I installed a Bosch 044 fuel pump about 6 months ago on my Jaguar LS1 swap. The pump makes a surging sound at random every second or two, almost like it's getting a little gulp of air or something. It's done this since the day I installed it. It does not matter whether the tanks are full or empty, or if one tank or another is selected. Under heavy throttle and/or high RPMs, the car will hesitate, almost like it's running out of fuel or the spark is being shut off just for an instant. If you keep your for in it, the car will jerk back and forth pretty violently. The problem got worse on my way home today... worse than it's ever been. It actually stalled a couple times while cruising, but started right back up.

Here's what it sounds like:

Normal Bosch 044 on youTube:
"Rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr rrrr rrrrrrrrrrrrrrrrrrrrrrrrrr"

My Bosch 044:
"Rrrrrrrrrrbrbrrrrrrrrrrrrrrrrrrrrrrrbrrrrrrrr rrrr rrbrrrbrrrrrrrrrrrrrbr"

I tested the voltage at the pump, and it's dead steady, reading the same as at the battery posts.

Here's a video link. Be aware that the Bosch 044 is a very noise pump.

The pump is installed inline by the bottom of the tanks. The pump sits very low. There is plenty of fuel in the tanks. I have a 100 micron stainless steel mesh cartridge Trick Flow fuel filter that I installed with the pump. It's all 1/2" fuel hose from the tanks, through the fuel tank selector valve, through the filter, and to the pump. The inlet-side fittings are -8 AN. There is also an LS1 Corvette filter/regulator in the engine bay. The tanks have plenty of fuel. The pump and inline filter have about 700 miles on them.

What the heck is going on here? Any thoughts?

 

I have heard that noise before.

That pump is starving for fuel is my thought.

A quick try, is to "pop" the tank cap, thus allowing it to vent, and observe if anything changes. That was the issue with one of my XJ-S's.

If nothing changes there, remove the "pre" filter.

Disconnect the fuel line at the front, attach a suitable length of hose, and into a container. ON the Ign, and observe the "flow".

Sometimes "over filtering" reeks havoc, and YES, we do this due to pump failure from gunk/rust/whatever, but these pumps are all designed for a good gravity feed of fuel to keep them warm and fuzzy.

Again, the XJ-S scenario. The small fine filter in the sump tank gets slightly blocked, and I mean slightly, and this interrupts the gravity supply to the pump, and the V12 is one unhappy beast. When removing that filter the debris is generally minimal, and that raises all sorts of other things that may be wrong, BUT, simply cleaning that filter, and all is sweet, it is that critical.

I believe this aided the introduction of "in tank" pumps across all manufacturers.

 

Thanks a lot for the response Grant.

Running the car with the filler caps open is easy. I can try that first. I've done it before, though not recently, and I do remember hearing the fuel flow back in and do not remember hearing any change in pump sound.

I think the second thing I want to check is the little screen filters at the bottom of each tank near the drain - are those the filter screens you were talking about? I know you referenced the XJS, but I think I've seen those on the XJ6. How do I take those out to check/clean them? Do they simply unscrew from the fuel tank drain under the car?

If none of that works, I'll disconnect the fuel pump inlet and start with pulling fuel from a container. If the pump sounds good then, I'll keep putting components back into the system until I get the noise again.

 

Ok.

The screens in the tank of the sedan under those large drain plugs are no where near as fine as the XJ-S one I was referring to, as the "S" is a totally different system.

Those "large" plugs should simply unscrew, BUT, some have reported tearing the tank apart. I have never had that issue, as all I have ever undone have simply done that, undone. Those screens are mainly for rusty debris, and the outlet pipe is not right in the bottom, but a small distance off the bottom of the tank, to keep it clear of most debris. A fairly primitive system, but it works, except when water gets in the tank, those screens are not that fine, as the XJ-S screen is.

Bear in mind that these pumps are NOT a sucker of any kind. They rely on a "head" of fuel from good old gravity to supply them.

 

The symptoms do sound and suggest fuel pump starvation. I think Grant is right on. As for trouble shooting... you could get a piece of hose and a gas can and simulate a working tank. Be sure to have a fire extinguisher at hand any time you work on a vehicle. If the pump quiets down with a known good supply source then dig in to your tanks, switch over valves, pre-filters, elbows, screens etc. Don't run the vehicle too long on the temp tank if your normal tanks are full because the return line could overfill the tanks.

 

Thanks again for all the info guys. I was thinking about pulling the hose off of the fuel selector valve and running it into a gas can. That would be the easiest first step for me, as all of my other lines are Push-Lock style... once those go on, the REALLY don't want to come off!

I should get to this next week. I'll post back on how it goes!