Cummins big cam or NTC 400 low power but starts good

[mattyt1984]

Not sure on what engine this is but it is stamped 400 HP. It will start ok but has no power and will not rev up like it should. I have good fuel pressure going in to pump but it just seems like it is starving for fuel. Any ideas what could cause this. There is no smoke or blow by. Also if I put engine under load it will stall out.

 

[Truck Shop]

BCIII--Does it idle smooth? Happen at once or slowly over time?

 

[mattyt1984]

Yes

 

[Truck Shop]

Yes what? I asked two questions.

 

[Truck Shop]

Remove the braded/rubber return fuel hose near back head. Slip another hose over it and run it into bucket. See if it runs the same.

 

[mattyt1984]

sorry yes idles smooth I just purchaed item was told it used to run good has been sitting for years.

 

[Truck Shop]

If the return fuel line swells inside cutting flow it will put pressure against aneroid and cut fuel back in pump. First place to look.

 

[mattyt1984]

I had fuel flow back to return i found if I plug it power increases. I put a valve on the return and let just a little through and it gets allot more power. What's could cause this?

 

[Truck Shop]

That means that PT pump is not aneroid equipped-The old trick to up rail pressure on early non aneroid pumps was put a pair of vise grips
on the return line-problem with that is it causes slow deceleration. Next item have that pump checked. Plus check the fuel feed hose first.

 

[funwithfuel]

Is that a stupid timing control valve hanging off the side there? I've known those to be a headache

 

[Truck Shop]

Is that a stupid timing control valve hanging off the side there? I've known those to be a headache

Correct-you notice the throttle shaft lever is on top of pump.

 

[funwithfuel]

Correct-you notice the throttle shaft lever is on top of pump.

Yeah, and i know nothing about how those things work. I do know STC is probably not getting energized and it's probably running retarded. Just my theory with absolutely nothing to back it up.

 

[Truck Shop]

Problem is that is not a true STC fuel system. I had a cummins manual on it but can't find it.

 

[funwithfuel]

The system on the older Komatsu excavators is simply on/off using a fuel shut-off solenoid. I believe the automotive version is thermostat controlled. I think. On the komatsu version, anything over idle blubbers and smokes, won't build any boost. It's terrible. I always recommend running the overhead OBC method, then see if the problem remains. I hate STC.

 

[JDirt]

I had a big cam that would start and idle perfectly, but seemed to be running out of fuel when you tried to take off, it had a tiny hole rubbed in the braided line from the tank to the pump. It was hard to find, but a cheap, easy fix.

 

[Truck Shop]

That pump is a PTG variable speed pump. Mainly for stationary engines.

 

[Truck Shop]

The PTG pump has two governors. The automotive/highway standard governor located
in the lower housing and a hydraulically operated governor in the top where throttle control
lever is located for load requirements. Having sat for a period of time the bottom governor
has probably stuck. Any moisture will collect in the bottom along with a possibility it has
had bio fuel which over a period of time will freeze up the governors in a PT pump. If it
will idle but won't gain rpm the governor is a good place to start.

So IMO I would have pump checked.

 

[mattyt1984]

Is this also a type of governor or regulator??? It's bolted to side of engine how do I test?

 

[Truck Shop]

It is the oil psi operated control for the governor located at the top of injection pump. Remove the hose going to top of pump, see if there is
any black engine oil in that hose or port. IIRC that side should only have clean fuel. That controller IIRC is not rebuildable only serviced
through Cummins because it's calibrated.

 

[mattyt1984]

I'll check tomorrow so the only way this engine is governed or rpm it's controlled it's by fuel pressure going to the rail?