Fuel Pressure Issues

[Pip-Boy 2000]

So recently ive have been having some hard start issues with my 00 A4 Bird. The engine would crank for between 3 and 7 seconds before it would start. After that it would run fine though. No rough idle or sputtering on WOT.

I did some pressure testing on it and it was priming up to about 50psi and would run at 45-46psi. The problem is that the pressure is dropping to 0 in about a minute to a minute an a half. I checked to see if i had a leaky injector or if the regulator was leaking but there was nothing. Anyone have any ideas what else it could be? I heard some people on here talking about faulty check valve/balls dissapating the pressure its supposed to hold back into the tank but I cant find any information out about testing that or what not.

[pace2006]

Re: Fuel Pressure Issues

Any strong gas fumes upon start up or any time when running? Ever replaced the fuel filter or fuel pump?

[Pip-Boy 2000]

Re: Fuel Pressure Issues

No strong fumes on start up. Don't see any leaks either. I just replaced the fuel filter and it had no affect. And i haven't replaced the fuel pump. I suppose i might add that the car has 163k on it with a rebuild done at 160. I sometimes hear the fuel pump whining so im sure the pump is near the end of its life but i wanna make sure of what the problem is before i start throwing money at it.

[Pip-Boy 2000]

Re: Fuel Pressure Issues

Anyone have any ideas? Im beginning to think its gotta be something with the fuel pump. If its a faulty check valve, is there any way of fixing/replacing it or do i need to just replace the pump? I'll probably be cutting an access panel for the fuel pump in the next few days to take a look.

[Rob Bell]

Re: Fuel Pressure Issues

Pip Boy, when you say that the pressure drops to 0 in about a minute, is this happening when the car is shut off? If so, it might still be the fuel pressure regulator. I'm not sure how long it's supposed to hold pressure, but hard starting and quick pressure drops at shutoff are symptoms of bad regulators. Just because the regulator is not leaking gas out of the vacuum line doesn't mean it's good. It just means that it's not bad in that it's leaking from the vacuum line. That would be the first thing I would look at. I don't know how much they cost, but if it's pretty cheap I would just replace it and see what happens.

[Pip-Boy 2000]

Re: Fuel Pressure Issues

Rob, yeah it drops to 0 fairly quick after the engine is shut off. As i said im not experiencing any driveability issues. Just a hard start. I should say my mpg has dropped quite a bit. I dont know if its related but i used to get 25 city 29-30 highway and now im down to about 22mpg with mostly freeway driving. anywho so i replaced the FPR and nothin. Still have the same issues. Any other ideas?

[cam98aro]

Re: Fuel Pressure Issues

after doing a bit of searching it seems that the fuel pump itself has a check valve on it, and when that check valve goes bad, it does what you describe

is the fuelpump stock? some non stock fuel pumps will bleed the pressure out quicker

next time you go to start your car, prime the fuel pump like 5 times and see how easy it is to start

also i have seen that with a full tank of gas the pressure will bleed out slower if it is the fuel pump.. two things to look out for..

[Rob Bell]

Re: Fuel Pressure Issues

Have you checked the condition of the spark plugs? I had a car once that had about 100K on it with original plugs. I could hardly get it to start when it was cold. But once it was running, it ran perfectly fine. I didn't have mileage issues, though. But anyway, I pulled the plugs and there was hardly any electrode left. This was before I knew that you had to change plugs as a maintenance item. It sounds like your fuel system may be OK, so that leaves ignition. I would start with the plugs, and start checking things on your way back. If your plugs and wires are original or old (like over 5 years), I would replace them because your car is now nine years old and they would be due anyway. So your not really out any money. Plus the expense is minimal.

[techsan23]

Re: Fuel Pressure Issues

Under the hood you have three lines running back to the fuel tank. You will see 2 of them hooked up to the fuel rail on the drivers side. The third is your evap hose that runs around the back of the block and into what I believe is referred to as the purge valve. I would check all of the hose fittings in this area and make sure everything is hooked up with no leaks.

[Pip-Boy 2000]

Re: Fuel Pressure Issues

The plugs and wires are brand new. Had my engine rebuilt a couple months ago and they replaced those. But that wouldnt explain the fuel pressure drop. And I'll take a look at the fittings later tonight and see if anything is loose but i havent seen any leaks thus far

[Blizzard242]

Re: Fuel Pressure Issues

lmao, this is too funny. I just replaced my fuel rail and took my original FPR and put it into the used one I bought. Now I'm having the same exact problem. Just started this morning. Runs absolutely fine after it starts. It does take about 2 seconds of cranking rather than starting the first 1/4 of a second of cranking then it runs beautifully. No pressure drops, no pressure spikes while driving. No fuel in the vacuum line.

It has to be the FPR. There are no leaks around my fuel rail. I had previously read that there's a check valve on the fuel filter so I was tapping that and watching my gauge.. Yeah no effect there. The filter is fairly new.

Pip-Boy 2000, (good game btw) i'm pretty certain we're both gonna be scratchin the **** out of our arms on the plastic cowl pins. I hate taking the fuel rail out just because of those damn pins. If you need any tips on how to do this as easily as possible lemme know. I've been there a few times.

[Pip-Boy 2000]

Re: Fuel Pressure Issues

Gotta Love that fuel rail. But to be honest id rather take that out any day over the heater hose assembly. Ive never bled more over my car in my life. Those factory pinch clamps are just a way of mocking the garage mechanic who has to reach past sharp cowl pins with an awkwardly placed set of pliers to just accidentally move the pinch part of the clamp out of reach leaving me cursing the automotive gods. But i digress, still havent checked out the evap line. Will get to that in the morning.

Anyone have much experience with the fuel pump assembly architecture? If it turns out the lines are all tight and the fpr is good since i just replaced it, what particular part could have gone wrong in the fuel pump assembly? I cant think of what else it could be further upstream from that.

[Blizzard242]

Re: Fuel Pressure Issues

Gotta Love that fuel rail. But to be honest id rather take that out any day over the heater hose assembly. Ive never bled more over my car in my life. Those factory pinch clamps are just a way of mocking the garage mechanic who has to reach past sharp cowl pins with an awkwardly placed set of pliers to just accidentally move the pinch part of the clamp out of reach leaving me cursing the automotive gods. But i digress, still havent checked out the evap line. Will get to that in the morning.

Anyone have much experience with the fuel pump assembly architecture? If it turns out the lines are all tight and the fpr is good since i just replaced it, what particular part could have gone wrong in the fuel pump assembly? I cant think of what else it could be further upstream from that.

I've changed my pump twice. There's really no other components back there that can go bad if your lines are tight other than the pump itself.