• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Wont start----- yes I have searched

BPB

BPB

NAXJA Forum User
Location
Battle Ground, Washington
I am working on a new to me 1989 xj 4.0 aw4 231. I bought this xj yesterday. The symptoms are that it will sit there and crank and blows gas fumes out of the throttle body. the vacuum system seems to be working backwards. If you pull a plug it blows out hot air when it cranks. when I unplug the cps it doesn't blow gas out the throttle body. I have fuel and I have spark. Here is what I have done.....

All plugs, wires, cap and rotor are new
replaced cps
replaced idle air sensor
replaced all vacuum lines
inspected egr valve it is new
checked all plug connections and order multiple times
disconnected cat
tried disconnection every sensor individually
checked for fuel pressure

Me, dellstopjeep, and goblazers_6 are all stumped. any suggestions before I check the timing chain?
 
If it is blowing back out of the TB your timing is not agreeing with the position of the valves. Intake valve should only be open when piston is heading down on the intake stroke.

Plug wires are wrong OR distributor is not indexed properly OR timing chain has slipped OR burned intake valve OR bent intake valve.

Firing order is 1-5-3-6-2-4 (too young, too old, just right).
 
I am thinking that the distributer needs to be indexed, it was lose when I got it. A little more history. the guy that I bought it from said that it ran just fine. He parked it and when her started it up it started backfiring and wouldn't accelerate. He said that they replaced all the ignition stuff, which they did. He did say that they tried to fix the timing. Will I be able to check the valve options with a compression tester? If so how?
 
OK! Something REALLY stupid, but your saying the vacuum system was like backwards, reminded me of this, and since you just got it............

Anyway, I once went over to help an older gentleman figure out why his car wouldn't start. Bottom line is that he had hooked up his battery charger backwards and the battery had actually reversed polarity and was cranking backwards. So this leads to a stupid question. Is the distributor turning the right way?
 
I have not checked on the distributor. I don't know if that is even possible on out ecu controlled vehicles. I am leaving town for the weekend, so I will have to get back to it on suunday.
 
Well I was able to get a couple hours in on it today... had eric's bachelor party all weekend. First I indexed the distributor. It fired up. now it is just running supper rough. Then i checked the compression in all cylinders, nothing amazing, but not bad enough to cause it to run like it is... this is what I got.
1-140
2-125
3-140
4-135
5-130
6-125
So we started experimenting with it idling. When I sprayed starting fluid in the throttle body, it would run better. Disconnecting the fuel injector cables did nothing. Unplugging spark plug wires one at a time did very little. I went through unplugging sensors. The throttle position sensor did nothing, the idle air sensor did nothing, but when i disconnected the brand new crank position sensor it died. I am going to buy a new tps tomorrow. Thinking about it I should have tried the map sensor also... any ways let me know if there is anything that you guys can think of that I am missing.
 
My father and I just bought an MJ from a guy a few months ago. I havent been around (school this summer) to work on it with him so naturally he hasnt been working on it either. Well I knew the guy before we bought the jeep from him so I didnt think that we had anything to worry about other than the obvious need for a new tranny.

Well we used a 4.2L 's bellhousing, placed a new CPS hole in it, mounted everything up, cranked it and ran like dog crap.


Well I was discouraged cause that (in my mind) meant that we f-ed up our bellhousing and would have ot locate another. well we didnt. The vaccuum hose to the MAP sensor got ripped out inadvertently while taking off and putting on the CPS plug....


I would check it out. I'm really glad I saw it before I decided to pull the bellhousing. Its a stupid little thing that will make it run like a turd.
 
If you were disconnecting injectors one by one, without any change in how the engine was running, you have a fuel problem.

As it was across all injectors I would suspect CMP or fuel delivery.
 
When you disconnect a spark plug or a fuel injector, the idle should drop and get rougher. If it doesn't, this leads to your problem. Spark plug or wires. Or fuel injector or wires. If the idle doesn't get worse from doing either of these things, that means that cylinder is not functioning.
 
I replaced the tps with a brand new one, nothing happened. All the plugs, wires, cap and rotor are brand new. I went through unplugging fuel injectors no matter which ones I had unplugged it would run on 3 or more injectors, and it didn't really change between having 3 and 6 injectors plugged in. It won't rev up unless you sit there and feather the throttle and it will maybe rev up a little. It back fires. I rechecked the distributor indexing.
 
The injector plugs are relatively cut for THE injector they go to other than the 5 and 6 MIGHT could be confused. If you misplace wire 1-4 (from what I've seen) then you must have really tried to mix them up, cause they are very self explainatory.
 
I am absolutely sure that they are hooked up right. It is time to make a decision. I can spend $200 and pull a motor with a guarante or move on to the timing chain. or for $100 have a shop look at it and run a full diagnostic.
 
What about removing the valve cover and checking the valve timing that way? Don't take it to a shop. Have you checked the timing with a timing light? I know it's not adjustable, but at least you could see if it's firing at the right time. Can you tell if it is the original motor?
 
All the rockers looks good, as do all the push rods and valve stems. I have been searching and I can't figure out how to use the timing light? The timing markings are not in visible from the top of the engine.
 
Last edited:
I think that I found the problem :party: I started taring it down to remove the engine and when i removed the fuel rail I noticed that all of the fuel injectors are all gummed up. I have never seen anything like that before. So I proceded to remove the intake manifold because the injector ports were also filthy..... I mean holly $#!t!! So when I got to the bottom bolts they were all finger tight. I think that exhaust has been getting into the intake manifold and caused all of the fuel injectors to foul. What do you guys think?
 
You must log in or register to reply here.

Similar threads

N
Can you help me diagnose my vacuum readings?
Replies
9
Views
2K
Saudade
Saudade
C
Cranking Time
Replies
6
Views
85
CBJeeper
C
O
2000 XJ Failed Colorado Emissions high CO
2
Replies
27
Views
2K
Ken M
K
J
Cranks, Fires, Dies - 1991 Briarwood Restoration
Replies
17
Views
3K
Jam Master Jay
J
I
High idle, smells like gas, running out of things to replace
Replies
2
Views
2K
Inverhyt
I
Back
Top