Died while driving, won't start and stay running now

[opethmike]

A few days ago, while idling in my drive-way, the DeLorean stopped running. I was able to start it right back up again, and didn't give it a second thought.

A few hours ago, while driving away from my house, the car died, so I coasted to the side of the road. Turning the key, it would crank, and fire very quickly, but would die right away.

One interesting thing that I noticed is that if I held the key in the start position (kept turning the starter), the car would keep running. As soon as I let go, car would die. Had to have the stupid thing towed back to my house.

Please advise as to where I should start my diagnostics.

[ccurzio]

Having just experienced similar symptoms rather recently, check your fuel system. When was your fuel filter last replaced? How's your pump?

[opethmike]

Fuel filter replaced this past January. I'll check the pump tomorrow; I tried swapping RPM relays, but that didn't help. How do I use my multimeter to check the pump?

[ccurzio]

Fuel filter should be all right then, unless some massive amount of gunk somehow got displaced and lodged itself in there recently. Not likely.

Try pulling the plug from the warm-up regulator and sticking it on the cold-start valve and see if your engine starts that way. (Open the engine bay and pull the gray plug out from the forward driver-side of the engine compartment, then pull the blue plug off which is slightly above and closer to the rear of the vehicle in the same area, then put the gray plug where the blue one was.) Don't run this way for too long, just see if it gets going.

[DeLorean03]

He cant do that. He's running EFI. It says so in his signature and avatar quote.

[AdmiralSenn]

Mike, I posted this on Facebook but I'll post it here too for future thread-hunters.

I had this EXACT same problem a long time ago and wasted a lot of time checking the fuel pump circuit.

The fact that it depends on the position of the key is your big clue - this is an electrical problem. In my case something had bumped one of the wires loose on either the main or auxiliary relay (I forget which) and it would only pass current in Start, not Run. I tightened the offending terminal (and the others too as a precaution) and it worked beautifully afterwards.

The only other thing I can think of is something wrong in the ignition switch - same circuit.

[opethmike]

Thanks Adam. I think that's a distinct possibility, because come to think of it, when I had the key in the run position, with the car off, I didn't hear my fuel pump, and I always do. Any ideas on how to test it, beyond just tightening the connections?

[DMCMW Dave]

Tighten up the wiring on the ballast resistors. You are getting coil voltage while cranking and then losing it when you let go of the key.

During crank it comes directly from the starter, when running it comes from the aux relay. Just pull off the three connectors on the resitors and tighen/clean them all.

[ccurzio]

He cant do that. He's running EFI. It says so in his signature and avatar quote.

I didn't see this. I pay attention to usernames and post content/context, and ignore signatures and avatars.

[AdmiralSenn]

Thanks Adam. I think that's a distinct possibility, because come to think of it, when I had the key in the run position, with the car off, I didn't hear my fuel pump, and I always do. Any ideas on how to test it, beyond just tightening the connections?

Honestly I would just pull the aux relay and look closely at the terminals. I think I just tightened mine slightly with a set of needlenose pliers. If any of the connections feel even a little loose or are really grody-looking, then you have at least part of your answer.

And of course Dave has an excellent point - I don't know what your ignition wiring is like but that's actually a more common failure point than the relay wiring, I would think.

When you get it running again I would recommend grabbing that part of the wiring harness while it's running and jiggling it back and forth. Make sure it won't come off, say, when you come to an abrupt start or accelerate sharply.

[opethmike]

Tighten up the wiring on the ballast resistors. You are getting coil voltage while cranking and then losing it when you let go of the key.

During crank it comes directly from the starter, when running it comes from the aux relay. Just pull off the three connectors on the resitors and tighen/clean them all.

Thanks, I will do so. By the way, I'm not much of an electrical guy; how can I use my multimeter to check the coil voltage? And, should I need to, how to use the meter to test the ballast resistors?


I didn't see this. I pay attention to usernames and post content/context, and ignore signatures and avatars.

Contributions still most certainly appreciated!


Honestly I would just pull the aux relay and look closely at the terminals. I think I just tightened mine slightly with a set of needlenose pliers. If any of the connections feel even a little loose or are really grody-looking, then you have at least part of your answer.

And of course Dave has an excellent point - I don't know what your ignition wiring is like but that's actually a more common failure point than the relay wiring, I would think.

When you get it running again I would recommend grabbing that part of the wiring harness while it's running and jiggling it back and forth. Make sure it won't come off, say, when you come to an abrupt start or accelerate sharply.

Thanks!

[WelmoedJ]

Thanks, I will do so. By the way, I'm not much of an electrical guy; how can I use my multimeter to check the coil voltage? And, should I need to, how to use the meter to test the ballast resistors?


Using a multimeter is actually straight forward: Dial Volt if you want to read Voltage, Dial Ohm if you want to read resistance.

In Voltage mode, one pin/ead to ground (usually a black lead), the other to the point to test: the coil Voltage can be tested at both pins + (15 if I'm correct) and - (minus=GND).
Voltage on the minus side depends, but will be somewhere in between 4.5 and 8.5 Volts while idling (at least those values have been read by me on various cars).

Voltage at the resistor pack can be tested the same way (blue/yellow from the starter, white/yellow to the coil).
In between is the starter relay (to switch the resistor pack to use both or only 1 resistor (each resistor is .5 Ohm), testing in Ohm mode.
There are in series while running (so 2x .5 = 1 Ohm), only one (.5 Ohm) while starting.

My car has a stronger coil (40kV Flamethrower); I have removed the starter relay and only use one resistor all the time (better spark).
Bill R. has done about the same (also using a Flamethrower or alike coil) and has paralleled his resistors, now only being half of a half coil pack, thus .25 Ohm.

Hope this helps.

[jmpdmc]

In case you do not have the Technical Information Manual, here are some of the diagnostic values you should see on a stock DeLorean in a troubleshooting chart posted by Rich: http://dmctalk.org/showthread.php?3142 Hope you can apply this to your car.



Jeff

[opethmike]

Thanks guys, I'll hopefully have a chance to dive into the car today. If I do, I'll update this thread with how it goes.

[Spittybug]

Adam/Mike; how did you guys wire your fuel pumps for the EFI systems? Are you using the existing one or did you replace it? I can help you with a real easy replacement.... from the RPM relay, the green wire is only hot on run and the brown is hot all the time. I use the green for the relay signal and although I use the brown for MS, LC1 and the injectors, I went with a dedicated hot wire from the battery for the fuel pump. I won't go into it here, but if you want a diagram, let me know.

[AdmiralSenn]

Adam/Mike; how did you guys wire your fuel pumps for the EFI systems? Are you using the existing one or did you replace it? I can help you with a real easy replacement.... from the RPM relay, the green wire is only hot on run and the brown is hot all the time. I use the green for the relay signal and although I use the brown for MS, LC1 and the injectors, I went with a dedicated hot wire from the battery for the fuel pump. I won't go into it here, but if you want a diagram, let me know.

*Shrug* I just used the existing RPM relay and wiring and left the MS fuel pump wire unused. It seemed simpler and I had just bought a solid state RPM relay anyway.

[opethmike]

I left it completely alone, the wiring for it is stock. I don't think its a fuel pump issue, as the engine will run and rev with the key in the start position; I suspect something like what Dave S. or Adam described as being the cause. Will hopefully get a chance to check today.

[opethmike]

Ding ding ding! Mr. Swingle had this one - As soon as I opened my engine compartment, I found that one of the connectors to the ballast resistor had fallen off of the resistor. It was VERY loose. I cleaned all of the connectors and blades, tightened up the one that come loose, and put it back on. Car fired up immediately and settled into a nice, burbly idle.

[Bitsyncmaster]

I powered my LC1 on the lambda power. If you leave your lambda relay installed you can use it. It only powers with the engine running and that is what you want for the LC1. That also isolates it some from the fuel pump noise.

[DMCMW Dave]

Ding ding ding! Mr. Swingle had this one - As soon as I opened my engine compartment, I found that one of the connectors to the ballast resistor had fallen off of the resistor. It was VERY loose. I cleaned all of the connectors and blades, tightened up the one that come loose, and put it back on. Car fired up immediately and settled into a nice, burbly idle.

The giveaway on this one is that it would fire while cranking and immediately die when you let go of the key. Not much else will cause that. Plus those resistors run REALLY hot so the connectors relax over time.

[opethmike]

The one connector was completely off. It was very loose, so I think the car's vibrations must have shaken it off. The others were snug, but I tightened all of them, just in case.