I'm glad it is running bad....I think?

[jeffscarstrucks]

I got around to installing the boost gauge today and the result was zero...zero boost!I've owned this truck since '97 and it has seemed less powerfull over a period of time but you kind of write it off after you drive it all of the time ;the decline is very gradual. I am glad that it seems to be a repairable problem but i'm not sure if I should just call it a bad turbo or look for something else. I did move the lever on the turbo through it's travel at idle with no change (no movement on the gauge) . I connected a vacuum gauge to the line and did get a minor vacuum reading at idle. At about 2500rpm there is a slight blow from the line but not enough to register on the boost gauge.(the compression fittings are not over tightened) It is a 93 mechanical 6.5 with 150k so it seems like diagnosis should be pretty straight forward. Thanks in advance for any suggestions, JEFF

[john8662]

The engine won't normally make any boost revving the engine up w/o a load. You'll have to go for a drive in order to get any boost that will register on the gauge.

If you still have no boost there are some things to check before condenming the turbo.

-leaks, intake and exhaust (crossover)
-make sure that the wastegate actuator is hard to depress

[jeffscarstrucks]

Hi John, Thanks. I did go and drive it and it looks like going up hill on a highway in high gear I can get about 6.5 lbs at 2200 rpm's. It seems like the boost comes in at 1850 r's and drops off at about 2400r's. This is about the range I use on a normal basis. This is all unloaded and I will be curious to see what happens with a 10k trailer hooked up. I am wondering if the turbo-master might give me a better use of boost in a usable range but more importantly I want to know if this is a normal range of boost with the stock set-up. It seems like the the old dog is a little weak but I don't see any signs of major problems or blow-by. It does have all original parts including the pump and injectors and I always use synthetic oil. Thanks Again, JEFF

[atom_c]

On my 95 I see exactly 5 lbs boost cruising at 60 mph and a max of 10 lbs laying into it up a grade, stock program. Check for cracks in you vacuum lines. Before I got gauges I was running with no boost for a while because the vacuum line was cracked most of the way through where it hooks onto the actuator diaphram.

[jeffscarstrucks]

Thanks Atom, I think that those are the kind of numbers I'd like to see. This is a 93 model with a spring type boost-load device and a mechanical pump with no electronics or vacuum pump. I am familiar with the 94-up as I have a 98 3/4t excab with 70k on it that I am going to sell in the next few weeks. I have had my 93 since 97 and i'd like to keep it in nice shape for a long time.(been paid for for a while!) Thanks, JEFF

[Bnave95]

Thanks Atom, I think that those are the kind of numbers I'd like to see. This is a 93 model with a spring type boost-load device and a mechanical pump with no electronics or vacuum pump. I am familiar with the 94-up as I have a 98 3/4t excab with 70k on it that I am going to sell in the next few weeks. I have had my 93 since 97 and i'd like to keep it in nice shape for a long time.(been paid for for a while!) Thanks, JEFF
I believe you have had boost,for with out some boost your EX. would smoke under any load. Your spring has gotten weak,and if you went with the Turbo Master, now that you have the boost gauge you would also have lower EGT. Just keep the TM at 10 psi of boost. Also when the TM is installed it is very hard to move the rod. The turbo waste gate stays open untill the boost starts loading the spring and dumping/bypassing the EX.

[Hubert]

Someone want to comment on the waste gate arm mechanism. Wasn't that part of the updates on later GM-X's turbo's. I think the earlier ones would wear and woller out bushing? causing the actuation forces to change and or allow leakage past waste gate??? Something like that. Might be a contributor to problem ??? Might check that too.

[jeffscarstrucks]

Thanks, I'll look at the wear areas on the gate rod and linkage tonight. I appreciate all of the guidance. JEFF