Engine/Transmission (1994 - 1998) loosing boost pressure at wot

[MAleksandrowicz]

i recently took out my fuel plate and grinded it to a 100. the boost goes to about 20 when i step on it and then begins to drop down gradually. is this due to my wastegate or is there a leak on one of the couplers from the intercooler. how can i adjust the wastegate.

 

[SRadke]

Sounds like a fuel shortage. You changed the filter recently? Possible bad lift pump?



-Scott

 

[mjs]

you will lose boost when the governor cuts in and you can loose boost when the load decreases from off line to speed . the waist gate should just stop it from increasing past the set leavel or just not enough fuel to support the upper rpm . at what rpm does this drop and is this pulling a hill or flat ground ? mike

 

[MAleksandrowicz]

more of when i am going up a hill at about 2400rpm it goes up to 20psi then moves down to about 15psi. it does this on flat also. when i first step on it there is a puff of black smoke and then nothing comes out after that. would that mean there is a shortage of fuel.

 

[HotRodCummins12v]

well, assuming that you modified the plate correctly, where did you put it back in?, if you modified it to a 100, there should be a little more than a puff of black smoke. try adjusting your plate and your AFC housing foward, you wont regret it, also hows your intake manifold gasket? ¿did you damage it pulling off the intake to do the job? did you adjust any screws on the back of the pump?

 

[mjs]

Thats what i was talking about . loss after a certain rpm 2400 sound like about rite for wear the governor cuts in . less full less boost . gsk's will cure some of this . but you will need to pay some more attention to the pyro when pulling hard at a hi rpm. if your gsk's are stock on an early truck they will cut back early . i think you can tell wear the defuel may start by free reving untill rpm stops . example 2900 max rpm defuel starts at 2300 rpm /3400 rpm defuel at 2900 rpm . mjs

 

[MAleksandrowicz]

my plate is forward all of the way the afc housing is forward and the star wheel is 5 clicks from being all the way lose. i put a brand new intake gasket on and i didnt mess with any of the screws on back of the pump. i am really lost.

 

[ProMac1K]

I bet you are just defueling. You can really notice it in an auto-equipped truck when you run the truck up in the rpm range with the trans in 3rd locked or D w/ OD Off. It will pull back pretty good, and you will be able to tell it.



Just for reference if someone happens to search for falling boost pressure or a boost leak..... I'm having a noticeable boost leak when maintaining throttle or cruising normally up to highway speeds. I originally thought it was the intercooler boots leaking since the lower ones going in and out of the cooler are enlarged from wear. After checking out the wastegate actuator, I found the actuator to be leaking air out of the diapragm when charged. I think this is the main contributor to my boost leak.

 

[mjs]

You Can Have All The Fuel In The World . Plate ,injectors & Even Block The Waist Gate . But If You Back Your Foot Off The Pedel You Will Loose Boost To . this Is The Same Thing The Governor Is Doing At 2300 / 2400 Rpm . By Insalling A Governor Spring Kit. This Will Extend The Defuel Curve From Coming In As Early. Mjs

 

[MAleksandrowicz]

how can i block the wastegate because i cant get over 20psi

 

[mjs]

If You Plug The Rubber Hose Off From The Afc Housing This Will Increase The Boost . You Only Need Enough To Burn The Extra Fuel Say 5 To 10 Pounds More Enough To Clean Up The Smoke Any More Is Hard On The Compressor And Makes A Hotter Air Charge So A Boost Controller Would Be The Best Bet. With Out That You Could Peg 35/40 # And Then It Will Stop When The Exhaust Chokes From The Restrictive 12 Cm Housing. Mjs