car runs for 2-3 minutes then dies.

[aharris82]

I would love some help solving this problem! :)

My car will start from cold and run for about 2-3 minutes, then cut out and not be able to restart. It will then turn over but not start. It'll then start from cold the next day and do the same thing.

Since I have spark, does this rule out all ignition related issues?

*After it dies, when you try to turn it over, I've confirmed i have spark to all 6 spark plugs.
*Reads 0.2 Ohms across the coil
*Reads 5.0V across the coil
*I tempsticked the water pump externally, and it cut out when the outside of the water pump hit just shy of 110F.
*I tried to measure fuel pressure between the control pressure regulator and the fuel distributor but I don't have the right fittings to get my gauge connected inline.
*I tried unplugging the oxygen sensor, which made no difference.
*Fuse slot 7 looks melted out, and the car operates no differently with a fuse in it or not. Slot 7 is Lambda, frequency valve, fuel pump, and control pressure regulator. I don't believe this is the problem, because it has been like this the whole time I've been driving the car for a year. Perhaps it is just jumped underneath?

Prior to this issue starting, the car was running fine.

[Bitsyncmaster]

The cold engine start will drive the frequency valve at 50% duty. After 2 to 3 minuets the O2 sensor is hot an drives the lambda to closed loop so the FV duty will change. With that info, it sounds like your mixture adjustment must be way off. You would need to try to do a base line adjustment since it won't run closed loop to adjust it via dwell meter.

[Michael]

I think Dave is on the money but if it was running fine one day and all of a sudden it's exhibiting this issue, something happened. Mixture doesn't get that out of whack without something big and probably obvious happening. Look for big vacuum leaks, unplugged or broke wiring especially around the CPR, frequency valve, microswitch area, etc.

Maybe even start with the basics like checking fuses and the battery voltage (also check voltage at the pump while it's running till it dies) so you don't spend an afternoon diagnosing in circles.

[Ron]

Sounds like you have spark.
For fuel, next time it dies give it a shot of starting fluid and see if it fires off. If so, check the filter (and as mentioned, that the pump is still working).

Does it just up and die, start missing first, smell rich, or...??

[aharris82]

Sounds like you have spark.
For fuel, next time it dies give it a shot of starting fluid and see if it fires off. If so, check the filter (and as mentioned, that the pump is still working).

Does it just up and die, start missing first, smell rich, or...??



It outright dies instantly after that 2-3 minutes. Until then, it runs as good as it has the whole time I've had it. It sounds/smells the same as it has. I'm not seeing how that could be related to the fuel mixture?

I bought the car at DMC-MW last year and had them do the Stage II upgrade before delivery, so its mixture was just dialed in a year ago. I'll look again for leaks, and try the starter fluid test.

[aharris82]

Also for what it's worth, the cold start valve has been unplugged since I got the car. DMC-MW unplugged when I first bought it last year, after the stage II conversion. The cold start valve was causing cold start problems back then, and it started fine with it unplugged.

[Michael]

*Fuse slot 7 looks melted out


https://images.idgesg.net/images/article/2018/08/11_reporting-incidents_alert_red-flag_attention-100768653-large.3x2.jpg

[David T]

You have several issues to deal with. Make sure the frequency valve is buzzing when it is running. Get the cold start system working again. Fix the melted out fuse #7. Check for spark the next time it dies. Could be a bad impulse coil but they usually shut the car down after 15-20 minutes, not 2-3.

[Helirich]

Well, the equation is spark + compression + fuel. The compression isn't going away, so it must be fuel or spark. Spark is probably the easiest to check. (It's also the most likely to quit fast)

Please let us know what it is.

[Ron]

He said it had spark...

[Rich]

Adding to the spark comments - Yes, the report is that the car has spark after it dies.

Does it have enough spark, though? Maybe there is a condition that somehow lowers the ignition voltage at some point?


The factory test per the Tech Info Manual is to look for spark to jump at least a 12mm gap from the end of the main high tension cable (after unplugging it from the distributor) to ground while cranking the engine.

Run the test immediately after the engine quits while it's most likely that the failure condition is still in play.

[aharris82]

You have several issues to deal with. Make sure the frequency valve is buzzing when it is running. Get the cold start system working again. Fix the melted out fuse #7. Check for spark the next time it dies. Could be a bad impulse coil but they usually shut the car down after 15-20 minutes, not 2-3.

already confirmed I have spark

[David T]

The quickest, easiest and "best" way to confirm spark is, as quickly as you can when it dies, squirt a little bit of Ether into the intake. If it runs even a little bit, you have a fuel problem. I would start in the fuel tank, Check the pick-up hose and filter. See if there is a lot of dirt or water in the tank. Check the boots and the electrical connections on the pump. Also check that you have a white splotch on the inertia switch and it is mounted to the side of the footwell. Because the #7 fuse melted out the fuel pump may be bad. Before they die they draw too much current and melt the fuse.

[aharris82]

Adding to the spark comments - Yes, the report is that the car has spark after it dies.

Does it have enough spark, though? Maybe there is a condition that somehow lowers the ignition voltage at some point?


The factory test per the Tech Info Manual is to look for spark to jump at least a 12mm gap from the end of the main high tension cable (after unplugging it from the distributor) to ground while cranking the engine.

Run the test immediately after the engine quits while it's most likely that the failure condition is still in play.



What should I be seeing for voltage across the coil during this? I was getting 5.0v, but I was told to expect 6-7. I was also told to expect 0.7Ohms across the coil, but I got a reading of 0.2.

[aharris82]

The quickest, easiest and "best" way to confirm spark is, as quickly as you can when it dies, squirt a little bit of Ether into the intake. If it runs even a little bit, you have a fuel problem. I would start in the fuel tank, Check the pick-up hose and filter. See if there is a lot of dirt or water in the tank. Check the boots and the electrical connections on the pump. Also check that you have a white splotch on the inertia switch and it is mounted to the side of the footwell. Because the #7 fuse melted out the fuel pump may be bad. Before they die they draw too much current and melt the fuse.

I did it with an induction timing light per Bill Roberston's video here: https://youtu.be/aa5Qk4qPZPs

[Ron]

Just because there is spark at the coil wire does not mean that it is getting to the plugs.
Firing off with starting fluid does...

[Bitsyncmaster]

What should I be seeing for voltage across the coil during this? I was getting 5.0v, but I was told to expect 6-7. I was also told to expect 0.7Ohms across the coil, but I got a reading of 0.2.

The stock coil is way below 0.70 ohms. I measured it by driving 1.00 amps into it and reading the voltage drop and I seem to remember it less than 0.40 ohms. I will have to look where I posted that. So anyway with such a low resistance your 5.0 voltage reading would be normal.

I found my post on the the HEI ignition.

Stock coil resistance is 0.387 ohms.

To measure resistance accurately, drive DC voltage into the coil from a bench supply until 1.00 amps is flowing. Then measure the voltage on the two coil terminal studs. 1.00 volts would = 1.00 ohms resistance. I read 0.387 volts.

[Ethan Rode]

Would suggest moving fuse 7 out of the fuse box with an inline fuse holder. If there's any interruption or voltage drop in that circuit the car won't run.

[Ron]

Sounds like someone may have done that already since it runs a few minutes and pulling the fuse makes no difference...

[Helirich]

The quickest, easiest and "best" way to confirm spark is, as quickly as you can when it dies, squirt a little bit of Ether into the intake. If it runs even a little bit, you have a fuel problem.

This has been my "go to" method for checking spark for many years. But the Delorean has put some doubt in it.

When I got my car, I cranked it while my son sprayed starter fluid in the plate. Never a pop. I knew the fuel was gunked up, so I figured I would work on that first. After a new pump, cleaning the tank and lines, the car started right up without doing anything to the ignition system. Why didn't it fire off on either? My guess is the long convoluted intake path is not very conductive to the starter fluid atomization.

[Ron]

...
Why didn't it fire off on either? My guess is the long convoluted intake path is not very conductive to the starter fluid atomization.My guess is that it was probably flooded or fuel fowled. It is way more volatile than gasoline. And it's so "hot" that if you use too much (or on a hot engine, especially a diesel), you risk over revving or pre-ignition. :dunno:
-
So, you haven't tried it since this problem started?

Another option: When it dies, quickly pull a few of the easy to get at plug wires, connect some spare plugs, ground them, give it a spin and take a look. (Exhaustive go to ;-)

[FABombjoy]

My guess is the long convoluted intake path is not very conductive to the starter fluid atomization.
Not at all, it will start. Even if you have an air filter installed. You can spray starter fluid on the the air filter and it will still kick over. Very helpful for diagnosing a disconnected fuel pump relay.

[aharris82]

Update from today - Spark appears totally fine. Fuel suspect.


Hooked in my fuel pressure gauge rig between the distributor and the control pressure regulator. Tried to start, no fuel pressure, and wouldn't start even from cold. Took my pressure gauge rig off and set back up to normal, still won't start. Plugged in cold start valve just in case, no difference. re-unplugged cold start valve as DMCMW had done.

This time it didn't even run for the 2-3 minutes and then dying, it's just not starting.

Tried starting with starter fluid in the intake, and it happily sputters with it and tries to start! I think ignition/spark is good, after this and all prior tests.

My melted fuse slot #7 - I pulled up the fuse panel, and discovered it isn't attached to anything. Someone clearly wired a bypass of it at some point.

I do have the DMCH fuel pump & sender module, done by the previous owner in 2016ish. (https://store.delorean.com/fuel%20pump/sender%20module-1.html)

I poured fresh gas into the tank today also, just to make sure this wasn't just bad gas.

So after I let it sit for a while, I started it up, and it ran it's 2-3 minutes again happily, then cut out.

After it died, I then tried jumping the RPM relay (slots 30&87), and nothing comes on. What does this tell me?

Also in case it's relevant, my car has a Stage II upgrade from DMCMW in 2020.


fuse 7 bypassed:
65916

Fuel pressure rig:
65917

Fuel pump:
65918

[aharris82]

Then after a while, once cool, jumping the rpm relay (30-87) does turn on the fuel pump and frequency valve, as it should.

However after it runs its 2 minutes and dies, the fuel pump and frequency valve both stay off, even with rpm relay jumped.

What does this mean?

[Ron]

...
Hooked in my fuel pressure gauge rig between the distributor and the control pressure regulator. Tried to start, no fuel pressure, and wouldn't start even from cold. First things first...
The valve should go between the WUR/CPR and FD. Double check all routing and rig the gauge like this:

65919

[Bitsyncmaster]

Then after a while, once cool, jumping the rpm relay (30-87) does turn on the fuel pump and frequency valve, as it should.

However after it runs its 2 minutes and dies, the fuel pump and frequency valve both stay off, even with rpm relay jumped.

What does this mean?

Jumping the RPM relay connector pins 30 and 87 should only run the fuel pump. Jumping 30 and 87b should only run the lambda. You can make a jumper that connects them both to 30 (power) and do your testing with that. If the pump is not running, get a voltmeter and verify you have voltage on the jumper first. If so, your connections after the RPM relay or the pump is bad.

[aharris82]

So I jumped the RPM relay (30-87) and the inertia switch both, and it ran and stayed running. I attempted to get gas 5 minutes down the road, and then it wouldn't start after I got gas. :(

Waited 15-20 minutes, and then it started, so I got home but it was not running well the way home.

got home, put the inertia switch back and rpm relay back, and now it's running and stays running. It is returned completely to the state I had it before when it would run 2 minutes then die, but now it is running.....FOR NOW.

I just turned it off, and restarted just to check and it is acting fine.

So now my problem is apparently intermittent. GRRRRRRRRRR

[Ron]

You removed the RPM Relay and jumped 30 to 87, but not 30 to 87b, and it kept running??

[Helirich]

One thing I would look at is the stand alone fuse (#7). You show the pic of it missing, but not the new fuse. On mine, the previous owner had installed a smaller wire inline fuse holder that would get hot and not let 12 volts to the pump. When you speak of the numbers on the relay, is it the brown wire you are connecting to the purple/white? That never fails to run my pump. (I have that same pump) Your jumper wire should be 12 ga so as not to reduce voltage to the pump.

[aharris82]

You removed the RPM Relay and jumped 30 to 87, but not 30 to 87b, and it kept running??

Yes, and I assume thats why it didn't sound excellent, a little jumbly and minor backfiring. Since that would keep the lambda offline?

[aharris82]

One thing I would look at is the stand alone fuse (#7). You show the pic of it missing, but not the new fuse. On mine, the previous owner had installed a smaller wire inline fuse holder that would get hot and not let 12 volts to the pump. When you speak of the numbers on the relay, is it the brown wire you are connecting to the purple/white? That never fails to run my pump. (I have that same pump) Your jumper wire should be 12 ga so as not to reduce voltage to the pump.

It's hiding somewhere, I haven't been able to find it. I will ask DMCMW and see if that's part of what they do when they install that pump.

[David T]

It would seem you disturbed the problem when you switched the parts. Most likely a bad connection somewhere. Make sure all of the connectors in the plugs are fully seated, not overheated and still have some spring in them so they grip their mates.

[Ron]

Yes, and I assume thats why it didn't sound excellent, a little jumbly and minor backfiring. Since that would keep the lambda offline?Yep.


It's hiding somewhere, I haven't been able to find it. I will ask DMCMW and see if that's part of what they do when they install that pump.There was nothing in the install kits or instructions I got, so I doubt they would do anything there unless they saw a problem.

I'm with David on checking connections and chasing the return line from the FD back.