D17 Diesel misfire

Allyn

Member
I bought a D17D at auction that started and idled pretty good but had a bunch of farmer engineering “fixes” that needed to be reversed. One of the “fixes” was to bypass the fuel filters with an automotive electric fuel pump and filter. I got it home and found that it misfired above 12-1500 RPM so I cleaned/replaced and hooked up the original fuel filters which didn’t help the running at all. The injection pump was leaking so had it rebuilt with no change. Next the injectors were serviced and new tips installed. Now it runs worse. I cleaned the intake plumbing, bought a can of new diesel and ran a line directly from the can to the injector pump with no change. I checked the valve lash/valve springs and none were too tight or too weak so there is no problem there that I can see although I am still working on it. The timing tab is worn so I can’t read values but I marked it before pulling the pump and set it back like it was. I tried changing the timing while it was running and couldn’t tell much difference one way or the other but the lines are so stiff it can’t be changed much without loosening them. All indications to me are that the original timing is ok. It sounds bad above 1500 RPM with some black smoke and a little gray. What am I missing? I have manuals that refer to energy cells. What do they do and could they cause this problem? Oil pressure is good and it was represented as not using oil.
 
Disconnecting the hose at the intake heater elbow had no effect. It has the later style paper element air cleaner.
 
sounds to me like valves are floating at higher rpm. check valve spring pressure , pry up on springs while running to increase presssure to see if it helps ,old diesels are known to stick exhaust valves
 
First, I hope you did not loosen the pump and turn it with the engine running--that can shear the injector drive shaft off in a hurry-good by pump. Second, that engine had a nasty habit of "fluttering" when not under load. Did you try putting a load on engine to see if it stops the miss?
 
Thanks for the responses. The valve springs are good but I found a crooked intake push rod. I couldn’t tell from engine sound or looking under the rocker cover but it showed up when I spun the pushrods. It still runs ragged at high rpm with no load but seems to level out under load. Yes, I tried changing the timing with it running. Sounds like it was my lucky day that the shaft didn’t shear.
 
We were told in school--because of the super tight clearances, moving body of pump while engine is running could interfer with internals and jamb. Most rebuilders will tell you same thing.
 
I can only think of an injector cracking at too low of psi. My Farmall 504 has had a light miss under load for +10 years. One day I was mowing pastures and it sounded like the engine was going to explode it was knocking so bad. It happened suddenly, kinda scared me a bit and I had ear plugs in! I changed fuel filter thinking maybe water.

I called a diesel guy dad knows and he said it sounded like an injector. He told me what to look for when I pulled them. Sure enough, one was wet. Specs for that injector was 1050 psi +/- 50 psi. He tested it, it cracked at about 300 psi. He rebuilt just that injector, set it to 1100 psi, ran like a top and gained power.

You had the injectors serviced, but did they set them to the correct psi? Other than that, I have no idea. Could it be your cam has a worn lobe? Cracked sleeve letting water in? My first thought was injector because my tractor also knocked at low RPM and light load. I could gap it open and it would run better, but still knock occasionally. Really, really bad sound.

CT
 

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