bumblebeer
Registered User
Well, much to my wife's dismay, I've bought another idi.
This one is a 92 250 4x4 extended cab zf5 with a really nice cm flatbed. 4.11 gears and 285/75r16s on aftermarket bullet holes. Painted in the always timeless Rust-oleum flat black. Not a clean truck, but exactly what I was looking for. I'll post some pictures later.
It was used on a cattle operation to haul a feeder back and forth between the barn and field. Ran every day, but short trips. Supposedly has a rebuilt engine in it with roughly 100k on it, but I'd take that with a huge grain of salt. The injection pump has been rebuilt, and the story roughly matches the milage displayed. Although the psom had a blown fuse when I bought it so who knows? The PO seems like he kept up oil changes and fuel filters and that's about it...
I've been steadily going through it.
The wiring is atrocious. Some due to rodents some due to the PO. Completely rewired all the lights, and I've been steadily rewiring in sensors. It was missing pretty much everything but power to the fuel shut off solenoid, oil pressure, temperature, and tach.
Changed all the fluids. PS pump had ATF, trans had gear oil, don't think the rear diff had ever been changed. I've got some AutoRX and Delo in the crankcase, and synthetic everywhere else.
Smoked like a freight train when cold. Turned out to be a bad glow plug. Went ahead and replaced them all. Was very happy to see they were motorcraft. No more smoke after that.
The transmission makes a weird noise when getting started in first or reverse, but I think it's got a SMF so that'd make sense. But other than that it was running really good. And getting great fuel mileage. I was touching 20mpg if i took it easy.
Figured I'd pull the injectors and pop test them just to confirm they were good. And that's when things went downhill...
They were not good. Like at all. Leaky but no drip. Atomization was terrible, and they didn't really have much of a pop, and no chatter at all. Just kinda pissed out when the pressure was high enough and then stopped when it wasn't. And that pressure was on the low side for all of them. Around 1600.
So I decided to rebuild them. And that really sucked. A lot. Like one of those old hoovers with the bag they use in schools and hotel rooms. I understand why good injectors are $400+ Anyway... after spending way more time on it than I wanted to, I got it done. 8 injectors popping at 1850 (+/-)50 with good spray pattern and nice chatter.
So I got them installed. And of course the next step was to time it with the newly rebuilt injectors. Got the DTI meter hooked up and went to 2000 to get a baseline, and holy hell! It was running at 11.5 btdc. I can't even imagine what it was before with the lower pop pressure injectors. So I set it down to a reasonable 9.5.
Next morning, it was back to smoking like a freight train at startup. It smoked a bit after warming up as well, but it was very whispy. And fuel economy was suffering. Down to about 16. Spent a while running down various rabbit holes, air intrusion, leak back over night, bad glow plugs or controller, etc. Finally decided to do a comp test.
I don't have the results in front of me, but 5 of 8 cylinders were 425-475. The other three were under 400 with the worst being 350. Ok, not great. But not the worst either. Least they all had some compression.
So I buttoned it back up and got it running. Cracked the injector on the lowest compression cylinder, #7 btw, and after a second or two, no smoke. Changed injectors with another cylinder just to be sure, and yep, problem stayed with the cylinder even with a different injector. Opened it back up, put a little 15w-40 down the glow plug hole and let it sit a half hour or so. Turned it over for a few seconds, then did another compression test. Got 425. So sounds like bad rings and or a grooved cylinder. I'm assuming due to washdown from the previously bad injectors.
So now I come to the actual reason for today's post, and thank you kind soul if you've stuck with me this far. I monkeyed around with the timing this evening, and I found that if I bump it up to 11 which is technically within factory spec of 8.5 btdc (+/-) 2.5 Although it seems an argument could be made that with ulsd the base of 8.5 should be bumped up to 9.5. Anyway... The smoke nearly disappeared! Just barely a hint of greyish smoke. Of course the engine was already warm, but it was still a noticable improvement over the more retarded timing.
I know the solution here is to replace the rings and possibly sleeve the cylinders, or pull the other 7.3 I have and swap it out. But I don't have room for any of that at the moment. I've got a couple other projects taking up space in the shop that will have to be finished first. Assuming I'm planning to pull the engine at some point anyway, what would I be risking by advancing the timing and continuing to run it as is now until I'm able to get to fixing it properly? Would probably have to wait until fall.
This one is a 92 250 4x4 extended cab zf5 with a really nice cm flatbed. 4.11 gears and 285/75r16s on aftermarket bullet holes. Painted in the always timeless Rust-oleum flat black. Not a clean truck, but exactly what I was looking for. I'll post some pictures later.
It was used on a cattle operation to haul a feeder back and forth between the barn and field. Ran every day, but short trips. Supposedly has a rebuilt engine in it with roughly 100k on it, but I'd take that with a huge grain of salt. The injection pump has been rebuilt, and the story roughly matches the milage displayed. Although the psom had a blown fuse when I bought it so who knows? The PO seems like he kept up oil changes and fuel filters and that's about it...
I've been steadily going through it.
The wiring is atrocious. Some due to rodents some due to the PO. Completely rewired all the lights, and I've been steadily rewiring in sensors. It was missing pretty much everything but power to the fuel shut off solenoid, oil pressure, temperature, and tach.
Changed all the fluids. PS pump had ATF, trans had gear oil, don't think the rear diff had ever been changed. I've got some AutoRX and Delo in the crankcase, and synthetic everywhere else.
Smoked like a freight train when cold. Turned out to be a bad glow plug. Went ahead and replaced them all. Was very happy to see they were motorcraft. No more smoke after that.
The transmission makes a weird noise when getting started in first or reverse, but I think it's got a SMF so that'd make sense. But other than that it was running really good. And getting great fuel mileage. I was touching 20mpg if i took it easy.
Figured I'd pull the injectors and pop test them just to confirm they were good. And that's when things went downhill...
They were not good. Like at all. Leaky but no drip. Atomization was terrible, and they didn't really have much of a pop, and no chatter at all. Just kinda pissed out when the pressure was high enough and then stopped when it wasn't. And that pressure was on the low side for all of them. Around 1600.
So I decided to rebuild them. And that really sucked. A lot. Like one of those old hoovers with the bag they use in schools and hotel rooms. I understand why good injectors are $400+ Anyway... after spending way more time on it than I wanted to, I got it done. 8 injectors popping at 1850 (+/-)50 with good spray pattern and nice chatter.
So I got them installed. And of course the next step was to time it with the newly rebuilt injectors. Got the DTI meter hooked up and went to 2000 to get a baseline, and holy hell! It was running at 11.5 btdc. I can't even imagine what it was before with the lower pop pressure injectors. So I set it down to a reasonable 9.5.
Next morning, it was back to smoking like a freight train at startup. It smoked a bit after warming up as well, but it was very whispy. And fuel economy was suffering. Down to about 16. Spent a while running down various rabbit holes, air intrusion, leak back over night, bad glow plugs or controller, etc. Finally decided to do a comp test.
I don't have the results in front of me, but 5 of 8 cylinders were 425-475. The other three were under 400 with the worst being 350. Ok, not great. But not the worst either. Least they all had some compression.
So I buttoned it back up and got it running. Cracked the injector on the lowest compression cylinder, #7 btw, and after a second or two, no smoke. Changed injectors with another cylinder just to be sure, and yep, problem stayed with the cylinder even with a different injector. Opened it back up, put a little 15w-40 down the glow plug hole and let it sit a half hour or so. Turned it over for a few seconds, then did another compression test. Got 425. So sounds like bad rings and or a grooved cylinder. I'm assuming due to washdown from the previously bad injectors.
So now I come to the actual reason for today's post, and thank you kind soul if you've stuck with me this far. I monkeyed around with the timing this evening, and I found that if I bump it up to 11 which is technically within factory spec of 8.5 btdc (+/-) 2.5 Although it seems an argument could be made that with ulsd the base of 8.5 should be bumped up to 9.5. Anyway... The smoke nearly disappeared! Just barely a hint of greyish smoke. Of course the engine was already warm, but it was still a noticable improvement over the more retarded timing.
I know the solution here is to replace the rings and possibly sleeve the cylinders, or pull the other 7.3 I have and swap it out. But I don't have room for any of that at the moment. I've got a couple other projects taking up space in the shop that will have to be finished first. Assuming I'm planning to pull the engine at some point anyway, what would I be risking by advancing the timing and continuing to run it as is now until I'm able to get to fixing it properly? Would probably have to wait until fall.
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