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help with Wastegate solenoid / wastegate duty cycle

Chicagomike

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I recently purchased a '94 C2500 suburban 6.5Td. The old owner was 93--and there has been a lot of deferred maintenance which I've been working to correct prior to winter setting in. As part of this--I ran the free version of GMTD tech-scan to help detect any issues. I have no codes and none in memory---which is always good.

The problem I'm having is that the "wastegate duty cycle" is showing as "zero". I've checked vacuum and I'm getting about 27-28 on pump side of solenoid---and about 16-17 at actuator (after solenoid)--so plenty of vacuum. The actuator is fully forward at idle--and very difficult to move back. (also good I think)--but is relatively free with engine off.

My thinking has been that if duty cycle is 0--then wastegate is open--and there should be no boost--and little to no vacuum at actuator. but I have plenty of vacuum at idle at the actuator.

The boost sensor reads at 29 ---which is about barometric pressure here in Chicago. However, the barometric pressure reading is showing 14--which results in a "calculated" boost of about 15---which is clearly wrong.

I don't want to just start replacing parts willy-nilly--but not sure where to begin on chasing down the real problem at this point.

I've been told various conflicting things about barometric sensor and boost sensor. One person indicated that the barometric sensor on firewall just provided a "key on" reading and then handed over to the boost sensor. others have told me that the barometric sensor provides PCM with barometric data ongoing.

There's no real "smoke" issue and truck seems to run relatively well--albeit a little weak.

This is a "F" engine type and I've done no mods except LeRoy diesel's excellent lift pump relay kit and PT wiring's excellent glow plug wiring harness.

I installed new glow plugs, new injectors and a couple of sensors.

Any help or advice appreciated---thanks
 
Check for leaks on the vacuum components especially the tubes/hoses.
Usually, the wastegate solenoid is bad when you are having issues.
 
I think everything is normal you need to subtract atmospheric from the reading. The only thing that seemed a bit off was the vacuum difference before and after the solenoid. I'd be checking for leaks in the lines especially if it still has the stock plastic lines
 
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