Builds 1990 LJ78 in Montana (1 Viewer)

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Got out on the highway properly yesterday for the first time in years, which was cool, but something's still not quite right. After I get up to temp, I get a very rough idle when stopped in gear. smooths out in park and is fine with a little gas.

I know, air in the fuel lines. I've replaced all the rubber front to back on those lines twice over at this point (yes including the little line at the back for the return feed). I've been over them myriad times in the past looking for leaks and went over them again yesterday but didn't find anything, and don't think I'm going to. I need to get a bicycle pump and pressurize them front-to-back to make 200% sure.

I still haven't rebuilt the IP, so it could be that, honestly the prospect of tearing the injection pump out and getting it back in and timed right intimidates me, but I suppose while I was in there I could get the boost compensator apart and swap in a new diaphram. I'll search for some 13bt ip removal threads, grateful for suggestions.

The other thing that's tugging at the back of my mind is to check out the fuel tank. I've never had a look at the top of it. Nor have I ever seen the feed lines going down in there. I know there's a sludge filter at the bottom of those lines (77023-22040) maybe that's gummed up.. Is there an access port to the gas tank on the lj78?
 
Does the engine run ok in all other conditions? What is the rpm when stopped in gear? This might be a long shot but I was thinking if the kick down cable is out of adjustment it might have an effect on the idle speed in gear, and would also cause harsh shifts. Torque converter stall speed and idle speed adjustment might have something to do with it as well.

It is totally possible that the IP is getting tired too, and not putting out enough pressure for the new injectors at low rpm.
 
so. I'd estimate the idle in drive at about 800-1100. It is def more pronounced in gear, but when I have it in park and throttle it up to 1100 or so, the flutter in the idle reappears, and then smoothes out again around 1250
 
If it will exhibit the same symptoms in neutral or park I would definitely lean toward a fuel delivery issue, whether IP or air in fuel.
 
pradoblivious said:
so. I'd estimate the idle in drive at about 800-1100. It is def more pronounced in gear, but when I have it in park and throttle it up to 1100 or so, the flutter in the idle reappears, and then smoothes out again around 1250
Click to expand...
My 13B-T did the exact same thing. Rough idle around 800-1,000 RPM, smooth above. NEVER figured it out.
 
Got tires (fenders are off because I'm replacing the trim). Still wrestling with the oil pan leak that fipg has it glued up there pretty good.

1650766507968.png
 
The new shoes look good! What size did you go with?

I had to use one of these when I removed the 1HZ oil pan, I would never have gotten it off otherwise: Amazon product ASIN B07X6LRBFT
 
Just a quick update, things are progressing slowly as usual (or maybe regressing?). The truck is back at the engine-rebuild shop; long story short I pulled the oil-pan and got it resealed nice and tight, but still had oil seeping down the flywheel housing. Turns out the rear-main seal is leaking.

Rebuild shop is waiting on a new seal. The next and last big engine-bay item on my list was the IP, which I was going to pull and get rebuilt. Instead I think I'm going to have the rebuild shop pull it since it's in there anyway, and I'll get it sent out for a rebuild and have them button it back up and time it. Hopefully that will take care of the last of my nagging oil leaks and weird fuel-supply issues and I can move on to suspension.

I need knuckles, tie-rod ends, stabalizer, shocks and springs. The plan has been to do variable rate springs with a <3" lift. Before/meanwhile I'll need to sort out the exhaust. One of the many huge mistakes I've made with this truck was reworking the exhaust to exit out the back rather than where airheadnut had it (properly, out the side). When they did that, they wrapped the exhaust beneath the drive-shaft, thereby making it impossible to re-work the suspension.

By the way the truck is riding WAY smoother with those new tires on it. I'd had so many problems stacked up I told myself I'd do tires last, but I'm super-glad I impulsively took advantage of that sale at costco and got some ko2's.
 
Got the IP out and shipped today.

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So much space in there now! Going with MD Distributors for the rebuild, same guys who did my injectors, mostly because they're in texas so no shipping. I asked about the boost compensator, because I was wanting to get the diaphragm in there replaced -- I'm sure it hasn't been touched in 30 years. Anyway they said they'd replace it no-problemo so yay.

One of the things I noticed off the bat looking at the pump is that it appears to be the type designed for manual transmissions, as evidenced by this plate on the back, which should have a vaccume line for the tranny on autos. This truck is, of course an automatic, and a snowflake.. my 13bt and a440f came from different donors, and required some custom fab to mate. Evidently the bj74 that donated my motor was a manual.

1657921179118.png


So I'm curious how much of a problem that is. I've had low-rpm/idle fuel delivery problems since the swap, is this a possible culprit?


Here's some video of the space where the IP isn't just for fun.
 
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Finally got the pump back in and timed. I wasn't thrilled with how it came back slathered in spray enamel, but it actually looks pretty good in there now (since the engine rebuilders also spray-enameled the crap out of the block, it kinda matches)

1661046004906.png



I would say the truck is running great but every time I do, that ****ing rough idle starts up again and it starts spraying oil from some new and exciting location. SO FAR though, it's been running pretty well. I've had it out on the highway and up to around 800 egt and it came back down and idled fine. I parked and returned to not a pool of oil collecting beneath my engine-bay. Do I finally have this thing running right?! Can I finally get it back on the road?! Can I finally graduate from wtf engine internals to fun problems like suspension and intercooling and stupid tacticool lights??

can I... gasp finally go to a meetup?!
 
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pradoblivious said:
Finally got the pump back in and timed. I wasn't thrilled with how it came back slathered in spray enamel, but it actually looks pretty good in there now (since the engine rebuilders also spray-enameled the crap out of the block, it kinda matches)

View attachment 3092568


I would say the truck is running great but every time I do, that f***ing rough idle starts up again and it starts spraying oil from some new and exciting location. SO FAR though, it's been running pretty well. I've had it out on the highway and up to around 800 egt and it came back down and idled fine. I parked and returned to not a pool of oil collecting beneath my engine-bay. Do I finally have this thing running right?! Can I finally get it back on the road?! Can I finally graduate from wtf engine internals to fun problems like suspension and intercooling and stupid tacticool lights??

can I... gasp finally go to a meetup?!
Click to expand...
The ultimate “shake down” trip would be to East Tennessee in late September. 😁
 
That’s fantastic! Hopefully you’ve got it sorted now and can hit the road without worry. Really anxious to see it sometime.
 
Truck is STILL RUNNING GREAT. I've been steadily sacrificing sheep in my driveway and keeping it parked fully encircled by an uninterupted band of Himalayan salt to keep the evil spirits away. That and the 30 grand and 5 years Ive poured into this engine seems to have finally taken care of the myriad mechanical problems.

I'm feeling such an inarticulate optimism about things I went ahead and mounted the roof tent last night!

1661651110151.png


Before this latest 7 or 8 month-long stretch of oil leaks and rough-idle problems I'd gotten the AC compressor rebuilt, and back into the engine bay, but it's just been sitting there without any r134, so I decided to charge it up today and see where we are on that front. It's doing this thing where the clutch kicks on and kicks right back off again. It looks like this:



Doesn't that motor sound nice?! Anyway, on this truck the AC on switch is wired to a relay that runs both the compressor and an override circuit for my spal radiator fan. Placing my hand on the fan, I can feel it doing the same wa-bump wa-bump wa-bump on and off thing, so I think I have a bad pressure-sensor switch. Ran out of light before I could short the relay to test things out, but I should have some time to play with it tomorrow.
 
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