Boost Problem

[RogerD]

I have a 1995 Suburban with a 6.5 in it. The vehicle has 166,000 miles on and is 100% stock and I have replaced one pump and one PMD. The truck has always run great and the hardest it is driven is pulling a bass boat back and forth to the lake during spring and summer. Recently at about 65MPH the check engine light started coming on for short periods of time. A mechanic checked the code for me and said it was a boost problem or lack of boost. I started investigating and discovered that when running there was no vacuum to the wastegate solenoid. I could move the wastegate rod very easily with my fingers. Hoses and the vacuum pump were eliminated as a cause. I did discover that I had vacuum going into the vacuum control switch but no vacuum coming out. Thought the switch had to be the problem. Went to GM parts and purchased new vacuum control switch and installed. This made no difference at all in vacuum to the wastegate. Puzzled, I continued to try things with no success until I thought that maybe some way the vacuum hoses and gotten mixed up going into the vacuum switch and so I reversed the hoses and now everything works great and the truck even runs better than before. Gas mileage seems to have gone way down but it runs great. With either conditions I never notice or saw any black smoke under load.
My questions are:
1) Have I fixed anything or is this just putting vacuum to the wastegate all the time like running hose straight form the vacuum pump to the wastegate? If there is vacuum going into the vacuum switch and not coming out what other things could cause this since it is not the switch?

2) With vacuum at wastegate all the time or with hoses reversed am I going to damage the truck by over boosting it or overheating? Truck runs great and am tempted to leave it like this but think it should be fixed.

Any ideas or thoughts will be greatly appreciated.

Roger

[Marty Lau]

Roger;
I had the same thing happen and what I did was put a TurboMaster boost controller on. You can get them from eith Kennedy or Bill Heath they cost like $69 and you never have to worry if you vacum again.

[gmctd]

Raw vacuum supply is the center port on the wastegate solenoid, rear port is to the wastegate servo.

Solenoid ports vacuum to the wastegate and vents excess thru a third port at the electrical connector end.

IMHO, unless you have a full set of gages - EGT, Boost - wastegate control is better left to the PCM.

[Marty Lau]

Originally posted by gmctd:

IMHO, unless you have a full set of gages - EGT, Boost - wastegate control is better left to the PCM. I agree if you are going to ADD boost and even if you are not it's good idea to have gages. I think if a fellow is very carefull you can get by with out if keep the stock chip. I change to the Boost controller followed the instructions on spring lenght to set to "stock boost". I ran about 10 days with out gages. No codes were set and truck ran well. I installed gages and turned out the boost was set just bit higher than stock 8-9 PSI rather than the 5-7PSI for stock. After gages I turn up the boost with new chip and went back to stock. (See Link)http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=005912
(MaxETork report)
Any way when stock chip help protect the engine by defueling if you over do it. (I don't think I want to rely on that forever tho.) Again until guy can afford gages I still think it's better idea to go to a manul boost controller than keep fixing & refixing the vacum system.