i just noticed that a lot of Jags dont have the fuel temperature sensor, but mine does. and it looks as if the plastic sending unit has been broken off.

can anyone tell me what color the wires are that go to it, because during the rebuild i noticed a rogue wire was spliced into the IAT that wasnt on the schematic. Then i got to thinking that if i was as cheap as the previous owner, i would probably just splice it into the IAT instead of buying a new one.

The car had no top end when i bought it. i found a bad TPS and a bad vacuum advance to be the issue. However, once i did the TPS, and patched some of the junk wiring around it, i disconnected the wire that had been spliced into the IAT, and the car has never been right since.

i thought i remember reading on here that if the FTS gets a certain reading or goes bad, then the ECU will max out the fuel pressure to clear the line.

i still havent gotten all the new wiring spliced in yet, so i was just looking for some input since i wont be able to test it for a few days.

 

anyone have any pics of theirs?

 

@M90

(I'm assuming your fuel temp sensor is on the underside of your fuel rail ?)

I don't have a good picture handy but I can take one tonight if you need one

From memory, on my facelift car, the fuel temp sensor looks like the water temp sensor, although it doesn't have the fancy connector, it only has 2 male spades.

On my car the fuel temp sensor activates when the fuel temp goes over 175deg (I think). Once it activates a vacuum solenoid closes so that when the fuel pump runs for the 2 seconds at ignition on, the fuel pressure regulator allows more pressure at the rail, in theory to combat vapor locking. My system "works" but it's never been able to fix my hot starting problem...... (I have now fixed my hot starting problem by installing a remote control system where I can run the fuel pump constantly before I get into the car and try and start it. This has been working like a charm since I installed it)

While troubleshooting the hot start issue I disconnected the fuel temp sensor, and while the car started ok, it ran badly. Main issue was when you revved it, the RPMs would go up then come down all the way and the car would just stall.

So, it sounds like you could be getting max pressure at the rail which is not allowing the car to run properly.....?

 

well im pretty sure its multiple issues, but the car hasnt been right since i tried to tackle the TPS replacement and goofed around with that wire. its certainly indicative of high fuel pressure, although i havent tested it. its running crazt CRAZY rich. mine is a white and pink wire IIRC, and the sensor is definitely electric.

and my FTS isnt under the rail, it sticks bolt outright of the side of the rail between 2b and 3b IIRC.

 

You fuel temp switch wire colors are both Y/K (yellow/pink). The switch when open creates an open circuit for the intake air temp sensor. This increases the pulse width of the injector creating a rich running condition until the temp drops and the switch closes. If your switch is broken you should jump them together so the ECU gets the correct intake air temp reading. The later cars had a vacuum fuel temp switch which would prevent vacuum from going to the fuel pressure regulator which increases the rail fuel pressure. If you have a vapor lock issue just cycle the key several times to clear the rail of vapor and bring cooler fuel from the tank.

Is your fuel rail bent? Or is it camera distortion? You need to replace the injector hoses and ditch those clamps.

 

yes, its bent. not sure why. certainly made cutting the fuel hose interesting.

and as of ten minutes ago, ive got all new hoses and got rid of the clamps. i bought some EFI type clamps just incase the barbs leak.

anyone know what pins the fuel temp sensor is on the ECU, so i can locate it on my schematic. i only managed to find one of the temp switch wires.

 

The fuel temp switch is wired in series with the intake air temp sensor. One wire is to the temp sensor the other is to the reference voltage wire at the TPS.

 

ok, that makes sense. my schematic doesnt show the temp switch or the wiring.

should be interesting trying to wire it back up.

 

if its wired in series, does that mean i can just leave it out altogether when i get the new harness finished? it just basically jumps the IAT right?

 

If you do not want the switch then yes just do not create a spot for it. As I said it is in the reference voltage wire going to intake air temp sensor. Mine was broken when I bought my car and I just jumped the wires together.

 

you just jumped the wires together? wouldnt that bypass the IAT?

why not just cut out the circuit altogether?

 

The sensor is in series with the intake air temp sensor. If you jump the IAT wires then yes you bypass it. I meant jump the fuel temp switch wires together. This way you don't have an open circuit to the ECU for IAT. Take a look at the wiring diagram. If you need a wiring diagram the JDHT DVDs are the best bargain.

 

ive got a wiring diagram, but it doesnt have a temp switch.

 

Hi Temp == Temporary ?
I re-broke mine whilst cleaning..
Seems to have been glued up previously..
So I don't know if it worked - or will work - after I repair it..

 

I dont bother with them. They were/are fickle, and just more stuff to go wrong at the wrong time.

I left those wires aou when I rewired the engine bay, along with the cold start wires.

 

AOU?

Aussie term? Australian Outback Upgrade? Another term for pitched?

 

Yep.

When I got rid of all that rubbish, coz I can, the fuel economy went up, the speed increased HEAPS, and you could actually SEE the damn engine.





Now doing similar to the S Type.