John Deere 70 diesel motor won't start

KBarnett

New User
Working on my John Deere 70 diesel tractor, replaced the pony motor after breaking a couple rods. Installed a used pony and it runs great. But i cannot get the diesel to start now. It ran last November when i parked it. I bled the fuel system up to the return line back to the fuel bowl, the left #3 bleed plug won't flow anything tried to blow it with compressed air but got nothing. Should i remove the manifold that is bolted to the injectors? I was also wondering if something broke in the speed control rod for the governor when i had it loose changing the pony motor/ Looking for any help with troubleshooting.
 
Make sure your transfer pump is putting out. I had trouble with the one on my 720 a couple of years ago. Just a thought.
 
Put a gauge on the fuel pump , turned it over with the pony motor "not sure if that is fast enough " i couldn't make any pressure had fuel flowing thru though. Pulled the pump apart and the spring was a bit short on check valve ball made sure it was clean added washer to spring tried again still no pressure. Done for the afternoon.
 
Are you getting fuel through the filters? check both bleed points,also look in your tank to see if your fuel is still good.
 
(quoted from post at 19:11:17 03/12/17) Are you getting fuel through the filters? check both bleed points,also look in your tank to see if your fuel is still good.

iirc there are more than two places to bleed the fuel system
 
If there's no fuel at the bleed plug on the left side of the block, there's no fuel in the common supply gallery to the injection pumps and it ain't gonna start.

To get there, the fuel has to be pumped by the transfer pump (or sneak past it, which doesn't happen very fast).

Have you cranked it long enough for the transfer pump to get everything full of fuel, to the point of reaching the #3 (LH) bleeder, or, (if you can do it safely) dragging it around with another tractor past the point you are ready to give up?

On the 830's you can easily remove the steel ball from the fuel pressure regulator in the transfer pump, and they will gravity-bleed. NOT so with these, all the fuel needed to fill the lines, filters, ans fuel gallery needs to be PUMPED through the transfer pump. (I guess DEERE just called it the "fuel pump".)

GOOD LUCK!
 
P.S., the system should bleed and fuel reach the #3 plug eventually, no matter what position the "rack" is in, even in "shutdown" position, or even if it's stuck.
 
Make sure you have at least 5 gallons of fuel in the tank. Open the sediment bowl valve, open the primary bleed on the filter canister housing (Left side FW side of tractor)wait for fuel to flow out of the primary port. If it doesn't flow try slightly pressuring the tank. Once you have flow on the primary, close it and open the secondary bleed (right side of canister housing). Once you have flow there close it and open the third bleed port on the end of the fuel rail (left side of tractor). When you have flow there it should start if the pump rack is not stuck. You must get fuel flow at the primary port before you can do the rest. If you don't have flow there trace it back through the supply line, transfer pump, sediment bowl and the bottom of the tank looking for any blockage.
 
"<font color="#6699ff">[b:654c4848f0][i:654c4848f0]open the primary bleed on the filter canister housing (Left side FW side of tractor)wait for fuel to flow out of the primary port.[/i:654c4848f0][/b:654c4848f0]</font>"

"<font color="#6699ff">[b:654c4848f0][i:654c4848f0]Once you have flow on the primary, close it and open the secondary bleed (right side of canister housing).[/i:654c4848f0][/b:654c4848f0]</font>"

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"<font color="#6699ff">Once you have flow there close it and open the third bleed port on the end of the fuel rail (left side of tractor).</I></B></font>"

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Mike....I think all 70 diesels had the solid cast iron pump housing cover and the 3rd bleed port, unless they were upgraded at some point. The late 720 diesels and all of the 730 diesels had a large bleeder valve on/in the cover to relieve the pressure on the pumps back to the fuel tank. Those do not have the 3rd bleed port.
 
Found time to work on it again. I tried everything i could to bleed the fuel lines. Finnally pulled the valve cover and removed the injector supply lines and let the pony motor run long enough to get fuel thru the injectors took about 5 minutes before i saw a constant flow of fuel.
Closed it back up and fired right up. Thanks for your insight i appreciate it.Plus i learned a little about diesel engines too.
 

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