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-   -   Truck running rough and not driveable - help (http://www.risingsun4x4club.org/forum2/showthread.php?t=3102)

subzali 02-18-2007 01:20 AM

Truck running rough and not driveable - help
Driving home tonight. Truck has sat for about a week or two, ran fine a month ago when I was driving it everyday, and has run fine since even though it's been more or less sitting, but it's been started and run for a few minutes every weekend for the past couple of weeks. Fuel was basically empty.

Tonight I filled it up to about 3/4 and was driving up to Golden (~50 minutes). Running on the interstate at about 60-70 that whole time, running great, making great power, smooth, then I got onto I-70 West from I-25 north. I had gone through just under a 1/4 tank of the new gas (85 octance, which it has run for 2 years with no problem). There is a small hill there, and I immediately noticed a lack of power, but it wasn't just the hill, there was something not running right with the engine, it was immediately dogging down to 50 on just a slight incline. Once I got on the flat I couldn't get it to pull above 60mph and then it started hesitating like the brakes were sticking intermittently or something. Then on a corner the engine quit for a split second (my Lockright made the truck lurch pretty suddenly) and then starting running again, but getting rougher. So I was getting close to Wadsworth and it was running pretty rough with no power, so I shut the engine off and coasted to a stop. Tried to get it started again, didn't want to start so I waited for a minute and then it started again, but I have to keep it revved up to keep it running and it runs really rough. Made it to Treeroot's house, and made some diagnostics.

This is what I've checked - 10/76 FJ40 with stock engine etc.:
-No oil leaks anywhere (oil pressure is good)
-All vacuum hoses that had previously been hooked up are still hooked up (checked multiple times)
-All wiring at the carb (I think) that used to be there (though not complete I don't think, the truck ran fine with/without it) is/was still there, as far as I could tell. Don't know what most of it does or would do if it was hooked up...
-Dizzy looked fine on inside (electronic '78)
-Glass bowl showed good level of fuel in carb even while running (not starved before it reaches the carb)
-Primary barrel has plenty of fuel being squirted into it (not fine mist, kinda "droplety," but that shouldn't make the truck run rough should it?)
-Secondary barrel doesn't look like it's ever been used, but I don't think that has anything to do with this. That's a separate issue.
-Plug wires all tight. Pulled them one by one with the engine running, the only ones that made any difference to the way the engine ran (engine speed slowed down) were #3 and #4 (made engine drop in rpm). Unplugging 1,2,5 and 6 (one at a time) didn't change the way the engine ran at all. What? :confused:
-All plug wires arcing to plugs, so the plugs are getting voltage and should be firing.

Yeah so don't know what else to check. Thoughts on what might be wrong?
-Something jammed in a jet in the carb, or fuel not being misted causing problems.
-Bad fuel? Should I get fuel additive and see if that helps?
-It happened pretty suddenly, but I couldn't find anything that changed. So either electrical or fuel related I think. But what changed?:confused:

This is my only vehicle until my red truck gets a new timing chain tensioner, so the sooner I can get this fixed the better.

corsair23 02-18-2007 01:43 AM

I'm a lousy mechanic but I don't see any mention of checking the fuel filter?

Maybe just coincidence but with a near empty tank and then fill maybe some gunk on the bottom of the tank got stirred up and migrated to the fuel pick up and is blocking fuel to the engine?

Like I said though, I'm a pretty lousy mechanic especially when it comes to diagnosing problems.

One more thought...How is your battery? On my 40 I was getting some 'surging' in 4th gear like the engine wanted to die and wouldn't put out full power. Dinked with the carb and all sorts of stuff but couldn't figure it out. Later (I don't drive it much) I replaced the battery 'cuz it was dead and I've haven't noticed the surging or lack of power since....

Oh, and if you get in a bind and need a vehicle for a few days, my 40 could certainly benefit being driven :)

subzali 02-18-2007 02:03 AM

Thanks Jeff! I might have to take you up on your offer if I don't get this figured out! Anyway I don't think it's fuel filter because the glass bowl shows plenty of fuel, even when running, and fuel comes out into the carb pretty good. I think I'm going to pull/maybe replace it tomorrow anyway, but not sure it's causing the problem.

Having a hard time understanding why the battery would have anything to do with this? Engine runs off alternator once it gets started...I guess I can pull the battery and see if anything changes...and maybe put a battery from a friend of mine in there...truck is still at Treeroot's house and if anybody wants to go mess with it you're welcome...I have the keys though.

nuclearlemon 02-18-2007 08:16 AM

i would guess bad fuel. put a couple of things of gas alcohol in there and run it a bit. it will take a little while for it to work. i don't think you've got points, but check for that also.

subzali 02-18-2007 08:23 AM

yeah, fully electronic ignition so no points.

Uncle Ben 02-18-2007 09:59 AM

It sounds like either bad gas or overly rich. How much black soot in in the tail pipe? :confused:

subzali 02-18-2007 11:42 AM

There's not too much...but there was unburnt fuel coming out I did notice when I came up to a stop sign driving it home from Mike's. Couldn't go above 40, still running really rough...I'm thinking maybe now it's related to vacuum advance? :confused:

-I noticed the PCV was very erratic...but I just recently cleaned it out and it was fine.
-Still need to check the fuel filter...but if I can see fuel in the glass then that should be fine right?
-I put HEET into the gas tank and have run if for about 20 minutes since then; it's been in the tank almost an hour now, no change.
-It was spitting fuel back up the carb last night when it was about ready to die, then today it actually backfired and I saw exhaust coming out of the carb once. I have the valve cover off to check the valve springs, but now I'm thinking it has to do with vacuum advance or something on the fully electronic dizzy? I don't know how to check timing or vacuum or anything, any tips?

wesintl 02-18-2007 11:45 AM

I would drain the tank and refill. There is nothing like bad gas to make you think it's something else. I've had it a couple times and it is truely a PITA.

subzali 02-18-2007 11:58 AM

Okay, valve on the firewall side of cylinder 5 has like 1/8" or 5/32" of play (engine is warm). Is that bad? Others are tight, a couple have a small amount of play. Even if this isn't related, I'm assuming it's bad?

subzali 02-18-2007 12:25 PM

1 Attachment(s)
So if cylinder is not at TDC then I guess valve clearances don't really mean much right? Either way, the intake valves (I think) on 5 and 6 have a lot of play.

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