Calling all Experts: The unsolvable low boost issue - Diesel Bombers



Ford Powerstroke 99-03 7.3L Discussion of 99-03 7.3 Liter Ford Powerstroke Turbo Diesels

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Old 01-05-2017, 09:46 PM
PowerStroker525's Avatar
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Default Calling all Experts: The unsolvable low boost issue

I'm a heavy diesel tech I cant figure this out.
My buddy also heavy diesel tech cant figure this out.
His buddy 20 year ford tech cant figure this out.
35 year Ford Tech with endless Certs spent 4 hours on it and...... he cant figure it out.

The main Character:
2000 Ford F350, Crew Cab, Auto, 7.3, Garret GT38 Turbo, Banks Down Pipe 4" back exhaust, S&B Cold Air, Riffraff FRX, no chip.

The Story goes..
Bought this truck for a killer deal. Purs like kitten. Runs and sounds great until you get on it and it just falls on its perty face. Hooked my scan tool up and its throwing a low boost code.

Turbo impeller and wastegate= good
Pressurized Boost System= good
Checked up pipes and manifolds= good
Map Sensor= good
EBPS= good

Decided perhaps its a fuel issue creating a low boost problem

screens in tank= good
Fuel Pressure= good
Fuel Filter= good

Thought maybe its a high pressure oil issue

HPOP= 2800 psi down full throttle
IPS= good
IPR= good

This is when i had enough and thought hell maybe this is some wierd kind of PCM malfunction or something. So I took it to the best dealer i knew with the most seasoned tech in my area. He spent 4 hours with it checking over all the specs, Flashed the PCM. I gave him $250 he looked at me with eyes of bewilderment and said idk maybe you just need a chip to run all that banks stuff............ Kill me.

Any ideas fellow Strokers?
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Old 01-05-2017, 09:59 PM
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Can you actually read boost pressure?
First thing I want to know is what the boost pressure actually is. It sounds like you may be having a drive pressure issue, you could be underfueling the engine causing there not to be enough volume from the exhaust ports to spin the turbine wheel as fast as it needs to.
I would rig up a boost pressure gauge and a drive pressure gauge and get those readings before anything else.
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Old 01-06-2017, 08:07 AM
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No I I'm not I'm actually only reading that off Manifold Absolute Guage Pressure on my scanner.

I definitely am leaning towards it defueling and so is everybody else but what would cause this? The fact it needs a tune to compensate for all the extra air? Seems out there.

I'm mildly familiar with drive pressure. What readings am I looking for when compared to my boost reading? Example: let's say my real boost is 13psi at the plenum what would a drive pressure be normally? What pressure would indicate it defueling?

Thanks for the reply a fresh mind is a breath of fresh air.
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Old 02-18-2017, 11:59 PM
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I apologize about the delayed response. If you see a drive pressure of 13-15 I would be thinking it has a fueling issues. If you are reading 25-40psi I would not have those same concerns, with drive pressure you are basically just reading the pressure in the exhaust manifolds before the turbo, did this issue start once the parts were put on?
What are your actual boost readings?
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Old 06-19-2017, 10:05 AM
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Have u tried to install a banks big head wastegate. The waste gate could b sticking. Happened to me. It wouldnt fully engage till one day when i got on it really hard it just so happ3ned to pop free
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