Engine/Transmission (1994 - 1998) Low Boost, Low Power, & High EGTs After Mods

[MMcCallie]

I'm stumped. I pulled off the AFC and went for a test drive but only got a little more smoke and power. EGTs still quickly reach near 1,600 degrees and boost just 33 psi. So I think that rules out a problem with the AFC. Before I had my head replaced and ported with a custom intake manifold and elbow my truck had dyno'd well over 500 hp reaching over 47 psi boost, cleaning up much of the smoke and EGTs near 1,500. I've solved oil and boost leaks but still can't get the truck to run any better.



I've adjusted the 100 plate, Star Wheel, and AFC fully forward. Pre-boost fuel screw is also fairly far forward, I backed it out after putting it further forward because it was hazing heavily at idle. The mechanic who did the work had made some major mistakes and I don't know what else he did for tuning, it was over my head. On one test drive we made 42 psi and 1,400 EGTs but power felt weak with no smoke so he made adjustments for more power but never got that much back, not even 32 psi and he said he wasn't sure what the problem was.



I now have lots of smoke, the mid range cleans up a little better but is still heavy. Mid range power is pretty strong. When it gets to 30 psi it feels as though the engine is being choked, no more boost but tons of smoke. The wastegate line on the turbo is pinched so it should be capable of much more boost to clean up the smoke and make more power. I've tried turning everything back and had very little power, 19 psi and 1,100 degrees, still very noticeable smoke. Truck runs much better with everything forward.



I've checked the governor arm and when I move the throttle by hand with the fuel lever in the run position, it hits just above the bottom of the plate at just over 1/2 throttle and slides up very smoothly. Definitely not getting stuck under the plate. I also had my local mechanic help me check and adjust my throttle linkage to make sure I'm getting full fuel and I am.



What else should I check? Fuel filter is only a few months old. Lift pump leaks only when being primed. I'm obviously getting tons of fuel with the heavy black smoke and I see no drops on the ground. Power kicks in right at 7 psi and mid range is good until about 24 psi boost. Like I said, can't find any boost leaks but what is a good method for finding a boost leak that can't be seen? I had drivability issues that were solved with a valve adjustment. I'm at a total loss as to what else could be wrong. Suggestions?



Thanks,

Matt

 

[Missouri Mule]

Do a search for "Boost leaks". You should find info how to pressurize the intercooler by using pcv pipe. Check clamps,loose boots and check for holes.

 

[KYOUNG]

Check your fuel pressure after the filter, it will black smoke even if not getting enough fuel...

 

[Missouri Mule]

How's your air filter? Fuel pressure test good idea you can check out overflow valve at the same time.

 

[MMcCallie]

I have a True Flow XDI intake and I keep it clean. I built a ram air hood scoop out of exhaust tubing that starts at the front of my hood and shoves lots of cool outside air directly to the filter. The filter is foam with lots of surface area and I keep it clean usually by hand pulling out the few leaves and other debris, etc. It is also just a few months old and still black. Best filter I've ever used by far.

I also had the overflow valve replaced only about a year and a half ago. When I prime the lift pump by hand I can eventually hear the overflow valve weep. I don't expect a problem there but it could need replacing. Does anyone know if the overflow valve could hold an engine back by more than 15 psi boost and cause high EGTs?

I ordered a BD fuel pressure gauge for my X-Monitor which I hope will arrive before the weekend. My fuel filter is just a few months old, I had gone through 3 in a two month period getting some bad fuel from a station in town last fall but have been getting better fuel since.

I will be surprised if I have a flow problem because since I got the
valves readjusted correctly, the truck starts easily and quickly like it always has. I also have tons of billowing black smoke and power on the bottom to mid end. This 10,000 lb truck can easily break traction once it gets to about 20 mph going around corners with 37" tires. But after the boost gets over 20 psi the climbing slows and boost hits a wall just over 30 psi, no longer cleaning up smoke and having horribly EGTs and far less power, not right with a 4kGSK.

I'll try the old starting fluid trick to check for leaks first. I've had success that way before. You let the engine run and spray some fluid around all of the air filter, turbo, boost tube, and intercooler clamps, hoses, and other connections. If there is a leak, the RPMs will rise because a diesel's engine speed is increased by adding more fuel. Just have to make sure the fan doesn't blow the mist toward the air filter. A boost leak would be a nice simple solution I just have a feeling its something else.

 

[MMcCallie]

I can't find any boost leaks. I sprayed a light whiff of starting fluid at the air filter while the engine was idling and the RPMs instantly rose for a couple seconds. Tried the same thing all around the intercooler, hose clamps, everywhere I could think of and experienced no such rise again. Still billowing extremely thick black smoke that makes traffic stop behind me. EGTs still too high and boost way low. Are there any other tuning tricks I can try? Could rack travel be out of adjustment? I still have yet to check fuel pressure.

 

[KYOUNG]

A boost leak will not SUCK starter fluid, you are not dealing with a vacuum, you are dealing with positive pressure... ... . change your fuel filter again!!

 

[MMcCallie]

Still the same after a new fuel filter. I also clicked the Star Wheel back to just ahead of center and still have tons of early smoke. I may need to back off the pre-boost screw some more. I still think there is something out of adjustment because the mechanic said something needed to be adjusted and during one test drive we made over 42 psi. He made some other adjustments and we never got it back. Wish he'd answer his phone. However I'll check for boost leaks when I get another chance. Does anyone have a link to the most descriptive instructions of how to locate a boost leak?

 

[MMcCallie]

WOW! I got taken for a ride big time! Had my local mechanic build a pressure kit. Disconnected the boost tube coming from the turbo and mounted an air chuck to the custom rig. My new custom made air intake manifold is leaking tons of air out of about a dozen places. Most are underneath, hard to access places. Couple small leaks on top.

Rob Watkins of Performance Car & Truck, Diesel Performance in Golden, Colorado did all of the new head work. First thing I knew Rob messed up was that he adjusted the valves so poorly one was an 1/8" off. Second huge clue was all of the oil leaking from my valve covers because he did not machine the rocker arm pedestals to clear the ARP head studs. Now, I'm finding that even though I asked him if he checked his welds for leaks and he arrogantly replied that his fabrication skills are so meticulous and perfect that he doesn't have to, it turns out his fabrication skills are downright incompetent and my air is blowing out the intake before it can get to the engine.

I've left Rob many voice messages asking him to call me over the past few weeks and he has not once tried to call. I paid the man thousands of dollars for his services. I hope this will be a warning to everyone to never let Rob work on anyone's vehicle. Not only is the service slow and incompetent, the work is of horrible quality and the man shows no character, integrity, or pride in his work.

I'm hoping that when he machined off the intake manifold of this brand new Cummins head I had to buy, that he did not warp it beyond reuse. I am having to pay my local mechanic to fix Rob's work. The injector pump will have to be pulled and the manifold taken off to check how flat both surfaces are and to find where and what welds are leaking. So, ya'll were right, I have major boost leaks!!