Terje

I have a 1992 Cherokee 4.0 HO auto transmission 125Kmiles here in Norway.

The engine hesitates at low rpms (below 2500) and won't start when engine is hot. I have replaced the following parts. TPS, CPS, plugs, fuel filter, rotor, distributor, air filter, oil and oil filter. Idle valve is cleaned. Engine turns when hot but just won't start. It is fuel at the fuelrail. Have not measured the pressure.Battery is fully charged,No check engine light.Fuelpump runs for about 2 seconds when turning ignition on. It smells gasoline after trying to start .Any ideas?

Gee oh Dee

I've heard about injectors getting too hot and vapor locking, but I'm not sure if it applies to your year.

Terje

If i crank for a long time it almost start and it ignites on 2-3 cylinders and dies again. If I let it cool down for several hours it will start an run porly, black smoke before it runs smooth. Can temp sensor or coil give sympthoms like this? Fuelpump relay maybee.?

Diesel

No but Stator can, sounds like its vaporlocking

Gee oh Dee

Thats what I thought as well.

Diesel, do you know what years are covered by the injector heat shield TSB?

I thought it was late 90s early 2000s, but I could be wrong.

If this is indeed the cause of your issue, its a really simple fix.

Terje

My son commented the exhaust smells strange!!!, and he is right. It is the beginning of winter season here in Norway and the outside temperature is about 30F.

Diesel

1803103 - 4.0L ROUGH ENGINE IDLE AFTER RESTART FOLLOWING A HOT SOAK
Date: 09/05/03 (supercedes 1802702 dated 09/06/02)
Model Year(s): 1999-2004

Description: NOTE: This bulletin applies to vehicles equipped with a 4.0L engine. This bulletin involves the installation of a fuel injector insulator sleeve.

Details: Customers may describe a 20 to 30 second rough idle following the restart of a heat soaked engine. This condition may be most noticeable when the engine is restarted following a prior 10 to 20 minute heat soak in hot ambient conditions of approximately 32 C (90ºF) or higher. This condition may be consistent with short city stop-and-go driving trips and can be aggravated by the use of fuel with a high ethanol content. Depending upon various conditions a MIL may occur due to DTC P0303 - Cylinder #3 Misfire.

This condition may be caused by heat from the exhaust manifold that following engine shut down migrates to the area around injector #3 and causes fuel vapor to form within the injector. This in turn may cause a momentary misfire of cylinder #3 until the fuel vapor is cleared of injector #3. The insulator sleeve lowers the injector #3 temperature to a point below which the fuel will not normally vaporize.

If vehicle exhibits a rough idle, and if a misfire of cylinder #3 is observed following a 10 to 20 minute hot soak, perform the Repair Procedure.

Parts required:
56028371AA Ignition Wire Shield

Repair procedure:
1. Cut insulator sleeve, p/n 56028371AA, to make two (2) insulator sleeves about 25-30 mm (1 in.) in length. See diagram.
2. Install one sleeve around injector #3, with the slit on the upward facing side of the injector. Install the other sleeve with the slit on the downward facing side of the injector.
3. Confirm sleeve is flush to intake manifold surface around injector.
4. Check injector #3 wire and ensure that the injector is rotated to a 2 o'clock position (from driver’s side of vehicle).

Terje

Today it started at once and ran perfect. Decided to try to get some error codes out of the computer. Last time no error codes, today code 51, oxygen sensor stuck at lean maybe caused by map sensor. New sensors are ordered.

Gee oh Dee

That'd be a cause of your issue.

Also sounds like the TSB doesn't apply to your year.

Terje

Oxygen sensor and map sensor are changed. Everything seems normal when testdriving. So far so good. Hope this was the last fix.

Fidishund

Google vapor lock you might be getting it