I have no fuel pressure where do i start to find the problem
Okay, hey, the fuel pump circuit. With key on, the pump should turn on for about two seconds to put pressure in the line and in the fuel rail on the engine, where the fuel injectors are. When the engine is cranking, the pump is turned on again by the vcm (Vehicle Control Module-the engine computer) signaling the fuel pump relay, just as it did with key on. After the engine is running, the pump is kept on, usually by the oil pressure switch.
No fuel pressure? Then the pump is not turning on, or the fuel filter is completely blocked-which is rare.
You can start at the Underhood Fuse Block. Here is found the fuel pump relay and the fuse for the pump. The fuse is designated ECM-B Fuse and it's 20 amp. If the fuse is good, put your finger on the fuel pump relay. Now have a helper turn the key to on, not start. If the circuit is good to this point, you should feel movement- a slight click. If you feel nothing, and the fuse is good, then the VCM is not sending a signal to the relay OR there is a wiring problem from one side of the relay to ground. If no click or movement under your finger-you will need professional help to diagnose further-checking of the signal from VCM and/or checking the ground wire for that side of the relay.
If you definitely feel a click at the pump relay, and the fuse is good, the power to the pump is sent out from there on a gray wire. Get under the vehicle at the rear and find the electrical connector for the gas tank, and pull it apart. Now you need a test light or voltmeter to check for power on the gray wire in the connector. You might miss the two second signal with key on, so have your helper hold the key in start. While the engine is cranking, the gray wire should have power-battery voltage. If it does not, big problem: possibly a broken wire or short from pump relay to there at the gas tank.
If the gray wire has power with engine cranking, you're almost home: Either the pump has definitely failed OR the ground for the fuel pump is bad. The ground wire is black and it shares the same ground point as your rear exterior lights, so if the lights work, the ground can be assumed to be good also for the fuel pump. And then you need a new fuel pump. But check the gas tank connector carefully for any sign of corrosion, loose terminals, anything like that amiss. Not likely, but check anyway-you don't want to put in a new pump and then find a loose connection! Good luck.
May 05, 2014 |
1999 Chevrolet Blazer