88 jeep cold start problem

[mbessey]

Jeep takes several cranks to start when ever motor is cold. If you hold the key on jeep will stay running. Let off of key it will die. Eventually it will stay running. Replaced fuel pump and filter, TPS, fuel modulater, Runs really rough with TPS plugged in and runs smooth with it unplugged.
took it to two different shops and was told replace fuel pump. The fuel pump had been replace about a year earlier but went ahead and replaced it all any way. I can hear fuel pump come on. I've heard about a fuel pump relay? about and Idil air control motor? At a loss for what to do. Shop I took it to fried my started, left only one bolt holding it in. and left of inspection plate to fly wheel. Need help.

[bgwilly]

you might want to check the pickup in the distributor mine had the same problem but it cranked forever . also try to clean the trottlebody with carb cleaner and a tooth brush hope it helps you

[oljeeptek]

Originally Posted by mbessey

Jeep takes several cranks to start when ever motor is cold. If you hold the key on jeep will stay running. Let off of key it will die. Eventually it will stay running. Replaced fuel pump and filter, TPS, fuel modulater, Runs really rough with TPS plugged in and runs smooth with it unplugged.
took it to two different shops and was told replace fuel pump. The fuel pump had been replace about a year earlier but went ahead and replaced it all any way. I can hear fuel pump come on. I've heard about a fuel pump relay? about and Idil air control motor? At a loss for what to do. Shop I took it to fried my started, left only one bolt holding it in. and left of inspection plate to fly wheel. Need help.

Sheesh-I'm never shocked at tech's laziness any more. All it takes is 2 minutes with a fuel pressure guage at start up to check proper electrical op, pump op etc. Can you get one to hookup? Leave it on overnight and see how far the press drops. It should have some residual even overnight. How much is not as important as that it should jump up to 47psi immediately on key up and hold. If its slow you could be getting air trapped in the fuel line until it bleeds through. If it checks ok, you dont need a pump, and the relay and circuit is fine.

You need to have a good map sensor signal, and coolant temp sensor input for cold start. The 2 wire sensor on the engine, not the switch on the radiator.

The tps should have .7-.8v on the signal wire at closed throttle. (still plugged in) I think the signal wire was the dark blue one, if memory servs

The Sync (Distributor) sensor can give you some trouble if its bad. The good news is you can unplug it on this year. It will start after 2 full engine revolutions during cranking. Its not necessary to have it for running. The computer bypasses it.

The cps @ the rear of the engine needs to put out .7-.9v AC (yes AC) during cranking or it'l not start well and die at idle. Ohms won't tell the whole story.

You could also have ecu trouble, but it's not often they go bad.