Hey guys, I found this site today at work looking to fix one of the hauling trucks. It's a 91, intercooled, and gutless. No tach, but for probably the last 400rpm before you hit the governed rpm, it makes a little power, almost what it should be making, and you can start to hear the turbo. No smoke at any point, and you can't hear the turbo if you rev it in neutral.
I checked out "the sticky", and adjusted the compensator two turns, but it had obviously been tampered with before, the cap was pryed all out of shape. This made a decent difference in the low end power, it gives off just a hint of smoke in first and second, but it's not above what a stock truck can do.
My real concern, though, is that the torx head on the compensator is about a full thread below the top of the jam nut, it was just a hair over flush when i started. Does this sound like it's been adjusted before, or do they usually wind up about in this spot?

 

That's been turned way in already. Check the line between the AFC cover and the manifold. If it's broken or leaking the pump will not add fuel when the boost comes up. Also check the throttle linkage for full travel.

Put that smoke screw back where you found it, all it does is make smoke. The extra fuel it adds at low boost will make EGT's very toasty under load with that laggy 21 cm turbine housing.

Honestly, the truck sounds about normal for a stock '91 or '92. Those things were real dogs from the factory.

 

I think you will like this site. If you had a boost gauge we may be able to check other possible problems.
some times these older trucks get boost leaks in the intercooler or boots, this will cause low power and no smoke in the stock settings.
Theres lots more adjustments to do but I would also suggest installing a pyrometer before too many more mods.
Like wannadiesel said, check your throttle linkage, you can lose lots of power there. The linkage gets worn and you stop getting full throttle.
Good luck

 

A smaller exhaust housing would make a noticable difference.

 

Don't forget to check both your air filter,and fuel filter. My 93 started acting up last week,mainly less power than usuall. I changed the fuel filter,and it runs fine again.From the looks of it I think it still had the factory installed filter in it

 

Wow, quick responses too. I like that.
Forgive me, but i should have posted all that I have done so far-
New air and fuel filters
changed the oil (it was needing it, previous mechanic did no maintenance)
checked i/c and tubes/bellows, no leaks, cracks, or fatigue noticed
I did look at the throttle linkage, I had one of the office girls hold the pedal down, and the pump linkage does go all the way to the stop screw. The screw still has it's factory cap on it, doesn't look like it was molested.
Like I said, previously there was no smoke whatsoever, not even starting up with your foot on it. It had no power -at all- until about 2200-2400rpm, then you started hearing the turbo. Unfortunetely, that dead spot is a killer. Starting out on any kind of an upward slope, I could just make the 1-2 shift, max it out at about 20mph, if I went for third, it would bog down, and i would wind up going all the way back down to first. Empty, the truck couldn't break a tire loose from a first gear roll on gravel, now my 69 F-250 with 400k on a 300-6 and c4 auto can do that without flinching. To say it was weak is an understatement.
I checked the hard line from the head to the compensator, it's fine. My only other thought was the possibility that the diaphragm in there is torn, and maybe turning that screw in just made a mechanical connection, enough to give it a little power in the lower rpm ranges.
If I pull that cover off, nothing's going to fall out, right? I mean, there isn't a spring in there that's going to launch itself onto the shop roof once I take the screws out, right? I just need to maintain some level of availability on this truck, I can't take it down for more than a day right now.

 

You can pull that cover with 4 screws on it. There is a spring but it isnt strong. That is where you can pull the diaphram and look at it. you can also turn that eccentric cone to allow the pin to ride on the lowest part of the taper. You can read about it in the tech section.
There is also the star wheel which can be adjusted down for quicker fueling or up to slow it down. The fueling is related to boost on that adjustment.

 

the 2-3 shift on the getrag is a killer, especially with a heavy load! how much are you pulling when this happens? you will get tons of opinions here but let me add my .02

first, some pumps don't respond to the truning of screws as well as others, don't assume something is majorly wrong.

Ok to start out, the importance of an Exhaust Gas Temperature (egt) gauge is HUGE. don't want to be melting any pistons. As far as lack of power tils 2200 rpm the exaust housing on your truck is so huge it takes forever to spool the turbo. since it is a 5 speed you loose everything you worked to build at about 2700, not a huge power band to say the least. one of the cheapest mods is the "3200 spring" can be found for around $20 and make it such that you can rev each gear out to 3200 before it defuels. this will also help a ton with the 2-3 shift that you hate so much right now. you'll get to rev 2nd out far enough that 3rd isn't so bogged down when you get into it. this mod also requires no fueling change therefor (correct me if i am wrong guys) is safe to do without a pyro. this i would say should be your #1 mod. after that i would look into a smaller turbine houseing. hope this helps.

 

more so than the 93's?

 

when you get the afc cover off you may find that some one has turned the star wheel all the way up trying to control smoke for a smoke test or some one just turned it the wrong way.
it would make sence with you large lag, if the boost had to come way up, before the afc spring would ad adisinal fueling!

 

While you have the fuel cone and diaphragm out, look down the hole that the fuel cone sits in and push the throttle lever to full power. You should see a little pin pop out the front side of the hole. If not, use penetrating lube and a small screwdriver to work it free. You will have to push it back in before you put the fuel cone back.

Miciahfied hit the nail on the head, but I would add a pyro even with a 3200 RPM spring. It's easy to "accidently" put the main fuel screw back a little tighter.

Jeepsuck, the '91 intercooleds and the '92's had the 21 cm turbine housing and they run pretty much like 4X4_Welder describes when stock. They respond well to tuning - my motor is out of a '92.

 

then i guess that wouldnt apply to me with my 12cm wastegated bank$ unit,

 

I thout that the Banks housing was a 14cm/wastegate housing?

 

i kinda thought that myself while i was posting but i am totally ignant. i didnt buy it so i only know what i've read here. i think you may be right though.

 

Update-
I pulled the housing apart, the cone in there was at the minimum fuel setting, so I put that at about 90º, and turned the screw back out. It's still a dog off the line, gives a little puff when you first start it, but no smoke under a load. Standard load for this truck is a 5,000lb or 6,000lb mini excavator, 4,500lb loader or Kubota, on a 2k trailer. Even towing the 3,000lb mini-x, this thing wouldn't go from second to third on a hill. Now, towing the 5k is about how it ran towing the 3k. Not powerful, but a little safer on the road.
I can't get my boss to shell out the $$ for a pyrometer and boost gauge, I did tell the drivers not to lug the engine to help keep it from overheating though.
Changing air and fuel filters didn't make any difference.
I do need to change the tranny fluid, though. Did I read on here somewhere to use 15w40 diesel oil in there, or should I run a synthetic gear oil?