Engine/Transmission (1994 - 1998) Where has my boost gone??

[STeichert]

I could use some help figuring out why I'm losing boost in my '96 5 speed with a number 10 plate. It has gradually got less over time while the EGT's are now nearly out of control. I pulled a trailer yesterday, and even when it was empty it was hard to keep the EGT's in a safe range. The most boost it will build now is 23 lbs, and it used to get over 35. Going down the road with no trailer at 65 I have 0 lbs of boost, and it used to be between 3 & 5 lbs of boost. I have pressure checked everything from the turbo to the intake manifold and have no leaks. My boost gauge will build with shop air that slowly bleeds off over time, but I think that's normal. I'm at a loss of what else to check, any tips would be helpful.

 

[fest3er]

Is your power level normal? I'm thinking not. I had that problem not long ago, but ignored it until boost was *really* liniment: couldn't pass slow-moving vehicles, couldn't maintain speed up a 2% grade, couldn't get more than 8PSI boost, et al. ) Turned out the lift pump was ABENDing.



So put a pressure gauge on and check your fuel pressure. If it's lower than expected, suspect your lift pump. Use your nose and sniff for fuel on the left side of the engine. If you smell #2, you probably have a holed fuel line or something else letting fuel out.



On old trucks, fuel lines should be suspected before other problems, especially with 'gradual' boost and power loss.



Reminds me of an old PP&M folk/peace song:

Where has all my boost air gone? Long road trips ahead. 

Where has all my boost air gone? Can't pass the semis. 

Where has all my boost air gone? To my dying lift pump. 

When will I make repairs? Oh when will I fix my truck?



Why won't my lift pump move fuel? Can hardly start the truck. 

Why won't my lift pump move fuel? Sounds like an air leak. 

Why won't my lift pump move fuel? Cuz my fuel lines're all holey. 

When will I make repairs? Oh when will I fix my truck?



Where has all my fuel gone? I filled up yesterday. 

Where has all my fuel gone? It's now on empty. 

Where has all my fuel gone? Out the tailpipe as black smoke. 

When will I make repairs? Oh when will I fix my truck. 



Where has all the black smoke gone? Passing 'vettes in a flash. 

Where has all the black smoke gone? My truck is such fun. 

Where has all the black smoke gone? Gone to boost air like it should. 

When will I make repairs? Oh when will I fix my truck. 



Where has all my boost air gone? Long road trips ahead. 

Where has all my boost air gone? Can't pass the semis. 

Where has all my boost air gone? To my dying lift pump. 

When will I make repairs? Oh when will I fix my truck?



[size=-2]Copyright 2010, Neal P. Murphy. All rights reserved. [/size]

I think four (five) verses are enough, eh. Maybe I'll bring my guitar to Spring Fling and sing a song of diesel woe.

 

[STeichert]

Power levels are still very good. They might not be quite where thy should be, but are close. I had not even thought of fuel issues. My lift pump is new, as is the return hose behind the fuel filter. The plate is about 2/3 forward & the AFC star wheel is about the center of the hole. The truck will blow black smoke, but not more than normal. Fuel pressure gauge is a good idea.



You should do a verse of where has my money gone? I wonder that at the end of every month.

 

[KYOUNG]

Fuel filter stopped up?

 

[fest3er]

Right. I forgot filters. One filter I hadn't changed in a while; it had 1/16" of asphaltene on it. The replacement had a bad o-ring; when I removed it, the top o-ring was flopping around loose.

So the lift pump should be OK. If power level is 'fading' but everything else seems normal, fueling is the first thing to verify.

 

[GAmes]

One other thing is to check to see if the fuel shutoff lever is going all the way up. A had an instance once where the rod only went part way up. The result was reduced power, although I don't recall high egts. I would think if it is a fuel delivery problem that egts would be low as well.

 

[STeichert]

It's not the fuel filter, I have changed it several times. I have a manual pull lever for my fuel shut off with a good return spring that holds it all the way up, but I have checked that and it's not the problem. I agree that if I wasn't getting enough fuel that my egt's would be low.



Would a cracked exhaust manifold or turbo problems cause this? And if so, how do I know what to check or look for?

 

[xpetecx]

check your fuel lines and your pickup tube. i had that problem and it was my intake pick up tube.