Replaced crank sensor, because Jeep wouldn't start and tach didn't move when I cranked engine. Ran for a few minutes, then stumbled and cut off. Won't restart. I tried to get codes with the key and it doesn't show anything. Check engine light goes out and never flashes. Thanks for any advice.

 

Sparkplugs and fuel pump?

 

Ok. Jeep would sometimes crank but not start. Replaced crank sensor. It started right up, ran for a couple of minutes then died and would not restart. Replaced coil, ignition pickup, distributor cap and rotor. Started right up. Let it run for 10 minutes. Turned it off, and it will not start again. Pulled a plug wire off, put a screwdriver in it, and got spark. You can hear fuel pump run when key is turned on. Also I took cap off of fuel rail, pushed in valve, and got fuel. Any ideas would be appreciated.

 

You say you have spark? What color of spark is it? Our Jeeps need a strong blue spark. Any other color will indicate a weak spark and can cause lots of problems. I would also go to the parts store and rent a scanner to pull the codes. Your jeep will not give you codes with the key if it is newer then 96. Also, you should rent a mechanical fuel pressure gauge to get the pressure. Since you have a 98 you should have 49psi +or- 5psi. BTW, just pushing the valve on the fuel rail only tells you that there is fuel not if you have the correct pressure.

 

Thanks. I will look into that. Also the tailpipe is black and sooty like it has been loading up if that helps any?

 

Starts right of way if I hold throttle body open, and release when it starts. But won't start by cranking alone.

 

Bad IAC?

 

Took apart iac and cleaned it. Still does the same thing. Do I just replace it?

 

Did you test your throttle position sensor?

 

I had a problem recently where the jeep would run sometime and stall sometimes and not want to start and just acted all weird, turned out to be a broken then hand twisted ground wire for the wiring harness, where it grounds near the dip stick. Have you tried, while running, wiggling every wire under the hood and seeing if that does anything? That's how I found my issue.

 

Include the pcm connectors in the wiggle test.

 

Checked tps this morning. Had 0.79 volts in idle position, and 3.94 volts wide open. Moving on to the ground wire and pcm wire wiggle test now, assuming tps is good. Going to borrow a fuel psi gauge tonight to check fuel psi.

 

You need an ohm meter for testing the tps. Measuring voltage is not accurate enough. Reason being, there are to many variables while checking the voltage (specifically supply voltage) whereas the ohm test tests only the tps. Just attach a lead to each end of the field and slowly open the throttle to be sure the resistance change is uniform to the speed it's opening at. I personally had an issue with my idle, it was the tps connector. My stalling issue was the pcm connectors. Before that it would die because there was a coil supply problem so I rewired that with a new coil. Then at another point the distributor connector writing kept acting up. Stupid jeep electrical gremlins.

 

Checked t.p.s. with ohm meter and it was good. Wiggled all wires and connections with it running and found nothing. Hooked up fuel psi gauge. Turned key on to activate pump and had 43 psi. Held throttle body slightly open so it would start. 46 psi running. Shut car off. Pressure leaked down 18lbs. In 10 minutes. Squeezed fuel line from pump and it still leaked down.

 

Hey you sound like what I had! It ran until it was warmed and then it would die, wouldn't start and pisses you off...

I know you said you can hear your fuel pump running, but check the pressure and, most importantly, the volume. I replaced almost every single sensor and refreshed every singe connection, but no go. Decided to replace my fuel pump on a whim and it lives! Since I replaced my fuel pump it has ran quieter and I think the loud pump means its going out.