A few months ago, the fuel pump went out. We dropped the tank, and replaced the fuel pump (aftermarket pump bought from Schucks). After 2 weeks of casual driving around town, the pump goes out again. So we let the truck sit for a while because we didn’t really need it. This past Monday, we replaced the pump again. This time with a OEM pump bought new from a GM dealership. Today is Thursday, 3 days after installation. My wife drove 200 miles to another town for military-related training. Now it’s not starting again and she’s stranded there. Again, same problem. The fuel pump isn’t coming on when she turns the key.
Any ideas on why this is happening??
Are you sure it is the pump, and not the circuit?
Did you replace the filter sock and fuel filter with the new pump?
Maybe, the fuel pump isn’t running because it isn’t getting any electrical power (12 volts). Did you do any troubleshooting before when it “failed”?
Some GMs have a “prime” electrical connector that’s free in the engine compartment, next to the plastic cylinder containing the fuel pump relay. By jumpering from the battery positive to the prime connector (red wire with unconnected end), you can get the fuel pump to run. This jumpering bypasses part of the fuel pump relay, and Vehicle Control Module (VCM). Do you want to see the wiring diagram at www.autozone.com?
Do you have any particular Chevrolet 1500 vehicle: P/U, Sub, etc? Electrically, there are some differences among models, years. There are, also, some similarities.
I’ll give that a shot…thank you for the advice.
I would guess the fuel pump relay is the real problem but proper testing will reveal if that is true or not.
We replaced the relay already, and that didn’t do anything. We had a couple other thoughts last nights. My wife said when she parked it, she went into a a place to eat some teriyaki, and when she came out, the truck wasn’t starting. She kept at it, and after about 10 tries, she said she heard the fuel pump engage and the truck started. So that makes us wonder…could there be a problem with the ignition not sending a signal to the pump?? Could there be a short? Maybe the first pump we replaced wasn’t bad, but maybe a short of some sort?
Yeah, its intermittancy does suggest the possibilities you posted. Since the problem is so often happening probably the best way to find out the truth is to attach a voltmeter to the pump power line near the pump, get it to fail, and see if the pump is getting voltage.
Here’s a thought- are you sure it isn’t the security system inhibiting the pump? I don’t see the year (except pre-2000) but older Chevy’s had a issue with the VATS/PASSKEY system where the small wires would wear out in the ignition cylinder. This prevented the security system from seeing the chip resistor in the key.
The result is the engine will crank but not start- the fuel pump and injectors are inhibited by the security system.
If the security lamp is illuminated after the initial lamp test, this is your indicator that it is a security issue, not a failing pump. The intermittant nature of your problem is exactly how these tend to fail.
Good thinkin’ TwinT.
Another possibility that comes to mind is a defective inertia switch. That’s designed to shut the fuel pump off in the event of an accident.
most gm products have a fuel cutout switch built into the oil pressure switch sending unit. could be a bad oil pressuring sending unit. what year is the truck exactly?
its a 1997 chevy full size pickup
As has been said before, don’t disregard the wiring and the connector. I’ve been there done that. Also bad wires can cause a pump to go bad and there are such a thing as bad pumps. Had three in a row. Who knows where they are made now.
The way the oil pressure switch works though is that it provides a second electrical path. If the relay was bad but the switch good, it would start after oil pressure built up from cranking. You would have extended crank but would still start. If it was running and you disconnect the relay, the engine should continue running if the oil pressure switch is good. I’d suspect a wiring problem.
In the wiring diagram, I don’t see an oil pressure cut-out switch. Look for yourself at www.autozone.com.
The fuel pump Prime Connector bypasses the Vehicle Control Module (VCM). So, if the VCM were preventing fuel pump operation, bypassing it would avoid that.
On the “1997 full size Chevy pick up”, did you ever find out what size engine? Model? V6? V8? Flex fuel? Any other little detail?