Cummins 4bt

[David-L]

A buddy of mine has a Timberjack 610 forwarder with a 4bt Cummins in it. It will sit over night and will bleed out the fuel system as he says. He has changed the transfer pump and checked fittings for tightness and that is good. Has to prime it with the pump in the morning to make it run. Is there a check valve somewhere in the system or the injection pump. I have the same motor in my skidder but have not had any fuel issues other than a weeping transfer pump which I replaced. He's 70 and likes to have his first tree down before daylight, I'm not kidding either.This not starting thing without priming is getting on his nerves he says. Thanks, he doesn't due computer. His name is Jim and owns Mellon Forestry Services.

[4x4American]

I had a pin hole leak in the fuel lines on my 89 dodge with a 6bt, and it made that thing about impossible to start.  After I changed the lines, you barely had to bump the starter and it'd fire up.  Throughout the process of me chasing the air leak, I replaced a bunch of things.  One of them was a little gasket up in the fuel heater, I got the new one from a certain type oil filter at the wal mart and it fit perfect, I had found that p/n on firstgen.org I think.  I would psi test the fuel lines to look for a hole.  If you can, put air psi into the fuel tank, and see where the fuel comes out.  If you open the fuel cap, and put your blower chuck in there, and then just take a rag, and wrap it up tight as you can and push it into the hole a little to make it real tight, then give it just a little bit of pressure, you don't need much.  And then have someone else watching for a leak.

[4x4American]

What town in Mass is his machine in?  I have a friend who lives in Belchertown and works near Springfield I believe, and he's a good equipment mechanic.  I bet he'd go take a look at it if he can't figure it out

[RHP Logging]

There is a check valve on the return line to the tank.  I think you can get it from Cummins.  When mine had failed and I was waiting for the part I put a shut off in its place and at the end of the day just closed the line up.  Make sure you open it back up again upon starting!

[kiko]

Any idea which injection pump he has?   Rotary, inline P ,inline A , or other. if it has the side by side fuel filter set up there is an oring between the filter housing and the head.   It is a special oring so it is a good idea to acquire a new one before removing the filter head as not to end up leaving the machine down. 

[David-L]

We are both in Petersham, Mass. i will check in with him tomorrow about the return line check valve. Does that come off the injection pump or the fuel rack? Of course that means getting to his landing before sun up. Will also try the air trick if thats not it. Minimal psi i assume. Thanks

[David-L]

Never looked at his motor set up but will tomorrow and keep the o-ring thing in mind. Mine had side by side but just loosend up the primary when bleeding after the new transfer pump. He has a simple problem I am sure , air. Not sure of the pump but would guess rotary. Just looked at my manual and i have and he does to the Glass element filter water seperator. I had the spring clamp fail or weaken  on a John deere tractor once and caused this problem also. The clamp holds the  glass filter to the fuel plate, maybe an issue.

[4x4American]

Ok cool so just on the oppsite side of the Quab. 


PM me if you want his number.  Hopefully it's nothing too complicated

[David-L]

Would that be Rick Shaw. I will p.m. you. Always good to have some backup once and awhile. Thanks.

[danbuendgen]

The fastest and easiest way to find a air leak (like said) is to pressurize the fuel system with a air compressor. Turn your regulator down to 10 psi or you will start blowing seals. Once the system is pressurized, the leak will show up quickly. Usually the best way to pressurize the system is to use a blow gun with a rubber tip and put the air to the fuel tank breather vent. Take one person to hold the blow gun and one to check for leaks. Or rig up a spare fuel cap with a air chuck. Drill a hole in the spare fuel tank cap and tap it or just use something to seal it up.
What year forwarder/Cummins does it have? Most of the injection pumps the 4/6b series use are the Bosch VE (older rotary pump) or the in-line Bosch P-1700. If the leak is before the lift pump, it will suck in air as the engine is running and no leak will show but it should be running rough and stall out here and there because the lift pump will suck in air wile running. If the leak is after the lift pump it should leak fuel in between the lift pump and injection pump wile the engine is running.
GOOD LUCK

[4x4American]

yes, my leak was in the fuel lines, and after you got it going, it ran fine, but I wasn't pulling any heavy loads with that death trap!  Also, before you go trying to make some fancy cap, try the rag method, it surprised me when it worked.  Like I said don't give it too much psi it only takes a little bit

[redprospector]

I've had a 4b, and 2 6bt's act like you described. All 3 times it was the return line leaking. One of the 6bt's was the banjo fitting on the back of the head, a new seal and it was good as new. The other 2 weren't as easy to find.

[David-L]

The head or the head on the filter elements. I will have a look and Dan yes I recall my pump being a bosch rotary and his fwd is the same years as my 240, 1995. I appreciate all the help, I am not a diesel mechanic but can turn a wrench. thanks and I will update.

[danbuendgen]

David,
I have never had issues with the hard fuel lines or banjo bolts (not saying it's not possible) in any of my Cummins engines. But I have had issues with pumps leaking (lift pumps and injection pumps) dew to age/the new crap ULSD fuel they have now. It's a dryer fuel and it dry rots any natural rubber over time in older style fuel systems. Now I add one ounce of 2 stroke oil (Wal-mart's tc3w) per gallon of diesel fuel for lubing pumps and seals. Works good. Cheaper then the snake oil fuel additives they sell, and works better too. I get a extra MPG in my work trucks when running it also.

Remember, if you pressurize the fuel system, MAKE SURE TO TURN YOUR REGULATOR DOWN TO 10-15 PSI!

[David-L]

Took a look today at my friends forwarder, it's a 97 but has the same motor as me. Bosch rotary pump and two fuel filters. The return line says out on the top of pump and is steel to a brass elbow then goes to braided fuel line back to the tank. Is the check valve in the pump or is it the brass elbow behind the filters. Thanks.

[David-L]

Can someone tell me what psi the fuel in the return line is at. wondering what keeps the check valve open during run time?

[redprospector]

The head. It was in a 97 dodge, may be different. I'm not posative, but there should be a check valve in the pump.

[David-L]

Learned that its really not a check valve , but a flow restriction valve . We think it might be that and are getting one. its on the pump return line fitting.

[danbuendgen]

A 97 Dodge has the Bosch P-1700, the pump David is working on seems to be the Bosch VE rotary pump. The P-1700 has a Over Flow Valve (OFV) it's job is to regulate the fuel pressure on the low pressure (lift pump to injection pump) side of the system. As far as I know, the VE pump does not have a OFV.

David, If you need to test the return line for pressure, I would guess the specs would be 10-15 psi. There should be a reducer fitting someplace past the pump. This reducer fitting takes the place of the OFV on a P-1700.
Does your buddy's engine run smooth or rough when he gets it going? If it runs smooth you have a leak between the lift pump and injection pump and a fuel leak should appear. If it runs rough, the leak in before the lift pump, it's running rough because it's sucking air into the system. The restriction valve you are talking about, should just be a fitting with a tiny tiny hole drilled in it. I bet you it's not the issue. The only issue that can cause is it can get dirty, and plug up. Just take it off and inspect it and give it a good cleaning. No need to replace it unless it gets cracked.

I bet you the issue is air in the system, not the restriction fitting. How far are is the machine from Brattleboro VT? If your not too far I could swing over and check it out. PM me if you want.

[4x4American]

P7100 you mean eh  ;)

[danbuendgen]

P7100 you mean eh  ;)

Oops. Yep, your right.

David,
Another good place to get info on the Cummins B series is any of the Dodge Cummins forums. The older Dodges (89-93) uses a 6bt with the VE pump. I like cumminsforum.com and 1stgen.org

[David-L]

My pump is not the same as his, Mine is a rotary but has some kind of diaphragm thing on top of it. It is not a inline pump. This was a reman motor in my machine with 1,560 hrs on it at current. Don't know if they used the same fuel system off the old motor. Was done before I took ownership.

[ehp]

David, your skidder is the same fuel pump style as mine . I got a 98 - 610 but never looked at what its got for a pump on it

[ktm250rider]

I have a similar problem in my excavator with 4bta engine.  I have to bleed it to get it started.  It runs good above 1000 rpm.  When I drop it below it starts to stumble, and eventually stalls. 
Today, I had it running and shut off the engine.  After sitting for 10 min, it wouldn't start.  No smoke at all through exhaust.
I'm gonna try the pressure test.  I noticed that when I try to prime with the hand pump, I can hear what sounds like air leaking after each pump.
Of course all this is on the back side of the engine, with the counterweight blocking any view of the lines.

[barbender]

I had an older Dodge with the rotary pump, and it developed a leak on the low pressure side of the injection pump. It ran just fine, but I would have to prime it to get it started. Yours sounds like a supply side issue as well.