I have a 1997 Chevy Tahoe LT, it has a Vortec 5.7L engine w/Throttlebody F/I. 2 years ago I replaced the electric Fuel pump in the fuel tank with a BRAND New unit. Recently the engine stalled out a few times on the way home, I was lucky to restart it and make it home. So I put in a new fuel filter.NOW When I turn the key on I can hear the fuel pump come on,it seems to pressurize the system & then the Fuel pump stops. Then I start the engine,it starts Right up & Runs fine.The fuel pump comes right back On and Off again while The Engine Runs FINE for about 2 to 3 minutes. Then I hear the pump stop pumping (I can hear it) at the same time my 12V test light indicates loss of power at the pump immediately after engine stalls. Then fuel pump will not turn back on for several hours. Any Ideas??
So is the pump shutting down after the engine stalls or before? It is suppose to shut down after the engine stalls. The stalling may not be related to the fuel system.
By-pass the relay and see if you can run the pump after it shuts down to rule out the pump and wiring from the relay to the pump.
If there is fuel pressure, the fuel pump doesn’t need to run. Why should it? It’s already built up pressure. The fuel pump is supposed to stop running when the engine isn’t running.
Put a fuel pressure gauge on it and see for yourself. The problem is something else if there is fuel pressure. Fuel pressure doesn’t go to zero because the fuel pump stops running unless there is another problem…such as an internally leaking fuel pressure regulator (if the fuel system has one).
Take a look at the ignition (spark) system. Use the repair manual.
Instructions you need: http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c1528008f213
The fuel pump relay is turned on for a few seconds when the key is turned from OFF to the Run position. The pump relay will close again when the ECU sees the start signel and/or the Crank Position Sensor signel. The ECU will drop the ground to the FP relay if the CPS signel is lost.
So as hellokit advised check the ignition system it also gets its signel from the CPS through the ECU. Also check the FP relay, CPS, the wiring from the CPS to the ECU and from the ECU to the FP relay. Use a DVM on the grounding wire to the FR relay to see if the ECU command is being lost.
Hope that helps. Get back to us as you delve deeper.
Are you sure you have a TBI 1997 5.7 Vortec? (Vortec being head design) GM primairly stopped TBI in 1992. Your 5.7 should have the sequencial version of CPI (CSFI) in 1997. Interesting if you actually have a factory version of a 1997 5.7 with TBI.
If your Tahoe is a CSFI car and you put a TBI pump in you will be having problems.
How are you identifing your Tahoe as having TBI?
You’re right, this vehicle doe not have a TBI.
Then I hear the pump stop pumping (I can hear it) at the same time my 12V test light indicates loss of power at the pump immediately after engine stalls. Then fuel pump will not turn back on for several hours. Any Ideas??
Check the pump relay for drive signal and output power. If both OK, check wire harness condition. If all OK, probably the pump itself. Disconnect pump harness and drive manually to see if it runs and then stops after a few minutes.
If I recieved the instructions “Disconnect the pump harness and drive manually to see if it runs and then stops after a few minutes” I would not have a clue as to how to comply,could you explain?
I see what you mean. I left out the it in my typing haste.
Disconnect the pump harness and drive it (the pump) manually to see if it runs and then stops after a few minutes.
Does that make more sense? In other words, I’d disconnect the pump at the most convenient harness connector and power the pump directly.
Chevys don’t have to be hot-wired, in that fashion, to get constant power directly to the fuel pump. A hot-wire [fuel pump primer connector] is right there near the fuel pump relay waiting for somebody to connect a fused wire, from the battery, to it. If you look for a red wire, with a female connector, near the fuel pump relay (which is, probably, in its own plastic cylinder), just “hanging around”, that will be the jumper wire to connect the hot-wire to. This wiring diagram, Fig. 22, makes it clearer. Scroll way down to Fig. 22. http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c1528008f3ce
I don’t see any benefit to hot-wiring the fuel pump. If someone wanted to know if there were fuel pressure after the fuel pump quit, all one has to do is connect a fuel pump gauge to the fuel line. Is that so hard?
I don’t see any benefit to hot-wiring the fuel pump
It eliminates everything except for the pump. Fast way to find out if you have to drop the tank or not. YMMV
Not many people out of the mechanics world know that GM vehicles have this feature,it is good you presented this info.
I would like to somehow come up with a list of vehicles that have this feature and in addition a book (something like the VW for idiots book) of pump relay locations how to jump the relay and how to easiest test for voltage at pump,this is hard with in-tank pumps and it is not clear to most DIY’s when (what key position) they should be seeing voltage and what systems inhibit fuel pump operation. There, now you have my “get rich” book idea.
A little knowledge can be a dangerous thing. There have been too many fuel pumps burned out by people who though that the fuel pump just has to be powered at all times that the ignition is turned ON. It’s not so. The fuel pump only needs to run enough to keep fuel pressure at certain values. Anything more will shorten the life of the fuel pump.
Again, check fuel pressure, first.