Boost Dropping...

[Hunter4x4]

I seem to be loosing boost - not a lot, and I'm not sure why, or if it's even a problem.



When I bought this truck 2 years ago with 144k on it I'd get 11-12 max boost, and It would run 4-5 at 65-70 on the highway. I added a BHAF and Powerwagon injectors last summer, and in addition to a NOTICABLE performance increase, my boost would max out at about 15, occaisionaly 16, and run at around 6 at 70 MPH.



We recently had a real bad cold spell, and a short time after that I noted the boost numbers had fallen off. I did some surfing with the search feature but was having a hard time getting a reading on what my problem may be. My tire pressure is the same, EGTs are running about the same, and performance doesn't really seem to have fallen off. If anything, fuel mileage has slipped a little. Boost max's out at about 11 or 12 now, and I run at aobut 2 or 3 at 70 mph now.



I looked under the hood and can't see anything obvious in the turbo intercooler plumbing. I squeezed and felt all the connections while it was running but as I said, nothing that I could see.



I also checked the boost gauge plumbing, but again, nothing obvious.



I don't know if the cold caused something, or was purely coincidental.



The only engine mods are the ones noted, i. e. , I haven't tweaked the pump at all. Recent maintenance includes an oil change 1k back and a fuel filter change 4k back.



Like I said, it seems to be running just fine, but I'm baffled at the boost drop. Thanks in advance for any input!

 

[Stomp]

You might want to check the lift pump. When mine started dying I started loosing boost. Its somthing to look at or at least check.



Stomp

 

[GeraldGordon]

Did you look at youer air filter if it all dirty you wil not get as much boost

 

[BushWakr - RIP]

Your outside temps suggest you are, like me here, running on "winter grade" fuel.

Frankly that stuff stinks... .

I loose about 75'ish RPM, the idle is choppier, I see a bit more smoke in general, I loose about 1 1/2 to 2 mpg as well and, the general performance seems to decrease with it to.

That will account for some of your boost losses I think, then as noted the lift pump pressure should be checked and you should also try pulling the start/stop fuel solenoid and removing the rubber tipped plunger and spring, then, reinstall it.

You will need to use the manual shut off to shut down the engine but I'd like to see you eliminate the solenoid as a possible source of your problem... . I'm thinking that it may be sticking or not functioning properly/fully and letting fuel pass when it shouldn't.

The next item would be your guide pin function.

Inside the afc housing, under the rubber diaphram you'll find the guide pin. It protrudes from the lower forward side of the afc bore.

Remove the afc diaphram/cone and then cycle the throttle open. The guide pin should begin to pop out. It may not come out fully but it should show some kind of movement.

Recent developements have indicated that even if the pin is a tad stiff in it's own bore it will come out some.

Check that too.

Let us know what you find.



Remember, do one thing at a time and observe results and then do the next item so you can determine which item resolves the problem... or not...



pb... .

 

[LEggers]

I cleaned my air filter one time several months ago and gained 3 PSI WOT.



Check it clean it or replace it...

 

[Hunter4x4]

Update: I finally got around to changing the filter last night and that got me most the way - but not all the way - back to where I was before.



PB: Do you think that was all it was? I'm thinking I probably still want to do a little PM as outlined in your earlier reply?



As always, thanks for your input, gang!

 

[phillips5]

If the air was full of moisture the filter gets weter and weter and less air can get through espesually if it then freezes.

 

[Hunter4x4]

Said I'd get back to yuo all!!



Found out where the boost was going!! The bellows between the turbo and the pipe into the intercooler had rubbed a hole in it about the size of a dime from rubbing on the inner fender rubber/flex/closeout material!!!



I 'checked' all of the bellows, but what I didn't do was grab each one and check a full 360* circumference.



In the process I found a great shop in Adrian, Michigan - Diesel Performance Specialists - who helped me find my little oversight!! Dough speciallizes in later Rams, but definitely know enough about 1st gen and diesels to help me out!!



In the process I got a good VE pump lesson, and we turned up the govenor just a tweak. I'll do more after I get the transmission beefed up!! She'll hit 2,900 RPM - make a nice difference on the freeway when you're cruising at 65 and need to jump on it!!!



Thanks again for all your help!!



Mike

 

[Hunter4x4]

Whoops! Couple typos in the last post! Sorry about that. The worst was 'Dough' should be 'Doug'!! Let me know if you need any more info about Doug's shop!