1998 Tj..long cranks..
I have a 1998 TJ I bought from a buddy of mine and the only problem I cannot get to the bottom of is a long crank ...when I say long I mean like 10 sec+. This TJ is a 1998 automatic sahara 4.0. The jeep cranks right up on cold mornings with no delay. It seems to have the long cranks when it is warm outside or after jeep has been running.
Things I have replaced or cleaned:
1. Replaced Fuel pump, pressure regulator, two screens. Did not replace sending unit. (the pressure regulator was shot as i had no pressure with previous regulator, it cranked right off after I replaced the regulator but shortly returned with long cranks. It is holding pressure good with jeep on and with jeep off with new regulator but still long cranks.)
2. Replaced CPS sensor
3. Cleaned throttle body with throttle body cleaner.
4. Removed IAC and cleaned it with throttle body cleaner
5. Recharged KN air filter. (When I removed the air filter and ran it with no filter it cranked right up everytime so I recharged the filter but when I replaced the filter it continued with the long cranks.)
6. New spark plugs. (wires were changed just prior to buying)
7. Replaced upstream 02 sensor.
8. I tried knocking on the starter prior to starting but still long start.
9. I have used lucas treatments two seperate times when filling up with gas with no luck.
Things I know wrong or missing on jeep:
1. Jeep has no cat converter nor does it have a downstream 02 sensor.
2. Has a broken bolt on exhaust manifold on the underside of manifold nearest to the firewall.
3. The battery is about 3 years old. But havent had any trouble with it dying or holding a charge.
It had a rough idle but after re-tourqe mainfold bolts it went away(this is when I found the broken bolt.) Long cranks was there before and after I did this.
I hope I have provided you guys with enough information, if not let me know.
Almost sounds like old time fuel boiling. As we called it back then "Vapor Lock"
OK lets try this. Run it get it good and hot, shut it off and let sit.
Try and start it. If it doesn't fire right up, take a little gas or some carb cleaner and dribble some into the throttle body. Now go try and start it. If it attempts to fire up or fires up and runs a few seconds, you have a fuel delivery failure.
If memory serves me there should be some hard asbestos (?) heat shields around the injectors. Their job is to help prevent heat from cooking the fuel in the injectors.
If they are missing or damaged, more then likely the engine heat is boiling the fuel in the injectors, so when you try and fire it up all you are getting is some fumes. Until the fuel flow cools down the injector enough to actually let fuel flow out and into the intake.
The missing cat and O2 sensor is a no no. It's not helping your mileage or power, your jeep was designed to have em on. No reading from the O2 could very well have your jeep running full rich.
Should have set a check engine lamp. Might want to see if the lamp even works. Should come on when you turn the key to the run position then go off after a few seconds.
Not saying, but maybe someone pulled a bulb to eliminate the lamp, and you may have all kinds of codes actually stored in the ecm. Be worthwhile to have it checked.
Places like Advanced/ AutoZone/ etc will do it for free.
Thanks for the reply and sorry for the delay in posting this reply..Got busy today with work..
I forgot to mention i only get like 6 mpg and I agree with you I m sure it is the fact i have no converter and o2 sensor
Yes they must have removed the check engine light bulb. No light but always reads two codes. I have ran previous scans and always get codes p0138 and p0141 and i do not figure they will go away since i have yet to put a converter and sensor in. That is all going to change tomorrow though. I noticed under the jeep where you plug the downstream o2 sensor in to the wiring harness there is another adapter similar to the one for the o2 sensor but of course the end is a little different. Any idea what this goes to? i have looked all over and yet to see anything that appears to be unplugged under there.
I will try what you suggested to test for in the beginning of your post tomm and will post my findings.
thanks again for your quick response...
I dribbled some gas in and still long cranks. I noticed no change in cranking with the gas.
Get "EVERYTHING" Back to factory specs. This is a computer controlled engine. I.E... If the computer reads there is no or low O2 at position x, it will richen the fuel curve to adjust for it. and so on and so on.
It is absoutly Impossible to do anything about any issue with this motor until it is brought back into full compliance with the manufactures specs it was designed with.
In short, Its like trying to ride a motorcycle down the road with the rear tire off. Sure you can ride it on the rim... But really?
Manufactures spend millions on R&D for our computer controls. tricking one by adding a "Chip" or the like is one thing. Removing a componet completly is a complete game changer.
Sorry if this sounded like a rant. Wasnt meant that way. I just see alot of folks do some goofy things for whatever reason, and then months later cant fingure out whats wrong. I know you bought it that way but your better served to get it back to factory specks. clear all codes and start from there.
By the way the Cat is neither her nor there as long as the second O2 has been moved to the rear about 24" or so from the stock location. its looking for a lesser ohm reading than the first indicating that the cat is doing its jib. but best to add one and get the issues resolved.
All the best. :punk:
Converter and 02 sensor replaced, all codes cleared.
So you got any ideas why the long cranks are there?
Looked over your list of replaced parts, didn't see a fuel pump relay in there.
I've seen heat induced failures on them from time to time. Just as you described.
As a matter of fact the a/c went out on ours today. I flipped the a/c relay with the horn relay, a/c fired right up. Figured I'd run out and grab an new relay, so I installed the old relay in the horn slot. No horn. Get home horn now is working with old relay.????
New relay is in a/c slot, put the original horn relay back. Tossed the old a/c relay.
I did swap it with the horn relay and both seem to work fine.
I have read numerous threads on this and have seen ppl mention the timing may be off or bad starter.
Any thoughts on those?
Only other 4.0 (was in a Grand Cherokee, same engine) I've seen with this problem ended up having a bad crankshaft position sensor. Finally went out and wouldnt start at all. Replaced the sensor and all was well, no more long starts.
For some reason sometimes if I start the engine, turn it off right away (usually because I forgot to unlock the glovebox), then when I go and start it it will crank for an extremely long time before starting, like you have described, and eventually it will start sputtering as a couple cylinder fire then if I give it gas it roars to life.
No clue why, I'm thinking CPS/CPK sensor or maybe the fuel pump itself. I'll be following along.
Also have replaced cps/cpk sensor.
I have not replaced the the MAP sensor, temperature sensor, TPS sensor. I know these may not be a problem or even have anything to do with it. I m just trying to get somemore input.
Ok I believe we can close this thread as I believe I have found the problem.
I went back over everything listed and when I was re-checking the fuel pressure I noticed it was not going above 30psi when running. Previously the pressure regulator had went bad and at that time I replaced the fuel pump at the same time i did the pressure regulator. The pump I bought was a foreign made pump from oreilys. I replaced it with one from napa yesterday and since then no more long cranks and pressure is where it is supposed to be.
I appreciate everyones input..thanks
It took two new pressure regulators to fix the same problem in my TJ. The first pressure regulator turned out to be defective.
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