Strange Starting Problem? any ideas what it could be

[SargDeath]

Lately my 90 xj once and a while wont start. I can leave it and come back later and it will start. This is a difficult problem for me because it isn't always a problem so I am afraid one day it just wont start when I am in the bush.

When i turn the key I the engine turns over no problem and the starter is working just fine. The problem is I am not getting any sort of firing

I can also hear the fuel pump engage when I turn the key as well

the last time it happened I was at a friends and we started trying to figure it out. I thought maybe there was no spark at first, so I checked the coil, cleaned the cap and rotor checked to see if there was a spark, everything checked out to the distributor cap.

I then pulled my return line off my fuel pump to make sure fuel was there, a little fuel puked out so I reconnected the quick disconnect.

I then pulled a wire off of a spark plug turned the engine over agian to check power through the wire then with the wire off of one of my spark plugs the engine randomly started again, along with some fuel puking out of my return line because I wrecked the O ring in there. Fuel wasn't puking out before when I turned it over after I pulled the quick disconnect so the sudden rush of fuel made me think it could be a fuel problem again but I recently replaced the fuel filter and pump and don't think it could be the pressure regulater valve but I could be wrong.

So that is as far as I have gotten, any ideas would be appreciated. Hopefully it isn't an electrical problem.

[4.3LXJ]

You may have inadequate fuel pressure. To be sure, you need to check it with a gauge. Blue is the Renix expert, but you also may have a starter that is just a little slow too.

[SargDeath]

My starter is only a couple of months old as well It still sounds nice fast and consistant. I am going to pick up a shrouder valve this weekend. If I have any problems with the pressure I will probably pick up a new pressure regulator

[SargDeath]

There is no ignition at all going on in the combustion chamber. So there is no sputter or real engine movement.

[4.3LXJ]

Crank shaft position sensor might be going bad then. They can do stuff like this sometimes before they quit entirely.

[SargDeath]

Crank shaft position sensor might be going bad then. They can do stuff like this sometimes before they quit entirely.

Yup I have allready replaced that as well not that long ago unless it is faulty

[Punisher]

Have you fixed the problem yet?
I had this problem and I went throught everything and come to find out that the flywheel was cracked around the bolt area where its bolted to the crankshaft... check out my thread for some photos and you can see what im talking about...

http://www.xjtalk.com/showthread.php?t=4633&page=2

[pvt.tadpolxj]

Hey sargdeath. you might try cranking for a few turn"s and then drop her down into Nuetral and try it.. if that is a improvment. you could rebuild your NSS switch...:driving:

[Thomass]

Fuel wasn't puking out before when I turned it over after I pulled the quick disconnect so the sudden rush of fuel made me think it could be a fuel problem again but I recently replaced the fuel filter and pump and don't think it could be the pressure regulater valve but I could be wrong.

The pressure regulator, works on a vacuum, before getting an new one, make sure that the vacuum-hoses are all in good order. even an cracked vacuum hose can create errors in many different ways.
And, checking cost only time...
Than, if your checking the hoses, you also might check the hose between the map censor and the throttle body and the rubber part in the throttle body where this hose enters.

[cherok]

The starter is earlier mentioned, is this the starter relay?
If not check this relay.

[freegdr]

mine is an 89 ive been thru what you are talking about next time it dont start open the hood a tao the top of the map sensor and see if it starts mine did every time