# John Deere 1520 Fuel Injector Pump Question



## seasail757 (Dec 29, 2018)

I have a 1971 JD 1520 Diesel Tractor with 8000 hours. She's a old girl that I refurbished. I started her one morning and she wouldn't throttle up to speed. It began blowing dark smoke and running rough. From the symptoms, a buddy of mine told me to pull the fitting/fuel line going into the top of the fuel pump and there was a small plastic ball that could be stopped up with junk. This fitting/plastic ball allowed fuel to go back to the fuel tank. He said to knock the ball out, reinstall the fitting and fuel line and move on. On inspection, there was junk there and I cleaned it first and put it back. Started her up and she ran great for a minute and stopped up again. I pulled the fitting again, saw junk again and just knocked the ball out. Started it up and it ran fine. Idled great and throttled up. VICTORY, I thought. I let it run for about 5 minutes to recharge the battery, then it shut off. It would start, run for a few seconds and then shut off. I replaced the fuel lift pump thinking that could be the culprit. That wasn't it. I had the fuel pump tested and was told that the solenoid was loosing current and shutting off the fuel after starting. I purchased the solenoid, pulled the top off the fuel pump and saw that there was bits of debris in the pump itself. The debris came from the old solenoid from a black "covering" that was over the spring of the old solenoid. I syringed all the fuel/debris out of the fuel pump all the way to the bottom of the pump and put fresh fuel back in the pump, installed the new solenoid, fired her up and she ran awesome for about 5 seconds and started to throttle down on her own and shut off. I tried to get her back up and going again but it wasn't happening. I opened the fuel line at the fuel pump and fuel squirted out under pressure. I closed the line down and she would start and run 5 seconds and shut off. I went around to the fuel filter and opened the bleeder valve, the fuel came out under pressure again and then I closed it off. Again it would start, sound great and then shut off. Without bleeding a line somewhere, the tractor would not start. Every time I let the pressure off the fuel lines it would start for a few seconds and then shut off. I have left the lines open when the tractor was running to see if it would continue to run but eventually again after a few seconds it would cut off. I have bled all the lines that I know of. So my question is...has the debris that I found in the pump ruined the pump or stopped up the injector valves or both? This is the same junk that I found in the fuel fitting that I knocked the little ball out. Is it normal that when you bleed the pressure off the fuel system that is runs and then shuts off and will not stay running? It is a Stanadyne pump. Even though my 1520 has that many hours, I'm not ready for her to be a yard ornament yet, however a fuel pump rebuild or replacement is very pricey giving the tractors age and hours. I know enough about this to get by but am now reaching out for better clarification and hope.


----------



## thepumpguysc (Jan 25, 2015)

The flex ring inside the pump has deteriorated & is breaking up..
I'm VERY surprised u didn't know that.. especially if u had the top cover off & have seen the black plastic pieces.. {mouse turds/coffee grounds}
Its VERY common.. Your friend should have told you its a temporary "fix".. & the engine rpms will sky rocket out of control sooner or later & grenade all over your yard..
WHAT HAPPENS IS, the flex ring pieces clog the return connector{ball} & fuel cant enter the pump.. kinda like holding your finger over a straw..
No fuel OUT=NO fuel IN..
& what do u think happened to all those bits of flex ring material?? They went straight back to your fuel tank & clogged the fuel RETURN LINE..
IF u blow the line out going back to the tank, it'll probably run.?? BUT for how long??
The ONLY repair for that symptom is a pump o/haul. The flex ring inside the pump IS BROKEN.. I have 30+ years in injection pump rebuilding.. if u would like to send me a prvt msg & discuss it.. feel free to contact me.. Just click on my screen name in the left hand side.. TPG


----------



## JimLiberty (Sep 16, 2020)

Good Afternoon,
I’ve been working on a 68 JD 1520 and am at my whits end. The primary issue is that the injection pump wire & starter solenoid positive wire is melting as soon as I turn the key to start it. I’ve replaced several parts (Solenoid, injection pump insulators, ignition switch, and all wires). Still having the same issue. Please advise! 

Regards,
JB


----------



## thepumpguysc (Jan 25, 2015)

What r u doing about a ground from the pump solenoid.??
Does it have a ground strap from the sol. stud that goes over to a top cover hold down screw.?? If yes, good.. just make sure u don’t hook anything else to that stud..
The pump is grounded to the engine block..


----------



## JimLiberty (Sep 16, 2020)

That was intact but I replaced it anyway. Nothing else is attached. I even bench tested the solenoid for the injection pump and it operates fine. Thanks for the reply 




thepumpguysc said:


> What r u doing about a ground from the pump solenoid.??
> Does it have a ground strap from the sol. stud that goes over to a top cover hold down screw.?? If yes, good.. just make sure u don’t hook anything else to that stud..
> The pump is grounded to the engine block..


----------



## thepumpguysc (Jan 25, 2015)

Let’s do the breakdown..
On the sol. u have the tube insulator.. u lubed those n worked them up into the cover.
Then there’s the “flat” insulators, then the flat washers n lock washers n nut.
Does that sound familiar.?


----------



## JimLiberty (Sep 16, 2020)

I definitely remember all of those parts. I got a full kit from the JD parts department in town. I did not have an inch/lb torque wrench but I was sure not to over tighten. I feel like I did everything correctly but from the evidence it seems to be an issue that has occurred before. Wires spliced everywhere and some wrapped in masking tape! It was quite the mess. Any ideas on where to find a full wiring diagram? 



thepumpguysc said:


> Let’s do the breakdown..
> On the sol. u have the tube insulator.. u lubed those n worked them up into the cover.
> Then there’s the “flat” insulators, then the flat washers n lock washers n nut.
> Does that sound familiar.?


----------



## thepumpguysc (Jan 25, 2015)

Sorry, no..
If u feel like the solenoid installation is a/the problem, feel free to put it in a 1 price small box from USPS for 9-10.00 & ship it to me & I’ll assemble it correctly for u..
All it’ll cost u is shipping back..
U can contact me by clicking on my screen name on the left hand side of the page..


----------

