lacarpe

I have had my stock gm fuel pump replaced three times in one year. I was wondering if anyone else had this happen to them. Each pump was replaced at a dealer for long crank starts. The dealer checked the tank for rust or water and found none. They also checked the pressure regulator it is ok. I was wondering what brand of fuel pump to try next? I own a 1995 Z28 with a LT1 motor and everything is stock.

96capricemgr

Long cranking the only symptom?
Did it hold pressure on shutdown, did it prime pressure quickly?

Sounds to me like you have a defective service department not a defective series of pumps, the rest of us find the stock pump to work just wonderfully till we outgrow it's ability to feed more HP.

I would be looking for a new service provider who will look for electrical issues, bad grounds, corroded connections those sort of things.

I hope you only paid for the first pump and labor and they have done the rest for free.

lacarpe

Only paid for the first one. But had two different dealers install pump. I thought maybe first dealer missed something. However same result using dealer number 2.
The presssure would leak down to 15 psi. until after a long crank would get 50psi and engine start.

mrmint69

If you put a pressure gauge on it and the pressure stays stronge then the pump is not the problem with long cranking. If it bleeds off there are several things that can cause it. Sounds like the pumps are not bad and they replaced because they couldn't find the right problem. If they went bad they missed something that was causing them to go bad. I went thru 3 pumps on my other vehicle in two years but they were cheap aftermarket and the OEM I finally went with, has been going strong for 5 years. I hope you only paid once also!

96capricemgr

Pressure leakdown can be the regulator or the checkvalve at the pump, dying pumps I would look at electrical, slow pumps I would look at electrical too.

Dealerships are parts replacers, few "technicians" actually understand systems the way and enthusiast does.

BC2002SS

do you know if they replaced the rubber hoses that connect the pump to the sender. A hose could have a split that only shows under pressure

96capricemgr

with stock parts that should be teflon. Many aftermarket pumps have come with black hose NOT rated for submersion and those do fail but not that quickly.

lacarpe

Each time after the pump was replaced. Pressures were fine and car started without long crank time. Worked fine for about three months. Then long crank time dealer would check pressures find very low and replace pump. If I had a wiring or fuel line or regulator problem why does it start good for the first three months?

Injuneer

Have you checked the voltage AT the fuel pump? Operating the pump continuously at the wrong voltage can damage it, causing performance to deteriorate over time.

There is nothing inherently wrong with the stock fuel pumps, other than the fact they seem to die shortly after running out of fuel.

lacarpe

Thanks for the idea. I have not checked the voltage at the pump. Do you know what the correct voltage is? I am aware of the failure due to low fuel and avoid that problem with always having atleast half a tank of gas.

Injuneer

You want at least 12V, higher (13.5) is better. I wouldn't recommend anything over 16V, but it's unlikely you would have that condition unless you are running something like a Boost-A-Pump system. I'd be more concerned running it with inadequate voltage.

lacarpe

Great thanks. I suppose the place to check the voltage is right at the pump wires that feed it in the fuel tank? If that is the case I guess it is time to cut a door above the tank as I read about here in this forum. Your idea is that a lower voltage say 9 or 10 volts instead of 12 over time could cause a pump to fail. That makes some sense but why does the pressure bleed off and cause a long start I thought that was a check valve or check ball problem. Could a lower voltage cause that?

Injuneer

Check the voltage at the harness connector over the rear axle.

http://shbox.com/1/fuel_pump_wiring.jpg

Read voltage between the gray and black wires.

Something appears to be causing the pump to deteriorate prematurely. People are driving these cars with 200,000 miles and the original fuel pump. I'm just trying to come up with something that can cause the pump to lose efficency over time. Can we relate that directly to problems with the check valve? I don't know, but to me the small amount of time it takes to check the voltage, and the fact that apparently no one has checked it to this point, seems to make sense.

If the voltage it OK, then we have to look for another cause.

lacarpe

Again thank you. I will check the voltage.

lacarpe

I finally got the voltage checked. It read 10.5 volts. Any ideas on what to look at next? What about the relay under the that clicks when you turn the key? Could it be not sending 12 volts to the fuel pump?