Fuel pressure

[gtacs]

Hi all,
I just had the fuel pump replaced under the recall. Even though the time frame passed since it was never done on my car they paid for it all. But, I just got the vehicle back from the dealer and I noticed it starts real hard (meaning I have to let it crank over 8-10 times before it will start). The service manager told me that the fuel pump is getting broken into the engine, or air in the lines. The car runs great once it is running, I have driven it for two days and still have the hard starting issue. I did a little troubleshooting myself. With the engine running my fuel pressure is around 55psi @ the fuel rail, when I shut the engine off the pressure drops to 0psi within a couple of minutes. I did not have this issue with the old pump, and I have an appointment to go back to the dealer. I was wondering if anyone had any further troubleshooting ideas/tips to narrow the problem to the pump or another component.

Thanks

[vtl]

Hi all,
I just had the fuel pump replaced under the recall. Even though the time frame passed since it was never done on my car they paid for it all. But, I just got the vehicle back from the dealer and I noticed it starts real hard (meaning I have to let it crank over 8-10 times before it will start). The service manager told me that the fuel pump is getting broken into the engine, or air in the lines. The car runs great once it is running, I have driven it for two days and still have the hard starting issue. I did a little troubleshooting myself. With the engine running my fuel pressure is around 55psi @ the fuel rail, when I shut the engine off the pressure drops to 0psi within a couple of minutes. I did not have this issue with the old pump, and I have an appointment to go back to the dealer. I was wondering if anyone had any further troubleshooting ideas/tips to narrow the problem to the pump or another component.

Thanks

Did you measure how fuel pressure builds up on start?

[gtacs]

vtl,
yeah after the car starts the pressure is about 55psi but drops to 0psi in a couple minutes.

[vtl]

vtl,
yeah after the car starts the pressure is about 55psi but drops to 0psi in a couple minutes.

I'm talking about how it develops/builds up before engine starts. Attach the gauge, key in position II, observe.

Also it may help if you switch key between II and I a few times. Give it 5 seconds in II, move back to I, repeat. Fuel pump works a few seconds in II, but it may not be able to build enough pressure if there's a leak.

[gtacs]

I see, I'll check that tonight. Could I hook a compressor up to the schrader valve and pressurize the system up to around 50psi and check for leaks? Would this yield any valuable information?

Thanks

[ssicarman]

I see, I'll check that tonight. Could I hook a compressor up to the schrader valve and pressurize the system up to around 50psi and check for leaks? Would this yield any valuable information?

Thanks

I suspect that that would be a bad idea. The system is supposed hold pressure in it after it is shut off. If it is dropping to zero with in minutes there is a problem.

[vtl]

I see, I'll check that tonight. Could I hook a compressor up to the schrader valve and pressurize the system up to around 50psi and check for leaks? Would this yield any valuable information?

Thanks

No, don't do that. I don't know if your model year has a fuel return line or PEM-controlled fuel pump, but fuel release valve is not holding up the pressure. Latter case (PEM) would mean the pump was installed improperly.

[Astro14]

I see, I'll check that tonight. Could I hook a compressor up to the schrader valve and pressurize the system up to around 50psi and check for leaks? Would this yield any valuable information?

Thanks

You only hook up a fuel pressure gauge - that's what the schrader valve is for... And if it's not holding pressure, then go looking for leaks.

If you don't smell fuel, already, though, I doubt your system is leaking anywhere other than the pump itself.

Since the problem started with the new pump, I would be asking the dealer to fix what they "fixed"...

[pbierre]

There is a check valve in the fuel pump that only allows flow in one direction. When the pump shuts off (engine off) this check valve is supposed to close tight, and this keeps
the fuel pressure at the manifold so that the car will start quickly.

The loss of fuel pressure back down to 0 within a few minutes after shutoff, combined with no fuel odor, points strongly to you have been given a defective fuel pump.

Take the car back to the dealer with your fuel pressure measurements, and ask for a new fuel pump, one that can hold backpressure when the engine is off.

[Joegolden]

There is a recall? I have been out of the loop for a few years but just picked up a 2006 xc70 that is throwing a CEL that is fuel pump related. My mechanic to.d me it is not giving the right pressure or the pressure varies or something like that. My car drives fine 99 percent of the time but does stall sometimes ona cold start. It can stumble as well on a cold start. Where can I find more info on this? Thanks