I have put a 1st gen 92 dodge cummins powertrain with a 46RH in a 10,000lb RV and it runs great. It came out of a D350.

Recently, I stopped on a 20% grade coming out of a campground (Limekin state park, California) and when I went to start again, I put my foot to the floor and got almost nothing! The engine just sat there; the turbo produced no boost...it just sat there at a very low RPM, creeping forward churning against the converter and never fueled up enough to produce boost and get things moving.

I stopped. I floored it again. It repeated the same behavior again...never spooled up. This time, while creeping along, I lifted and stomped again, and this caused it to fuel just enough to kick the process into action and it began to build boost, spool and suddenly I was launching up the hill like usual.

My question is; what should I do about this? Smaller turbo housing? Turn the star wheel? I already have a fuel pin. I have never touched the star wheel or full power screw.

Thanks in advance, B

 

The Bosch VE inj pump had been used for many years before the Dodge application in VW diesels, Isuzu, etc. To meet emissions requirements for 92, Cummins required the highest injection pressures of any other application. The cam plate that actuates each pumping element wears at an alarming rate spreading bits of metal through out the pump giving them a relatively short life. The AFC circuit is designed to give that little puff of smoke to get vehicle moving and the boost sensing section takes over and adds additional fueling as boost builds. Turbos are a load sensing device and will never build boost at a dead stop beyond 5-7 psi. 2nd issue is your transmission, it will never last in a 10K lb vehicle. It could have been in a stall or your injection pump is starting to fail. The only thing a turbo housing or star wheel adjustment will help is in roasting tranny.

 

I'm trying to draw some conclusions from your post.

Is the conclusion that my injection pump is worn out and my transmission is dying a terrible death? If so, how soon will this happen? I have a whole lot of miles on this combination so far with no ill effects noted...more miles than most RVs see in a lifetime. I've been to 8,000ft and back to sea level over and over again...that's what I use it for.

The injection pump was new when installed; I had it rebuilt because the mill had 150K miles on it, and the transmission is by ATO and built and shows no signs of fatigue/wear/destruction. The converter is quite loose intentionally; to help preserve the drivetrain; and the power level is very reasonable, less than 250hp. I have more transmission cooler on this transmission than I have engine radiator, so that is not an issue...the transmission hot-side fluid is at about 180deg F and the cold side goes in at about 140deg F climbing steep mountain grades. A similar combo is used by an ATO customer in a car hauler that hauls more weight than this and spends more time on the road than off; he makes a living moving cars around. My trans was built the same as his and ATO was willing to warranty it.

So, making the wild assumption that my stuff is not self destructing yet, the issue seems to be that starting from a dead stop won't build boost. Why not; if the converter can spin 2000rpm from a dead stop under load, why wouldn't it fuel and build ANY boost? The gauge read near zero; not 4-7. I can power brake it in my driveway and the turbo spools up fine and I see the gauge move. I can stop on hills now, start from a dead stop and build boost and climb. It's just that one incident where it occurred. Perhaps the cold transmission fluid caused the converter to not allow the engine to rev high enough to get the fuel pump to richen the mixture? Perhaps the AFC circuit didn't work because I depressed the accelerator slowly on the hill being nice to the drivetrain instead of rapidly? The rapid stomp is what made it come to life. Does the AFC circuit work better if you stomp it? If that's all it is, I'll learn how to drive it under these conditions and not change a thing. I'll go read about the AFC...that sounds like that might be a clue.

 

Can you tell me where I can read about the AFC's "Puff of smoke to get things started" feature? I've read a half dozen articles describing the operation of the AFC but I don't see this part of the functionality covered anywhere. It seems logical that there should be some sort of accelerator-pump-like behavior; but I don't see it.

 

My apologies on suggesting anything was breaking. Not knowing history of donor truck in your post made me go to most obvious symptoms. The accelerator pump like initial puff I was speaking of is called 'no air fueling' and the star wheel does control that. But before you mess with anything, you could check the AFC U shaped tube from intake manifold to top of pump for cracks or breaks. What kind of boost do normally see? Was engine smoking in the one incident? The AFC is meant to respond to boost and give fueling to match. Have you noticed how when you are driving at a constant speed and driving up small hills how you hear turbo spool up but engine tone doesn't change? That's what makes a turbo a load sensing device. That's how AFC is designed to work. Sorry for confusion. But I quit having VE pumps rebuilt around 17 yrs ago. They ALWAYS come back, have used strictly Cummins Recon pumps ever since. And no, stomping on throttle won't help.

 

I will check the little tube. If it leaked a little, the AFC would be most sensitive to this when there is little/no boost...good point; maybe it's loose or leaking. I know I've had it off before. I'm sure it's connected, but tight and not damaged...not sure. I'll check it out.

Normal boost was 15ish psi before the fuel pin and almost 17 after. My turbo is stock. The exhaust is 3.5" from turbo exhaust brake (2ft) and 4" the rest of the way out (10ft).

During the gutless hill-climb incident, there was no smoke and no boost. I had to park on the grade to speak with the camp host, then depressed the accelerator slowly and gently to climb the hill. It was very steep and I didn't want to beat on anything...and typically never have to. When I got all the way to the floor and it still felt and sounded like 1/4 throttle...I was shocked. I backed off slowly, accelerated again slowly...then in frustration, lifted/stomped, and then it took off rather quickly and I backed off the throttle some and climbed the hill out of there. I looked out the side mirror when it was lagging hard and saw nothing. I looked again when it started to climb and saw a little gray; not a lot.

Could the lack of warm-up do something? The engine was 40deg F or so, started, allowed to idle for a few minutes then I pulled onto that hill. My grid heater and fuel heater are both deleted. Well, sort of. The grid heater is manual on a button and I didn't use it. The fuel heater has been deleted.

 

The fuel heater is for Alaska type temps and ULSD is much less prone to gelling. The air intake heater is less a starting aid and is meant as a smoke control after start up for EPA approval. A Cummins will start at 0 degrees unaided but it won't like it. Use that blockheater whenever possible. It will be easier on batteries, starter, and fuel system itself. Since you were on such a steep grade, the one incident might have been due to trans fluid being aerated or not picking up at all, hence the stall comment. Did you use an intercooler?

 

I'm not too familiar with the VE pumps, but a combination of the star wheel, and I believe they have a "smoke screw" on the top of the AFC as well.. the "smoke screw" is you no-boost fueling, while the star wheel controls when it starts to give more, and at what rate... If it doesn't ever smoke much when you stomp on it from no boost, I'd tighten the smoke screw (I think it's under a protective cap) a little, that will give a bit more fuel to help spool the turbo and get you moving.

Might want to check the turbo shaft for play while you're in there.