So ive been chasing an issue in my 85 xj6 for awhile now. At first issue presented itself with sluggishness and or engine wanting to die when under load, ran fine in idle. Ive gone through plugs, wires, cap and rotor, fuel pressure regulator, fuel pump, filter, vacuum lines, and just today replaced coil and resistor, also changed gauze filters in tanks. now issue has progressed to engine choking out when it gets warm or after running for about 15 to 20 min. a mechanic " Dr Jag " here in Albuquerque told me i should check the fuel temp sensor. Said it should read 250 ohms running at 90 degrees c. now since im not a mechanic if it reads higher or lower does it need to be replaced or is something else causing this issue? before i start chasing the issue again i wanted to see if i could get some feedback. Also if anyone can think of anything else that would cause this issue id be greatly appreciated.

Matthew Rinaldi
Rio Rancho NM

 

I suspect he means the coolant temp sensor?

There IS a fuel temp sensor, though. It's the brown device on the fuel rail with two vacuum hoses. You can bypass it by running a single hose from the pressure regulator to the vacuum source. It allows max fuel pressure when the fuel is hot to prevent vapor lock.

The coolant temp sensor give more trouble, historically. If it gives a "cold" reading to the ECU when the engine is actually warm or hot, you'll have too much fuel and the engine will be "running rich". If you don't have a multi-meter you can simply replace it...only $20 or so. It's on the water rail...#2 or #3 position from the front. Also carefully inspect the plug/connector forthe coolant temp sensor. Corrosion, loose wires, loose terminals will cause a problem

Cheers
DD

 

i changed the fuel temp sensor with a used one i know works and same issue. i ran it in the garage untill it got warm and just cut out just shy of 90 degrees c. then would start and quickly shut off. i had my buddy come start it while i checked for any leaks in the boot . when he started it i noticed the fuel pump. was only staying on for a couple seconds upon ignition then turning off thus engine dying. now i know the pump is almost brand new but its a possibility that its bad. the part that makes me doubt its bad is that when the engine cools down it starts just fine and pump stays on. im baffled. any ideas???????

 

Remove the fuel pump relay from the socket. In the socket find the terminals that go to the white/green wires. Use a jumper wire to apply 12 volts to the white/green wires. You should hear the pump run. If so, start the engine and see if it stays running.

The fuel pump relay is on the firewall with a couple others. Just look for the one with the white/green wires

Cheers
DD

 

ok im going to go try that. now another thought and this may simply be a rookie oversight. my ac needs to be charged . havent done it at all this summer because couldnt get the car running. i was reading through some pages in the haynes manual talking about the fuel cooling system. sounds to me that it uses the coolant from the ac to cool the fuel. now, if the fuel was too warm is there a sensor that would shut off the pump to keep the engine from running, kinda like a fail safe?

 

i had an issue similar 2 years ago. car would start fine, idle fine and then drive like a champ. after 5 or 10 minutes of driving it would choke a little then stall. it wouldnt start back up for a while and eventually stall once it did.

replaced the ignition coil module and distributer. car has been fine since

 

No.


Cheers
DD