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Discussion Starter · #1 ·
I have a 1991 wrangler with the 4.0. Recently finished up everything with installing a np435 and took it out for a drive. Everything was fine for the first couple miles, went to homedepot which is about 4 miles away then left to go to dinner with my friend. When I got on the highway and tried to accelerate the jeep hit a wall at around 2500 rpm and would bog down then backfire. This proceeded so I pulled off the road and grounded out my positive terminal thinking maybe I threw off my o2 and it needed to be reset since at the same time I installed a tj downpipe. I didn't notice a check engine light so I didn't think to check for codes before doing this.

Started the jeep back up and the same thing happened, I was able to limp it to the next exit 1/2 mile away while the problem continually got worse to the point of any throttle and it would bog out. Finally it died and left me on the side of the road. Couldn't get it to start at all. I got my buddy to tow me home and then when checking the distributor I noticed the seal had gone and there was oil inside. Changed out the distributor and timed it per the instructions below yet it still won't start. Cranks for days yet no start.

It has good fuel pressure at the rail and as of this morning I changed out the cps yet no change. I posted pics of how i currently have it timed, I tried notches all around so advanced and retarded but didn't have any change. The bogging seems like either a map or tps to me yet neither of those should cause a no start situation. When I pulled a plug and grounded it I could see spark and there is definitely fuel in the cylinders, they reek of it when I pulled plugs to run compression. Compression was within 10% on all cylinders. Any ideas?
 

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I would start with new plugs... I have seen plugs go bad because of fuel wetting (reeks of fuel).... after that IF it starts......or tries to, possibly disconnect new exhaust (possible plugging) and see what happens.

If no start (or try) after new plugs, check plug wires to ENSURE in right order an dposition.
 

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Discussion Starter · #3 ·
I was planning on replacing plugs but I doubt that's my issue, I'd be surprised if all 6 somehow went bad at the same time
 

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Check the crank sensor, you may have damaged it or it's connector when reinstalling the transmission. Also, is the check engine light coming on when you first turn the key on like it's supposed to? If you are not getting that light when you first turn the key on, the computer is likely bad.
 

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Discussion Starter · #5 ·
Replaced the cps this morning but that didn't change anything. Light comes on and I can run codes but since I pulled the battery they were all cleared.
 

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Ok, have you checked all your fuses? Both fuse blocks, inside the cab and under the hood? By check I mean seeing if they are blown and removing and reseating them in case one has a bad or corroded connection.
 

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To me it sounds like your running rich for whatever reason. The fuel pressure at the rail was it high? Could your fuel pressure regulator be going bad? Is there a fuel return line? Could it be pinched or clogged?
 

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I see you replaced the distributor, don't take this as an insult, but double check that the distributor is not installed 180 degrees out. The last 4.0 I rebuilt, I stabbed the distributor in after midnight, after turning wrenches all day on it. Well, of course it failed to start and as tired as I was I said, screw it, I'll look at it tomorrow. After a good night's sleep and some coffee, the first thing I checked was the firing order and found I had stabbed it wrong; stabbed it right and it cranked right up.
 

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Discussion Starter · #9 ·
Checked all fuses and they are good. I have another fuel pressure regulator I can try. I'll also make sure distributor isn't 180 out, I installed it around midnight after wrenching for 3 days straight so installation error is always a possibility
 

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How it was acting is exactly what mine did with a loose fuel pump ground did you happen to have any kind of issue with your fuel guage because the sender and pump share a ground and its a common problem
 

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Discussion Starter · #11 ·
I can hear the fuel pump prime when I turn the key to the on position
 

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Mine would stop running the same way yours did then fire right up after it was towed to the shop, id check the pressure in the rail as well as for air bubbles when you do so
 

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Discussion Starter · #13 ·
Got it running, it turned out to be my engine ground. I got spark but it was weak, cleaned the ground with brake cleaner and a brush and she started right up. Still confused as to why that had problems after an unrelated issue but oh well. It was covered in trail crap and oil gunk
 

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Sometimes that's how things go. You find other problems along the way to the major issue. Frustrating for sure.
 

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Discussion Starter · #15 ·
So that was an unrelated issue, must have messed with the ground when I was initially checking things. Drove the jeep fine for the rest of that day then the next day the problem resurfaced. Exact same symptoms and same progression though this time I made it to a parking lot where I disconnected 02, checked all wires, unplugged coolant temp, cleaned intake, etc all with no change. Also read my codes, only one was 51, essentially it was running lean.

Got her towed home and checked the fuel pressure again, this time it was 0. Last time I checked it when the vehicle wasn't running so only after the pump initially primed. Turned the key and still heard the pump prime so I figured it must be a block. Pulled the line going into the fuel filter and still no fuel. Got a buddy to help me drop the fuel tank and there is my issue. The mesh filter before the fuel can enter the fuel pump was dark and clogged. When I pulled the pump the fuel inside didn't even drain out, the only spot it could was on top.

My theory is that when I had more fuel it was fine but when I got low the fuel level wasn't high enough to hit the clear spot on the filter and it couldn't be pulled though the bottom and sides; essentially I ran out of fuel since the pump couldn't pick it up. Installed the fuel pump without the filter and she started right up. Ran pressure, 39 after prime and 32 at idle so perfect. Filter was $3.95 at autozone and explains every problem I had.
 

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Discussion Starter · #17 ·
Did you check your fuel pump ground im telling you it is more than likely the problem and fixing it is free
It's fixed now, it wasn't the ground it was the fuel pump strainer. I have my fuel pump ground wired to a switch, if it isn't grounded the pump won't prime and the fuel gauge shows more than full
 
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