Yet another long crank time problem, but not the usual.

There is one strange and annoying problem which I have with my jeep..
When I start it in the morning, usually there are no problems - fires up straight away (regardless of very low outdoor temperature, and regardless of being RENIX that is..). However, if I stop it after running for just under a minute (while still very cold), for whatever reason, the next thing is that I cannot start it anymore. It cranks, and cranks, and cranks..

1. battery is fine - it spins the starter and at it all sounds healthy.
2. fuel is alright, as I can even smell it after some time cranking (seems obvious to me, as it is not starting, but injectors are doing their best).
3. fuel can't be problem as I run on LPG also, so when I switch from petrol to LPG, there is no change at all.

Then I leave the jeep, frustrated, going by foot wherever I was intending to drive.. and when I come back, an hour or so later, just out of curiosity I try to start the damn thing. Guess what, it starts right away!

I'm thinking maybe ignition is bad? but how could it be that it starts great, then dies, then starts again after some time.

Oh, and well, if the car is warmed up, I can turn it off, and start it again without problems.

Anyone experienced anything similar?

One more thing.. I know that I have problems with NSS, sometimes it just won't spin it at all in P (but N works).. however, NSS can't make it spin but not fire, right?

Thanks

A friend of mine had the same problem on his XJ and was a bad contact in the wiring connection on the ECU....but it was a H.O. not a RENIX.

Good luck .

First thing I would do is to take the extra few minutes to VERIFY with 100% certainty that you're missing the spark part of the equation when the engine is symptomatic. Once you're sure what you're missing, the list of usual suspects gets a whole lot shorter....

Pull a plug, keep it attached to the plug wire, place the electrode near a good engine ground and have a buddy crank the engine while you watch. You're looking for a strong, blue, snapping spark. Lack or spark or yellow/orange spark isn't good.

I'll place my bet on CPS. Like stated earlier check for spark when it doesnt start. If no spark replace CPS.

CPS I swapped also, not for a new one, but surely different condition. And it didn't change.
Bad connection to the ECU sounds realistic, as I had to remove it and put back number of times few months ago. But can't really remember if that was the time when it started acting like. I related it more to cold weather.

Surely, spark checking is on my list.

How do you start? No gas pedal, which is the right way.
If you start no pedal, try starting with 1/8 th pedal or just a little gas pedal.
The IAC can stick shut and you won't be getting enough air for a start. Especially if it is really cold out and/or your battery is a little weak. The IAC seems to mess up more when the battery is weak, seems it needs all the electrical power it can get to function properly. The oil and other junk in the seat and around the IAC plunger gets stiff when it gets cold and it may work poorly. The grease inside of the IAC (from the manufacturer) gets really thick and stiff over the years, a couple of drops of oil squirted behind the plunger (pintle) can loosen things up a bit and help functioning. Don't try to pull the plunger (pintle) out of the IAC, this can damage it.
When you said you can start fine after it's warmed up, it made me think of the IAC, I've seen it before. Though the CPS can also be temperature sensitive.
Two separate systems for start and run for the fuel. During start power for the fuel pump is supplied from the starter relay. Not likely but something to check if all else fails, I've seen some pretty nasty looking starter relays inside, they aren't sealed well at all.
Like mentioned check for spark, this can narrow it down a lot. No spark or fuel is likely to be the CPS. Sometimes unplugging the CPS and plugging it back in helps for one more start. Sometimes heating (or cooling) the CPS helps for one more start (I've used a small bucket of cold water on mine before, I can't see a small bucket of hot water hurting much).

You can have spark with a CPS issue why does everyone thing you don't


CPS tell the injectors to fire fuel. So usually with CPS you will have spark and fuel at the rail but no fire.

XJ Stryker said:

You can have spark with a CPS issue why does everyone thing you don't


CPS tell the injectors to fire fuel. So usually with CPS you will have spark and fuel at the rail but no fire.

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Yes but fuel can't be issue for the reason that I'm smelling fuel after extensive cranking, which means that petrol is going inside, but just not burning. Also, I can try starting on LPG, and that makes same symptoms. LPG system that I have is really dumb one, basically it just sprays evaporated gas straight into throttle body. It can't go wrong with it.

mr_W said:

Yes but fuel can't be issue for the reason that I'm smelling fuel after extensive cranking, which means that petrol is going inside, but just not burning. Also, I can try starting on LPG, and that makes same symptoms. LPG system that I have is really dumb one, basically it just sprays evaporated gas straight into throttle body. It can't go wrong with it.

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If the IAC isn't opening you may be air starved at startup. Try starting with the gas pedal slightly depressed, less than 1/4 pedal and see what happens. Once the plugs get fuel fouled, especially in cold weather, it can take awhile or even require removing them and cleaning before you get a decent spark.
Something else to think about, with fuel prices the way they are, some gas station owners cut there fuel with water and add a little alcohol to keep it in suspension. Or the fuel just has a lot of condensation in it. Water coated plugs don't fire worth a darn. Usually not a serious issue when the motor gets hot enough to evaporate the moisture off of the plugs, but even then may cause a poor running motor.

8Mud said:

Something else to think about, with fuel prices the way they are, some gas station owners cut there fuel with water and add a little alcohol to keep it in suspension. Or the fuel just has a lot of condensation in it. Water coated plugs don't fire worth a darn. Usually not a serious issue when the motor gets hot enough to evaporate the moisture off of the plugs, but even then may cause a poor running motor.

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I bet the fuel in Serbia could be an issue. To test the "water condensation on the plugs" issue, you could try starting it on LPG and turn the key off at the usual problem time, then test for restart issue.

No doubts that fuel quality is very low here, however what puzzles me the most, is why it starts so nicely when really cold, but next minute it is complete no-go!?

I'd still suspect the CPS - especially the connector. If you could beg or borrow a known good unit and the problem goes away, all is good - or install them on another properly running Jeep, and see if the problem recurs.

I realize your neighbors or friends just may not have a similar Jeep, but I imagine Jeep parts are a bit pricey in Serbia. I'm frugal, I don't like buying if I don't need it.

Testing for voltage drop thru that harness and proper electrical output specs can help. It should change when you wave a magnet near it. I don't have that at hand, but I'm sure it's buried in this forum somewhere.

mr_W said:

No doubts that fuel quality is very low here, however what puzzles me the most, is why it starts so nicely when really cold, but next minute it is complete no-go!?

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The IAC parks itself slightly open, after you start and open the throttle it closes. It may be sticking shut. If it sticks shut and the throttle plate closes (you let your foot off the gas pedal) it chokes the motor.
After the motor heats up and the oil and gunk around the IAC gets soft from the heat, the IAC works better until the next time it gets cold.
But like mentioned the CPS can also be temperature sensitive, but most times you can measure that with an ohm meter. The ohm specifications allowable tolerances IMO are a little generous.

TEST YOUR CPS BEFORE YOU DO ANYTHING ELSE!

Test#1 - Get a volt/ohm meter and set it to read 0 - 500 ohms. Unplug the cps and measure across the CPS connector's A & B leads. Your meter should show a CPS resistance of between 125 - 275 ohms. If it's out of that range by much; replace it. (* - Note: HO engines are measured from the B & C connectors and should have near zero ohms.)
Test#2 - You'll need a friend to help ya with this one.
Set your volt/ohm meter to read 0 - 5 AC volts or the closest AC Volts scale your meter has to this range. Measure across the CPS leads for voltage generated as your friend cranks the engine. (The engine can't fire up without the CPS connected but watch for moving parts just the same!) The meter should show .5 - .8 VAC when cranking. (That's between 1/2 and 1 volt AC.) If it's below .5vac, replace it.