I have an 80 xj6 and I have replaced the coolant temp sensor with a few different one and none of them help. I have to have it pluged in to get it started but then I have to unplug it and bypass the sensor to keep it running. it doesn't matter what sensor I try it doesn't help. one of the 4 or 5 I have is the right one for it but they all do the same thing. just wondering if anyone knows whats wrong with it

thanks Willis

 

If all your sensors behave the same then I'd assume they are not the cause. Jumping them out tells the car it's at operating temperature. Is it? Does it reach 88 degrees?

 

So, with the engine running you unplug the sensor and bypass it. If you don't, the engine will die? very odd, because normally the engine should die the instant you unplug the sensor!

Weird.

How does the plug and wiring look?



The link you provided whose several different sensors. Which are you using?

Cheers
DD

 

I'm not thinking there the problem now either just not sure what would cause it to do what its doing. it dose get up to temp but it wont run right with it plugged in but it also wont start if its not pluged in

 

it wont die with it plugged in, it just wont run right. and it will die when its unplugged, I have to put a piece of wire from terminal to terminal in the plug to keep it running, and it runs great that way but it just wont start without it plugged in the sensor




bosch not sure of the number
standard tx18
standard tx107
and a couple others

 

So it needs the additional fuel that the sensor calls for at a cold start, but with the sensor active it receives too much fuel when running to run properly.

So are you pulling the connector off while running and then quickly jumping the connector? And it runs reasonably fine after start with the connector jumped?

If so, that would suggest, to me, that you have a rich condition that the ECM is adding to during the warmup to operating temperature and that resulting mix is too rich to run. Telling the ECM that the car is warmed up by jumping the connector removes one factor enriching the mix and gets back to a burnable mixture.

What's your fuel pressure?

 

I'm not sure if it is getting to much fuel because before when the sensor was bad there was all sorts of black smoke and now there is not but I guess it must still be because that's what the sensor does.


yes pulling it off and jumping it quick or restarting it.


I will check pressure tomorrow morning and let you know.

 

25 to 30 psi running and about 35 with the key on not running

 

Low if anything, but not far out of spec. Certainly not a cause of a rich condition.

How have you set your AFM mix adjustment screw? Does opening it up counterclockwise make any change in the idle? Open will lean the mix and should help. If it has no effect it's passages may be blocked.

Do you have a multimeter? I'd be curious what your current temp sensor says when cold and when fully warmed up. It should stop having any effect when warm but you indicated that, even with the engine warm, reconnecting it causes it to stop running.

 

A bit low. That could be your problem. Should be about 36 psi when cranking and when running, although 'running' pressure will vary a bit (2-3 psi maybe) according to engine vacuum.

Just for the record....it may not have anything to do with the problem at hand....but the pump is not supposed to operate by simply turning the key 'on'. If yours does, the circuit has been modified, which isn't unusual.

Cheers
DD

 

Don,
Im actually planning on connecting a pre-start momentary switch to run the pump and restore fuel pressure after sitting overnight. I hate that first crank not firing right up.

From the s57 diagrams it looks to me like I want to energize pin 86 on the pump relay. This is the trigger cicuit that's energized by the diode pack when you lift the flap in the air flow meter. Is that the standard or at least a good method?

Or am I just wrong about my fuel pressure dropping being acceptable? Jaguar docs suggest a slow pressure drop is acceptable as long as there are no leaks?

And now back to your regularly scheduled post.

 

If the fuel pump is healthy it'll repressurize the fuel rail in about 2 seconds so there really shouldn't be any significant delay in starting.

(A million years ago, convinced I could improve starting, I thought it would be clever to rig up a priming system. I used a delay module that power the f/p circuit for 5 seconds whenever the drivers door was opened. It didn't make any difference in starting but it was fun rigging it up . As years went by and I drove and worked on more Series IIIs I realized that none were 'instant' starters.)

Anyhow, try this simple experiment before you go thru any effort. Put the gearshift in any position except "P" or "N". Turn the key to start and hold it for a few seconds. This operates the fuel pump and pressurizes the fuel rail. Now try starting. Any change?

Cheers
DD

 

I turned it and it didn't make any differnce

 

I will check that out, yesterday it ran great with it plugged in when it got warmed up. firs time its done that in a long time

 

its a new pump but I guess that doesn't really mean anything
but it runs so good with that sensor unplugged, do you really think that could be the problem?


It runs in the run position but not started not the on position sorry about that

 

I checked it and it was 0.25 when it was warmed up and it runs good when its warmed up and plugged in its just that in between cold and hot. computer maybe?

 

I might have had it on the wrong line before, now I'm checking it right after the pump and there is 35 running

 

Have you carefully inspected the senor wiring and plug?

Cheers
DD

 

35 psi is good


Cheers
DD

 

the wiring looks good from what I can see
but I checked the plug and with the key off I get good ground from both wires but with the key on I get ground from the black supply wire but I get power from the blue orange wire witch is the return wire, I'm guessing there shouldn't be power there.


could it be the computer?