350 fuel problem

[gab]

Greetings!
i recently bought a 1968 straight 350 crawler diesel and i'm having issues bleeding on of the 3 injector/line.

when i bought it i noticed the engine was running rough and would feel like starving for fuel as i was going uphill. Anyway, i parked it in my garage and proceeded on the maintenance of the machine. Changed all fluids and all filters. Still it was running pretty rough and i noticed ALOT of fuel dripping out of the return lines where they attach to the injector's tee. Lines where old and cracked and no clamps, so changed them added clamps...still leaking until i decided to double the clamps at each joints. I tought injectors were sending too much fuel back so decided to get new ones. Got the new injectors installed, purged the system and crawler started and sounded really well.

Came back next day to try it and see how much power it has but when i started it sounded really rough, lots of white smoke, occasional backfires, tried to move it and it would want to stall as i was releasing the clutch. Throttle lever didnt seem to change anything.

So i tried to bleed the injectors again, the two furthest ones from the driver's seat were looking good but the last one was blasting fuel mist...couldnt get a steady flow. Unhooked the line from the IP to that injector (this is the one that attached under the pump) and turned the engine over to see if fuel was coming out of the pump. It was, but just dripping...no steady flow. Also as i was turning the engine over it popped the rubber cap i had put on the injector to protect it. seems it popped from back pressure...is this normal? to have back pressure in the injector when the line is unhooked?
should a steady stream of diesel come out of the pump when i crank it?

dont know if thats relevant but tractor as been started with ether most of the time by previous owner.
also the check valve in the return line is not there anymore...and the vent tube in the fuel tank is weld sealed at the bottom but i believe the cap is pretty loose.
Also fuel flows free in the system pass the lift pump...i mean the lift pump doesnt stop it. my return line is always flowing

So i am looking for an answer as to why fluel isnt going up to this injector. Thanks!

[gregjo1948]

That's a lot of questions. A steady stream coming out of pump-NO. I believe the pump is the same as a gas engine distributor. It is how the cylinders are timed to fire. Fuel should come from one at a time and the pressure will force the injector open. The "check valve " needs to be there. I'm assuming you're referring to the one right by the injector pump. I'm thinking that valve only lets fuel into the pump and not back towards the injectors. You can get one for about $15.00.00 at a JD dealer or maybe Lavoy has them. White smoke and no throttle rpm change, leads me to think there may be water in the system and/or filters are plugged up. I'm certainly not an expert on the fuel systems but sound like you should hope some of the other guys on this forum will chime in on the subject. JimB - Lavoy - Leonardl and etc.

[Jim B]

Yes, the injection pump (IP) on your 350 works as a distributor, delivering fuel to each cylinder at the proper time for firing, not a steady stream to the injectors. The check valve should be in place at the IP outlet as it prevents fuel, or air, from getting into the pump through the excess fuel return line which goes to the tank. The check valve also lets any air bubbles, from bleeding or coming in with incoming fuel, out of the IP and vents it out of the system through the fuel tank. Without an injector (injection nozzle to be correct) in place at the end of the line, the IP doesn’t build significant pressure so the fuel will dribble, maybe slightly spurt from the pump or a loose line. The nozzle has a spring loaded valve in it that "pops" and sprays the fuel into the cylinder when set pressure is reached.

In an effort to get by and save having an IP rebuilt, people often remove, or break the check ball out of, the check valve when the pellethane ring in the IP starts to break up and plugs the check valve. Too much back pressure defeats the pump and will lower power, even shutting the engine down. If your check valve is missing it is possible the return line is plugged some where between the pump and tank. The return line leaking at the injectors, and needing double clamps, may indicate a plug is between the injectors and tank, since it is the same line as from the IP. The return line must be clear and unrestricted from the IP, past the injectors and back to the tank. You need to confirm it is clear.

With a clean rag under the area to catch things, carefully remove the small cover (held on with two screws) from the side of your IP. Look to see if there are any small bits that look like mouse turds behind that cover. If there are it is a sign the pellethane ring is failing and the pump needs a rebuild. You can try running it for a few minutes with that cover loose and leaking some fuel. If it runs better/properly that is another sign blockage is defeating the pump and the IP likely needs a rebuild.

The fuel transfer (lift) pump will let fuel gravity flow past it. I don’t understand what you mean by your return line is always flowing, unless you are saying you have fuel flow out of the IP if you remove the return line when the engine is stopped. If so I expect it is gravity flow if the tank level is above the open fitting.

The tank should be vented properly. The intent is that the fuel cap, with a gasket in it, can be tight so the operator doesn’t get fuel slopped on him during operation as can occur with a loose cap. If the tube is damaged and that is why it is welded shut at the bottom of the tank you may have to live with it or design a different vent.

Your IP should have a tag on it. You can use the model info (like DBGFC) on that tag to find a Stanadyne/Roosamaster manual on line and get a better understanding of how your fuel system works. Here is a link to one of these DB manuals as a sample of what I am referring to. You may not find your exact one but how they operate is similar for the most part. Understanding the system's workings will help your trouble shooting efforts.
https://www.stanadyne.com/dealerportal/ ... /99523.pdf

If you determine your pump needs repair, I recommend having it done properly and calibrated by a qualified injection pump shop. Just my thoughts, HTH
Jim

[gab]

Thank you guys for taking the time to reply. I know the subject has been discussed plenty already on the board...i tried to read everything i could find but didn't seem to find answers to my specific situation.

So i understand the dribbling out of the pump is normal and i think fuel does get to the injection nozzle because when i removed the exhaust manifold i could see the ''exit hole'' of the cylinder (the one i'm having trouble with) was wet.

I think what's happening is some of the fuel and compressed air is being sent back out the cylinder through the injection nozzle through the fuel feeding tube of that nozzle on the compression stroke. Creating some sort of counter pressure with the pump in the fuel line...maybe explaining with i'm seeing fuel mist coming out as i try to bleed it. I believe there should be some kind of one way valve in the injection nozzle preventing that from happening. Do you think this brand new injection nozzle could be faulty? and if so is that something that can be repaired or you just get another one?

As for the things you asked me to check, i confirm that my return line is clear all the way through and also removed the timing window on the pump and everything looked clean there...

[Jim B]

Yes, new injection nozzles can be faulty. Not knowing where you got them, like everything else the quality isn't there with a lot of cheap parts that are being sold. If you have air and fuel blowing out the port where the line from the injection pump hooks to the injector, it is no good. Take a look at the manuals, you will see the design of the nozzle makes it a check valve, when working properly. If you got the injectors from a reputable shop they could have pop tested them for you before you took them to be sure the cracking pressures were in spec and they should stand behind a bad one now. They can be repaired but are normally replaced. JMHO
Jim

[LeonardL]

Jim has already said pretty much everything I would have said on this. Great job as always Jim and thank you. Personally, I think it's time you take a look at a combination of things. And it's probably not what you're going to want to hear. You do need to confirm that your injectors are okay and functioning as they should and get your fuel system back to what it should be. Injectors, check valves, vents and return lines all have their purpose. When everything is right then you shouldn't need clamps on your return lines at the injectors. I always hate it when I see this stuff has been eliminated or screwed with.

I think you need to check your compression of each cylinder because the former owner was using ether to start the machine. Ether can destroy compression rings, warp valves, crack cylinder heads, crack pistons and cause scoring of the piston skirts and cylinder walls. All of which leads to low compression.

When these Deere motors are right then they don't need ether to start unless it is like stupid cold outside. Then it should only be used sparingly. Low compression will cause white smoke, hard starting and poor performance in general. But!... it doesn't answer your other symptoms. It may be part of the other symptoms but not the complete cause of your problem.

If you have confirmed that all of these things are okay and are known to be good, then it usually points to one thing and that being the IP. The white smoke and poor running could be because the governor ring has come loose inside the IP. If these rings have only turned loose, pulled away from the little studs that retain them, then they may not have the tell tail pieces of debris that is usually found behind the timing window. Sometimes they will shear out and pull away from one side and not destroy the ring like they normally do. Thus leaving the impression that nothing is wrong with them.

Even with this condition your IP will still try to send fuel to the injectors even though the ring is junk. White smoke, rough idle and no throttle up are all indicators of the timing being so far off that your fuel is being delivered at the wrong time.

I am a bit puzzled by what you describe as blowing back and backfiring. I can honestly say I have never seen a Diesel engine backfire. I've had them knock like crazy and sound like a hammer was being used on top of the pistons but never a backfire. Not going to say it isn't possible because anything is possible I suppose.

I think you may end up with a combination of things. Like bad compression as well as your injection pump and maybe even bad injectors. You need to confirm what is good and what is bad. Process of elimination will lead you to the root cause.