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Runs fine for about 15 minutes then dies

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kevmills67
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Runs fine for about 15 minutes then dies

Post by kevmills67 » Thu Dec 14, 2017 4:10 am

I saw the thread about the starting and stalling, this isn't the issue I am having. If it is covered in another thread, I appreciate anyone redirecting me there.
This issue is on a 1980 633. As far as I know it started as an intermittent issue. I suppose we could be talking about two different issues though.

First time I noticed it was over a year ago. I took the car to the store than pulled into the driveway, loaded a bunch of things into the trunk to take up to my son and when I got in to start it a few hours later, it just turned over, didn't fire. I took everything out, put it in another car and drove it to him. Next day, I went out expecting it to just turn over but it started right up. With it running I pulled up the carpet in the trunk, inspected all the wires. I thought maybe me putting things on them in the trunk had created an issue but everything looked fine and jiggling the wires trying to get something to happen didn't do anything either.

I did not have the issue again for another few months. One morning, went out to start the car and nothing. This time I sprayed ether into the intake and it ran on the ether and then died. Did this a few times, same result. Figured I would deal with it later. A few days later went out to start it and it fired right up. Drove it for another month at least and then it happened one more time, same thing. Drove it home fine, parked, went out a day or two later to start it, nothing, just turning over, no starting. When it wasn't starting I checked the electrical in the trunk (I can hear the fuel pump) to the lift pump and it was working. A few days later, the car started right up. Then, months later, I was driving it because it seemed to be just a phantom issue and I have towing through auto club if (when) it stops. I drove it a considerable distance, missed a turn, turned around in a parking lot, pulled out into traffic, accelerated and it just died. I coasted to the side of the road but try as I might, it didn't start. I took a break, had lunch with my wife, tried again, nothing. Had it towed home. By time it got home, it was happy again, I started it on the tow truck and backed it off the truck. This made me think there was a short or something, possibly a stuck fuel pump that would jiggle loose with movement or when it cooled off. A few days later decided to try and track it down again. It started, I let it run, seemed to be running fine, got in it to drive it and it died. Cranked but wouldn't start. I again checked and had power to the lift pump in the tank and can hear the pump. After that, it seemed the car would start and run about 15/20 minutes then die and not restart until later (another day at least, did not keep going out to see how long before it would restart)

In the last week, I have installed a new multi-purpose relay from Bosch, a new fuel pump and filter and a new ECU. When the car stalls, I still get fuel pressure at the line (I have a new spare FPR somewhere but really don't think it would run perfectly for 15/20 minutes and then stall if it was an FPR issue) and if I use ether it starts so there is spark. Obviously fuel injectors are not working but why? What would make them work perfectly for 15/20 minutes then nothing? Remember, I have already replaced the ECU and have the same issue with the new ECU as the original one. I am usually pretty good at figuring these things out but I am stumped and this car is not OBD I or II. Anyone ever had this issue or have any ideas what it might be? I REALLY appreciate the help/

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hornhospital
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Re: Runs fine for about 15 minutes then dies

Post by hornhospital » Thu Dec 14, 2017 2:24 pm

Do you have a spare coil? Try swapping it when the car dies. Ether is easy to ignite, so a weak spark will still fire it up, but gasoline, not so much.

Anyway, it's something to try.
Ken Kanne
'84 633CSi "Sylvia"; '85 635CSi "Katja";'87 325is "Odette"; '93 325is "Elvira"; '95 M3 "Ashlyn"

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Re: Runs fine for about 15 minutes then dies

Post by jps635 » Thu Dec 14, 2017 4:32 pm

I don't know about the early cars but my 85 635 died in mid stride was either the crank position or speed sensor failure. It took weeks to figure this out as both tested ok, but eventually fired up only to die once warm. I still don't know which was faulty so replaced both.
'85 635csi JPS (RA2-66)

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Re: Runs fine for about 15 minutes then dies

Post by GRNSHRK » Thu Dec 14, 2017 5:25 pm

First, as this is your first post, welcome to the madness \:D/

As a point of reference, the L-jet system does not employ crank position or speed reference sensors that are employed in Motronic, so that's a dry hole [-X

I also have an '80 633 and the only times I've had any sort of intermittent running issues, it was always the combo relay, which apparently you have already exchanged :-?

I actually carry a spare in the boot, 'cause if it dies, you ain't goin' anywhere :-&

My intuition is telling me that you have a grounding issue, but where of course, is the question 8-[

What you describe is really odd behavior, again I've had mine for over 27 years and she's never done anything like that :-"

Where in CA are you :-?

I'm in the south bay and will be off between the holidays, so I "should" have some time to take a look, if you're close :-)

:mrgreen:
:mrgreen:
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kevmills67
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Re: Runs fine for about 15 minutes then dies

Post by kevmills67 » Thu Dec 14, 2017 6:39 pm

hornhospital wrote:
Thu Dec 14, 2017 2:24 pm
Do you have a spare coil? Try swapping it when the car dies. Ether is easy to ignite, so a weak spark will still fire it up, but gasoline, not so much.

Anyway, it's something to try.
I do have a spare, I will swap it in. Coil that is in there is an MSD that was installed last year but who knows, worth a try since I have a dozen or so extra coils. :-) Thanks, will give that a shot this evening.

kevmills67
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Re: Runs fine for about 15 minutes then dies

Post by kevmills67 » Thu Dec 14, 2017 6:57 pm

GRNSHRK wrote:
Thu Dec 14, 2017 5:25 pm
First, as this is your first post, welcome to the madness \:D/

As a point of reference, the L-jet system does not employ crank position or speed reference sensors that are employed in Motronic, so that's a dry hole [-X

I also have an '80 633 and the only times I've had any sort of intermittent running issues, it was always the combo relay, which apparently you have already exchanged :-?

I actually carry a spare in the boot, 'cause if it dies, you ain't goin' anywhere :-&

My intuition is telling me that you have a grounding issue, but where of course, is the question 8-[

What you describe is really odd behavior, again I've had mine for over 27 years and she's never done anything like that :-"

Where in CA are you :-?

I'm in the south bay and will be off between the holidays, so I "should" have some time to take a look, if you're close :-)

:mrgreen:
Thanks GRNSHRK, for the welcome and the offer. I am in San Clemente.You are correct on the reference sensors, etc, this model does not use them. I had an extra combo relay from one of my other same generation BMW's but didn't know where it was so I purchased a new one, but that wasn't the issue either. I kinda knew it wasn't going to be because I jumpered it and it didn't change anything. I've checked over all of the wiring, first thing I did actually, in addition to the wiring in the trunk. Having other cars that have notorious ground issues (Porsche 928) I check these all the time. (even in my Jeeps and Corvettes, LOL) It is odd behavior, I have had these cars for nearly 30 years and have not had an issue like this before which is why I am stumped. Suggestion was made that it was possibly a coil, I had discounted that because the coil is only a year old but worth taking a look at. I will feel pretty silly if that was it after all of the other things I've gone through. Going to check that out today and I will trace through the wiring again just to double check everything. Will provide an update. and thanks GRNSHRK and thanks to everyone for your ideas.

kevmills67
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Re: Runs fine for about 15 minutes then dies

Post by kevmills67 » Thu Dec 14, 2017 7:01 pm

jps635 wrote:
Thu Dec 14, 2017 4:32 pm
I don't know about the early cars but my 85 635 died in mid stride was either the crank position or speed sensor failure. It took weeks to figure this out as both tested ok, but eventually fired up only to die once warm. I still don't know which was faulty so replaced both.
Thanks JPS635, This year didn't have TPS or crank reference sensors. Easy to rule those out here. :-)

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603racing
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Re: Runs fine for about 15 minutes then dies

Post by 603racing » Thu Dec 14, 2017 9:25 pm

Have you done a noid light test on the injector connectors while it will not run? This will verify signal to the injectors during your no-start occurrences. I would also suggest putting an inline pressure gauge on the fuel line before the FPR to check it when it won't run. These steps may not pinpoint root cause, but they can help with ruling out certain functions.

As a shot in the dark... what about your plug wires? Have you inspected them?
'85 635csi - Dark Shark
'13 Jeep Wrangler
'13 Subaru BRZ

kevmills67
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Re: Runs fine for about 15 minutes then dies

Post by kevmills67 » Fri Dec 15, 2017 4:25 am

603racing wrote:
Thu Dec 14, 2017 9:25 pm
Have you done a noid light test on the injector connectors while it will not run? This will verify signal to the injectors during your no-start occurrences. I would also suggest putting an inline pressure gauge on the fuel line before the FPR to check it when it won't run. These steps may not pinpoint root cause, but they can help with ruling out certain functions.

As a shot in the dark... what about your plug wires? Have you inspected them?
Thanks, I have not tried the noid light, that was on my list for when I had a minute. I agree, that is probably where I need to start because it is starting and running on Ether and barring a really weak coil that may be igniting the Ether but not the fuel, it is obviously not getting fuel which means good starting place would be checking fuel injectors. I was hoping someone might have an option that didn't require me smashing my meat hooks into the intake manifold and pulling the connectors off the fuel injectors.

Ignition wires are good, replaced a year ago with the new coil. I haven't entirely ruled out the FPR but I think it is not real likely because when it starts, it starts right up and it will run and drive find for 15 to 20 minutes and then just nothing. The FPR on this car is vacuum controlled, if it were going to mal-function it wouldn't be likely that it would run 15/20 minutes and then die. I did check it out when all of this first begun. Put it on a vacuum pump tester and it held pressure so wasn't a torn/ruptured diaphragm at least. Again though, I haven't entirely ruled it out and I do have a spare so I will give it a try.

kevmills67
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Re: Runs fine for about 15 minutes then dies

Post by kevmills67 » Sat Dec 16, 2017 11:49 pm

UPDATE: I replaced the MSD Blaster 2 coil that was installed about a year ago with a brand new MSD Blaster 2 coil and started the car, it ran about 12 minutes and died, would not restart. I checked the fuel injector connections with a Noid light and got nothing which confirmed my suspicions that the fuel injectors were not pulsing when the car shut down. My logic would say ECU, possibly combo relay, BUUUUT, brand new combo relay, I purchased a new one thinking this might have been the issue, but it wasn't. I have since found my spare combo relay and it doesn't do anything differently either. Second guess would be ECU, same thing, ECU that is in the car now is a rebuilt ECU, tested again with a spare ECU from a BMW mechanic friend and still, same and what it was doing on the original ECU which I still have. Replaced the lift and fuel pumps along with the fuel filter even though I know none of those items will affect whether or not the injectors are getting signal or not. I am not sure what else to check. Have a spare FPR but that also does not affect whether the injectors get signal or not and since it runs perfectly for 12 to 15 minutes before just dying, not likely it is of any issue.

I've looked over all of the electrical, contacts, grounds, connections, wire condition, everything seems just fine. Also, if it was electrical, I think it would be more intermittent. It will run for 12 to 15 minutes each time. If I go back out tomorrow, it will start and run 12 to 15 minutes before dying and not starting again. Because it runs for about 12 to 15 minutes, I am wondering if it may not be something that heats up to a certain temp and causes the signal to the fuel injectors to cut out but I cannot think of what there is that would do that.

What else controls the signal to the fuel injectors? Why would it just cut out after a constant 12 to 15 minutes of running fine? Doesn't sputter out, or gasp for air or fuel, just like someone turned off the key.. or in this case, signal to the fuel injectors. Any ideas and suggestions are appreciated.

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Re: Runs fine for about 15 minutes then dies

Post by ron » Sun Dec 17, 2017 8:21 am

Try running it with the fuel tank cap off. It may be a vent problem.
They are ALWAYS rustier than you thought!!!!!!
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kevmills67
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Re: Runs fine for about 15 minutes then dies

Post by kevmills67 » Sun Dec 17, 2017 7:07 pm

ron wrote:
Sun Dec 17, 2017 8:21 am
Try running it with the fuel tank cap off. It may be a vent problem.
It is getting fuel, have plenty of pressure in the fuel line. The fuel injectors are not pulsing because they don't get a signal. Thanks any way.

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Re: Runs fine for about 15 minutes then dies

Post by ron » Sun Dec 17, 2017 9:38 pm

kevmills67 wrote:
Sun Dec 17, 2017 7:07 pm
[quote=ron post_id=210619 time=<a href="tel:1513498892">1513498892</a> user_id=155]
Try running it with the fuel tank cap off. It may be a vent problem.
It is getting fuel, have plenty of pressure in the fuel line. The fuel injectors are not pulsing because they don't get a signal. Thanks any way.
[/quote]

OK you have fuel pressure but if the tank is not vented correctly eventually the pump pressure cannot overcome the vacuum in the tank!

As I said, try it with the cap off and see if it runs longer than 15 mins.

What have you got to lose by trying it?
They are ALWAYS rustier than you thought!!!!!!
'88 High line.
'85 M #228
'85 M #207
'80 735i

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Re: Runs fine for about 15 minutes then dies

Post by Pod » Sun Dec 17, 2017 11:11 pm

If Ron’s suggestion fails to work, try disconnecting the fuel lines and blowing them through in case you have an intermittent blockage. I had similar problems which ended up with finding rust in the rubber pipe which runs between the tank and external pump.

kevmills67
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Re: Runs fine for about 15 minutes then dies

Post by kevmills67 » Mon Dec 18, 2017 3:43 am

ron wrote:
Sun Dec 17, 2017 9:38 pm
kevmills67 wrote:
Sun Dec 17, 2017 7:07 pm
[quote=ron post_id=210619 time=<a href="tel:1513498892">1513498892</a> user_id=155]
Try running it with the fuel tank cap off. It may be a vent problem.
It is getting fuel, have plenty of pressure in the fuel line. The fuel injectors are not pulsing because they don't get a signal. Thanks any way.
OK you have fuel pressure but if the tank is not vented correctly eventually the pump pressure cannot overcome the vacuum in the tank!

As I said, try it with the cap off and see if it runs longer than 15 mins.

What have you got to lose by trying it?
[/quote]

I will try just for you guys but as I mentioned earlier, I have tested the injector leads with a noid light. When the car stops running, it is no longer getting a signal to the fuel injectors, the light is not pulsing. Once the car stops running, I have full pressure in the fuel line. I have tested both the pressure and the flow once the car has cut off. The issue is the signal to the injectors cuts out and the fuel injectors stop firing. I am happy to run it without the cap on because I am that desperate but I know that having negative pressure in the fuel tank and lines won't make the signal to the fuel injectors stop working. Thanks for the ideas though and thanks for keeping them coming. If anyone knows what might keep the fuel injectors from pulsing after about 12 to 15 minutes, please let me know.

kevmills67
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Re: Runs fine for about 15 minutes then dies

Post by kevmills67 » Mon Dec 18, 2017 3:45 am

Pod wrote:
Sun Dec 17, 2017 11:11 pm
If Ron’s suggestion fails to work, try disconnecting the fuel lines and blowing them through in case you have an intermittent blockage. I had similar problems which ended up with finding rust in the rubber pipe which runs between the tank and external pump.
thanks Pod. The problem is that the fuel injectors stop pulsing after 12 to 15 minutes, no signal, tested a few times with Noid light.

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Re: Runs fine for about 15 minutes then dies

Post by kevmills67 » Tue Dec 19, 2017 1:33 am

additional update, the car is still doing the same thing. At one persons suggestion I let it run with the fuel cap off but it still stalled after about 13 minutes. Again, no signal to any of the fuel injectors. Starts the next day, runs fine, seems like it may warm something up and then, pow, no signal to the fuel injection. Wish this had an OBD 1 or OBD 2 to give me some input but it doesn't.

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Re: Runs fine for about 15 minutes then dies

Post by hornhospital » Tue Dec 19, 2017 2:11 am

Does it still have spark after it dies? I'm trying to determine if the whole connection between the engine and ECU is dropping out or just the injector connections.
Ken Kanne
'84 633CSi "Sylvia"; '85 635CSi "Katja";'87 325is "Odette"; '93 325is "Elvira"; '95 M3 "Ashlyn"

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Re: Runs fine for about 15 minutes then dies

Post by 603racing » Tue Dec 19, 2017 1:01 pm

I'm not as familiar with the early electrical and electronics. What sensors are there for fuel/ignition timing? I'm guessing there has to be at least one sensor for fuel timing even if the ignition timing is mechanical. If there is some sort of fuel (injector) timing mechanism, that would be my guess for the failure.
'85 635csi - Dark Shark
'13 Jeep Wrangler
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603racing
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Re: Runs fine for about 15 minutes then dies

Post by 603racing » Tue Dec 19, 2017 1:04 pm

Oh! Is there a temperature-timing sensor? Something that would trigger a different fuel mapping once the car is warmed up? If so, is it possible that it fails when the car comes up to temp? I had an older e30 Eta that wouldn't run because of a temp-timing sensor that had failed. Different fuel injection I know, but some of the older cars had 3 temp sensors that did some mystical voodoo stuff.
'85 635csi - Dark Shark
'13 Jeep Wrangler
'13 Subaru BRZ

kevmills67
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Re: Runs fine for about 15 minutes then dies

Post by kevmills67 » Wed Dec 20, 2017 6:42 am

hornhospital wrote:
Tue Dec 19, 2017 2:11 am
Does it still have spark after it dies? I'm trying to determine if the whole connection between the engine and ECU is dropping out or just the injector connections.
It still has spark, I can get it to fire and run on Ether after it dies out.

kevmills67
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Re: Runs fine for about 15 minutes then dies

Post by kevmills67 » Wed Dec 20, 2017 6:46 am

603racing wrote:
Tue Dec 19, 2017 1:01 pm
I'm not as familiar with the early electrical and electronics. What sensors are there for fuel/ignition timing? I'm guessing there has to be at least one sensor for fuel timing even if the ignition timing is mechanical. If there is some sort of fuel (injector) timing mechanism, that would be my guess for the failure.
I was on the same track, have to check. This car does not have a cam or crank sensor or throttle sensor for that matter. Will dig in a little deeper, I seem to recall my 735 had a sensor up by the harmonic balancer. Was going to check that next time I had a few minutes. If anyone has any input it is much appreciated.

kevmills67
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Re: Runs fine for about 15 minutes then dies

Post by kevmills67 » Wed Dec 20, 2017 6:47 am

603racing wrote:
Tue Dec 19, 2017 1:04 pm
Oh! Is there a temperature-timing sensor? Something that would trigger a different fuel mapping once the car is warmed up? If so, is it possible that it fails when the car comes up to temp? I had an older e30 Eta that wouldn't run because of a temp-timing sensor that had failed. Different fuel injection I know, but some of the older cars had 3 temp sensors that did some mystical voodoo stuff.
That is definitely a good idea and worth checking out. I'll do some research and check. Thanks for the idea.

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Re: Runs fine for about 15 minutes then dies

Post by 603racing » Fri Jan 12, 2018 1:46 pm

Any resolution on this?
'85 635csi - Dark Shark
'13 Jeep Wrangler
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