Jeep died when coming to stop. Cranks, but won't restart.

[dodgerammit]

Okay peeps. First issue I've had with my YJ. Driving to work a couple of days ago. Came to stop at the end of my road. Just as i did, the engine shut off.
WTF?
Tried restarting. It cranks. Like on the edge of starting, but won't. Fuel gauge shows 1/4 tank and has historically been very accurate.
Check engine light does illuminate on panel when key is turned.
I get out, swap relays around (both fuel pump and ASD relay get switched with non-important stuff). Still no worky.

Call wife and we go get a couple of gallons of fuel just in case gauge went bad or is sticking.
Put fuel in. Cycle key to prime a couple of time(I can hear the pump come on). Crank. Still doesn't start.
Take a cap full of fuel and splash down throttle body. It fires off, then dies in a couple of seconds.

Okay, so I have a fuel delivery issue.
Get it towed back to the house and switch to the old Grand Wagoneer for driving.
I am working a deeper diagnosis on it today.

Checked the schrader valve. Just a tiny hiss when pressed. Cranked engine. Same result immediately after. So pressure is either non-existent or quickly dropping.
Jumped the wiring in the relay box and allowed fuel pump to run. Fuel will stream from schrader, but not at a high rate.
Hooked my pressure gauge to it. Cranking shows no pressure. When fuel pump is hot wired, it also shows no pressure even after several seconds, though I can purge a stream of fuel out of the relief valve on the gauge.

So, it seems to be a fuel pressure issue. Whether it is occurring in tank or elsewhere. I don't have any noticeable leaks anywhere.

Any other testing tips to try to further narrow it down?
Anything else to check?
Would the fuel pressure regulator cause any of these issues?

Thanks!

 

[machoheadgames]

Could be regulator blocking flow too much or could be weak fuel pump.

 

[dodgerammit]

Could be regulator blocking flow too much or could be weak fuel pump.

Kind of where I'm at. Could also potentially be a split pickup tube. Just wanted to poll the audience.

So, no way to test regulator without just throwing a part at it?

 

[machoheadgames]

Kind of where I'm at. Could also potentially be a split pickup tube. Just wanted to poll the audience.

So, no way to test regulator without just throwing a part at it?

The pump picks up fuel itself through a sock and then pushes it up a 2” hose and then into a hardline in the fuel sender assembly. The hose could split I guess but never heard of that happening in anything except aftermarket fuel pump units. Any chance you installed one of those?

You can only really test to make sure the regulator is regulating fuel down to 31 psi at idle and 39 at high load (vacuum hose removed). Not much else you can check if pressure ends up below normal. It’s probably a weak pump of if aftermarket, split hose. But the regulator is a cheap option to try first, by throwing a part at it.

 

[dodgerammit]

The pump picks up fuel itself through a sock and then pushes it up a 2” hose and then into a hardline in the fuel sender assembly. The hose could split I guess but never heard of that happening in anything except aftermarket fuel pump units. Any chance you installed one of those?

You can only really test to make sure the regulator is regulating fuel down to 31 psi at idle and 39 at high load (vacuum hose removed). Not much else you can check if pressure ends up below normal. It’s probably a weak pump of if aftermarket, split hose. But the regulator is a cheap option to try first, by throwing a part at it.

Nothing aftermarket on my end. The PO mentioned he had the sending unit replaced within the previous year of me purchasing it, so it may be a cheapy parts store job.

I did watch a Jeep Solid channel video on YT that showed some tips. Dale is excellent on explaining all things YJ and 4.0. He showed how to pinch the return line to check regulator function (if stuck open). I tried that. Still no fuel pressure building even with fuel pump hot wired to on.

Tomorrow, I'll crawl under and make sure nothing looks pinched or split. There's a possibility of a rubber hose internally collapsing with age, so I'll possibly replace any old hoses I can easily access first before dropping the tank.

I did verify the coil is sparking just to double check, but my thoughts are if engine starts briefly when given a drink through throttle body, that narrows it to fuel delivery only.

 

[machoheadgames]

Nothing aftermarket on my end. The PO mentioned he had the sending unit replaced within the previous year of me purchasing it, so it may be a cheapy parts store job.

I did watch a Jeep Solid channel video on YT that showed some tips. Dale is excellent on explaining all things YJ and 4.0. He showed how to pinch the return line to check regulator function (if stuck open). I tried that. Still no fuel pressure building even with fuel pump hot wired to on.

Tomorrow, I'll crawl under and make sure nothing looks pinched or split. There's a possibility of a rubber hose internally collapsing with age, so I'll possibly replace any old hoses I can easily access first before dropping the tank.

I did verify the coil is sparking just to double check, but my thoughts are if engine starts briefly when given a drink through throttle body, that narrows it to fuel delivery only.

If the PO put in a typical aftermarket fuel pump assembly, there is a strong chance the 2” long hose on that connecting the pump to the outlet is split and not allowing pressure to build. Have to pull the tank and look at the hose for that one.



With the pressure not building even with pinching the return, I’d say you probably have a pump issue or the burst hose issue. If it’s the hose, then you need to get fuel pressure rated, submersible rated hose. Can find it on Amazon.

 

[dodgerammit]

If the PO put in a typical aftermarket fuel pump assembly, there is a strong chance the 2” long hose on that connecting the pump to the outlet is split and not allowing pressure to build. Have to pull the tank and look at the hose for that one.

View attachment 123502

With the pressure not building even with pinching the return, I’d say you probably have a pump issue or the burst hose issue. If it’s the hose, then you need to get fuel pressure rated, submersible rated hose. Can find it on Amazon.

Exactly what I'm being led to as well. That said, when doing the test for the regulator, I noted those engine side rubber line sections on the frame side are in sad shape. They could be collapsing internally. Either way, they need addressing now regardless. They will fail sooner than later.

Did find this decent how to on an upgraded replacement

Jegs has some 48" pre-made 6an lines for a bit less than what is shown in the video. I don't need the under hood gauge. I'm thinking of replacing those first, then drop the tank and replace the rubber lines and fuel pump.

 

[machoheadgames]

Exactly what I'm being led to as well. That said, when doing the test for the regulator, I noted those engine side rubber line sections on the frame side are in sad shape. They could be collapsing internally. Either way, they need addressing now regardless. They will fail sooner than later.

Did find this decent how to on an upgraded replacement

Jegs has some 48" pre-made 6an lines for a bit less than what is shown in the video. I don't need the under hood gauge. I'm thinking of replacing those first, then drop the tank and replace the rubber lines and fuel pump.

That is an option for those. @Plastic Fury got some from inline tube and had decent results. Probably the way I’d go if I needed the frame to engine connection. Thankfully all my fuel lines are in good shape.

 

[dodgerammit]

That is an option for those. @Plastic Fury got some from inline tube and had decent results. Probably the way I’d go if I needed the frame to engine connection. Thankfully all my fuel lines are in good shape.

I seen that write up. I just don't want to spend another $50 for the frame rail hard line as I just verified mine are decent. Just a tiny bit of very light external corrosion. Those rubber front lines are REALLY bad. It's a wonder they haven't already caused an issue.

I'm thinking new AN frame to engine lines (a bit overbuilt, but hey, it's for me) and some new rubber efi lines in the rear if that tank comes down.

Looking on Rockauto and they have differing options for the pumps as far as terminal connection styles. I'd imagine 15 and 20 gallon are the same pump. They're the same tank, just Chrysler tried to monopolize paying more for having a bit less plastic on the filler neck. Mine is a 20 gallon or has had the mod already done.

Any preferred pump brand if it comes to replacement?
Other sources or part numbers of pumps to check out?

Given the guy had the sender replaced, I'd like to just replace the pump itself if everything else looks fine. The gauge is spot on for accuracy.

Thanks again!

 

[machoheadgames]

I seen that write up. I just don't want to spend another $50 for the frame rail hard line as I just verified mine are decent. Just a tiny bit of very light external corrosion. Those rubber front lines are REALLY bad. It's a wonder they haven't already caused an issue.

I'm thinking new AN frame to engine lines (a bit overbuilt, but hey, it's for me) and some new rubber efi lines in the rear if that tank comes down.

Looking on Rockauto and they have differing options for the pumps as far as terminal connection styles. I'd imagine 15 and 20 gallon are the same pump. They're the same tank, just Chrysler tried to monopolize paying more for having a bit less plastic on the filler neck. Mine is a 20 gallon or has had the mod already done.

Any preferred pump brand if it comes to replacement?
Other sources or part numbers of pumps to check out?

Given the guy had the sender replaced, I'd like to just replace the pump itself if everything else looks fine. The gauge is spot on for accuracy.

Thanks again!

Understandable. Sucks having to buy the kit with the hard lines when lots of people don’t need those.

I don’t know much about pre-91, but from the research I’ve done, the best I’ve been able to determine is that from early 91 to somewhere around 93, the pumps were a brushed motor design and were larger, and supposedly they were Walbro brand. These are less common to find replacements for. They are the larger pump that have the studs and nuts for wires to connect to.



Supposedly some 93 and later had the smaller brushless motor, which was supposedly a Bosch (mine was and many others have said the same). It has a 2-wire connector on top.



The sending units are not cross compatible with the different pump styles because the pump sizes are different. So depending on what you find will really determine what you should buy.

My 94 had the brushless motor pump. It had Bosch written on it. I got another Bosch. Looked different but fit fine and worked fine for the little bit of time I’ve ran the engine. It did come with a hose as well, and I trust Bosch to give me a piece of hose that won’t burst.

Sending units from factory were 15 or 20 depending on what option you had. Most shipped as 15gal with the vent tube limiting capacity. Anything that came with advertised 20 gallon capacity would have the 20gal version sending unit. The funny thing is, it doesn’t make much difference either way. If you have the 15 gallon and trim the tube, you end up sitting on full for 75-100 miles. I know someone with the factory advertised 20 gallon on the YJ he used to have, and his still sat on full for a long time, like 75 or so miles. So apparently they are not that different, despite being two official different part numbers from Mopar.

Back to the topic of the earlier larger pump vs the smaller later pump: these can be interchangeable if you buy the sending unit that fits them. So if you wanted to swap from the earlier pump to later for better options, you’d just need the sending unit means to use the other pump. The overall height should be the same between the two because the tanks to my understanding are the same height.

 

[dodgerammit]

Understandable. Sucks having to buy the kit with the hard lines when lots of people don’t need those.

I don’t know much about pre-91, but from the research I’ve done, the best I’ve been able to determine is that from early 91 to somewhere around 93, the pumps were a brushed motor design and were larger, and supposedly they were Walbro brand. These are less common to find replacements for. They are the larger pump that have the studs and nuts for wires to connect to.

View attachment 123508

Supposedly some 93 and later had the smaller brushless motor, which was supposedly a Bosch (mine was and many others have said the same). It has a 2-wire connector on top.

View attachment 123509

The sending units are not cross compatible with the different pump styles because the pump sizes are different. So depending on what you find will really determine what you should buy.

My 94 had the brushless motor pump. It had Bosch written on it. I got another Bosch. Looked different but fit fine and worked fine for the little bit of time I’ve ran the engine. It did come with a hose as well, and I trust Bosch to give me a piece of hose that won’t burst.

Sending units from factory were 15 or 20 depending on what option you had. Most shipped as 15gal with the vent tube limiting capacity. Anything that came with advertised 20 gallon capacity would have the 20gal version sending unit. The funny thing is, it doesn’t make much difference either way. If you have the 15 gallon and trim the tube, you end up sitting on full for 75-100 miles. I know someone with the factory advertised 20 gallon on the YJ he used to have, and his still sat on full for a long time, like 75 or so miles. So apparently they are not that different, despite being two official different part numbers from Mopar.

Back to the topic of the earlier larger pump vs the smaller later pump: these can be interchangeable if you buy the sending unit that fits them. So if you wanted to swap from the earlier pump to later for better options, you’d just need the sending unit means to use the other pump. The overall height should be the same between the two because the tanks to my understanding are the same height.

Welp, definitely will have to drop the tank to make sure of what I have before ordering the pump (if it does come to that).

Thanks!

 

[Plastic Fury]

I seen that write up. I just don't want to spend another $50 for the frame rail hard line as I just verified mine are decent. Just a tiny bit of very light external corrosion. Those rubber front lines are REALLY bad. It's a wonder they haven't already caused an issue.

Yeah, that was kind of a bummer that I couldn't just purchase the plastic sections. So I have some brand new, extra lines laying in my garage now in case they are needed. My hard lines are in good shape but the rubber was in very bad shape and I just didn't want to risk burning it down after all the work I've put into it.

The first thing I did was drop the tank and replace everything. I purchased the fuel sender that came with the generic pump. I swapped that out for a Bosch fuel pump and then swapped out the 2" rubber line for some good fuel injection psi rated line while I had it out. Been running since April now and has been great.