Oil & Fuel JD950 injector pump problem

Richard275 · Jul 27, 2021

I have a JD950 that runs for about an hour, then quits. Loosen the bleeder screw on top of the injector pump and it fires right up an runs....for a while. Seems that as it warms up, the run time gets less, to where it'll only run a few minutes. Replaced the filter, both hoses, and clamps. Same problem. We then ran a solid line from the tank to the pump, bypassing the filter housing. Same problem.

CausticUrbanCoast · Jul 28, 2021

Sounds like it might be time to rebuild the pump or you have an air leak in one of your lines.

Richard275 · Jul 28, 2021

I was wondering if the pump might be the problem. Replaced both lines and clamps and nothing changed.

Richard275 · Jul 28, 2021

Anybody know how hard it is to pull the pump, and what risks are there?

zzvyb6 · Jul 28, 2021

It's not a pump problem. It's a fuel delivery problem. The fuel supply up to the injector is admitting air OR fuel is not reaching the plungers.

Run a hose and a gravity feed fuel supply directly into the injector fuel supply line. Watch for air blowback (OK injector issue). If it runs good for a while, fix the fuel line. Could even be the pickup hose in the tank that has a crack in it. See if a full tank solves the problem. It will run OK until fuel level reaches the split.

Tx Jim · Jul 28, 2021

Check to be sure fuel tank is venting IE not creating a vacuum.

K5lwq · Jul 28, 2021

It definitely will not be the pump. Like Jim suggest check vacuum on the tank. Next time it gives you a problem, loosen the fuel cap and see if it runs better.

Leejohn · Jul 28, 2021

Check your oil level in the engine see if it is making oil. If it is it could be a seal in the injector pump. The only thing to make it make oil is the HYD pump and injector pump.

CausticUrbanCoast · Jul 29, 2021

Rather curious why you are adamant that a 30-45 yr old tractor with known injector pump issues is not the problem? The rubber does wear.

Anyway aside from looking for the primary cause which is usually a leaking line or poorly coupled/damaged flare. Since the JD950 is a gravity feed injector pump, you know which side the air is leaking into it on.

The description indicates it is at or after the injector pump. if it was a tank/vent issue the lines up to the injectors would not bleed until the pressure went back to an acceptable level.

I would bet on a leaking line at one of the flare nuts. Most likely right at one of the injectors.

Suppose there is also the possibility of a fouled/cracked injector, but I have not heard of it happening with a gravity supply.

Richard275 · Jul 29, 2021

K5lwq said:
It definitely will not be the pump. Like Jim suggest check vacuum on the tank. Next time it gives you a problem, loosen the fuel cap and see if it runs better.

Already went down that road. Tractor would die, then fire back up in about thirty minutes. Really dirty air filter wasn't supplying enough air to the top of the tank and it would pull a vacuum and wouldn't let the fuel drop. New filter and that problem went away.