Help!! FZJ80 dies going uphill

[William839]

Hey everyone I’m out here in Moab and am having issues on the trail, the fzj80 is performing flawlessly freeway speed , everything else but when climbing steep trails it dies out , and I’m not trying to crash it , I’m thinking fuel pump when fuel is splashing around , 97 fzj80 182k miles . Please help!

 

[Azca]

Check your air intake tube for cracks. The angles and torque to the engine may allow enough air past the MAFF to cause it to die. If original, they are hard and prone to cracking.

 

[William839]

I checked it and it’s good ,

 

[Jefe23]

I had a similar problem last summer. My '95 would try to stall when going up steep trails and when I hit bumps. Ended up being fusible link/battery/ground related and I haven't had an issue since. Is it sputtering before dying, or just cuts out?

 

[William839]

It just cuts outs , I’ll check the grounds.. really don’t know why that would cause it on an incline .. I’m going to try and recreate it

 

[Jefe23]

Other things to check/observe:

- Make sure you actually have fuel in the tank (just in case the gauge isn't reading properly)
- Do you still have all gauges working? Lights? Accessories?
- Does it fire back up right away after it dies?

 

[William839]

Yes , going to go back to town and fill up now , had 1/2 tank,
All gauges and lights work
And yes it fires right up right away,

 

[Jefe23]

Hmmmm... The only times I've had fuel-related issues it would sputter a bit first before dying.

Let us know what you find out! I would still check fusible link/grounds to see if anything is mildly loose or shorting out somewhere. Easy visual/physical check.

 

[William839]

Yes will check everything over well once I get to town , I just don’t want to be stranded in Moab ...

 

[William839]

My fuel gauge is staying stuck on 1/2 tank... starting to think it’s the fuel pump

 

[leonard_nemoy]

There is nothing coincidental about coincidences. If your gauge is stuck on 1/2 and your running out of gas on steep hills than I think you are on the right track. Most likely your issue is being caused by a fuel delivery problem.

Remember that when you are rock crawling and doing serious offroading in low range your truck will burn about twice as much gas as normal. 6 mpg vs 12 mpg.......

 

[William839]

It’s not necessarily running out of fuel , it’s not sputtering out , it’s a quick stall, just shuts off , and I’m not sure why the fuel gauge is staying on when the key is off .. I was able to drive back to town but still haven’t diagnosed it.

 

[William839]

I’m leaning towards fuel pump not being able to push enough fuel while on an incline I’m not sure what else it would be , everything else has checked out okay so far. I’m surprised more people haven’t had this issue?

 

[Jason926]

I’m leaning towards fuel pump not being able to push enough fuel while on an incline I’m not sure what else it would be , everything else has checked out okay so far. I’m surprised more people haven’t had this issue?

William839, Have you resolved your issue? I have the same symptoms. I have identified to this point that it is something electrical. I have checked entire fuel system and all checks out. Mine actually blew my fusible link on the trail, which I replaced hoping that was finally the source of the issue. I went up yesterday and all was good until I put it in low to climb an incline trail. It fell on it's face as soon as I gave it throttle. I'm starting to wonder about wiring harness short or a sensor issue in the transfer case.

 

[GeoRoss]

You could have a shorted wire in the fuel pump assembly. In the past this caused someone the occasional cutting out/blown fuse on washboards. I think it was Norcal Doug

 

[ChaseTruck]

William839, Have you resolved your issue? I have the same symptoms. I have identified to this point that it is something electrical. I have checked entire fuel system and all checks out. Mine actually blew my fusible link on the trail, which I replaced hoping that was finally the source of the issue. I went up yesterday and all was good until I put it in low to climb an incline trail. It fell on it's face as soon as I gave it throttle. I'm starting to wonder about wiring harness short or a sensor issue in the transfer case.

Worn motor mount, causing the engine to move as response to throttle input/torque in low range, and shorting out something in the harness passing the EGR tube?
Perhaps checking which one of the fusible links blew might help?

 

[Therealtotodile]

Sounds like wiring. I highly doubt your fuel pump cannot handle the extra pressure in the system involved of going up a hill.

I had some bad fuel pump relay wiring issues that I chased for like a year before I figured it out. It was not intermittent though. Also I second the wiring harness, near the EGR. That could be making contact if the loom is burned, when your on an incline it may touch the EGR metal pipe. Check all your fuel system fuses. EFI, etc. gluck!

 

[Jason926]

Thanks Guys. I'll chase these ideas and report back.

 

[HTX80]

I’m leaning towards fuel pump not being able to push enough fuel while on an incline I’m not sure what else it would be , everything else has checked out okay so far. I’m surprised more people haven’t had this issue?

Had this happen to me last weekend. Did about 90% of an uphill trail just cruising along, maybe 4/10 difficulty. Rock obstacle ahead was a little gnarly, but nothing a 3" lift on 33s shouldn't be able to handle. Pressed the gas to bump the rock a little and the Cruiser instantly stalled. And I mean instantly — no bogging or hesitation, just off. I rolled back down the hill about 10 feet with my tail between my legs wondering, “WTF just happened?”

So I let her sit while I evaluated things. The tranny was pretty hot at this point from the sustained uphill crawl, and I needed a snack/beverage with the lady anyway. Took about a 15-minute break and fired the Cruiser back up. Took a different line this time and went slow. Got farther up to the REAL obstacle. Found my line, put it in drive (4LO, center locked), crept up to the rock, and gave it a little gas to bump it. Instant stall again.

After digging through MUD and the fuel-pump circuit, my current suspect is the fuel-pump relay. The 80 uses a two-speed fuel-pump circuit: reduced pump voltage under lighter-load conditions and full pump voltage under higher-load conditions. My theory is that the relay contacts on the full-power circuit are becoming intermittent. Both stalls happened the instant I went from creeping to applying throttle against an obstacle. The truck otherwise runs fine and will pull hard up mountain passes without stalling, so I'm not convinced the fuel pump itself is weak. Mind you I had almost a full tank.

New OEM relay is coming in the next couple days. I'll swap it out, hit the trail again this weekend, and report back. I'm also going to tear into the old relay afterward and see if I can find any visible pitting, burning, corrosion, etc. If anyone has experienced the same instantaneous stall under sudden heavy load, I'd be interested to hear what you found.

 

[William839]

My solution was a 12 valve Cummins in my 80 lol