Help identifying wire - and larger issue...
 

Greetings all,

I've recently purchased an 89 XJ two-door sport, 4.0L I6. I've got a list about as long as my arm of things to fix, and I'm learning a lot as I go. So far, I've replaced the shocks, fixed the non-working dash lights, recovered the headliner, re-wired the stereo and ripped out about a mile of unused, raggiddy old speaker wire, etc, etc.

One of the most immediate problems relates to starting the Jeep - it generally takes quite a few cranks before it catches, but then fires right up and runs just fine. Something like once a day, or once every other day it won't start up - usually after it's been sitting while I'm at work. The previous owner had mentioned that this might happen and showed me a trick. It seems weird, but works every time - here goes:

If the engine won't catch, he told me to pop the hood and pull a purple wire on the back of the block off, let it sit for 30 seconds or so, then put it back on. The wire has a black rubber cap over a brass connector and fits onto a post or plug that sticks out from the block, on the right side (when facing the engine compartment). Once the wire's connected, I hop in the Jeep and turn the key - it usually cranks for a little while, then catches. Every once-in-a-while I have to repeat the procedure again to get it to start.

I have no idea what the wire is/does and can't for the life of me figure out why the engine starts up after doing this procedure. I've tried to figure out what it is from my service manual, many searches here on CF and I've described it to a few other people.

I've been thinking that I should replace the fuel pump and filter (pump might be failing, check valve could be bad, etc.) but I don't know why the wire/plug would affect the pump.

Can anybody help me narrow this down?

Thanks in advance for your help - this site is a great resource!
John.

thats the ground wire prob has a bad connection
EDIT!! ignore this lol

wait purple wire? i think thats the coolant temp sensor for the gauge wire... doesn't make sense why that woulnt make it start...
since its a rennix jeep they always take forever to start lol
a pic of the wire would help make sure what wire your taliking about

http://www.lunghd.com/Tech_Articles/...ant_Temp_2.jpg
?
That wire is for the CTS.
Dont see why it would affect starting.

Yes, it will affect starting.
Pry about 15-20$, look for a short or replace it.

hey check that out! good find Defiance

o but wait! the ecu reads voltage from the cts on the side of the block not the one on the head. the head one is for the gauge. the one on the block under the intake is for the ecu
Attachment 46571

Defiance -

Great find on the picture - that's the wire all right. I'll check into replacing it tomorrow - the starting's been getting worse and worse - hopefully that'll take care of it.

I'll post up to let everyone know if it solves the problem or not.

Thanks!

John.

Hey guys -

Just in case you're interested, I thought I'd close this up. I changed out the sensor on Friday evening and (apart from a bunch of coolant spraying all over the place) everything went well. I also shot some dielectric grease in the connector and jammed it back on there.

Haven't had any trouble starting since then.

Thanks for your help!

John.