1995 Cherokee 4.0 4WD 130k miles.

Sometimes it will start fine. More often though, it dies less than 1 second after starting. Almost immediate.

I switched out the fuel pump relay-no difference.

The crankshaft position sensor was replaced about 2 years ago.

Is this more likely to be a failing pump or a failing CPS? Anyone have an opinion?

Anything else I should check?

 

So does it stumble and die or just dies like you'd turn the key off?

In the meantime, do with the ASD relay what you did with the fuel pump relay. Use a known good relay.

 

Use a fuel pressure gauge to see what's going on. Why guess.

 

It's very similar to how it sounds when you turn the key off.

I'll try the ASD relay--thanks.

 

Okay, thanks--I'll buy gauge and test the fuel pressure.

 

One more thing that could be related--I was reading something in a forum that makes me think the failure to start could be related to the neutral safety switch.

This jeep for years has occasionally refused to start in park. Usually starts fine in park. But maybe a couple times a month on average I have to put in neutral to start it. It won't turn over at all in park.

But I'm not sure if this could be related or is a separate issue.

 

Yes that sounds like NSS, probably needs a clean. But it doesnt cause the shutting down after starting; as far as my understanding goes, the NSS is involved in the process just prior to starting the engine. If its faulty, it will usually cause a no-crank condition.

 

This could cause a start, then die.

 

I thought the '95's had lost those?

 

I'm not sure. I thought they only went away when the returnless fuel delivery system came about.

 

Okay, fuel pressure is 35 psi when running. Seems to hold pressure after turning off as well.

Strange thing is it showed no pressure when turning the key. Then when I cranked it, it got pressure.

**edit** I think this is normal. the first two clicks of the key turning doesn't start the fuel pump. But the third turn of the key turns on the pump and cranks the engine, all in one turn.
But in any case, the fuel pump seems to be working. I may just try replacing the crank sensor since it's only $15.

 

Ohhhh.... a $15. crank sensor? sounds like trouble......I read there were issues regarding an OEM, no where to be found...Is this still true?

 

One of our fellows tracked one down from US Ebay, (NOS), apparently thats the only way to get OEM item, as they must not make them anymore

The other way is the junkyard, I have at least 3

I saw a demo of the difference between aftermarket and original, the magnet is much stronger, and will lift about 5 times the weight

I do have a cheap Chinese one, so I could do the test

 

From experience NO chinese electrical part is a reliable test option....Went on e-bay looking for an OEM (Mopar) to have on the shelf & found an application for a 1988 Grand Cherokee 4.0, but does not say it will work on an XJ.??? Is there a difference ???

 

I replaced the crank sensor, which involved a lot of time recovering a bolt that I dropped into the transmission.



Sounds like no one thinks much of the chinese sensors, but it's installed now so I'll see how it goes.



The sensor replacement did not however fix my no start problem.



I switched out the ASD relay with a new one—what’s strange is it starts 3 out of 4 times now, instead 1 out of 5. Could be this didn’t affect anything and it just decided to start more often now. I’m not sure but it did this right after putting the new relay in.



In any case, thanks everyone for all the helpful suggestions.



Any ideas on what I should check next?



To recap:

Fuel pressure seems good, crank sensor replaced, fuel pump and ASD relays replaced. It seems to malfunction much less often now. Other than that, problem is the same—it immediately dies after starting.