View Full Version : XJ-40 Fuel Delivery Problem

John Sides
02-24-2002, 12:52 AM
Have posted this today on Jag-Lovers [Modern] List, but wonder if anybody here has had a similar experience.

First, a little history... bought the XJ-40 in March 2001, have replaced the heater core, power steering pump, fuel pump/filter, repaired door handles and cleaned the throttle body (to eliminate the "hunting" idle) and for each problem, I've been able to get guidance/diagnosis information straight from the archives. But this problem has me stumped...

The car had 112,000 miles when bought last March. Now has 122,000. Just after buying it and with the heat of early summer, the fuel pump became noisy and we experienced an incident of vapor locking, replaced the fuel pump and the filter-both Bosch (unknown how old the filter was-so replaced it as preventative maintenance)... completely fixed the problem. Then, during middle of last summer-began doing the "hunting" idle bit. Cleaned the throttle body; left it attached to the car, as I didn't have a small universal for the ratchet--but Leaper ran great-no "hunting" idle.

Fast forward to two weeks ago. One morning the cat doesn't want to idle cleanly... sounds like it's loading up, then idle dwindles down until it stalls, and the fuel pump is noisy. I decided it was the fuel pump again, ordered another Bosch replacement (from Jag-Bits) and early on last Saturday morning replaced fuel pump so we could join our fellow British Automobile Owners Association (BAOA-Albuquerque) on the Annual Sweetheart's Day Run. The cat started right up, idled cleanly and no fuel pump noise (or very little-listening closely hunkered down by the l.r. wheel one could just hear it - man was I happy). Noticed on the way to the meeting place for the run, the cat stumbled leaving several traffic lights-once there, again it would not idle cleanly-and most importantly, the fuel pump again began to make noise even while idling-A LOT of noise. Tried to enjoy the run. Leaper began stalling out first every couple miles, then it wouldn't go a half mile before it would die out. At first, it would start right up again--then gradually began having to let it set a minute before cranking--but after that, it would start easily and run cleanly for a half-mile, then the rpm would drop--and stall. Finally got it home and put the old fuel pump back on-seemed to make less noise, but still after running less than five minutes-the fuel pump began making noise, the idle dropped, then Leaper stalled.

About this time, I notice the idle (even with cold engine) began to hunt. So, thinks me, I'll re-clean the throttle body. Measured the TPS voltage-.2 and 4.84-right on. Cleaned the throttle body-this time removing it(marked & removed TPS). Actually, it was very clean-really just wiped it out. Re-installed everything-remeasured the TPS voltage-same results-- .2 and 4.84 volts. Still has hunting idle and noisy fuel pump-don't have to wait now, the pump makes noise from the get-go. Bought and installed a local (NAPA) fuel filter-no help. Learned there's a general consensus that if there's something causing the fuel pump to be noisy, it will be found BEFORE the pump, not after. Realizing it could be a fuel pump gone bad within a year, and another new one, bad from the box... But, I'm thinking not, and at $160.00 for a pump, I'm doing some more diagnosing first.

Fast Forward to this weekend-removed gas tank to determine if there is a blockage-found nothing in the lines (now I have to order the gas tank return line because I tore it-don't ask images/icons/smile.gif . Did find & remove the magnetic-tipped drain plug -with 3/16" of metal filings attached to it (now that's scary-where do the metal filings come from???)

Now the question comes up-how to test/determine if there is a blockage in the tank, as even with removing the sending unit, you can't see much-only the line going from the (Input or Outlet?) into the "tube" or anti-surge holding tank.

Or does anyone think I'm looking in the wrong area? List, I'm in your capable hands now.

Also, received from mail order another Bosch fuel filter and installed it-don't trust the NAPA part.

Thanks in advance for your sage advice.

John & Beth Sides
Leaper - '88 XJ-40 122,000 (and not gaining any more)

02-24-2002, 01:06 AM
John, I won't pretend to have any idea where those filings came from, but it sounds like you are on the right track. As long as you have the tank out, you might as well have it "boiled out." When you take the drain plug out, is there enough room to stick your finger into the tank and feel around for what kind of muck might be floating around in there? If the tank is back in, try disconnecting the line from the tank side of the filter, then collect some "unfilterd" gas in a glass jar and have a good look at it. If there's a lot of junk in there it might be that some rust, etc. in the tank is choking up your pump.

If anyone else has any thoughts, please do jump in here graemlins/computer.gif

-- and do keep us posted, John.

Good Luck,

[ 02-23-2002: Message edited by: Jagdreamer ]</p>

John Sides
02-24-2002, 01:26 AM
Can't get a finger through the drain plug hole, but can see fairly well through the fuel guage sender-hole... But, there's a baffle in the way, so the outlet can't be viewed. But thanks, I didn't even think about having it pre-emptively cleaned.. I'll do that anyway and then will find out if it may have been a clogged outlet after all.