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diesel engine dies

My '97 Chevy Suburban diesel dies at random times. Nothing seems to trigger it; it usually happens when I'm just driving along, minding my own business; not accelerating or decelerating, turning, stopping, etc. Has happened with the fuel tank at every level: full, half full and quarter tank. When it dies, the dashboard lights do NOT come on. When I turn the key "off" and back "on", the lights come on and the engine will crank fine, but won't start. Ten minutes later, it starts and everything is fine. It may not do it again for weeks, or it may do it again in 10 minutes. This last time, the fuel tank was fairly low -- below a quarter tank -- and it seems to "buck" or "hesitate a little just before it died the first time. The dealer replaced the crankshaft position sensor and the fuel injector pump. When it started doing it again, they ran every diagnostic test they had and could find nothing wrong. Ran fine for a few weeks, then quit three times in 30 minutes. It's back there now.

Besides being misogynist, anybody have any ideas? (I'm literally a little old lady in tennis shoes, the mechanics area all male. She quits on me all the time, but won't do it for the mechanics.)
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Comments

  • It sounds almost like a faulty ignition switch. The contacts inside the switch can wear out from years of use, especially if you have a large bunch of keys hanging off your key ring. A faulty ignition switch will behave just as you described...the vehicle will die suddenly for no apparent reason.

    However, in the case of a faulty ignition switch, the driver can usually restart the engine right away and drive on. The fact that you have to wait 10 minutes before the engine will restart is not entirely consistent with a faulty ignition switch. I don't know anything about Suburban diesels, but it sounds like an intermittent electrical problem in the fuel system...like power to the fuel pump is being interrupted, or the fuel pump itself has an intermittent problem, or the wiring to the injector pump has an intermittent problem, or even an intermittent problem with the computer module.

    Unfortunately for you, intermittent electrical problems can be very difficult to trace. You're going to have to be persistent until some mechanic figures it out.
  • edited June 2012
    I would look too at the stop solenoid needed to stop a diesel. It is activated at the ignition switch and a check in wiring might be worthwhile. The solenoid is obviously working, perhaps being engaged when it shouldn't by loose or exposed wiring.
  • The intermittent nature of this problem lends itself to an electrical issue. The diesel doesn't use spark plugs so the electrical problem involves the fuel delivery system, but where?

    I wonder about the fuel pump(s). I believe you have more than one. One pump provides a good flow of fuel from the tank to the motor. The second pump takes that fuel and provides higher pressures to fuel injectors. One of the fuel pumps could be bad. Fuel pumps can fail intermittently until they go out completely.

    Electricity is used in the sensors and the computer system telling the fuel injectors when to squirt the fuel and how much fuel per squirt. A bad connection, bad sensor, or bad ECM could be the culprit. The ignition switch is part of this system. As is the "anti shutter" solenoid mentioned @JosephEMeehan.

    Finally, you need fuel filters on a diesel and they get gunked up by dirt, and water. Have the fuel filters been changed regularly over the life of the vehicle, and were they changed recently?
  • The fact that the dashboard lights do not come on when the engine dies suggests to me that this is clearly an electrical problem somewhere in the circuitry that's supposed to be enabled when the key is in the "ON" position. I'm inclined to suspect the ignition switch (key cylinder assembly) itself. Id want to start by checking for voltage at the relay that's energized whose contacts enable the necessary circuits to see if voltage has been lost there.

    You may want to try a shop that specializes in automotive electrical circuits. They'll have the expertise to trace the circuits via the scematics and track down the intermittant connection or determine which relay is likely to cause these symptoms.

    But I've recently been renminded that it's a good idea to check the fuses first. You might get lucky.
  • ALL great ideas. Thanks. The dealer swears they have checked all of these things. They put it on the computer and everything checks out fine. I like the idea of finding a shop that specializes in automotive electrical circuits. I think that's my next step. I had a new fuel tank put in several months ago. I think I'll have them check and see if there's any gunk in the tank or the lines. I'm suspicious of that too. Thanks for the help!
  • My vote is for the ignition switch based on the comment that no dashboard warning lights are present when this problem occurs.

    There is also the less likely possibility of a poor main circuit connection heating up and losing contact. (Battery cable, junction terminal, fusible link end, etc)
  • edited June 2012
    I'm inclined to put fuel problems at the bottom of the list of suspects simply because if the engine died due to loss of fuel all the dash warning lights should light up.

    But in hindsight there is another possibility. If a battery cable is corroded and/or loose and intermittant, the engine could die and there be no power to the lights. The battery is a part of the circuitry that operates the warning lights....and powers them.
  • The fuel shut off solenoid is on the injector pump. If the pump was replaced already, that should have taken care of that issue. (Mine used to keep on running when I shut the key off-kind of a problem with no way to shut the engine down.) Since there is no ignition required on the diesel, that pretty much leaves the fuel supply-either back to the injector pump, fuel pump, ignition switch telling the solenoid to shut down, or something else shutting the fuel off. It was a happy day when I got rid of mine.
  • Well, not really. If power were lost, which is what appears to be happening based on the lack of warning lights, fuel supply would die too due to loss of power at the pump. If a battery connection were to be intermittant, that could disable the whole shebang including the warning lights. For that matter, there may even be an internal problem with the battery itself.

    I'm not convinced that the root cause is loss of fuel. I suspect that loss of fuel is a symptom of the root cause.
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