Vented cap, new fuel filter, cleaned sump and filter. Now starved shortly after start up and used to take 20 minutes or so. Fuel pump operating but does make a whirring, slightly whining sound. Is the pump starting to fail? Will it fail gradually or all at once? Or is it fuel pressure valves? Any suggestions before I put in a new fuel pump?

 

A fuel pressure test would be useful here. Do you have a f/p gauge?

The RH (inlet) pressure regulator can be bypassed (and even removed entirely) if you wanted to experiment. FWIW I had the RH regulator fail on my XJS causing a starvation problem.

Cheers
DD

 

As Doug said.

The RH FPR is really used as a pulse damper, and has no actual "pressure" use. If it fails, and most do, it can jam shut, or partially open, and ceasation of engine running, or starvation is teh result.

The pumps do make a whirring sound, but in the big scheme of things barely audible. A few of mine have been noisier than others, and have lasted years, one (the HE) made a wierd screech and died within 30kms.

Age is niw a factor in anything on these cars.

Have a peek at the fuel line, where it enters the engine bay, on the RH side. SOME V12's have an adaptor/one way valve in the hose at this point. REMOVE it, as they also jam. I am not sure of your market, but we had them in the mid to late '80's.

 

As well as the above points, did you blow through the fuel line from the filter to the engine ?

Greg

 

I agree with checking the fuel pressure at the rail and also check the fuel lines for any damage, kinks etc.

Also you might want to check the voltage to the fuel pump. Low voltage can have similar effects.

 

Blew compressed air through supply side fuel line. The pump has 12 volts. Started it up and no problem this time for about 15 minutes and a 5 mile test run. Let it run, parked, and then started to stall on acceleration during second test run. I do not have a fuel pressure gauge. I will order a new rh FPV. The fuel pump can be heard running from inside the car. Is it time for a new one also?

 

Definately a female Jag.

I would strongly suggest removing the RH FPR, and save the money for something else.

That pump is very high on my to do list. If that is audible inside the car it is waaaay past replacement time.

I also suggest doing a test run with the fuel cap not fitted. Obviously a FULL tank of gas is not a good idea here. This proved successful to one I was chasing stalling on, so a 1/32" hole, dead centre in the cap sorted that car well.

 

I removed the RH FPV. Had 30 minutes of running and two test drives without stalling. Then on the 3rd run it started to hesitate again. A new fuel pump is ordered and on the way. I will replace the pump and see how it goes.

 

Just installed new fuel pump and the problem is worse. I seem to have air at the rail when I loosened the fitting. Did this a couple of times to try and bleed it out. It still wont get enough fuel. Should I be looking at something different than fuel supply? Would it be sucking air even though I checked and could not locate it? Deleted RH FPV. No in line one way valve. Blew compressed air through supply line. Cleaned sump and filter. New fuel filter and fuel pump. Could this be an air or ignition issue? It stalls, sputters, some backfiring.

 

Sent you a PM a few minutes ago, with some suggestions.

The EFI is self bleeding, so you have no control over that.

I am thinking ign coil/s, ign module, or that PITA coax wire to pin #18 of the ECU. The backfiring is my lead there, but also a very lean mixture, etc etc will also give that, but at the moment I am trying to keep it to simple items, not knowing the history of the car.

The TPS could also be dying, and that would confuse the ECU something serious.

 

Have you tested/replaced the LH fuel pressure regulator, or tested the fuel pressure in the rail? If not I think this is something you should do to eliminate this aspect causing the problems.

Greg

 

Fuel isn't getting from the tank to the sump. By accident, I pulled a little on the rubber hose and could hear fuel rush into the sump. I figure the lining of the hose is deteriorating and causing blockage. I will replace asap. Thanks to everyone for the help. I now have a new, not needed, fuel pump but at least the old is a serviceable spare. Can't have too many spare parts I think.

 

Yep, put the spare pump in the boot (trunk) and you will NEVER need it.

Put it in the box in the shed, and you WILL need it far from home.

Our XJ12 had a starter jamming issue some times, so a 1" socket onn a bar lived in teh boot, rarely used it, but it was there.

Spouse cleaned the boot out, socket and all, so next outing, starter jammed, went for the socket, &^%%$$##@@, she never touched the boot again.

 

peel, i'm due for a new fuel pump. wondering which model you went with.

 

If I did it correctly the link will take you to the fuel pump page with about 8 to choose from. I went with the Airtex pump for cost and all necessary bits it came with. I do not know if this is the best pump but has been working nicely for 600 miles.

http://www.rockauto.com/catalog/x,ca...8,parttype6256