Boost & EGT low

[Scooby]

I towed play toy up to a local mudhole last weekend, and I couldn't get boost above 10, and egt was not climbing like usual when putting a load on it. I have turbomaster, Heath computer, hi pops, s&s air cleaner. Usually have to ease up on throttle to keep egt between 1000 & 1100 pre turbo with 14 psi boost under load. Can't get there now, and no smoke under heavy accel. I changed Dahl and factory fuel filters. Put gauge in filter drain line. See 5 psi at idle, and it drops to 2 under accel. I've ordered a new delco lift pump and tank strainer. Any ideas?

[Dvldog8793]

Make sure the turbo master is not bound up or the spring fatigued. I have one of mine bind and need to be cleaned up and readjusted.

[Robyn]

If the TM is stuck open (Spring or bind or ...) there would be lots of black smoke.

Low EGT and no boost is likely due to lack of fuel.

With the symptoms present the issue has to be either in the IP or the electronics. (Computer)

Scan the thing and see if there are any codes showing.

It is possible that the computer has issues.

Clean filters x
Good fuel pressure x
No Smoke x
Low boost x

Pretty much point the finger at the IP or electronics.

As with any issue with the 6.5 regarding fuel delivery THE PMD is always in the cross hairs.

Swap the PMD with a known good spare/new unit and see if the issue resolves.

The other possibility might be the fuel shutoff solenoid is failing and barely opening the inlet port.
Check the solenoid (Swap in a known good one / new)

The other possibility is a failing fuel solenoid (inside the IP that meters the fuel flow)
Failures here will normally set a code and turn on the SES lamp

Another remote possibility is a restricted fuel return line...
Make sure the return is free flowing.

Good luck
Keep us in the loop

[Scooby]

No codes / light. Is it normal for the lift pump pressure to drop to 2 under accel? The lift pump that was installed dropped to 0 under load, so I stuck an old one in to see what it would do. That's the one that drops to 2. I have a remote fsd. I gotta look if I have one i can swap out.
.

[Scooby]

I found an injection pump I got off of Ebay back in 2003. I took the PMD off of it and plugged it in at my remote mount plate. No difference when I drove it. I also found another lift pump, which I think was the original GM pump as it had a familiar number on it. I didnt feel like swapping out another lift pump, so I'll wait till my new delco pump and tank strainer come from Rockauto this week. I can drive it if I need to. Runs fine unloaded. It just bugs me that the lift needle jumps to 10 then stays there, and no smoke.

[Scooby]

Well my new lift pump and fuel tank strainer came in so I dropped the tank, changed the strainer, and change the lift pump. I'm now holding 3 PSI under heavy load on the lift pump, but boost still stops at 10 and EGT just slowly creeps up. No smokre at all. There is just over 100k on the injection pump, and 50k on injectors. I tried another PMD as well. No difference. Truck has 205k on it, and it has a small coolant leak into oil . I put heads on it 2 years ago trying to stop the leak, but still there. I've put a lot into this thing the 13 years I've had it. I just don't know if I wanna do a pump now. Dealer did last one under warranty right after I bought it. Kind of sad. Any words of wisdom would be appreciated.

[JohnC]

...boost still stops at 10 and EGT just slowly creeps up. No smokre at all.

And this is bad because... ?

[Scooby]

And this is bad because... ?

I have always been able to easily get 14 pounds of boost. EGT response was much quicker before. Under heavy acceleration I would always be some smokes. I can sit in the garage and power break it, no smoke.Something is wrong. With maxi torque and high output injectors I have never been at a loss for egts climbing. I can't get to 1000 now. I have never held the pedal to the floor in this truck in the 13 years I have had it. I did towing a couple weeks ago and like I said the egt pre turbo never got to 1,000.

[JohnC]

Well, if it's not smoking and boost is down then fuel delivery is the problem. It takes heat to make boost, so if fuel delivery is off boost will be off, and probably this explains your EGT issues, too. As long as you have positive pressure at the pump inlet, that's not the issue. Did this start before you had the 8 psi pump, or after?

Generally, 10 psi boost, no smoke and low EGT's would spell nirvana..

[Scooby]

Did this start before you had the 8 psi pump, or after?

Generally, 10 psi boost, no smoke and low EGT's would spell nirvana..

I never had an 8 psi pump. The pump that was installed was dropping to zero on acceleration. An old one I tried did a little better, and the new one I just put in holds 3 under accel. Maybe a failing lift pump messed the injection pump up? I dunno. Problem started out of the blue. Well, I hadnt pulled my mud truck in quite a while, but I usually get on it pretty hard going up a few little hills we have near my house, Just to get a quick thrill. I hadnt noticed anything different till I towed my toy on my gooseneck 2 weeks ago. I took off on a slight grade, which doesnt occur a lot in Florida, and I litterally held it to the floor and the EGT only made it to 900, and it wasnt pulling well at all. Ive never held it like that, and usually I would be backing off to keep the EGT under 1000 or 1100 at most. Im planning on calling Bill Heath Monday to see what he says. Truck has his computer and injectors, and turbomaster. I dont think I want to put a pump in it. May be time to say bye bye to the truck and a whole bunch of upgrades I have done the last 13 years ! What exactly is nirvana? Lol!

[JohnC]

I never had an 8 psi pump.
Sorry, I guess I had you mixed up with someone else. If you have 3 psi at the pump inlet then it must be the [injection] pump that's holding you back. The only other possibility I can think of is the chip has some sort of limp mode and something triggered it.


What exactly is nirvana? Lol!
"The term "nirvana" is most commonly associated with Buddhism, and represents its ultimate state of soteriological release and liberation from rebirths in saṃsāra."

[Scooby]

I talked to Bill Heath today about this problem. One thing he suggested was to check the MAP sensor connector. And also see if the sensor is plugged up. The connector lock is broken but the thing was plugged in. The sense hole was clear too. I decided to see what it would do with the sensor unhooked. No difference. No light, boost and egts acted the same. Could the sensor be bad and not telling the pcm there is boost, and it pulls back on fuel?

[Robyn]

Depending on the programming that is in the new ECM a defuel should set a code.