966 hard to start

Tbone8 · Nov 15, 2011

I had the fuel pump overhauled on a 966. I bought the tractor in non running condition so I never heard it run. Engine was overhauled also. Anyway, it starts really hard, belches out a lot of grey smoke and shortly there after, smooth running. I can hear when I start it and turn it off, fuel dumping into the tank from the return line. Is that supposed to be happening? It has all new filters, no air leaks I can find. I really could use an idea or two to troubleshoot this.

Wisconsin Cowman · Nov 15, 2011

Better find out what they did to it when they rebuilt it. I maybe pull the injectors and a test them. How cold has it been during the nights?

pete 23 · Nov 15, 2011

I can't say that I ever heard fuel returning tank on that model, unless you have cap off and ear to tank. I would check the fuel return fitting coming out of the back side of the pump. It should have a small orfice hole in the fitting. This keeps a good head pressure in pump when cranking to fully fill the pumping plunger. Early models had a spring loaded check valve which could fail and work it's way back inside control section of pump and cause run away engine. Saw it happen, threw rod out side knocking pump off tractor so that stopped it. When you use the hand primer pump you should feel a substantial amount of resistance as you are pumping fuel through this small orfice once filters and pump head are full.

Tbone8 · Nov 15, 2011

It has good resistance when I use the hand primer. When you pump it, I can hear the fuel returning to the tank same as when I crank the engine and when I shut it down. It was overhauled by George's Diesel in Iowa. He is supposed to be very good and has done 3 other pumps for me. Is that orifice fitting on the pump or on the return line? Thanks guys!

pete 23 · Nov 15, 2011

The orfice is in the elbow that screw into back side of pump. There are a couple different styles. I used to be able to just look at them and tell if it was orfice or not but last one I took off to check looked just like the old original but it was the orfice type. Being pump was just repaired it is no doubt sealed so no doubt you are somewhat restricted as to what you can check without warranty problems. There is a increased fueling piston inside that could be sticking and causing problem. Another fly in the ointment so to speak is that once you crank for a while, oil pressure moves that increased fueling device to normal run position so you get less fuel delivery and that can add to the starting problem. However, old saying goes, hard start cold engine is engine problem, hard start warmed up engine is pump problem. Valve recession, head gasket thickness, piston height over block, bowl in piston displacement all can lower comp ratios. Even wrong valve settings and there are two different setting on intake valve depending on what camshaft you have. Gets complicated. Oh, cranking speed , critical.

966 hard to start

Tbone8

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Wisconsin Cowman

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pete 23

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Tbone8

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pete 23

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