Losing Fuel Pressure after priming

[Impala131]

***Resolved***

The problem was a bad aftermarket fuel pump (Airtex). I bought a Delco Fuel pump from RockAuto and installed it, and my problems were cured. Just another story that confirms that Airtex make a crap product. Just letting everyone know for future reference.

****

I have a 1999 Grand Prix GTP. Old fuel pump kicked the bucket, and I was able to replace it without too much trouble. No issues prior to replacing the pump.

Now, the car runs fine, no issues with idle, cruise, or WOT. But it does have an issue starting up: I have to hold the key for several (5+) seconds.

The fuel pressure gauge reads a solid 50 PSI when the pump primes, but once the pump stops priming, the pressure almost immediately drops to zero. After starting the car, the fuel pressure goes back up to around 40PSI and stays solid there. No driveability issues.

I found that if I start the car while the pump is still priming, it starts right up. Seems pretty obvious the hard start issue is due to the drop in residual fuel pressure between the priming of the pump and starting the car. There are no obvious leaks in the fuel system.

So, did I get a bad fuel pump? I would imagine the FPR can cause this type of issue, but it was fine before the old pump died.

[02NavyBlue]

I'm not 100% sure, but I think that would be the pump's fault since it goes up to pressure just fine when it's running. If it were the FPR I'd think it would have a hard time keeping normal pressures while running. And like you said you didn't have that issue with the previous pump. Pull the vacuum line from the FPR after running the car and see if there's any gas in it just since it's easy to do.

[tech3627]

I would be willing to bet it is a defective fuel pump. If you want you can pinch off the pressure line just before the pump when the system is pressurized to see if the rest of the system holds pressure, but be careful sometimes you can crack the plastic fuel lines.

[Turbocharged400sbc]

aftermarket pumps tend not to have the one way checkvalve on the outlet port.

without it the pump flows more but pressure drops as the fuel flows back through the pump, as you said a change in habits is all thats in order unless your pump hose is loose/leaking

after a while youll get used to cranking after 1-1.5 seconds so the pcm see's the rpm signal in time to not shut the pump off at the 2 second mark

[Iceman6669]

What year is your car and what pump did you use?

[BillBoost37]

Pretty common. Agreed, it's the checkvalve or lack of in the pump.

[Impala131]

It is an aftermarket Airtex fuel pump. Not the best of the bunch but it was the only pump the local parts stores had on hand. (She died while driving and I was able to coast into a small parking lot and I did not want to risk getting towed).

You may be correct about the check valve (or lack thereof). I'm can re-learn how to crank the vehicle over, I just don't want to work around something that is a problem that should be fixed.

Pulled the fuel rail, no injectors leaking either.

[Impala131]

Oh, also checked all the fuel line connections, and the fuel filter I installed right after getting my car home. All appear to be leak-free.

[crbquist]

I had the same exact issue with my racetronix fuel pump. I thought it was a "bad check valve" and dealt with it for about a year until I got sick if it and emailed PRJ (who sold me the pump). He said he has never seen a bad check valve in one of his pumps and to check the hose connection at the top of the fuel pump module. I then pulled the pump and noticed that the hose was not fully connected and that the clamp was angled. I reconnected the hose and clamp and bingo problem solved. Starts up fine every time and holds pressure when off.


Sent from my iPhone using Tapatalk

[Impala131]

I had the same exact issue with my racetronix fuel pump. I thought it was a "bad check valve" and dealt with it for about a year until I got sick if it and emailed PRJ (who sold me the pump). He said he has never seen a bad check valve in one of his pumps and to check the hose connection at the top of the fuel pump module. I then pulled the pump and noticed that the hose was not fully connected and that the clamp was angled. I reconnected the hose and clamp and bingo problem solved. Starts up fine every time and holds pressure when off.
Sent from my iPhone using Tapatalk

I may have actually read something about Airtex pumps having the same issue. I'll pull it out and have a look, it might be a similar problem to what you experienced. Thanks for the insight.

[crbquist]

I may have actually read something about Airtex pumps having the same issue. I'll pull it out and have a look, it might be a similar problem to what you experienced. Thanks for the insight.

Did you just buy a pump and install it into your original canister or is it an entire new assembly that you simply dropped in the tank?


Sent from my iPhone using Tapatalk

[Impala131]

This was a whole assembly unit: had the sender, strainer, vapor pressure sensor, everything.

I just popped the pump out to have a look, no clamps at the hoses, appears to be by design. The hoses just appear to be stretched tightly over the connections.

I tried to blow into the "delivery" side of the pump, seeing if I could get air to backflow. It seemed to seal pretty tight, I didn't seem to be getting any air by. A piss-poor test though, maybe it doesn't mean anything. Again, connections all looked good when putting things back together.

Also pulled the vac line of the FPR. No fuel or anything like that. The FPR seems to be performing fine.

Also, no evap codes coming up to imply that there are leaks in my fuel system.

I'm thinking that if Advance Auto will refund me for the pump, I should buy a Delco pump off of RockAuto. I don't really want to "live with" this issue.

[Iceman6669]

Just get a good aftermarket pump such as a walbro or Racetronix

[crbquist]

A lot of replacement pump assemblies of are poor quality and design. I would get a tengis or racetronix pump and install it in your original canister. That way you'll have a reliable pump and be set for future mods.


Sent from my iPhone using Tapatalk

[Impala131]

Alright, I'll give aftermarket a 2nd look and perhaps get a better brand.

As far as "future modding" I think I'm set, car has 261,000 miles and I'm pressing my luck already.

[Impala131]

Resolved. See edited 1st post.