hot_runner58

Just picked up this 1997 12valve. going through it, and it has a brand new turbo, but will only push 10psi wot. doesn't start to make boost til 1600rpm. Runs 5psi boost at about 2100 rpm going down the road about 55mph.
It has no line to the waste gate, and they built an angle iron bracket with a bolt to hold the waste gate.

Turbo is IMT p/n dxw300-0008. I can't find anything about this turbo on the web, so I'm at a loss.

The AFC housing has flat head screwdriver bolts and washers on it, so I'm assuming the last owner did something in there. Did they screw it up??


**** update: talked to the old owner finally. He CLAIMS it was pushing 20-25psi the last time he drove it about 4 weeks ago.

oliver foster

Ripped lower intercooler boots by the inner fenders are pretty common on 2nd gens....

hot_runner58

I did a quick run over with my hand today, but only at idle. I better pull inner fender tomorrow and check it good.

oliver foster

You should be able to check them out for cuts without puling the fenders.
I just threw that out there as I have seen a lot of cut lower intercooler boots on 2nd gens over the years.

hot_runner58

Hopefully it will be that simple. I have to test the grid heater parts also. appears not to be working.

I got this truck for $2k because they thought the trans was out. Only problem was there was a pin hole in the pressure line and it leaked all the fluid out. So a new line, and trans flush w/filter and truck is pretty good except for a few small problems. Just hope I don't loose my sanity trying to chase small problems.

hot_runner58

Some more info: removed AFC. Plate was already slid forward and is the stock plate. The AFC housing was slid also. Star screw was turned all the way forward. I turned it back towards the cab several rotations, as I had read in another thread about a guy loosing boost with the screw too far out. That hasn't seemed to make a difference. Triple checked boots for leaks and can't find any. My big question is this: When I took the housing off, the "foot" was cut at an angle. By that I mean that the portion that points back towards the cab was angled. It's angled from side to side, not up and down. Imagine when in the engine it is slanted from the engine out towards the driver's door. Is it supposed to be like this?

hot_runner58

answering my own question here, but the foot is slanted. I found a few search threads about it. My next thought for the night: I'm going to plug the relief line tomorrow and try that. I did notice today that while re-priming the fuel filter after changing it that I could here the fuel bypassing, the pump never got hard.

oliver foster

There is an Over Flow Valve [OFV] in the return line that allows the fuel to return to the tank. They do age and the pressure that they hold does drop a bit. You can try replacing it, but I don't think that is your problem.

If you do pinch off the return rubber fuel line gently as a test, DO NOT keep it like that for anything other than a short test. The pump needs a supply of fresh cool fuel circulating through it for cooling. I have used a small vise grip to gently pinch the return line shut before to test fuel delivery issues on my trucks.

gorms

Check for boost leaks from turbo outlet to intake horn, intercooler can leak.
Check fuel pressure.
Check that AFC reference line is seeing actual boost and is not leaking. This is configured differently from year to year.

hot_runner58

So I tested for leaks, found a bolt in the intake plenum that holds the fuel lines down to be missing. Replaced that, couldn't find any more leaks. I need to test fuel pressure still, I am thinking it is a fueling problem. I did plumb a boost gauge into the intake horn and shows 17psi, and the gauge in the pillar is showing 11. But the gauge in the pillar is plumbed into the intake runner, but I don't think there is that much psi difference just going through the grid heater, so guessing the pillar gauge is shot.

I am worried about it taking so long to spool since it seems to have the stock governor springs and defueling at about 2200-2300. Doesn't leave much room to help the engine if I'm pulling a load. I know with that bigger turbo your moving more air, but I don't imagine it's moving that much extra.

How do I test the reference line seeing actual boost? I saw a thread on removing the afc and covering the hole and seeing if the truck ran a lot better. If so it meant the rubber on the back of the afc was leaking.

gorms

A close visual inspection on the line feeding the afc and where it connects to the intake manifold, its usually a plastic line with push lock fittings. Some years it "T"s off to feed wastegate line, make sure that doesn't leak or the afc will see a delayed or no reference.

You can remove afc and hook up shop air or a hand pump to test the diaphragm, no more than 40psi and watch the foot move. Should start to move around 4-6 psi and full travel by 17-20 psi if stock. While you're there you could set full travel for your full boost to clean up any smoke.

At the end of the day it may be a good idea to check the angle iron bracket to make sure the gate really is shut.