removing that wire makes it so the ECM can never turn it off. Marc has this buried in an article about converting to a single pump.

https://www.zr1specialist.com/HAT%20Web/articles/Converting%20the%20ZR-1%20fuel%20system.pdf

There is a fuel pump test lead near the ECM, which looks like someone forgot to plug something into a harness. I think 90s had this lead lower in the engine bay. If you put 12V to that lead with the ignition key in the off position and measure the amperage going through the wire you're using to provide the voltage, then you can tell if one or two pumps are running. I think it's about 5A if one pump is running and 10A if both are running. It can help rule some things in/out.

[Ozruss90]

You are thinking primary fuel pump may be bad. Arn't you? I was wondering the same. Car may be starting on pressure generated by the secondary pump but secondary pump shutting off and with primary pump not working resulting in fuel pressure drop.

It now has a single pump conversion unit in it.

[Ozruss90]

More to rule something in/out before pointing fingers at any one root cause yet. :)

Below 176'ish (F) coolant temp both pumps run. Once above that only the primary runs unless the ECM commands the secondary to provide fuel as well.

So, if this is happening when the car is cold or at least well under that coolant temp, then either BOTH pumps aren't providing fuel as it'll idle on one easily, or there's something else going on.

I thought my primary pump had failed as it would die once over 176* when the secondary pump stopped. Long story short... the pump was fine and a harness connection inside the car had come loose where the primary pump gets its 12V from. I already had swapped both pumps out by the time I found it, so now I have a pair of perfectly good spare used pumps on a shelf. :eek:

The secondary pump can be forced to remain on >176* by depinning light green wire at C21 of the ECM as this wire is the signal from the ECM is used to turn the pump off. Removing that wire makes it so the ECM can never turn it off. Marc has this buried in an article about converting to a single pump.

https://www.zr1specialist.com/HAT%20Web/articles/Converting%20the%20ZR-1%20fuel%20system.pdf

There is a fuel pump test lead near the ECM, which looks like someone forgot to plug something into a harness. I think 90s had this lead lower in the engine bay. If you put 12V to that lead with the ignition key in the off position and measure the amperage going through the wire you're using to provide the voltage, then you can tell if one or two pumps are running. I think it's about 5A if one pump is running and 10A if both are running. It can help rule some things in/out.

The fuel pump in there now is a new single pump unit, and the green wire at the ECM has been de pinned as per the instructions that came with the pump unit.
Power to the pump is fine and tested the pump running and pumping fuel with the sender unit / pump out of the tank ( submerged in fuel ) It is pumping fuel as it should, therefore I?m assuming the problem is elsewhere..

[secondchance]

The fuel pump in there now is a new single pump unit, and the green wire at the ECM has been de pinned as per the instructions that came with the pump unit.
Power to the pump is fine and tested the pump running and pumping fuel with the sender unit / pump out of the tank ( submerged in fuel ) It is pumping fuel as it should, therefore I?m assuming the problem is elsewhere..

I suggest that you check the fuel pressure at the fuel rail before the ignition key is turned and after the motor dies after starting. Fuel pump may be fine but the command it's getting from the ECM might be screwy with reconfiguration of electrical connector.
Just my 2 cents.

[scorp508]

Power to the pump is fine and tested the pump running and pumping fuel with the sender unit / pump out of the tank ( submerged in fuel ) It is pumping fuel as it should, therefore I?m assuming the problem is elsewhere..

Ok, so, just to confirm my curiosity... this happens if the car is COLD as well? :)

[Ozruss90]

Ok, so, just to confirm my curiosity... this happens if the car is COLD as well? :)

Yes, it can?t be anything other than cold because it doesn?t run. The car has not been running for 6 months because of this problem. It cranks as normal then starts and runs for only 2 or 3 seconds and dies.

[Ozruss90]

I suggest that you check the fuel pressure at the fuel rail before the ignition key is turned and after the motor dies after starting. Fuel pump may be fine but the command it's getting from the ECM might be screwy with reconfiguration of electrical connector.
Just my 2 cents.

I will try and borrow a fuel pressure gauge to test pressure at the rail, to see what?s going on there.
? reconfiguration of electrical connector ? are you referring to the de pinned plug at the ECM ?

[secondchance]

I will try and borrow a fuel pressure gauge to test pressure at the rail, to see what?s going on there.
? reconfiguration of electrical connector ? are you referring to the de pinned plug at the ECM ?

Yes.

[Ozruss90]

Have tested fuel pressure at the rail and showing between 40 and 45 psi. Checked for any faults at the ALD port by bridging A & B. Only getting code 12, so no faults detected.

HELP PLEASE. I have a Corvette function coming up in a couple of weeks and need the Z running.

Question.. Should the engine start and run if the cam angle sensor was faulty ??? I pulled it out again today ( 3rd time ) just to re check, and it looks as good as new.

[DRM500RUBYZR-1]

OK, so fuel is apparently not the issue.
Can you confirm spark?
:cheers:
Marty

[Ozruss90]

OK, so fuel is apparently not the issue.
Can you confirm spark?
:cheers:
Marty

It has spark, as it does fire and run. BUT it only runs for a few seconds then dies. So someone is maybe shutting off Fuel or Spark for whatever reason. I don?t know. That?s why I?m here seeking suggestions. Desperate to get this up and running again . 😤

[RSLyrick]

Hi Russel,

Are there any ZR-1 owners near you ? I would propose an ECM swap test at this point if possible.

[Ozruss90]

Hi Russel,

Are there any ZR-1 owners near you ? I would propose an ECM swap test at this point if possible.

Closest one would be approx 2 hours away. It?s my previous ?90 ZR-1.
My current non running Z has a Lingenfelter 495 package in it. My old ?90 Z is stock standard. Would this create an issue by swapping the ECM?s ??

[RSLyrick]

Marc Haibeck has proved that ECMs are interchangeable between different MY.

To my knowledge nobody is capable of modifying the hardware of the ECM itself to add additionnal features, sensor inputs, control outputs. You can only adjust engine parameters with custom chips. If your ECM looks stock (visually) with no weird extra wire harnesses or a different housing, this is then a standard ECM.

So you probably have a custom EEPROM chip for your specific build (engine tuning) but the base ECM hardware should be identical to all of the other ones out there.

That would mean that if you put the old 90s EEPROM into your own ECM and plug the whole thing into the old 90s car, that should allow you to test the supposed faulty ECM in the old 90s vette.

I would not advise to place your ECM with the custom Lingenfelter chip directly into the standard 90s ZR-1 without really knowing what's going on in the chip. The 90s base engine may run poorly or not at all leading you to think that the ECM is faulty but it's actually not.

Maybe your ECM is running an Haibeck chip, you can visually check and then contact him based on the part number for more info. I don't know if Marc sells chips for Lingenfelter build.

I would appreciate if members involved in tuning procedure could confirm this statement before damaging a second vette or a working ECM...this is not a standard use case that we're talking about here.

[Ozruss90]

Marc Haibeck has proved that ECMs are interchangeable between different MY.

To my knowledge nobody is capable of modifying the hardware of the ECM itself to add additionnal features, sensor inputs, control outputs. You can only adjust engine parameters with custom chips. If your ECM looks stock (visually) with no weird extra wire harnesses or a different housing, this is then a standard ECM.

So you probably have a custom EEPROM chip for your specific build (engine tuning) but the base ECM hardware should be identical to all of the other ones out there.

That would mean that if you put the old 90s EEPROM into your own ECM and plug the whole thing into the old 90s car, that should allow you to test the supposed faulty ECM in the old 90s vette.

I would not advise to place your ECM with the custom Lingenfelter chip directly into the standard 90s ZR-1 without really knowing what's going on in the chip. The 90s base engine may run poorly or not at all leading you to think that the ECM is faulty but it's actually not.

Maybe your ECM is running an Haibeck chip, you can visually check and then contact him based on the part number for more info. I don't know if Marc sells chips for Lingenfelter build.

I would appreciate if members involved in tuning procedure could confirm this statement before damaging a second vette or a working ECM...this is not a standard use case that we're talking about here.

Sorry, not up to speed with all this. I?m assuming the Chip is located within the ECM. Is it hard to get to, and identify the Chip?? I would like to do this and then call Marc with my findings
Appreciate your help 👍

[RSLyrick]

Sorry, not up to speed with all this. I?m assuming the Chip is located within the ECM. Is it hard to get to, and identify the Chip?? I would like to do this and then call Marc with my findings
Appreciate your help 👍


Yes, there is a small compartment/door below the ECM where the EEPROM is stored.


1- Unplug the battery
2- Wear some ESD wrist strap (google it if you don't know what that is) to protect the circuitry from electrostatic discharge from your body to the electronics.

3- Unmount the ECM housing from the backet (no need to remove the 4 way connectors / harnesses). Only if you think that it would be easier for you to work on the ECM.

4- Flip carefully the ECM and lay it down on the (pre-protected) windshield. The ECM is not that heavy but made of metal, if you drop it on the windshield you could damage it. The harness is stiff enough not to let that happen but it doesn't cost you anything to lay a towel on it.


5- A gasket is used between the compartment access door and the ECM housing to prevent humidity from getting inside. Remove carefully the door to not damage the gasket.

6- Remove the small access door and there you can access the chip. If it's an Haibeck you will clearly recognize it thanks to the white label.




Here's a global overview of the process : https://youtu.be/jMkwEe93SYk?t=240


I insist on the fact that you MUST wear an ESD protection device (either a wrist strap or ESD certified shoes, to "ground" yourself. Not like in the above video, gloves like he wears are not considered as an approved protection method. People usually do not know how to properly handle electronics in unprotected areas like your home garage.


You can also pre-call Marc before doing all of this. Maybe he can confirm that you can safely start the old 90s with your current ECM...Nothing to loose getting advice from reknown experts. He can also give you some clear guidelines about your issues in general...

[Ozruss90]

Yes, there is a small compartment/door below the ECM where the EEPROM is stored.


1- Unplug the battery
2- Wear some ESD wrist strap (google it if you don't know what that is) to protect the circuitry from electrostatic discharge from your body to the electronics.

3- Unmount the ECM housing from the backet (no need to remove the 4 way connectors / harnesses). Only if you think that it would be easier for you to work on the ECM.

4- Flip carefully the ECM and lay it down on the (pre-protected) windshield. The ECM is not that heavy but made of metal, if you drop it on the windshield you could damage it. The harness is stiff enough not to let that happen but it doesn't cost you anything to lay a towel on it.


5- A gasket is used between the compartment access door and the ECM housing to prevent humidity from getting inside. Remove carefully the door to not damage the gasket.

6- Remove the small access door and there you can access the chip. If it's an Haibeck you will clearly recognize it thanks to the white label.




Here's a global overview of the process : https://youtu.be/jMkwEe93SYk?t=240


I insist on the fact that you MUST wear an ESD protection device (either a wrist strap or ESD certified shoes, to "ground" yourself. Not like in the above video, gloves like he wears are not considered as an approved protection method. People usually do not know how to properly handle electronics in unprotected areas like your home garage.


You can also pre-call Marc before doing all of this. Maybe he can confirm that you can safely start the old 90s with your current ECM...Nothing to loose getting advice from reknown experts. He can also give you some clear guidelines about your issues in general...

Gee, thanks very much for your assistance. Much appreciated. Midnight here in Australia where I am. Will do some more checking tomorrow 🥱

[XfireZ51]

R u sure its the cam angle and not the crack sensor?

[Ozruss90]

R u sure its the cam angle and not the crack sensor?

I?m assuming a typo and you meant CRANK sensor. No, I don?t know. The only reason why I have referenced the CAM angle sensor is that this, fire up and die straight away, situation started when I went to re start the car after pulling the cam angle sensor out to replace the O ring due to an oil leak
Should I pull the CRANK angle sensor out to check, and test (if possible) ?

Cheers, Russell 🇦🇺

[RSLyrick]

I think that you would get no spark at all if the crankshaft position sensor was faulty, as the ignition module selects which coil packs to energize based on the sensor output. Your engine is starting and holding for a while and you checked that you had sparks, that already sounds good to me.

If this sensor is working fine, you should logically get RPM readings as well.

If you want to test it (we never know), there's a nice method provided in the FSM which allows you to test without removing the crankshaft position sensor from the engine and make it easy to test (see 6E3-A-32) :

1- Get yourself an engine coolant temperature harness from a 1985-1989 C4 (PN : 12046623)
2- Unplug the actual sensor harness from the sensor and plug the floating engine coolant temperature one in with the two floating leads.
3- Measure the resistance between the leads
4- Should be a value between 965 and 1075 Ohm at 25?C (77?F) for a working sensor.

In any cases, try to give a quick call to Marc. Please, give us a feedback about it, I'm interested! :)

[Ozruss90]

Well it looks like the problem has been solved. I rang and spoke to Marc Haibeck yesterday and described my situation. He said start with the basics, has it got fuel pressure ? Yes confirmed by pressure gauge. When I told him it happened straight after removing the cam angle sensor, he suggested that I unclip the harness from the sensor to the ECM. I hadn?t done this as I had checked codes at the ALD port and no faults detected. I had also read in the FSM that the engine will still run without Cam sensor input, so assumed problem had to be elsewhere. Looks like the cam sensor is faulty and while connected to the ECM was causing an issue with the ECM. Once I unclippped that harness the engine fired up and idled as per normal. Very relieved to know what the problem was. Thank you Marc. 👍

NOW I have to source another sensor if anyone on here can help me out with one or steer me in the right direction to get one 🤞 would be much appreciated.

Cheers,
Russell. 🇦🇺

[RSLyrick]

Hey Russel,

Very nice ! :D It's weird that the ECM didn't throw you a DTC31...must have been so confused by the non-working sensor that it didn't know how to react (the failure was probably not landing into the "missing pulses" category or "extra pulses" one...interesting.

So, if I'm not wrong, you will face the second issue. The camshaft sensor lands into the "hard to find parts" section. No longer manufactured or stored.

Original PNs were : 10137658 / 10137658 / 213-141

I came across the following threads about modifying an aftermarket one.

https://zr1.net/forum/showthread.php?t=28584

Phil (Jagdpanzer) seems to be able to make some based on aftermaket parts : he provided his email in the above thread : pwasinger@aol.com

Latest requests were done in June this year, so it should be feasible to get one I guess.

[Ozruss90]

Hey Russel,

Very nice ! :D It's weird that the ECM didn't throw you a DTC31...must have been so confused by the non-working sensor that it didn't know how to react (the failure was probably not landing into the "missing pulses" category or "extra pulses" one...interesting.

So, if I'm not wrong, you will face the second issue. The camshaft sensor lands into the "hard to find parts" section. No longer manufactured or stored.

Original PNs were : 10137658 / 10137658 / 213-141

I came across the following threads about modifying an aftermarket one.

https://zr1.net/forum/showthread.php?t=28584

Phil (Jagdpanzer) seems to be able to make some based on aftermaket parts : he provided his email in the above thread : pwasinger@aol.com

Latest requests were done in June this year, so it should be feasible to get one I guess.

Thanks for your input. Much appreciated
Question. Do all year models of the LT5 take the same sensor ??
I have the opportunity to borrow one from an acquaintance who purchased an LT5 engine out of a pre production test car here in Australia. I was going to borrow that until I can get hold of another one.
To what extent does the engine run with the cam sensor disconnected? Can the car be driven and if so are there any restrictions on how it?s driven ??
Cheers, Russell 🇦🇺

[RSLyrick]

When I got my new sensor it was listed for 1990 to 1995. I do not think that there are differences but I have no certified proofs at hand. Maybe other members can comment on that.

Without a proper working sensor, optimal SFI cannot happen as the ECM doesn't have the info about the intake valve opening state. I'm not sure but additionnaly to the engine running poorly, you may get RPM limitations as well.

I'd like to add a bit more thoughts to this topic.

I'm still thinking that the ECM being faulty is a valid hypothesis. By that I mean, that the interface with the sensor is damaged or has failed. You didn't get a DTC31 that's the reason why I keep the hypothesis alive.

This is (probably) what happened to the Autofunk guys (https://www.youtube.com/watch?v=_-By-CEWRW8&list=PLlgMNmEnQ2umUz5D3c-7BDk9qjE8bqpGO&index=11).

Similar issues as yours but they managed to get a DTC 31 (camshaft sensor issues). Their ECM was faulty, not the sensor.

Did you get a DTC 31 when running the car with the sensor harness disconnected ? Just to be sure that the sensor interface is actually capable of computing what's happening at this specific pin.

Also have you probed the camshaft sensor output when ignition is ON ? should be at 0V when the slot of the camshaft reluctor wheel is in front of the sensor, 12V otherwise.

And the supply wire to the sensor when ignition is ON (12V) ?

[Ozruss90]

UPDATE:
After a phone call with Marc Haibeck, he suggested that I disconnect the harness from the cam sensor to the ECU. I didn?t think this would achieve anything due to, knowing that the engine would/should run without the cam sensor functioning. BUT, with the harness connected, and the sensor faulty, I can only assume that it was sending a bad signal to the ECU. Once I DISCONNECTED the harness, it fired up and ran as per normal. BINGO. I took it for run yesterday, to a car show approximately 30km away and it ran perfectly with the harness disconnected.
I borrowed a cam sensor off a friend and fitted that in today, and with the harness CONNECTED as it should be, it started up and ran perfectly again.
I can only conclude that the cam sensor was faulty and caused my initial problem.
All the car show & shine events are starting back up, now that our weather here in OZ is nice and getting better. So good timing. I?m happy as??.😁

Cheers,
Russell 🇦🇺

[RSLyrick]

Thanks for the update. It is interesting to see that we can run the ZR-1 without cam sensor on long distance...

Still surprising that you didn't notice any driveability issues, did you try high RPM driving ?. Not even increased fuel consumption ? Sounds like the ECU manages to perform good SFI only based on the crankshaft sensor then...

Do we have a useless sensor in our cars ? :D

[Ozruss90]

Thanks for the update. It is interesting to see that we can run the ZR-1 without cam sensor on long distance...

Still surprising that you didn't notice any driveability issues, did you try high RPM driving ?. Not even increased fuel consumption ? Sounds like the ECU manages to perform good SFI only based on the crankshaft sensor then...

Do we have a useless sensor in our cars ? :D

Hi RSLyrick,
My secondary key switch not working consistently at the moment but did rev past 5000 and run it up to 180kmh on the road s that I had available at the time. Seemed to run great even without the cam sensor connected. Go figure.
Marc did mention that the cam sensor was there just for fine tuning and making sure the engine met emission requirements.

Cheers,
Russell

[RSLyrick]

Understood, that's good to know. You probably only get higher fuel consumption then.

That could be interesting to check this, next time you go for a ride, having a quick look at the average consumption.

Regarding your secondaries operation, have you already started investigating ?

[Ozruss90]

Understood, that's good to know. You probably only get higher fuel consumption then.

That could be interesting to check this, next time you go for a ride, having a quick look at the average consumption.

Regarding your secondaries operation, have you already started investigating ?

Will check that out tomorrow, to confirm that they are working or not. I?m guessing that they are.

[Ozruss90]

O boy, Yes the secondaries are working. I need to pull the key switch out and fix it. At the moment I have to jiggle the key back and forth 20+ times until I get the spot that it will stay on. After not driving the car for 6 months, it put a smile on the dial having the secondaries working 😁😬
Happy ending 👌

Cheers,
Russell 🇦🇺