'75 JD 310 rpm issue

[runamok]

Afternoon all.
I'm having trouble with my 75 310. It starts fine, but then will quickly lose rpm and then die. At start up, the throttle operates as it should, but quickly becomes useless as it starts slowing down. The colder it is the longer it'll run before losing rpm and dying, but it's still just a few minutes.
I replaced the fuel filter this morning, thinking there was a fuel supply issue, but that doesn't seem to have helped.
I also checked the screen inside the injection pump, and it's nice and clean.
Any thoughts on what's going on here? I'm wondering if I should run through some injector cleaner, but it's not staying running long enough to really work much of that through the system.
Thanks all for any help you can give.

-Z

 

[Simon C]

Try blowing air back into your return line to tank. It should bubble heavily in the fuel tank. If it doesn't, something is plugged. Try putting 2 PSI into the fuel tank inlet with a blow gun and a rag ball over the inlet holding most of the pressure. If your putting too much air, you will feel it at the rag ball.
With the air on the tank check all the lines and filters for leaks. You will need two people to do these tests. If you find any leaks , fix and then retest.
Are you sure there is only 1 fuel filter, just asking, cause if you have missed one it is probably plugged.
Does it have a an electric fuel solenoid that is dropping out. Probably has only a mechanical lever to shut down. Not sure, you will know.
Try these things first.
Simon C

 

[runamok]

Thanks Simon,
I won't have help to do a leak test until Monday, but I put low psi air through the return line (leaves the top of the injector pump) and it bubbled in the tank like it should.
Next I did another check along the fuel lines. There's no second filter. Definitely a good call to check though.
There's no fuel solenoid, just a mechanical pump that feeds the injector pump. Just to make sure things were flowing, I removed the inlet to the injector pump and turned the key. Fuel came pouring through just as I would expect.
Hooked it all back up and it fired up, then slowed and died again. No change.
Any more thoughts?
Thanks again,
-Z

 

[Simon C]

You could possibly be sucking air in at the transfer pump on the side of the block. I did one recently for a friend, that when the pump was pulled of the block the fuel was leaking out onto the ground. You could very well be low on transfer pump pressure. Think it is suppose to be 2-5 psi running pressure. Maybe Pump Guy will chime in and give more accurate number. Think there may be a screen inside the transfer pump. If it runs anything better with 2 PSI on the tank, that is indicative of a blockage or transfer pump failure. Good place to start.
Simon C

 

[thepumpguysc]

That 310 has a RoosaMaster/Stanadyne pump yes.?
Remove ALL THE FITTINGS FROM THE TOP OF THE PUMP..
U should be looking at a hole..
Now start the engine and see if it stays running.. if yes.. put the fittings back in 1x1 until it shuts off..
If it’s the first one you put in, there’s garbage in the return connector.. blow it out..
Try it and let us know..

 

[runamok]

That 310 has a RoosaMaster/Stanadyne pump yes.?
Remove ALL THE FITTINGS FROM THE TOP OF THE PUMP..
U should be looking at a hole..
Now start the engine and see if it stays running.. if yes.. put the fittings back in 1x1 until it shuts off..
If it’s the first one you put in, there’s garbage in the return connector.. blow it out..
Try it and let is know..

I'll give it a shot in the morning.
When you say blow it out, do you mean to blow into the return line or into the return line fitting on the pump?

Simon,
I'll also check if the transfer pump has a screen or is allowing in air. Is there any reason not to just pull that off and make a new gasket out of auto parts store gasket material?

 

[thepumpguysc]

Sorry, yes remove the fitting/return connector again and use compressed air to blow it out..
It’s basically a 1way check valve and when it gets clogged, fuel can’t leave the pump.. therefore the fuel inside the pump becomes greater than the fuel trying to get into the pump, and it shuts down..
>No fuel out means no fuel in<

We’ll talk about the causes and fixes when u find out fer sher that’s the problem..

 

[runamok]

Thank you both. I'll report back in the morning.

 

[runamok]

I cleaned the return line (there is actually a screen in the fitting on the injection pump) and it ran a while, then died again. I removed it again and it was clogged. After a few rounds of this it seems to be running correctly. I'll report back after a couple hours on the machine.
Thanks very much for your help.

-Z

 

[HarleyHappy]

I expect that screen to run full Amok of crap again. Lol
Might need to clean out the tank and all the lines.

 

[runamok]

I had to unplug the return line screen maybe 20 times over a 2 hour period. So this leads me to wonder what disintegrated inside the pump.
Here's a couple pictures of the stuff clogging the return line. It feels kind of like plastic, hard but malleable.

 

[runamok]

I expect that screen to run full Amok of crap again. Lol
Might need to clean out the tank and all the lines.

Can you point me to a procedure for that?

 

[T-town]

I think your "plastic ring" in the injection pump has seen its last days... the 'pumpguy' will be the go to guy for that diagnosis and remedy.
If that is your problem, it (the IP) will need to be removed and 'sent out'.

very common problem.....

 

[thepumpguysc]

Google “flex ring failure”..
The pump will have to come off the engine to repair..

 

[thepumpguysc]

If the rpm’s start surging, shut it down and don’t restart it until repairs are completed.!!!
They have a strong tendency to shoot to max rpm and stay there till it vents the side of the block..

 

[T-town]

...and I would strongly recommend that you retain the 'services' of the pumpguy for that repair. There is an upgrade for that dreaded flex ring that will prevent reoccurrence.... and he will help you in procedure to remove ( correctly) your pump and to reinstall..... all for the best $$you will find.
He is truly an asset to this heavy equipment community.

 

[runamok]

If the rpm’s start surging, shut it down and don’t restart it until repairs are completed.!!!
They have a strong tendency to shoot to max rpm and stay there till it vents the side of the block..

It hasn't surged yet, but I'm not getting any work done climbing off the machine every ten minutes to clean the return line, so it's just going to have to come off. I'll PM you regarding your services in this regard.

Thanks again all. I very much appreciate the help.

 

[thepumpguysc]

Use my screen name at aoldotcom
Looking forward to hearing from you

 

[runamok]

Want to thank all of you, the machine is up and going.
Mike, thepumpguysc, rebuilt the pump and walked me through reasembly. The machine is back to work.

 

[thepumpguysc]

Thank you.. it was my pleasure.
I heard he does pretty good work.?? Lol