Negative boost
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Senior User
Joined: Oct 2008
Posts: 466
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From: Ontario, CAN
Negative boost
Truck ran fine all day. Sat for several hours and when I started it to go home, it reads 1-3 lbs negative boost when I am just cruising. Will jump up when I get on it but then drop right back down. IC boot problem?
Elder User
Joined: Oct 2007
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From: NJ
Correct me if I'm wrong, but since diesels have no throttle body, they can't produce vacuum, right? Isn't that why our trucks have a vacuum pump? So, negative boost (vacuum) must be impossible.
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Post Fiend
Joined: Jul 2005
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From: 21791
Negative boost, do you mean VACUUM? Yes, no throttle body, no vacuum other than the small ~.1 or .2 psi of vacuum at idle
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Thread Starter
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Senior User
Joined: Oct 2008
Posts: 466
Likes: 0
From: Ontario, CAN
Yes, it's a digital gauge and it reads -2 for boost. The truck runs fine with no noises. I assumed it was the gauge but thought I should ask before I tear into it. I guess it's time to go with the A-pillar and manual gauges and ditch this programmer thing for a DP.
Thanks for the replies.
What I mean by no noises is, the normal thrashing machine, 7.3 noises, is all I can hear.
Thanks for the replies.
What I mean by no noises is, the normal thrashing machine, 7.3 noises, is all I can hear.
Last edited by throwdown; May 2, 2009 at 02:35 AM. Reason: more content
, But It is still a 4 stroke.. you have a intake stroke.. you should have a vacuum.. Our Turbos push that much air.. even at idle???
still plays with trucks
Joined: Mar 2004
Posts: 1,743
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From: Twin Falls Idaho
In order to have vacuum, you mut have restriction. the 7.3 has no throttle plate. just as a gas motor has no vacuum at WOT. the diesel has none because their is not enough restriction. I would guess an old NA 6.9/7.3 would develop some kinda vacuum at partial throttle but our turbo takes care of that. Barney