Engine/Transmission (1994 - 1998) Pulled The Plate, Gutted AFC...Still no power. Help!

[CGriffith]

I'm working on a 6CTA8. 3 with a P7100 injection pump. The engine is basically a big block 6BTA. 504 C. I. with the same fuel pump and a HX-40. The engine has been rebuilt but I am unsure of the mismash of parts that were used. The pump is rated at 300 hp@ 2200rpm and 860ftlbs@1280rpm per the I. D. plate on the pump. No CPL # is anywhere in sight. The truck always ran good but I thought what the heck I'll slide the plate forward and see what happens. Turns out nothing. It makes 20psi of boost no matter what I do.

Here is a short list of what I did to try to find the problem:



Moved stock plate forward-no change in boost/top end smoke

Adjusted starwheel-more bottom end as expected

Plugged wastegate-nothing

Moved plate back-no change

Checked for boost leaks using cap over turbo inlet and compressed air-found none

Pulled plate-no change in boost/HP-WTF?

Gutted AFC spring and arm-still nothing except lots of preboost smoke

Wired up fuel solenoid to be sure it was opening fully and checked throttle movement for full throttle-everything checked out.



The truck makes 20psi of boost, which from what I have read means it is making about 280hp (20psi X 14HP/psi)- Got that # from Pittsburg diesel inj. According to cummins 20-22psi is normal for this engine.

The fuel pressure gauge reads 22psi idle/cruise and 8-10 at WOT. Is this enough? It has always ran well and I have had no problems until I started trying to up the HP. It makes 20 psi of boost and 1200deg pre-turbo no matter what I do. I think it's a fuel delivery problem because it doesn't smoke at WOT/full boost no matter what I do to the injection pump. I'm down to the injectors. Maybe someone put in really small injectors when it was rebuilt. I don't know what part # they are. Can I pull them and check without rewashering them? I'm kind of new to diesels so good advise is appreciated. TST claims a #5 plate should be good for 450hp/1200ftlbs so I thought if i slide the plate I would get a little something. That's how this all started. If I was happy with stock power, I'd still be happy. I have tried everything that I have read causes low power but haven't been able to solve the problem. Ideas?

Thanks

 

[Joe G.]

Fuel pressure is kind of low. For our 5. 9 engines idle pressure should be at least 18 PSI and about 22 or so at 2000 RPM with no load. At 8 PSI you are not getting enough fuel. That would also explain why you have low boost. You may have an overflow valve problem. Check that by clamping the hose from the overflow valve with some pliers and watch the pressure gauge. Don't leave it clamped very long, just enough to observe the reaction.

 

[Vaughn MacKenzie]

CGriffith, try replacing the overflow valve, and making sure the fuel shutoff solenoid comes up all the way when the engine is running.



Vaughn

 

[Cooker]

Sounds like a fuel delivery problem to me as well. 8 psi at WOT is not nearly enough.

 

[CGriffith]

Thanks guys. I'll check the overflow valve tomorrow. I already wired up the fuel shutdown arm to eliminate any problem there. I think some one must have put some small injectors in this thing when it was rebuilt. Would the wrong injectors cause this kind of problem? I have never pulled a set of injectors before. Could someone tell me if I can reuse the seals/washers or whatever when I pull one injector to check the part#.

 

[tURBOdIEZEl]

Sounds like a fuel delivery problem to me as well. 8 psi at WOT is not nearly enough.

at WOT in peggin' my 0-30 fuel pres gauge.