Hi All,
I was out cruising in my 97 XK8 when the engine died and the car coasted to a halt on a blind rural corner, perfect! Dash said engine stalled ( surprise) would spin and fire but not run. Got towed home, OBD2 message fuel pump relay failure. Swapped relay but no change. Fuel pressure at bleed valve at the injectors is low, basically flows out, but doesn’t squirt out at high pressure. The pump seems to be running. Fuel is present either side of the filter, but I’m not sure if there is high pressure either side. Car has 86K kms on it, I assume original fuel filter. What chance it is blocked ( please please) or is the pump not putting out enough pressure? Is that something that happens?
Any suggestions, please?
Thanks,
Kevin
Could be both. For sure, change the filter. It’s worth doing as routine maintenance even if it’s not the cause, but there’s a good chance it’s plugged.
Examine it for debris - it could indicate the root cause of the problem. But if it checks out as OK, and the new filter doesn’t help, then unfortunately it could be the fuel pump. They get tired, and possibly pushing fuel through a partially clogged filter sped up its demise.
On most fuel injected cars there’s another filter (the “sock” around the fuel pump inlet pipe) so you’ll want to check that out anyway. Thus pulling the pump assembly would be needed to take that step. If there’s debris in the primary fuel filter there’s a good chance the sock is clogged too.
Dave
Thanks Dave,
I’ve been doing some research and it looks like pump failure isn’t unheard of, but replacement looks pretty painful, especially removal of the fuel line. I haven’t been able to remove the filter as I can’t get the lines out, not seized in there, just not enough fore and aft movement to clear the fittings. I’m sure it can be done, I’ll just have to perservere. Bummer working under a car on axle stands these days, not as supple as I once was.
Cheers for the advice,
Kevin
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On fuel injected cars the symptoms of fuel blockage is the same as running out of gas: You just slow down and stop. If it is a partial blockage, then sitting with the ignition on for a few minutes will allow the car to restart and then quit again. A dead fuel pump would not then restart.
I got the filter out and it was full of grot; when I initially blew through it, it seemed blocked, only a small amount of air came through and then it cleared a bit. I washed out a lot of silt just to see what was in there. Fingers crossed, but would a blocked filter cause a fuel pump relay error? I have readied the tank for removal, what a huge pain, but if it’s just the filter??? Any likelihood? Draining the tank was a drag, so I don’t really want to put more fuel in and then have to drain it again if possible, but if a blocked filter COULD cause that error, I’ll give it a go. Does the computer measure fuel rail pressure to determine if there is a pump failure, or some other criteria?
Thanks for the guidance, I’m a bit in the dark with injected engines.
Ill say, whether it was right or not lol, i didn’t drain my tanks on either my xk8 or xjs (same filter) when i changed the filter. Only what was in the line line and filter came out. A clogged filter could definitely cause an issue. Just be careful, if it was that clogged, you may find the Jag having loads more power after replacing it 
It would depend on the type of time and patience you want to invest. If you want to know what’s going on and put the time into it, just change the filter, put a gallon of fuel in, and see how it goes.
If it will not develop sufficient fuel pressure (and/or run) then disconnect the filter again to see if it’s gunked up. If it is, it’s probably on the pump side.
The fuel pump relay could be going bad - relays can act intermittently when going bad. Or, an overworked fuel pump could have caused the relay to fail. So it’s worth swapping the relay with a known good one or a spare.
Ultimately, it may come down to the fuel pump being bad or the sock on the end being plugged - if lots of debris were getting to the main filter then the sock could be in bad shape.
And then there’s the big question - where is all this gunk coming from? If it’s a rusting fuel tank (don’t know if the XK8 had a plastic tank or not) then nothing you can do will address this problem long term until that’s fixed.
Dave
Thanks Dave,
Current situation is, I’ve cleaned out the filter, put some gas in and bypassed the relay to feed 12V to pump. Pump is running, gas coming out of the fuel line in seemingly sufficient quantity and pressue, but I’m not getting any build up of pressure at the fuel rail. Have a new filter coming. I would expect fuel to end up at the rail eventually, but doesn’t seem to be getting there, Is there anything after the filter that could prevent the pressure building ie regulator or something? I can see the lines coming into the engine bay on the left inner guard, one to each rail, so I guess there must be a 1 into 2 union somewhere along the line. Is it just a splitter? Or does the main line feed both rails via the crossover tube with the bleed valve on it, and the the line from the right bank feed back to the tank?
Thanks.
Usually, if the rest of the fuel system is healthy, pressure can still be built up even with a leaky regulator. The pump should be able to build up significant pressure even without a regulator, but after the pump is shut off the pressure will drop right away (whereas with a good regulator it will take a few minutes for the pressure to bleed off, sometimes a lot longer.)
It could be that the pump is on its way out. It can still flow fuel under free flow conditions, but can’t move anything once there’s a restriction. Maybe you can listen to the pump while free flowing and compare to when everything is closed and showing no pressure.
Can’t think of any in-situ tests to verify fuel pump health though. I guess you could test for voltage just to see if the relay is at least delivering enough juice to energize the pump properly.
Dave
Resolved. After spending hours and hours crawling underneath the car, unable to release the snap fit fuel lines, I waved the white flag and towed the car to my neighbour who has a hoist. With decent access, the lines were freed in a matter of minutes and we diagnosed the pump as faulty. A trip into town secured a generic replacement that fitted directly in, and an hour or so later, normal service resumed, just the boot trim to reinstall. The hoist turned an impossibilty into a breeze, lying on my back I just could not contort myself into the shape required to access the fuel lines and had resorted to dropping the rear suspension. Fuel tank was full of grot, so was cleaned out, new fuel filter, so hopefully no more issues.
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Good to hear. Thanks for telling us what was wrong.
All good, code thrown was P1230 Fuel pump relay failure.
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My car, a 2001, had most of what you described, and it turned out to be the fuel pump itself, and I have learned this is common on my vintage. Maybe they have fixed this fault, maybe not. My car took over a thousand dollars to make it run again. The rear suspension needs to be dropped then you can get to the tank and the pump. Hope you get lucky.
Difficulty getting access to the fuel pump must be for open cars. On my coupe access is from the top, a lot easier. I have not replaced my pump but when I removed the rear deck to recover with new fabric the pump is right there.
Glenn
Perhaps so. In the convertible, the tank sits beneath the rear shelf, so needs to be manouvered out at the right hand side to extract the pump, so obviously the fuel lines need to be removed. Like most things, once youy’ve done it once, the next time doesn’t seem so daunting, but this was plenty frustrating at the time. It also seems it was largely my own fault, albeit unwittingly. I dismantled the old pump and there seems to be no issue with it, internals all good. Looks like the fuel filter got blocked and the back pressure just blew the output hose off the pump. But after the hassle of removing it, I wasn’t prepared to go through the risk, so replaced the pump anyway. So cautionary tale, keep an eye on those fuel filters, unfortunately, out of sight, out of mind. Wouldn’t have happened to my S1 Sov, the fuel bowl is in the engine bay in clear sight, and would be painfully obvious well before it caused fuel flow issues.