negative boost pressure

[eaglehawk]

Ok, my boost pressure gauge is showing up to a negative 2 before start and at idle, not positive boost, negative. I have replaced the map sensor with 2 different new sensors and that did not change anything. It is a E 99 with a 2000 model year computer and this problem has plagued me since I bought the truck where it seems to run extremely rich.

Any ideas would be appreciated, In addition to this problem I have lost 4 mpg

[Young-SC-Owner]

You won't be building any sort of boost at idle.


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[eaglehawk]

No I shouldn't, but it shouldn't be negative either. In addition the loss of fuel mileage.

[Young-SC-Owner]

It's impossible to build vacuum on a diesel, that's why we require hydro boost for brakes, and have a vac pump.


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[eaglehawk]

Originally Posted by Young-SC-Owner

It's impossible to build vacuum on a diesel, that's why we require hydro boost for brakes, and have a vac pump.


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True, but that is not the concern though

[Young-SC-Owner]

What's the concern then


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[eaglehawk]

what is causing the poor fuel mileage, the negative boost reading and the unburnt "rich" diesel smell at the exhaust. trying to figure out what has changed that caused the fuel mileage to take a dump after upgrading the turbo to a 38r. I lost 6 mpg and we cant find why it is doing what it is doing and why it is dumping so much unburnt diesel through the exhaust.

[Young-SC-Owner]

Have you changed anything other than a turbo? Are you in a northern state? Possibly switched to winter blend? I said before, you CAN'T have a neg boost reading it's probably just a sensor or gage anomaly.


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[Zaairman]

I think you have two unrelated issues here and you're just pissing money away at MAP sensors without a diagnosis. Plus, with a manual boost gauge, it shouldn't read from the MAP sensor. Sounds to me like your boost gauge is screwed up.

I've never heard of "Farmer on Farmers" tuning, perhaps that is the issue...?

[Young-SC-Owner]

Originally Posted by Zaairman

I think you have two unrelated issues here and you're just pissing money away at MAP sensors without a diagnosis. Plus, with a manual boost gauge, it shouldn't read from the MAP sensor. Sounds to me like your boost gauge is screwed up.

I've never heard of "Farmer on Farmers" tuning, perhaps that is the issue...?

Unless he deleted a post, I see nothing that correlates to your reply!
But I totally agree with given info


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