Hi, I am italian from naples, I have Jaguar XJS 3.6 1985.
I renovated the car 3 years ago and has never had any problems. Last month after traveling 40 km the engine lost power. I replaced the fuel filter, the fuel pump, coolant thermostat, I clean secondary fuel filter after fuel pump, but the problem recurs.
My mechanic can not find the problem, as soon as you drive 35/40 km the engine loses power, if I stopped the machine 15/20 minutes the engine finds power. Please can someone help me?

 

My mechanic can not find the problem, as soon as you drive 35/40 km the engine loses power, if I stopped the machine 15/20 minutes the engine finds power. Please can someone help me?

 

I am not sure if the 3.6 litre has the same plumbing as the V12 but there is a swirl pot under the battery (I think) that can get partially blocked.

 

You are right Steve. There is the same system.
Unclenry: Look at this diagram:

Pipe 14 from the main tank can collapse internally, particularly if the fuel tank cannot draw air into itself as fuel is used up. Try a road test with the fuel filler cap loose, and see if that helps. If so post again about what to do
Also the tank (1) has a filter 18 inside; this filter may be blocked and the tank may be full of dirt.
Also pipe 19 may be kinked as it has to go into the fuel pump from below.
Look at al these areas and let us know what you find.
All these points can cause fuel starvation - which your problem sounds like.

 

Does it do this regardless of RPM? What does it do revved in park? What does it do at the same speed but with the gear manually selected?

 

Hi. my car has manual gear. When I try to increase RPM the engine loses power and to return home I keep low RPM and speed not exceeding 60 KM / H.

 

the tank (1) and its internal filter are clean

 

So maybe replace the flexible from main tank to sump tank? but also do the loosen filler cap test. The symptoms you have are classic gradual fuel starvation ones, and a period of not running allows the main tank to regain atmospheric pressure and so the pump can deliver again.
Also, if it stops again, carefully loosen a fuel union in the engine bay, wrapping it with a cloth and see if there is fuel there under pressure or not.

 

Definitely sounds like fuel starvation as Greg said.
I had a similar thing ages ago with a Hurricane (re-bodied Spitfire) kit car.
It took me 9 hours to do 65 miles.
Turned out that rust flakes in the bottom of the tank were getting sucked into the pick up pipe and just stopping the engine dead.

 

Hi,Today I drove for 100 km and during the trip, to solve the problem, I tried to turn off and turn on the machine and the problem disappeared.
this happened 6/7 times and every time the problem disappeared. ?????!!!!!?????

 

That is exactly what happened to me; as soon as the pump was switched off the crud fell off the end of the suction pipe and cleared it so it started again.
You need to check inside the tank to see if there is any rust or something else in there that is blocking the end of the feed pipe.

 

I would clean/change pipe number 14 and 19 in the Greg's model. What do you think?

 

I think you would be better advised to proceed methodically. First definitely establish it is fuel starvation by testing for pressure when the stop occurs. Then report back/proceed to the next stage: test for tank breathing (filler cap loose test); ensure feed to sumo tank is clear; and so on.

 

Today I drive for 20 km and the problem is back. I opened the tank cap but it did not happen.
The engine lost power and then it turned off. I waited 30 minutes with the hood open and then the car started again; after another 20/25 km the problem is back.............

 

You might replace the CKPS on the front of the engine????

Seems like all the AJ6/16 engines had problems with the Crank Angle Sensors (Crankshaft Position Sensor) and the V12 had probs with the Engine Speed Sensor also.

bob

 

Good point.
BUT, when the engine stops, find the fuel supply union into the fuel rail on the feed side from the tank. Wrap a rag round it and slightly undo it and see if there is fuel pressure (cannot miss it, if there is fuel will hiss out at about 2.5 bar pressure).
If there IS fuel pressure, then it looks like an electric/electronic problem, and the CPS is a very possible candidate as Bob says above. It looks like this:

And is bolted to the front of the engine at about the 11 o clock position in relation to the crankshaft pulley. It is worth changing it in any event. It is part no. 17 in this diagram:

https://www.jaguarclassicparts.com/u...over-3-6-litre

 

Always worth doing. Pipe from the main tank to the sump tank collapses internally under suction. This is another possible cause of your problem, BUT test for fuel pressure when the stoppage happens.


If it is NOT fuel, then the crank sensor is a possibility (see above) and also the ignition module (3 in the diagram in this link):
https://www.jaguarclassicparts.com/u...dule-3-6-litre

 

Hi, today I did a new test with a pressure gauge.

initially it was 2.5 atm, but after 25 Km the ploblem is back and pressure gauge was like in the picture (1 atm).

 

OK
So it is fuel pressure. This is what I would do:

• Change the flexibles to the sump tank and from the sump tank to the pump (14 and 19).
• Change the main filter (behind the spare wheel) EVEN IF NEW. Make sure it is connected the correct way (there is an arrow on the filter which should go into the pipe going TO the engine, NOT the pipe coming from the pump).
• When the filter is off, undo the fuel feed to the injector rail in the engine bay and blow out the fuel feed line to the engine with compressed air.
• re-check the inside of the sump tank (undo 14 and 15) and make sure that the metal pipe is not blocked and that the filter (18) is clean.

Good find on the fuel pressure. If after the above it still happens, change the pump.
I believe you have already changed the fuel pressure regulator? If you can try a new one there too, it would be a good idea, and it could be (just could be) the FPR is giving up when the engine bay gets hot.
Greg

 

Further to the above post, I have had another thought. It is just possible that the ECU is, after the car has been running for a while, failing to keep sending the "run" signal to the fuel pump relay. Next time the car stops, ask someone to keep turning the engine over on the starter, and listen to see if the pump is running while the engine is turning over. If it is not then:
It would be worthwhile "hot wiring" the pump - that is to say rigging up a feed to the pump that comes on with the ignition, and then testing to see if the fault disappears.


It would be unwise to drive the car like this permanently, but it would perhaps indicate the fault more precisely, as either the ECU signal failing or a feed fault in the ECU to pump relay to pump wiring.
Greg