i have a ,99 tahoe that runs when it wants to and not when i need it to. it turns over fine, i’m not getting any power to the fuel pump relay. i thought it was the security system shuting it off. but the last time it did it i had it towed to the dealer and they said it wasn’t that. they couldn’t find anything wrong ether. well it started for them and i drove it home where it still is cause it will not start again. any ideas whats causing this?
How is the oil pressure sender? Some engines shut off power to the fuel pump if oil pressure drops too low, and a failed sender can cause this also. Of course actual low oil pressure could also be the culprit.
oil presure is good when ever it starts 70psi cold 50psi hot, 45psi just turning it over, could crank sencor do this without putting out a code?
How about the inertia switch, which is designed to shut off the fuel pump in the event of a crash? If your vehicle has one the owner’s manual will tell you where it is and how to reset it.
Change the fuel pump relay with another in the relay box, under the hood, usually in a relay box. If no difference, check for voltage, DURING CRANKING, on the green/white wire which comes from the VCM (Vehicle Control Module). This voltage powers the fuel pump relay which powers the fuel pump.
I don’t know the decision information the VCM uses to turn on the voltage to the fuel pump relay. It may be a signal from the oil pump pressure switch. Your repairer should, definitely, obtain this kind of information.
The fuel pump circuit: click on “Fuel Controls ©(1999)”: http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c152800a65ec
This could be a Crankshaft Position Sensor problem. If the computer doesn’t detect a crankshaft rotational reference signal due to a defective sensor, it won’t allow the fuel pump to run or allow ignition. That’s because as far as the computer is concerened, the engines not rotating, so there’s no reason to allow these systems to function.
Is the cause, of the no-start, a non-running fuel pump (or, fuel injectors not injecting fuel)? Let’s test that assumption by spraying a two second shot of Starting Fluid into the large black plastic intake tube, and cranking the engine. If the engine runs a few seconds, the assumptions are correct. Then, check those components. Let us know.
it does try to start when i spray starting fluid in it, the problem is it’s not getting any power to the fuel pump relay, well i’m getting power at the orange wire, but nothing at the green/white, theres power coming out of the vcm on the green/white, but loses it somewhere along the way to the relay’