Hi guys
I have a 2001 XKR coupe 55K miles. I recently changed the fuel pumps (secondary was dead so changed both via sub woofer) and filter. When I changed the fuel filter the tank was nearly empty (yellow light was on) but I still had around 2 gallons drain from the main line. When I've changed filters in the past I normally only get maybe 1/2 pint drain from the lines. Also if the car is left 24hrs it takes 3-4sec to start vs 1-2 sec when car has been driven in the last few hrs. So I suspect an air leak in the fuel rail or fuel regulator not closing. Note car runs fine, both fuel pumps run fine and no problems under hard accel e.t.c. Also no DTC codes being thrown

I have visually checked the fuel regulator vacuum pipe looks fine. I dont have a fuel pressure gauge. But I guess next is to check to see if fuel pressure drops over time. I suspect yes.

1/ Is there a way to test the fuel regulator ?

2/ If I need a new one can these be changed without removing supercharger? I see the fuel regulator includes the return pipe/bracket that goes back under the supercharger and connects to the left side and has a long support bracket that bolts to the left side. JTIS does not seem to cover replacing fuel regulator.

Thanks
Simon

 

Best way is to check the actual fuel pressure over time to see how long it holds (must at least hold it for 2 hours or so, but is ok to drop).

If it doesn’t hold it long enough (could also be a leaking in the tank i.e. via a fuel pump), then indeed you get some boiling in the fuel lines and a slow start after a while.

 

What brand replacement fuel pumps did you use?

 

My car has both Fuel Pumps replaced (with oem Pumps) and Starts exactly the same as yours. Also, just like yours, the Car runs perfectly.

Even if I switch the Ignition off-to-on several times to "Prime" the Fuel System, the Cranking times are not changed, 3-4 sec Cold and 1-2 sec Warm.

I assumed that this was normal.

 

I got the Bosch ones made in Germany seem to work great. As I dont see or smell any leaks anywhere I'm thinking the fuel regulator is stuck open hence the 2 gallons of fuel that came out when I changed the fuel filter.

I assume that is not normal. As the pumps are high in the tank and the fuel came out of the engine side of the fuel filter I would guess the fuel was drawn from the tank (bottom as tank was near empty) through the return line round the fuel rail and down and out the main line i.e. engine side of the fuel filter.

 

Be aware of Bosch pumps that says on the package “made in Germany”, at least for some pumps this is a clue that these are counterfeit ones as they are actually made in the Czech Republic.

 

These are the ones I bought

New Premium Quality Bosch Fuel Pump | eBay

Came in the correct box and he has 99.6% feedback and sells a lot of fuel pumps (bosch/ac delco) so I'm sure if he was selling fakes he would have been outed long ago. The Made in Germany is etched onto the side of the lower plastic area of the actual pump along side a bunch of other codes.

 

The fuel pressure reg needs a vacuum from the intake manifold to work, as the engine wasn't running this is not the case.
If there was a fault with it while running it would throw a code, it's monitored by a denso unit, hope that explains the drainback.

Logically speaking, the thing you change usually leads to other symptoms, that's why our learned members question the pumps, as that's what was changed, symptom driven diagnostics so to speak

 

All I know is that at least for the popular Bosch 040 and 044 pumps that if they have "Made in Germany" on the box and stamped on the pumps itself they are not the genuine ones. If you want to be sure, then best to ask Bosch themselves if the specific pump you have is also made in Germany, or how you can detect if a pump is genuine or not.

 

There is a one-way check valve in the pump itself. It is possible it is not holding as tightly as the new ones as in your OEM pump. http://www.aa1car.com/library/fuel_pump.htm

 

I had the problem before I changed the pumps i.e. 3-4sec starting after car sits for 24hrs. Hence I thought maybe fuel pump problem. When I tested the old pumps (original) that was when I found the secondary was dead. So I changed them both and the fuel filter.

I assume the fuel regulator is closed when engine is stopped and then opens as a vacuum if formed via the inlet manifold. Hence my thought that maybe the regulator is not fully closing when engine is stopped and so the fuel flowed back via the return line from the tank. Also if it was the pump check value then the fuel flow would have been from the rear of the fuel filter and not the engine side.