95 Wrangler wont start....

[markusgov]

My 95 Wrangler, 4.0 fuel injected, wont start when the weather gets cool (70 degrees or less). It will crank great but wont start. As the day goes on and temp goes up, it will start. It runs rough for a few seconds, then levels out and will continue to run fine for the rest of the day. But, the next morning after the temp drops again....no start. Fuel pump was replaced in April. Can anyone please help?!

[Glamissand1]

Fuel filter and screen also I hope. Has this happened only after fuel pump? Try replacing the fuel pump relay. How does it turn over fast or slow? I try to do quick bumps on the starter and listen for a fire and stop cranking, stop wait repeat. Need to check for spark to see if its weak or non existent.

[markusgov]

Yes to the fuel filter and screen. And yes, pump was replaced several months ago and this only started happening about 2-3 wks ago. I forgot to mention that I tried starting fluid with no luck.
When I turn the key on, I can hear the fuel pump for a second. So, I've kind of ruled out fuel system. But they're cheap, and if that's what you think I should try, I will.
I turns over fast. I haven't checked for spark yet but will. The cool temp thing is what has me stumped, but clearly playing a big part. I put a heat lamp under the hood by the coil & distributor, but no luck. Thanks for your help Marc. Any advice is appreciated.

[Glamissand1]

If starting fluid failed its either spark or compression, and id lean toward spark. The Crank position sensor tells the comp when to spark, and is a magnetic pick up that my be just out of range in cold temp. When was her last tune up? plugs, wires, cap, rotor?

[markusgov]

Last tune up was about a yr ago. Plugs, wires, rotor, etc... Also changed crank shaft position sensor, and cam shaft position sensor because of another problem I was having at the time. I didn't realize cold temps could affect the CPS.

[Glamissand1]

If the cps is old and beat down runnin its last legs it can. I'd recommend chasing the power down to where it stops. If you have power in then check all the grounds. Did you get any kind of ignition on starter fuild?

[markusgov]

If the cps is old and beat down runnin its last legs it can. I'd recommend chasing the power down to where it stops. If you have power in then check all the grounds. Did you get any kind of ignition on starter fuild?

No ignition with starter fluid.

[diforbes]

I have the exact same vehicle with the exact same problem, been troubleshooting it as well and I do think it is electrical (things contract when cold), tho have not figured it out yet..any resolution with yours?

[drallabg]

good luck.... I get rough idle after heavy rain... gotta love Jeeps!

[diforbes]

Still troubleshooting, but one thing that is interesting is when I try to start it when it is cold only the brake and seatbelt lights come on, not the check engine light. Later, when it is warmer, same thing, but after turning over for 15-20 seconds those lights go out, check engine light comes on, then it starts....

[jonzjeepyj]

Its your capacitors in your ECM. Next time, turn on you Jeep but don't crank it. Wait for 20-30 sec until
you check engine light comes on and it will crank every time. Your capacitors are getting old and need
time to build up and store power before it will power your ECM. You can either purchase another ECU for
around 200-250 bucks and plug and play or you can rebuild yours with capacitors from radio shack for
about 5 bucks. There are write ups all over the net on rebuilding your Jeep's ECM.

Good Luck !

John

[jonzjeepyj]

Any luck finding your problem ?

[diforbes]

Still not starting, tried to follow your suggestion, here's what happened:

7 AM: Turned it on but did not turn it over, seatbelt lights go out, another 30 seconds, no check engine light, try to turn it over, will not start.

Noon: Turned it on but did not turn over, seatbelt lights go out, another 30 seconds, no check engine light, turn the key, turns over a couple times then starts, as it starts check engine light flashes.

So perhaps cold is too much for capacitors? At 7 AM was around 50 out, noon 70. It did seem to start better at noon than it had previously at the same time.

Still think it is the ECM? I have no problem rebuilding it if you think it may do the trick, hell spent the summer rebuilding everything from the exhaust manifold back, that looks like a piece o' cake in comparison...

[superj]

its definitely some type of electrical. maybe bad solder somewhere in the ecm?

on bmws, the solder is bad in a board behind the gauge cluster and makes some of the gauges not work, or work erratically. when i bought an 84 325es, those particular gauges didn;t work so i pulled the cluster and reflowed the solder in the whole mother board. worked like a charm after that and not a single problem with it anymore

[markusgov]

At 7:30 this morning & 55 degrees, it would crank like crazy, but not even attempt to start. I was going to pull a spark plug and see if I had any fire but I didn't have time. Will start now & ran rough for about 15-20 sec and likely won't miss a beat all day. All my lights do come on like normal.

[markusgov]

Did you say yours wouldnt even turn over at 50 degrees?

[superj]

are your wires form the battery good? check the resistance they are reading. i know its backward as they should have more resistance as they warm up but you have tried everything else

[jonzjeepyj]

My friend had to let his sit for over five minutes until it built up enough power.
He would literally turn it on in his garage and go back inside for five minutes. I
only said 30 sec because you said it took that long for your check engine light
to come on. Just sit in your Jeep and watch and wait for the check engine light,
up to 6-8 minutes long. it should be long enough. If not, I will send you a link
on how to rebuild your ECU if you want it.

[diforbes]

Did you say yours wouldnt even turn over at 50 degrees?

Turns over, but will not start.

[diforbes]

My friend had to let his sit for over five minutes until it built up enough power.
He would literally turn it on in his garage and go back inside for five minutes. I
only said 30 sec because you said it took that long for your check engine light
to come on. Just sit in your Jeep and watch and wait for the check engine light,
up to 6-8 minutes long. it should be long enough. If not, I will send you a link
on how to rebuild your ECU if you want it.

So it is around 12:30 PM, turned it on and let it sit. Seatbelt light went out, about 10 seconds later, check engine and shift arrow flashed then went out. Started right up. So I guess the cold just makes it take longer to get enough energy as you suggested initially. Will prove out tomorrow AM just out of curiousity, but think I am heading to radio shack for parts. If you have a trusted link on rebuilding the ECU, pls post.

Thx for the help.