Need help with big Cummins.

[ride172]

I hope there is someone around here that is familiar with the old 855 mechanical Cummins engine. The truck ran and drove perfect for about 300 miles. These were short trips around an hour long. I took it down to get 8 new drive tires yesterday. They found and replaced two cracked brake drums and mounted the new tires. When I went to drive it home I noticed a lack of power when I shifted into high range. The truck felt like the turbo wasn't working and wouldn't rev past 1500rpms. In the lower range the truck pulls good and the turbo spins up. But when in the top three gears it has no power and the boost goes down. It has the PT pump on it. The air filters look good. What would cause a sudden loss of power. The truck was only at the shop for a couple of hours.

[ride172]

Oh yeah, I didn't smell any hot brakes on the way home. The truck would roll up to stop lights in neutral so I don't think the brakes are over adjusted. Just no power in higher gears. It is also a little slow to decelerate when upshifting. If I don't use clutch I have to wait about 3 sec for the rpm to fall enough for it to slide into gear. It used to upshift almost immediately.

[ride172]

Changed the fuel filter today. Cleaned up some small electrical lines that go to the fuel pump. I also cleaned the small filter in the pump.

[xjrev10]

First thing I would say is fuel filters, then air filter. If not those, must be internal pump problems. Really smokey?

[86FUBAR]

Not to familiar with that engine but check lift pump fuel pressure , make sure there are no blockages in the feed line from the tank and I'm not sure if it has it but there might be a spring loaded check valve at the pump in the fuel return , if it's stuck partially open there would be a definite lack of power . An old truckers trick was to use some vice grips and pinch the fuel return line just enuf to boost the pressure in the injector pump and give more power.

[ride172]

Thanks for the info guys. The truck smokes grey for about 10 min when you start it cold. It clears up really well and throws a little smoke when you get in the throttle but not black smoke. It doesn't roll any coal. I never thought to check the air cleaners. My mind was set on fuel issues. I'll look at them after I get my 8mo old son in bed.

I had an old mechanic today tell me to look in the tank really well. He said one time he had a truck that would run great for hours and then just about die. They worked on it for a month before they found a half disintegrated beer can in there that was blocking the intake every so often. The driver had changed the fuel filter and when he was priming it. He tried to use the can on a wire to dip fuel out. He forgot it was in there. Its usually always something simple.

 

I'll look into the check valve. I hope I can figure it out without having to tear into the pump. It is a really big motor. Has that straight six torque. When it runs right. Thanks again.

[cruiser54]

Keep in mind you can get a "flapper" inside the fuel delivery hose from tank to pump. 

What happens is the inside of the hose comes apart and blocks the fuel flow. 

 

If it's old at all, consider replacing it just for giggles.

 

BTW, I built an 855 BC2 to 625 horsepower. I love those motors.

[ride172]

Here's an update. I put air to the filters and didn't get much of anything out of them. I had looked at them when I got home the other day. But I think I'm going to cross them off the list now. I think I'm going to get some new fuel lines made for it. The return line is way too long because I think the truck had two tanks previously.

 

Cruiser, I sure would like some tips on cranking this engine up when I get this issue tackled. This 855 is the NTC 350 and I'm pretty sure it's a big cam. I'm just not sure which big cam it is. I think it is a II or III. The truck is a 1980 Kenworth W900. But who knows what has been swapped out in 36 years.

 

I should get a chance to road test it tomorrow. My wife has been working the last few nights and two car seats won't fit in the cab. I'll post up the results then .

[cruiser54]

Here's an update. I put air to the filters and didn't get much of anything out of them. I had looked at them when I got home the other day. But I think I'm going to cross them off the list now. I think I'm going to get some new fuel lines made for it. The return line is way too long because I think the truck had two tanks previously.

 

Cruiser, I sure would like some tips on cranking this engine up when I get this issue tackled. This 855 is the NTC 350 and I'm pretty sure it's a big cam. I'm just not sure which big cam it is. I think it is a II or III. The truck is a 1980 Kenworth W900. But who knows what has been swapped out in 36 years.

 

I should get a chance to road test it tomorrow. My wife has been working the last few nights and two car seats won't fit in the cab. I'll post up the results then .

Hey, if you're getting new hoses made up, ask the guys to make the supply hose bigger in diameter!!!

 

I had a 78 W900. 

 

These guys are the greatest and helped me with my horsepower goals. 625 horsepower with no black smoke. Only heat waves....

 

http://pittsburghpower.com/meet-our-team/

[ride172]

So should I make the return line smaller in diameter to restrict flow and build more pressure? I was also thinking of a small bar clamp (think that's what it's called). The fire department used big ones to pinch poly gas lines I've cut through the years. That way it would be adjustable just like the vice grips.

[ride172]

Double post... How fun

[cruiser54]

No. Add air, not fuel. Get this problem fixed and we'll go from there. 

[ride172]

OK. The new fuel filter has the truck ripping and snorting again. I had a bunch of fine black particles come out of the filter and they settled down to the bottom of the jar I poured it in. I didn't have any water to speak of in there. I'm unsure if the black stuff is slime left over from algae or if it is the inside of my fuel lines. I'm still going to get new lines made and I'm trying to find some Bio-kleen biocide.

 

How much bigger should my supply line be? Can it be too big?

 

Also, I was getting about 23psi manifold pressure climbing a hill with my foot in it at about 1800rpm. I was in the high side of 7th (13sp fuller). Does that sound like what I should be getting? I could of gotten a couple more lbs of pressure but I didn't want beat on it too hard.

[86FUBAR]

Look on the engine for the data tag that has the CPL # , I'm not sure we're it's usualy at on that engine but once you have that you can look up in a service manual what the specs are supposed to be i.e. Boost psi / rated HP / RPM . Etc... To me 23 psi sounds good but that might not be what it's rated at.

[cruiser54]

OK. The new fuel filter has the truck ripping and snorting again. I had a bunch of fine black particles come out of the filter and they settled down to the bottom of the jar I poured it in. I didn't have any water to speak of in there. I'm unsure if the black stuff is slime left over from algae or if it is the inside of my fuel lines. I'm still going to get new lines made and I'm trying to find some Bio-kleen biocide.

 

How much bigger should my supply line be? Can it be too big?

 

Also, I was getting about 23psi manifold pressure climbing a hill with my foot in it at about 1800rpm. I was in the high side of 7th (13sp fuller). Does that sound like what I should be getting? I could of gotten a couple more lbs of pressure but I didn't want beat on it too hard.

Just go the next size bigger on the fuel line.

 

CPL is located on the accessory drive housing above the air compressor.

 

23 is good. Only way you'll ever be able to safely maximize the output of that engine is to install a pyrometer that reads off the exhaust manifold, not after the turbo. 

[ride172]

Update on the truck. It is scheduled to go in the shop on Wednesday to get a wheel seal, overhead ran and a DOT inspection. This afternoon someone contacted me to haul 120 tons of crushed asphalt. I'm going to make the first loaded trip with it tomorrow. Hope I can get all the asphalt moved. At least I'll know how the truck pulls with a load on.

Pyrometer is on the way. I just don't have a hole for it in the dash. There is so much wiring and lots of air lines and oil lines back there. I'm afraid if I mess with it the truck will catch fire. I need to trade out the amp gauge for a volt meter.

I'll post what the mechanic has to say about the motor when I pick it up.

[cruiser54]

Update on the truck. It is scheduled to go in the shop on Wednesday to get a wheel seal, overhead ran and a DOT inspection. This afternoon someone contacted me to haul 120 tons of crushed asphalt. I'm going to make the first loaded trip with it tomorrow. Hope I can get all the asphalt moved. At least I'll know how the truck pulls with a load on.

Pyrometer is on the way. I just don't have a hole for it in the dash. There is so much wiring and lots of air lines and oil lines back there. I'm afraid if I mess with it the truck will catch fire. I need to trade out the amp gauge for a volt meter.

I'll post what the mechanic has to say about the motor when I pick it up.

Make sure you get the special pyrometer probe that's metal so you can install it in the manifold. 

[ride172]

Good evening. Well I got the truck picked up from HD Truck Repair and I think their mechanic did a good job on my overhead. The truck sounds great. It doesn't grey smoke as bad when cold and it just feels smoother. The trans shifts better too. I don't know why but it seems the rpm's are right where I need them when its time to upshift. It just pulls it right in. It does seem like it has a few less ponies but more torque. My butt dyno might be wonky too. The mechanic found a few things needing repaired on the truck but gave the engine a clean bill of health.

 

I can't for the life of me find the oil filter on the truck. The owner of the shop looked for it with me and he couldn't locate it either. Do you know where it would be Cruiser? In the pan? Inside the oil cooler? It damn sure doesn't have a spin on filter anywhere. When I picked the truck up there was a filter on the seat and a gasket but they were locked up and had gone home already. The filter is a drop in. I just can't find the housing.

 

Another question I was messing my Jake brake and I got it to work one time and then flipped it off and now I can't get it back. I tried wiggling the switch on top of the clutch pedal. No worky.

 

That's all I can think of now. I know I will have more questions later. Hope everybody has a safe and fun memorial weekend. Don't forget all the fallen military men and women. They died fighting for their country and acknowledging their sacrifice is what its all about.

[cruiser54]

Should be a spin-on on the passenger side. 

 

 

Look at the switch on the throttle at the injection pump. 

[ride172]

There is not a spin on on the passenger side. My fuel filter is on the frame on the passenger side. There is not an oil filter anywhere I can find. There is a round thing mounted perpendicular to the oil cooler on the front of the engine by the fan. I was told this was a "pre cooler". It is about the size of a coffee can. Could it be in there?

[cruiser54]

Does it only have a bypass oil filter mounted up on the driver's side of the cab? 

[ride172]

There is no filter anywhere that I can see. I followed all the oil lines and I can't find anything. I could make $200 a day betting people it doesn't have one. A few mechanically inclined people have looked at it and they all walked away scratching heads. I am in NE right now but when I get home I'll load up some pics of the engine.