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Think I have an odd situation, Have a 2007 Chevy 3500 diesel, died the other day and will not start.....it will not crank with the key, the fuel gauge is not working and the engine light does not come on when the key is turned on and no fuel pump or pressure.....now I can go under hood to the relay center, checked the relays they are good, I can make the pump come on and I can crank the engine with the relay, and can spray carb cleaner into the intake and it will start and run.......has me baffled

Edited by Greyfurhunter

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I certainly don't know for sure, but one possibility is the ignition switch (e.g., ACDelco D1426D for "classic" or so-called "old body style", or OBS).  This is just the electrical contact part of the ignition switch, not the key/tumbler part.  They are known to go bad (I carry a spare when I travel even though I've never had a problem).  When bad, they cause strange things to happen.

 

Diesel, right?  Fuel pump?  Added lift pump?  Stock is vacuum from the tank, through the filter, and to the CP3 (or CP4 on later models), then into the high pressure rails.

 

Also, it's extremely dangerous to shoot any sort of starter fluid into the intake because it can run away and destroy the engine.

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Yes I have thought of that, I am pretty sure it is something electrical, I may give that a try, I did forget to mention that I cannot connect to the PCM with my scanner, I can access any other system on the truck can see data on the TCM BCM and such. Truck just has 32k on it we just use it to haul cattle.

 

It is diesel, and the fuel pump does not run when the key is turned on but will run if I trigger the relay and build pressure but will not when the key is turned on...…

 

And yes I know I don't like doing that but vaporized it and did while was cranking  so hopefully not do that wanted to make sure it wasn't a PCM issue, but like I said it would start and run when I did that

 

 

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I second ignition switch.

All power supply to make the truck run goes through the ignition switch.

 

:)

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I don't think it's the ignition switch, as you already have accessory, ignition, and crank signal. You mention no check engine light is illuminated upon key-on, and that you don't have communications with the ECM. This is telling, as it indicates serial bus data is down. If I had to guess, you have a 5V signal shorted to ground via one of the many sensors on the engine. If you can, I would check for that first, and potentially bad ECM grounds too.

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Yes I'm figuring I have a a wire issue somewhere, had this happen one other time and I found a bad relay under the hood, crank/run relay I think it was, swapped it out and everything worked great, started and ran fine, used the truck a couple of times to haul did fine, drove back home been sitting a few weeks now went out to start and doing the same thing again, checked the relay again and is fine this timenever done while driving just when went to start up, got the scamatics the other night but haven't had time to look and see but everything that isn't working seems to be run of the computer, engine light, fuel pump, fuel gauge, starting and cranking

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