# 1989 Jeep Wranger 4.2L V6- Cold starting/leaving car parked overnight starting probem



## ksmooth (May 18, 2007)

My 1989 Jeep Wrangler Sahara 4.2 Liter V6 Has a cold starting problem and tends to stall when i get it started but when the car fully warms up and shut off the car and try to restart it, it starts fine so I know its weather related, when it warms up the stalling goes away.and I am very frustrated because I replaced so many parts like:

-Carberator (Since its new im guessing that the choke is adjusted to specifications)

-Ignition coil

-Did the tune-up (distributor cap and rotor, pcv valve, spark plugs and wires, fuel filter, air filter)

-Fuel pump

-EGR valve

-Oxygen sensor

-Battery and cables

-Thermostat

-Fixed all vacuum leaks

After all these replacements, i still have this problem..As a auto tech myself I can not find the root cause of this problem..Had 2 master techs look at it and still could not find the problem.. please help..any suggestions are welcome..thanks in advance


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## cjessee (Aug 22, 2005)

alternator?


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## ksmooth (May 18, 2007)

alternator output is good, thanks anyway


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## gnaltj (May 19, 2007)

Your problem could be the fuel pressure regulator. If this valve has thrash holding it slightly open it prevents the fuel rack from getting full pressure as it allows the fuel to leak over to the fuel return line. Morning starting problem is because fuel injector rack has bled off all pressure during the night. Try turning ignition key to "on" position, Wait until you hear the in-tank fuel pump shut off, then turn key to "start" . Hope this helps.


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## qldit (Mar 26, 2007)

Good Morning ksmooth, that is an interesting problem, you mention a carby but that sounds like an EFI system you have, if so it probably has start sheduling in a closed loop situation and shouldn't be apparent, so most of the other engine stuff shouldn't really have great effect.

I would suggest doing a complete compression test before getting too involved with further troubleshooting.

Your description is often similar to low compression in a cold situation.

If it has injectors I would try injector additive in the tank with some decent premium fuel, they often get a bit gummy and it is probably more noticeable when cold.

How is the ilde speed when the engine is hot?

Cheers, qldit.


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## ksmooth (May 18, 2007)

its not fuel injected..it has a 2 barrel carb on it..i did a compression test and the test shows that the rings are bad..do you think that that could be the culprit?


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## qldit (Mar 26, 2007)

Good Evening ksmooth, I usually do a simple compression test with all the plugs removed and record all the pressures, then squirt a teaspoon or so of oil down each plughole and do the pressure test again, if there is any marked variation in pressures it generally indicates rings, if not and it remains similar, suspect exhaust valves.

If the cylinder pressures are out of a reasonable range (lowside) and there is much crankcase pressure and vapour it is pretty damning.

Typically when an engine is cold the compression can be significantly lower than when the engine is properly warm and oil residue and expansion has an effect.

Sometimes running watery low viscosity kinds of engine oil can increase the effect of low compression due to worn rings. 
Using a decent 20-50 multi viscosity oil may help.

Actually I only ever use Valvoline products and it helps to mask these kinds of problems in older engines.

When you complete your compression test if you leave a teaspoon of oil in each cylinder then refit the plugs, see what difference it may make when you start up the next morning, that would be the writing on the wall! (Disregard any initial smoke) 

Save some oil to oil the wheel on your wheelbarrow full of money if rings are the case.

It does sound like a low compression problem and hard cold starting is typical, but for it to be really prominant the rings would have to be pretty bad.

What mileage has it got? An 89 (if original) would likely be way up!

Sorry to bear potentially bad news for you.

By the way, a simple and very useful tool to make for confirming these kinds of problems is to use an old spark-plug and remove the ceramic center section, then braze a suitable air adapter into the metal plug body.
This tool is invaluable when fitted to an engine sparkplug hole with the workshop air connected, 80 PSI or so is all you need, you can tell by the sound of air leakage within the engine or manifold when the respective piston is suitably positioned and with a bit of experience with different engines soon can determine the engine and valve condition. It is the final confirmation in degree of problem.

Cheers, qldit.


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## jflan (May 29, 2005)

I have a 1985 Jeep Cherokee 2.8 with 404K on it and it's in a similar state. 

Low compression plus a failing choke pull-off make cold-starting a bit tricky. 
Been thinking about trying a manual choke. 

It just passed emissions testing and is still easy on oil so I keep running it the way it is.
Another Valvoline engine 20-50 Geritol (the high mileage stuff in the brown cans)
Been thinking about a crankcase breather line plumbed to the clean side of the air filter


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## qldit (Mar 26, 2007)

Good Evening jflan, great minds think alike!! 
I did that on a vehicle with a felt type airfilter, it wasn't long before the actual filter began to clog, so I ran it for ages with no air-filter, not a good policy but the engine needed major work anyway, so it did give an extended life.
In the end it really had some crankcase pressure and was really blowing oily fumes and oil was dripping out of the air filter housing, so I shoved steel wool in the breather system to try to reduce oil vapour, that worked till the fibre timing gear eventually lost a few teeth.
It was into the 300 K plus area before it died which I thought was pretty good.
It sure owed me nothing at the end!

Isn't it amazing the mileage you can get out of some of these engines!

I haven't seen anything with as much mileage as yours on an original motor, that is incredible! 

I love using Valvoline oils and products, they certainly are worthwhile.

On one occasion a chap gave me a Toyota Hi-Ace to have a look at, it had a nasty death rattle, I dropped the oil and changed it to the 20-50 Valvoline XLD and it made a hell of a difference, it really surprised him and more especially me!! LOL!!!

I will be interested to see how your amazing machine fares.

Yes, when the cold starting becomes a problem that is really the writing on the wall, sometimes a small bottle of "ether" in the glovebox can be very handy!!

Cheers, qldit.


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## jflan (May 29, 2005)

"Yes, when the cold starting becomes a problem that is really the writing on the wall, sometimes a small bottle of "ether" in the glovebox can be very handy!!"

Hmmm....
Maybe a remote switch in the cabin for easy application of a morning shot of ether !


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