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Discussion Starter · #1 · (Edited)
Hey guys, been a while since I’ve been on and now I’m in need of some tech advise.

Recently, my swap (1995 F150, VE-pump 4bt) has quit making boost after about 30-40 minutes of driving. Before this point, it’ll max out at maybe 12-15psi. Fuel pressure gage (between lift and injector pump) shows good steady pressure, EGT (before turbo) doesn’t climb when the engine isn’t making boost but should be, and there’s no smoke either white/gray or black. I’ve ran several tanks of fuel thru it from different stations. Anyone have any ideas?

Thanks
 

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Do you have an intercooler?
Check the AFC line is not leaking and also check the fuel slide pin is free.
No smoke would say no fuel and with good pressure that only leaves the IP is not suppling enough fuel.
For giggles once turned my fuel pin (after market) to the back side effectively eliminating the afc/fuel pin operation and 10-15 psi was the max boost my 6BT would make.
Cheers Steve.
 

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Also, check the fuel control plumbing attached to the intake chamber. If that little pipe is broken or disconnected the pump won't increase fuel for more boost. Also, check your air plumbing. Could have a leak that opens up as it warms up. Had to go back and review your original build. You have one item that should be replaced if you desire better boost response and power. 12-15 PSI boost is nothing. You changed to the HY35W turbo. That is a very poor unit for a 4bt. Compressor is just too big. The HX30W is light years better. Back in the day when you did the swap that HY seemed to be good but as time went one we learned a lot. On a 4bt smaller is better. Most guys use either the 44mm HX30W or 46mm Super HX30W. Neither will have 4" exhaust outlet but that can be worked out. That change would be money well spent. I didn't see it in your build but you should have an intercooler. Cummins had one on all 4bts over 105 HP. Hot air makes poor power but with only 12-15 PSI boost your power is only about stock 105 HP. Neither of these items explain you loss of boost.
 

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Discussion Starter · #5 ·
The engine is slightly modified w/ a 3200 RPM spring, the VE pump has been bumped, and the injector tips where cleaned up. The turbo is stock, I can’t remember what Cummins used OEM. No intercooler at this point.

I’ll loosen up the fill cap and see if that does anything. I didn’t think of the possibility of forming a vacuum in the fuel tank b/c the fuel pressure never seems to change, but that’s an easy fix to try.
 

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you might check the the wastegate actuator and make sure the rod didn't come off or some how its not closing. that would dump exhaust pressure and then not make boost or as much.
 

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I thought you'd changed the turbo to the HY35W. The stock turbo would be the small H1C which not a great performance item either. That turbo has long ago become obsolete. Cummins didn't use it beyond the 120 HP engine with aftercooler. The 130 HP 4bt got the HX30W 42mm. Any turbo above the one that you have would need an intercooler. Your boost level sounds pretty normal for that turbo. After all, the engine was only 105 HP and without more boost capability that's about all you can have. Turning the fuel up doesn't help because the turbo just can't use it properly. Redark1, if he kept the stock turbo he has no wastegate. Just a huge turbine housing. Either 16cm2 or 18cm2 depending on model. Its boost is very slow and very limited.
 
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