vacuum issue

[anp4god]

I'm looking for a little advise. My turbo gives me issues every now and then, usually when I'm climbing a hill and pulling a small load. The boost gauge will stay at 0. It seems pour out black smoke at the same time. Usually if I step on the pedal heavy the waste gate will close (I think) and the boost will shoot up to 10 or so and I'll get power again. Also, the egt really starts to rise when there is no boost. Is this a vacuum issue? I don't know if it's related, but I have also noticed the vent/air conditioner controls don't like to switch until I let off the pedal. It seems like I am having low vacuum or possibly a leak.

[JohnC]

Before you "step on the pedal heavy" do you let up on it? If so, this temporarily clears the fault that lead to low boost. Yes, most likely a vacuum problem. Troubleshooting has been covered extensively in other posts, so search and discover...

Your heater issues are sympathetic as there is no vacuum control for the hvac.

[anp4god]

Thanks. I am ordering a remote PMD heatsink and "bullet proof" PMD tomorrow. When I get the truck running later this week I might look at the vacuum system to see if there are some bad hoses. I should probably just change all of them that I can.

After thinking about it I realized I am mixing non-turbo vacuum system information with turbo. Obviously a turbo charged engine cannot use the manifold as a vacuum source. DUH!

I'll do some research on switching to the mechanical waste gate setup. That might be a better solution in the end. I'm wondering about California emission rules though.

[DmaxMaverick]

The availability of vacuum has nothing to do with turbo/non-turbo. It's a Diesel thing. Diesels engines (most all, anyway) have no throttle in the intake, therefore, no significant restriction to allow a vacuum condition. If you have more than a couple inches of intake vacuum, at any time, your air filter is plugged (or other intake plumbing issue). If you need/have vacuum on any GM Diesel, you need a pump.

If your WG system works, then falls off then returns, for one reason or another, the vacuum system is probably working properly. The black smoke is an indication the PCM isn't reducing fuel to lower boost, so your boost is not exceeding limits. This sounds like an inability to properly control the WG. This could be caused by any number of electrical problems, failing WG solenoid, improperly routed vacuum lines (try reversing the vacuum lines at the WG solenoid, and shoot some WD40 into each port), vacuum system/line leak, or a failing vacuum pump. The pump should develop and hold 20"+ vacuum (22-25" is ideal), and the PCM should maintain about 15" vacuum at the WG actuator (when not in a maximum boost condition). At engine idle, the WG should be pulled tightly closed, and you should not (easily) be able to move the WG linkage.

Another possible cause for loss of boost and black smoke is a plugged air filter, or collapsed/restricted/obstructed intake pluming.

If you are subject to CA emission testing, you may have to keep and maintain the vacuum system. Check the 8th digit of the VIN. If it's an "F", the vacuum system is not required to be in compliance, as the only function of vacuum is the WG system. If it's an "S", then vacuum is required to operate the EGR system, and you will fail an emission test without it. CA emission testing does not require a test under load, so boost or turbo operation is not an issue. If your EGR system works (if required), you are not blowing black smoke, it idles smooth, and your SES lamp isn't on (instant failure, regardless of the reason), it will most likely pass the test. Always have a NEW air filter installed for the test.

Also, nothing you've described indicates a PMD issue/failure. Generally, they work or they don't, and have no effect on boost or black smoke.

[anp4god]

There I go again, thinking because I'm a jet mechanic I can figure out cars! Thanks for the clarification/education on vacuum. It does make sense having a little understanding on intake systems. I just haven't used the info for awhile and I guess I'm rusty. I'll try the suggestions you mentioned for inspecting the WG system. Maybe that is rusty too!

The PMD issue is completely different. The typical stall, wait for cool off, restart, stall again. No DTCs, lift pump tests good pumping plenty of fuel out the drain T with the engine running.

I'm putting on a new grey Stanadyne PMD with an FSD heat sink from Accurate Diesel. I'll post how it goes. First impression of them was good. They answered the phone and answered my questions at 3:30am Monday Pacific time! Online ordering was also simple.

[anp4god]

Remote FSD and grey Stanadyne PMD arrived today. Install went pretty smooth except I wouldn't have needed to fumble around with the ground screw as the new PMD came with the 6" adapter harness from the old style PMD to new style PMD connector. So I removed and reinstalled the ground for nothing. (tried to save time and got started before the parts arrived!)

Also, most places I've read says that there should be plenty of length on the engine harness to connect to the PMD if it's located on the intake manifold. My harness didn't budge more than an inch. I could hardly hook up the extension/adapter harness.

That being said, Accurate Diesel was great to work with. The new PMD came with the requested #9 resistor preinstalled and the PMD was installed on the FSD heat sink already. Just had to remove the 2 bolts from the intake, and bold up the heat sink. Plug and play! Truck started right up and has ran good.

[Yukon6.2]

Hi
Feels good when they start again.Now all you need is a 6 ft extension so you can actually get the new FSD somewhere that is cooler,preferably somewhere out of the engine compartment.
Thomas