Only starts when out side temp reaches 60+

Only starts when out side temp reaches 60+


1991 4.0L - AW4 - 231 - 112K

I have no power to the fuel pump and coil.

I've replace every sensor, relay, etc from my running 92 into the 91 and vise versa and still nothing but all components are good working order in the 92.

Once the out side temp is above 60 degrees Fahrenheit it starts right up and runs great.

This has been a long battle and I could really use some fresh ideas on this one.

Items replace and checked:

CPS
TPS
coil
distributor
ECM
Fuel Pump
all under hood relays and fuses.
plugs
wires
cap
rotor
fuel filter
injectors (rebuilt and tested)

On a cool morning- you might try running a hairdrier in a area, say on one side of engine compt, or under dash, etc. A few minutes of heat and test again. Repeat, narrowing down to smaller area. Might take a few minutes to soak in.
Good Luck

The temperature probe in the T-stat housing is used by the ECU for cold starting, just a thought but you could try a new one and see if it helps. There is also a group of earth wires on the engine block at the rear on the passenger side, you could try taking them off and cleaning them up, might help. Good Luck.

Hallo. Yes.Jeepcreep, good idea. Not only the CTS (Coolant temp. Sensor), but also the MAT (Manifold Air temp sensor) is related to temperature for a right fuel mixture. These sensors were not mentioned in vwfoolwhy's list.
Easy to test with a Ohmmeter.


"92 XJ

I'll test those sensors and change out as well, but will they really cause no power to both the fuel pump relay and the coil.

The Hairdryer has been something I've been wanting to try so I'll give that a shot Monday morning.

Remember I'm swapping every thing from my running DD 92 the only difference between the two is 92 is a 5 speed with out any power options.

So unless it pertains to the tranny and the power options every thing is interchangeable and doesn't cost me a thing (until I find the problem).

Pleas keep the ideas coming any thing and every thing will help nothing to small or to out of this world.

Thanks for all the help!

Mike

but will they really cause no power to both the fuel pump relay and the coil.

Hallo. The only thing ,I know about the relation between the fuel pump and coil is the ASDR (automatic shutdown relay). But you renewed it already. Maybe check your ignition switch too.( switchs the relays from both).

vwfoolwhy said:

Pleas keep the ideas coming any thing and every thing will help nothing to small or to out of this world.

Thanks for all the help!

Mike

Click to expand...

Have you tried stickers? I gained 2mph per sticker placed:laugh2:

Both the CTS and the MTS checked fine and swapped out for good measure.

I also changed the IAC for good measure.

First thing in the morning I'll start with the Ignition Switch heating it with a Hairdryer and then move on from there.

I had a S-10 with a similar issue. I found out it was a bad solder joint on the ECM. Found it using a heat gun. Tried heating everything under hood then everything under dash. When I heated the ecm it fired right up. I turn on the A/c for a bit and it would die. Bought a new ecm and it fixed the problem. (JY ecm) Pulled open the old one and just touched a dull solder joint with my solder gun and tried it and it worked from then on.

My thought at first was the ECM thats why i swapped it out with my 92.

The 91 ECM runs fine in my 92 and the 92 ECM runs fine in the 91 (when it starts)

The 91 now has it's ECM back in it.

Didn't get a chance to test out the Hairdryer approach to day will tomorrow.

I bought this 91 XJ for a $100.00 from the original owner due to the fact it needed Brakes and Exhaust but it also had a rap that the owner thought was the engine but i knew as being the Flex-plate.

I drove it for three months with it giving me a hard time starting every morning. What i thought was the fuel pump on it's way out because it would take cycling the key a few times and cranking it over before it would run the fuel pump.

In late August the Flex-Plate Finally let go (broke all the way around the crank bolts. It sat for a few months until i found a replacement Flex-Plate.

In November i finally replace the Flex Plate and the J started and ran great (This was during a warm spell). A few days latter it wouldn't start for nothing and i didn't hear the fuel pump so i figured it must have finally quit. December I ordered a new fuel pump and put it in. Of course it's now cold and winter so the new fuel pump didn't work.

So from December till now i check every thing over and over it was only with in the last few weeks that it would start in the middle of the day and only on warm days.

It's become a joke that hey it's above 60 the XJ will start and of course it does.

Mike

When you say no power to the coil and fuel pump, is that being checked while you are cranking? You know that in run, they only get power for 3 seconds unless the CPS tells the ECM that the motor is running, right? Have you checked for power to the ASD relay?

Yes i checked the ASD Relay and its not getting power at prestart or crank.

the entire wiring loom is open and exposed at this time due to tracking down wires and looking for shorts in wires.

have you swapped ignition switch? that little guy controls the show..

i had the same problem with an 87.. the rod would slide smooth but the grease in it would gumm up the contacts...

worth a try.

You should be able to jump the ignition switch to test if it you get power to ASD then. Or test for power in point at ECU/PCM.