• 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.

4.0 Crank No Start

E

EKO1984

NAXJA Forum User
Location
Wichita, KS
First of all, killer forum you guys have here. My hobby is F-bodies (Camaro/Firebird), but I'm also into Jeeps. I've had a 93 XJ (2DR, 2WD, 4.0, auto) that I've used as a beater for a while. Last month that randomly died on me, so I ended up buying a 91 YJ (4.0, 5sp). But the reason I'm here is for some help on my XJ. So, hopefully you guys can add some insight. I'll just copy/paste from my posts on the F-body forum I frequent.

So it went down like this. Friday night I checked the fluids before I went for some Chipotlaway. I started it up to check the trans fluid and after a few seconds it stated making a high pitch squealing. Kind of like a belt but not really. It eventually went away and I shrugged it off. Acquire Chipotle. Profit. Saturday morning, I go to move it, and it's cranking but not starting. Begin troubleshooting in the apartment parking lot in the cold/wind.

Side note: It's been knocking for a while, so I've been using straight 30 weight oil.

Test 1: Fuel
Got me a nifty fuel pressure gauge with a plastic lens that melts when you get fuel on it. Super. Anyway, it had 39 psi at the rail when cranking, just like the spec says. I hit it with some starting fluid anyway. No change.

Test 2: Spark
I pull out a spark plug. It's crudded up (ash) so I replace them along with cap and rotor. No love. I can smell fuel on the plugs. I put a plug up on the valve cover so I can see it through the open hood and I get a bright blue spark both directly off the coil and off the distributor.

Test 3: Compression
Got me a nifty compression tester that looks remarkably like my fuel pressure tester. Now today it had been raining/snowing and it's currently in the low 20s and the wind is blowing about 20mph. This means I'm only checking one cylinder before I die of hypothermia. I screw it in and crank it over a good 4-5 times. 90 psi.

Hypothesis:
Using a heavier oil to keep oil pressure above the "holy crap, that's low" level combined with the cold temperatures as of late led to oil starvation of the cam bearings. The squealing was the cam bearings voicing their discontent about oil starvation. After the engine cooled, the cam seized or had mega-heavy resistance and caused the timing chain to skip a tooth. Now the cam is retarded (I only checked one cylinder), and thus the no-start condition.

What say you? Time to go car shopping?
Click to expand...

Since the weather was nice this morning, I went out and did a compression test on the rest of the cylinders today. Something is definitely facked. Here's what I got:
#1: 75 psi
#2: 70 psi (was 90 last weekend?)
#3: 100 psi
#4: 80 psi
#5: 80 psi
#6: 110 psi
Click to expand...

UPDATE:

Development #1: Went to NJ for 2 weeks to see family/friends over Christmas. While I was there, I bought a 91 YJ
biggrin.gif
. While driving it back to KS, the fuel pump died in Troy, IL (near St. Louis)
frown.gif
. Got that fixed and decided to check the timing on the XJ that this thread is about.

Development #2: With the timing mark on the damper lined up with 0 BTDC, the rotor on the distributor is about 10-15° ATDC. Doesn't make sense to me. If anything, I would think the cam would be retarded, not advanced, if the chain slipped. Either way, valve timing is off and so is the spark timing. Looks like I found the problem, finally.
Click to expand...

Pictars:
100_0357.jpg

100_0358.jpg

100_0354.jpg

100_0355.jpg


Have I found the problem? If so, should I start looking for a used engine? Thanks!
 
Timing is not adustable on the 4.0L but the dist can be indexed wrong.

If you have fuel and spark the only reason I can think for it not starting is that it's flooded or the dist indexed wrong. Can't say I've seen a 4.0L jump timing before but in the realm it's possible. You can try cranking it over with the throttle wide open this turn of the fuel as a clear flood feature.
 
Last edited:
with the 1 cylinder at tdc of the compression stroke, the notch on the crank pulley/harmonic balance should be lined up with 0 on the timing scale and the rotor should be pointing at the 1 terminal on the cap or about the 5 o'clock position.
 
I tried starting with the throttle open, and that didn't work either. Can the distributor just skip a tooth like that? If so, how would it be advanced and not retarded? I never pulled the distributor on this truck.
 
EKO1984 said:
I tried starting with the throttle open, and that didn't work either. Can the distributor just skip a tooth like that? If so, how would it be advanced and not retarded? I never pulled the distributor on this truck.
Click to expand...

It has to be held wide open before cranking and held. Any other position will add more fuel. Cleaning the plugs and cranking it over with them out will also clear it out.

It shouldn't jump a gear unless something is broken. Give me a minute and I'll PM you something.
 
Got your PM. Thanks. Should I try to re-index the distributor? Am I correct in thinking that the rotor should be pointing at #1? From the pictures posted above, it clearly isn't. My thought is, if the distributor is suddenly off, something broke internally in the engine. The rotor still spins with the engine. I just want to be sure that something did break before I swap out engines. I'd be royally pissed if I swapped engines and it turned out to be a coolant temp sensor or something. :laugh2:

Thanks for the replies so far, everyone.
 
You should look at the picture in the link I sent and see if it's like yours, if not then reindex it.
 
Just my $0.02....but compression seems to be the main issue. I've had experience where compression was lost (or too low) due to flooded condition that diluted oil and/or washed cylinder walls so that compression couldn't be achieved. Pull dip stick and smell. If smells like gas, try trick below to temporarily boost compression.

To eliminate compression as culprit, try squirting a little oil in cylinders through spark plug hole, then crank. If that works, I'd suggest oil change with 10w-30.

Let us know how it goes.
 
Question--

When you crank the engine, does the rotor turn?
 
Dipstick does smell like gas. When I crank the rotor is turning and I am getting spark. I tried switching coils from my YJ becuase another person I had looking at it thought the spark looked weak. Didn't even cough. I pulled off the air duct from the filter box and put my hand over the throttle body as someone else cranked and it was barely sucking my hand down. It felt like I could differentiate between the 2 cylinders with higher compression. I hit it with starting fluid and it did nothing but spin. When I looked into the manifold it was all wet with starting fluid. It's hardly pulling anything in, it seems.

Could it be something as simple as it was too cold the morning I tried to start it, and a sensor was over-limit and flooded the engine? When i tried to start it, it just spun. It never fired. I guess the only think left to do is spray some oil into the cylinders and re-check the compression. If that doesn't bring it back up, I guess this motor is toast.
 
You must log in or register to reply here.

Similar threads

O
0331 Strikes Again...?
Replies
11
Views
297
Ol Blue
O
G
Engine low on power
Replies
7
Views
2K
Gotitjr
G
O
2000 XJ Failed Colorado Emissions high CO
2
Replies
27
Views
2K
Ken M
K
4
Timing gear?
Replies
3
Views
100
4x4JeePmaNthINg
4
J
Running just fine then dies at idle on street
Replies
4
Views
2K
90xj06
9
Back
Top