I just bought this truck and am trying to get it all ironed out. When I bought it the owner was really frustrated with it. He had just had the Injector Pump rebuilt and it was running but not near as well as it was before. Then the alternator started overcharging, and he quit and sold it to me. My first thought about SLUGGISH acceleration was lift pump pressure. I put a gauge on it and found it to be in the neighborhood of 5-6psi. I couldn't get it below 3psi at WOT. Anyways I pulled the 1/8"NPT out of the intake manifold right below the heater grid and put a gauge in it. I find no boost at idle and when you rev it, it seems to suck the gauge down. WOT you might get a couple of positive PSI but something is obviously wrong. A quick look at the turbo and it us turning... all the clamps on the Innercooler and boots seem to be intact. I guess a leaking innercooler? It would seem like something HUGE to be loosing almost all the boost. Any pointers? What about my fuel pressures are they somewhere in the acceptable range? I think that this should be simple right? This 91.5 has no waste gate or anything of that sort that could be causing this...right? The engine just sounds rough and noisy, rather then smooth and crisp. Could this all be due to the boost? I think there might be still air getting into the fuel from a leak or something possibly too. Thanks a whole bunch.
-Greg Beaman

 

Don't worry, it's normal to see no boost at idle or throttling it. The engine/truck has to be under load to see boost. Take it for a spin, and check again. On the fuel pressure, on a stock setup, you want to see no less than 3psi under load. I would say your lift pump is within spec.

On the idle quality, that could be a bunch of things.

 

If the PO had the injection pump rebuilt I would take a look at the timing. It could have been installed incorrectly and may be way out in either direction. The timing marks on the case and pump may not be a good indicator if the gear got jumped a tooth in the install. It would be a good excuse to pull the front cover and do the KDP and check the timing marks while you're in there. There have been several threads on this topic lately, a search should turn something up.

Also air being pulled into the fuel line between the tank and the lift pump will cause retarded timing and rough running with lowered boost and raised EGTs. Plumb in a section of clear line just ahead of the lift pump and check for bubbles.

 

Thanks for the replies guys. I got to thinking and thought maybe the boost was right just sitting in the drive way. I will try to figure out a way to plumb the gauge into the cab so I can watch it while I drive. I went ahead and pulled the grill as the PO hit a deer and messed up the A/C condenser. I thought the innercooler might have a hole too. Good news, the innercooler looks great! Anyways, I think the rough idle is probably air. I am suspect of the new fuel filter probably installed at the same time as the injector pump. I think the WIF sensor and drain is leaking a bit. Maybe air is getting into it there. I think I will put a clear hose on the return line and put it in a bucket and inspect for bubbles. The clear hose before the lift pump would not catch bubbles picked up after the lift pump. As far as timing. The PO did the pump without removing the timing cover so I don't think the gear can jump a tooth without the cover removed. The timing looks funny too. The original marks are considerably off of where the pump is set now. The PO told me that he timed it with the timing pin to TDC and then installed the pump and bolted it up without moving the pump as set by the rebuilder. So it should be right. I went ahead and retarded it back to the original pump setting and the truck wouldn't even start. Put it back where it was and it cranked right up. I can't advance it much more without hitting the intake manifold. Could the KSB be hooked up incorrectly or the wrong one for the year? It is a 91.5 innercooled 2wd auto tranny. Pretty well stock. Thanks again and I will keep digging.
-Greg

 

I bet most of the trouble is timing. Add some and see how it runs.