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91 Troop 186,??? 2.8L v6
It cranks for half a mintue some times i have to crank, stop, crank, stop, crank until finally it starts up. I thought fuel pump, but i realized its fuel injected so pumping the gas really didnt help as much as i thought it was. So i am starting to think its one of two sensors around the carbs. But know today i was a quarter tank over the half way mark, had no problem starting, untill it got to half way, then it started to act up again. When it does start its kinda like chung chung chung vroom. What H is going on, I realize i need to getta manual asap this damn truck is driving me crazy. Its worth 600 Ive probably spent 600 on fixes.Someone help me out if u can.
 

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Jumper the fuel pump test connector under the hood to make sure the fuel pump is running and try it again.
The ecm receives a signal from the distributor to turn on the fuel pump. As long as it gets this signal AND the engine is either running or cranking the fuel pump should be running. Safety feature, as they don't want the fuel pump to continue to run in case of an accident etc. if the engine isn't also running.
If the ecm isn't receiving this signal, the ecm will shut off the fuel pump after (2) seconds. If the fuel pump relay or the relay drive from the ecm fails, it will eventually build enough oil pressure from your numerous attempts at cranking to close the oil pressure switch and IT will then turn on the fuel pump.
That's why I suspect the fuel pump relay or something associated with it. Jumpering the fuel pump test connector to make sure the fuel pump is running should narrow down the suspects.
 

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I think your fuel is draining back into the tank. Electric fuel pumps have a check valve that can sometimes go bad, especially when they sit overnight.

When your tank is 3/4 full, there's maybe enough pressure from the weight of the fuel to keep the fuel from draining back into the tank.

You don't have to replace the expensive fuel pump to stop this. You could buy a check valve and install it close to the tank to solve the problem.
HTH, Chuck
 

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I have 3 90-91 V-6 troopers in the family. The oldist has 295,000 mles on it. None will start with out a short spin of the engine to get oil pressure up. Second spin, engine starts right up. They start right up rest of day.

John in LV
 
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