One of my UTVs just had an issue with the fuel pump. It was putting out 30 psi when spec is twice that. The engine wouldn’t start. So fuel rail pressure is critical
Casso did bring up an OUTSIDE shot, my xj40 caps had to be on tight not crooked or you would get a vaccuum leak BUT you would have a light on the dash?
Im still with pumps.
good luck either way.
gtjoey1314
Don’t forget the blue ‘donut’ seal in the fuel feed line in the cannister. When that fails, the fuel pump works but it is merely pumping fuel back in to the tank and you get little or no pressure in the fuel rail.
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Just so everyone remembers here the original poster, Reinaldo is talking about a 1994 XJS with the 4.0L AJ6 motor here so some suggestions that might apply to a XJ40 might not apply to a 1994 XJS
Got it but not the aj16…its the last of the distributor cars unless its a 95 my correct.
I’ve never lifted the bonnet on an S40…
But the S3’s were notorious for the temperature sensor going full open during normal operation. The computer would then be convinced the engine is overheating and shut off the fuel injectors in response.
Move the connector from the temperature sender to the nearest injector to test or limp the car from traffic to the mechanic on 5 cylinders.
Yes, it made no difference
Reinaldo - again I ask: [see above].
Did you change the filter yet?
Mike,
I think I am correct in saying (remembering?) that the fuel pressure reading in the fuel rail on an AJ6 engine does that because the FPR is at the exit of the rail before the fuel returns to the tank and Reinaldo has already told us that he only sees 2 or 3 psi at the fuel rail during cranking.
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Thanks Bryan for noting this. I admit I am ignorant about these matters but this design surprises me - I would have thought the regulator would be between the pump and the injectors to prevent a regulator failure from allowing the pressure at the injectors to be too great. Or is that not the purpose of the regulator at all? Then again I suppose if a regulator failure always results in the pressure being too low rather than too high the positioning before or after the injectors is a moot point.
The FPR is at the end of the rail and has to be as the system is set up for recirculating fuel. Placing it at the end of the rail maintains a constant pressure across the injectors. If placed before the injectors it would not be able to maintain pressure and recirculate.
Reinaldo,
Have you solved the problem yet and have the car starting OK now?
If so - what was the problem?
The XJS has fallen from priority and I need to have it wait for some time.
A tiny old lady hit my poor XJR with her Toyota while I was placing my mask in front of the driver’s door at the Home Depot parking lot and, in doing so, almost had my legs crushed with her car rolling backwards towards me. If she had not being yelling for help I wouldn’t have turned around and moved out of the way in time to avoid her car. Rear left door damage of, maybe, $2,000 or so. Next time that we need to go out, if it is before the XJR is back, it’ll be in the wife’s Z3, to which I need to do some work, as well.
I have a few things that I need to take care of before I can continue with my XJS effort, including buying a pump that I thought I had, but that I can’t find. Actually, no biggie since the XJS, with rare exceptions, is driven only to car shows and it hasn’t gone to one since Covid broke out and now it probably won’t be going to any show for at least a few months. The XJR is in the body shop and it’ll be ready in just a few days.
BTW, is the AJ6 F/P different from the V12 pump, or are they the same?
Wow! that’s rough.
Sorry to hear about those misfortunes but pleased that you avoided personal injury. Good luck with all of your repairs and will be pleased to hear when the XJS is ready to go again.
Yes, I’ll get back here as soon as I’m able to do more work on it.
Thank you for all the help!
Best to check the parts catalog against your VIN
Hello Reinaldo - glad to see that you were able to escape getting hurt - Tex Terry, II - 1991 XJS V12 Classic Coupe, 1986 XJS V12 Coupe - sent 10/19/2020 2021hrs. EDT USA
Much appreciated, fellows!!
Well, I thought I’ll inform this old thread that my beautiful XJS is running again. No, I did not replace the in-tank fuel pump myself, but I had a local independent Jaguar shop take care of it. A place with an impressive name: “Coventry Cars of San Diego” that specializes in vintage Jags. They did find some challenging issues, so I’m glad that, with absolutely zero experience doing this job, I decided not to tackle it on my own. I’m happy.
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