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Hello everyone,
After 10 years I finally got a replacement for my stolen Firebird. So I was given a 91 Camaro in a trade and I am having a hell of a time getting it to fire up.
I can get the engine to run while spraying gas to the intake but am not getting gas to the rail/injectors. I pulled the gummed up fuel filter out and had pressure on both ends as I was showered in old gas. Replaced the fuel filter and went to prime the pump to check for flow out the filter. I primed it a few times and got little more than a trickle. I can hear the pump buzz to prime for 1-2 seconds when the key is in the ON position but it doesn't seem to be delivering any fuel.
From what I have read on the boards Im either looking at a bad fuel pump or collapsed rubber lines coming off the sending unit. Before dropping the *** end and pulling the tank I wanted to make sure I am headed in the right direction and that this wouldn't be caused by a relay or other electrical issue.
Is it TBI? or V6/TPI? If it's not TBI, check the pressure at the fuel rail. I've never seen the rubber fuel lines be a problem. It's a lot more likely that the fuel pressure regulator, injectors, or pump have gone wonky. Pressure at the filter would seem to indicate the pump is pumping. Hearing it prime would suggest the pump is working. So check if you have fuel pressure at the front of the car.
It' a 350 tub. I disconnected the fuel lines from the intake manifold to see if I was getting anything up to the throttle body and they are dry. Pulled the fuel filter and I'm getting drips of fuel but that seems to be it.
You might have a pin in g of the aldl. If you do you can apply power to is and see if the pump turns on. If it doesn’t check for power at the tank connector. If that’s fine the pump is bad.
There might also be a red tail on the relay to apply power to.
I pulled the gummed up fuel filter out and had pressure on both ends as I was showered in old gas.
The system holds pressure. In-tank fuel hose is intact. Pressure on both ends indicates filter was completely plugged, which is going to be REALLY hard on the fuel pump.
Originally Posted by Bittner88
Replaced the fuel filter and went to prime the pump to check for flow out the filter. I primed it a few times and got little more than a trickle. I can hear the pump buzz to prime for 1-2 seconds when the key is in the ON position but it doesn't seem to be delivering any fuel.
ECM is triggering the fuel pump relay. Fuel pump fuse, relay, and wire harness are intact (but not guaranteed to be good.)
Two possibilities: 1. Insufficient power to fuel pump motor. You have SOME power, but it may not be enough. You must test the voltage AS CLOSE TO THE PUMP AS PRACTICAL, and it would be best to also test amperage. Amperage testing does not need to be close to the pump--but voltage testing is essential to be as near the pump as you can get. These tests must be done with the pump RUNNING. You must also test for voltage on the ground wire near the fuel tank.
It's common to lose ~1.5 volts on the power supply, and to have ~1 volt on the ground, for a total voltage drop of 2.5 volts. This is because GM used under-sized wire to power and ground the pump. If your alternator is putting out 14.2 volts with the engine running, you may have only 11.7 volts actually powering the pump.
14.2 - (1.5 + 1.0) = 11.7
If you have less than that, (less voltage, more resistance) you need to start fixing corroded connections, corroded relay contacts, etc.
I would expect 6--7 amperes of current flow through the pump. Less indicates high resistance in the circuit, or low fuel pressure. More indicates a failed pump motor or abnormally-high fuel pressure.
You can't test the wire harness inside the tank unless you drop and open the tank. It's REALLY common to see the in-tank harness corroded. New harness is available for about $20--$25.
2. Failed pump section of the fuel pump, or clogged pick-up filter. Replacing either will mean dropping the tank.
Originally Posted by Bittner88
I wanted to make sure I am headed in the right direction and that this wouldn't be caused by a relay or other electrical issue.
This could be caused by a relay or other electrical problem. You'll figure that out when you do the voltage and amperage testing.
Corroded and swollen wire from in-tank fuel pump harness, compared to wire from replacement harness.
Last edited by Schurkey; Apr 27, 2018 at 04:25 PM.
