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spankyjr1, Journeyman
Category: Medium and Heavy Trucks
Satisfied Customers: 2613
Experience:  I worked on all types of equipment semis,forklifts,farm,ect.
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Ok I have a 94 379 with a 3406B with a mechincal pump that

Customer Question

Ok I have a 94 379 with a 3406B with a mechincal pump that is controled by ecm it will only make 15 psi of boost and is a dog. It has a borg warner 178063 turbo near new and a new air to air that I checked no leaks new boots on the air to air and i did the over head adjustment on it. It does not use oil or water it will start when it's 30 degress out with no smoke and idols smooth. Whats the problem with this thing?
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Customer: replied 1 year ago.
the vin is 1XP5DB9X4RD344683
Expert:  spankyjr1 replied 1 year ago.

Hi Christopher, my name is ***** ***** you for asking your question, I will try and help you out.

When you have low boost the two most common things are leaks on boost side of turbo which you already checked and low fuel pressure.

You need to maintain at least 30 psi fuel pressure under a load or you will have low boost and low power.

Verify fuel pressure by installing a fuel pressure gage in secondary fuel filter head,test drive with a load,if fuel pressure is low first change fuel filters if you have not already,next bypass suction side of fuel system with a temparray new line running directly into fuel tank about half way down,,tie up with some rags around tank opening and retest,,if you know have good fuel pressure and power you have a leak on suction side of fuel system such as a hose or filter head,if you are still low on fuel pressure replace fuel transfer pump and hand primer pump if you have one.

If check engine light ever comes on during low power let me know what codes you have you can use cruise switches to check for codes,if you don't know how to get codes let me know.

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Expert:  spankyjr1 replied 1 year ago.

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