1996 suburban,6.5 turbo diesel. Boost pressure is OK ween cold. after engine gets fully warmed up [aprox 20 km] there is no boost at all. What do I look for and is it OK to drive it like this. Thanks John.
Country: United StatesMake: GMModel: 1500 SuburbanYear: 1996Engine: 6.5 turbo diesel
Replaced the air filter and installed a boost gauge.
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Hi there, my name is Cory. I have worked on lots of these vehicles. Let me break this system down so it is easy to understand, and easier to fix. The turbo on this system has a vacuum actuated waste gate that is computer controlled. The vacuum system on this vehicle is produced by the vacuum pump on the front of the engine on the passenger side under the alternator, and is belt driven. The vacuum pump sends vacuum to the waste gate solenoid by vacuum hose. The solenoid is actuated by the ecm which completes the path for vacuum to travel to the waste gate actuator on the turbo which allows it to build boost . The waste gate solenoid is on the intake on the driver side and is the first of three (or front one). Here the checks I do. First I check vacuum to the solenoid by unplugging it and either putting a gage or just covering it with my finger. If no vacuum is present check vacuum at the pump in the same way, be careful with that when it is running I usually use a long piece of vacuum hose to the pump. Or if there vacuum at the solenoid the idle engine and disconnect the vacuum hose at the turbo and see if there is vacuum there. There are two more possibilities. The catalytic converter may be plugged. To check this disconnect the exhaust pipe from the turbo to the catalytic converter and take a short test drive to see if you got boost. Next possibility is that the turbo can be seized to check this just remove the rubber hose from the air filter to the turbo you will be able to see the compressor blade see if it turns freely. Hope this helps let me know if I can help you further.
Hi. I used a piece of wire to hold the waste gate closed and took a short drive. The boost guage read the same as when the engine was cold ie, up to 5 psi. under moderate axcelleration. Would it do any damage to leave it wired up. I Thanks John.
Not sure if it would cause damage if you left it wired up, might cause it to stall on decel though. These vehcle don't get much more than that for boost 5 to 10 is normal for boost. Did you find the cause of the waste gate actuator not working?
Hi.I drove it for about 50 miles today, It ran great. Going up a hill from a stop the boost got up to 7 psi. While crusing at 55 mph the boost is at 1.5 to 2 psi.Before I wired it up I was looking at the boost guage about 15 miles from home and it just droped to 0 like a switch was turned off. I am starting to think the ECM is turning it off. Is there a senror somewhere that would cause this.The check engine light was coming on indicating a boost problem. Now it is staying off.I am not an agressive driver and the engine rarley gets much over 2000 rom. I am OK with leaving it wired in the closed position as long as there is no damage that is sure to occur.Your thoughts on this would be apprecited Thanks John
Yes there is gm calls it a map sensor it is located in the center of the intake it monitors boost in the intake. I am not sure if leaving the waste gate wireed open will or will not cause damage, it may overboost causing excessive heat in the cylinders and also cause a stall condition on decel. On these vehicles the vacuum pumps are very common to fail and the vacuum lines also break, Causing vacuum leak, i would still check the system as per the first post, just to be safe.
14 years of gm experience ase master tech with advance engine performance