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Discussion Starter #1
Ok, so I’ve run into a huge problem. My little run around farm tractor, a John Deere 755, won’t start. The motor has compression, everything electrical seems to work, with the glow plugs working too. However, while trying to turn it over, no diesel comes through the line. I have some clear fuel line on in different places, and there’s no sign of fuel being pulled through the pump and sent to the injectors. The connections to the pump appear to be intact and working, but I’m not sure, so I’ll check again. There’s no obstructions in the line and no air, as I’ve bleed it twice. It won’t start on starter spray either (diesel formulated). The pump used to make a electric noise when turning the key before starting, which I believe was to prime itself, which it no longer does. I’m thinking the pump is toast and I need a new one. Has anyone had experience with this or can confirm my diagnosis? Please help me figure this out.
 

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Kish JD 318/420/430
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Yes a pump should always make noise (priming) I'm with you that it is toast. But you need to confirm by opening the line and doing a fuel delivery test. Have you check all fuses too?
 

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Discussion Starter #4
Yes a pump should always make noise (priming) I'm with you that it is toast. But you need to confirm by opening the line and doing a fuel delivery test. Have you check all fuses too?
I have previously checked the fuses, they all function, but I’m going to go back through the electrical system and recheck to see if I missed anything. I’m with you on doing a fuel delivery test, but what is the best way to do that? I’ve never done it before, so I’d like to know the basics steps to make sure i do it right.

P.S. thanks for the quick response.
 

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Kish JD 318/420/430
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A quart or half gallon container for catching the fuel (it should be clean so that any fuel can be return into the fuel tank on tractor or what ever you use to hold your fuel in storage for later use, enough hose, stop watch or that function on a watch or smart phone. Place hose from the pump or somewhere it is handy to get at in the fuel lines into the measuring catch container. Start the stop watch at same time you turn the key switch on, let it pump for a minute, that should give you quantity and time.

I've added a link to the JD parts site for the fuel tank and pump: John Deere Parts Catalog

There are 6 choices for fuel pumps depending on the serial number (3 are expensive, 3 are inexpensive plus there are alternatives available also)
 

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Discussion Starter #6
A quart or half gallon container for catching the fuel (it should be clean so that any fuel can be return into the fuel tank on tractor or what ever you use to hold your fuel in storage for later use, enough hose, stop watch or that function on a watch or smart phone. Place hose from the pump or somewhere it is handy to get at in the fuel lines into the measuring catch container. Start the stop watch at same time you turn the key switch on, let it pump for a minute, that should give you quantity and time.

I've added a link to the JD parts site for the fuel tank and pump: John Deere Parts Catalog

There are 6 choices for fuel pumps depending on the serial number (3 are expensive, 3 are inexpensive plus there are alternatives available also)
I hope to do the fuel delivery test today, or tomorrow at the latest, however I have one major question I need answered. When the injection pump works properly, how does the priming sequence work? Is there a small electric pump that primes the main one before startup, and if there is, is there an electrical component that can fail, leading to a stoppage of the priming sequence and the eventual destruction of the pump? My question is mostly to make sure that if I rebuild the pump, that another failed component won’t simply lead it to blow up again shortly after installation.
 

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Kish JD 318/420/430
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The pump we are talking about is either called a fuel pump or lift pump (usually an electric, it has it's own internal pressure regulator that shuts off when the pressure target is met). It's job is to pull the fuel from the tank from the pickup/strainer push it through the fine fuel filter and deliver it to the injection pump. The injection pump job is to build enough pressure to fire the injectors in a timed/sequence (mechanical injection system). The injectors atomize the fuel into a very fine pattern to mix with the proper amount of air in a ratio that supports combustion.
 

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Discussion Starter #8
Two s
The pump we are talking about is either called a fuel pump or lift pump (usually an electric, it has it's own internal pressure regulator that shuts off when the pressure target is met). It's job is to pull the fuel from the tank from the pickup/strainer push it through the fine fuel filter and deliver it to the injection pump. The injection pump job is to build enough pressure to fire the injectors in a timed/sequence (mechanical injection system). The injectors atomize the fuel into a very fine pattern to mix with the proper amount of air in a ratio that supports combustion.
Two small add on questions, then I’ll probably be pretty well set. One, could the lift pump go bad on its own, without killing the injection pump, and that might just need to be replaced? I’m guessing if one goes, so two does the other. Two, is the lift pump completely separate from the injection pump, or are they built into each other? If it’s separate, where is the lift pump located?
 

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Kish JD 318/420/430
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Q1 - Yes, replace only the fuel/lift pump. Injection should be okay. The lift pump is located between the fuel tank and the injection pump.
Q2 - Separate from the injection pump

Here is a representation: John Deere Parts Catalog

It will be mounted to the frame or a support, might be mounted to a casting along the drive train.

The other thing to check is the fuel solenoid shutoff valve that should be close to the injection pump. make sure it is opening correctly. You should get the TM for the tractor to help you out. It is an investment that will help in troubleshooting, location of parts/items, testing procedures, etc

Please take time to click on the two links labeled "John Deere Parts Catalog" in post 5 and this post, those should help you out.
 

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Discussion Starter #10
Q1 - Yes, replace only the fuel/lift pump. Injection should be okay. The lift pump is located between the fuel tank and the injection pump.
Q2 - Separate from the injection pump

Here is a representation: John Deere Parts Catalog

It will be mounted to the frame or a support, might be mounted to a casting along the drive train.

The other thing to check is the fuel solenoid shutoff valve that should be close to the injection pump. make sure it is opening correctly. You should get the TM for the tractor to help you out. It is an investment that will help in troubleshooting, location of parts/items, testing procedures, etc

Please take time to click on the two links labeled "John Deere Parts Catalog" in post 5 and this post, those should help you out.
Ok, so what you’re saying is that it’s more likely the lift pump went out, and that the injection pump is still functioning, at least that’s what I think you’re getting at. So all I’d likely have to do is just replace the lift pump and it would run again, after I bleed the line of course.
 

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Kish JD 318/420/430
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Correct, but I would still do a fuel/pump flow test to confirm it. Hate just throwing money at things, That is why I said to also check fuel shutoff solenoid too.
 

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My 955 did the same thing. Turned out there was a break/leak in the short rubber hose (in the diesel fuel tank. (Cheapest Deere part I have ever bought!). Part #20(has no actual part number). John Deere Parts Catalog
I would make sure you have a good hose there for sure. My 955 has the glass fuel bowl/filter. Is there any diesel there? (This would all be part of the fuel delivery test).
 

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Discussion Starter #13
Correct, but I would still do a fuel/pump flow test to confirm it. Hate just throwing money at things, That is why I said to also check fuel shutoff solenoid too.
The fuel shutoff solenoid is brand new. I replaced it a couple months ago because it wasn’t working and I believe that was the issue. While inspecting the tractor today, I attempted to locate the separate fuel pump (not the injection pump), but I couldn’t find it. Could it be in the diesel tank itself? Or under the tank? Those are the only two places I couldn’t check.
 

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Discussion Starter #14
My 955 did the same thing. Turned out there was a break/leak in the short rubber hose (in the diesel fuel tank. (Cheapest Deere part I have ever bought!). Part #20(has no actual part number). John Deere Parts Catalog
I would make sure you have a good hose there for sure. My 955 has the glass fuel bowl/filter. Is there any diesel there? (This would all be part of the fuel delivery test).
There is fuel in the secondary fuel filter, as I put in another filter before the original first one (where the bleed screw is), however the injection pump doesn’t seem to create any pressure when the motor turns over. The same amount of fuel remains in the filter.
 

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Follow the fuel line from the injection pump back to the fuel tank. The lift pump is in the line between them. It is number 5 in the picture below.



Sent from my iPhone using Tapatalk
 

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Discussion Starter #16
Follow the fuel line from the injection pump back to the fuel tank. The lift pump is in the line between them. It is number 5 in the picture below.



Sent from my iPhone using Tapatalk
That little pump looks pretty similar to a canister fuel filter. I cannot find the lift pump at all in the line, anywhere I can see anyway, however there is a non stock filter installed by a JD backyard mechanic type. I think it’s possible he replaced the pump with a filter, maybe thinking it was a filter. Where the little canister filter is on my line, there’s a wire going to it but not connected, which is what I assume is some kinda power wire to a pump that’s not there.
 

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Kish JD 318/420/430
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Seeeesh, that just screams for fuel issues, if it has been replaced with a fuel filter, look closely at it, may be the wire/connector broke off due to age/corrosion/vibration. You may have found your issue. Injection pump don't suck well, they like a little pressure to get fuel into them as they compress it up to a higher pressure.
 

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Discussion Starter #18
Ok guys, I think I’m on the trail of what’s going on. My lift pump has accidentally been replaced with a canister fuel filter, so I need to get a new lift pump and install it. What I’m guessing though, is that without the lift pump around to prime the injection pump, maybe the injection pump finally blew up. The tractor ran without the lift pump for a long time, so I don’t know if permanent damage has been done or if I just need a new one or not. We used to just crank the tractor over and over and over until it roughly started, then it would run fine.
 

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Kish JD 318/420/430
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I would try the fuel pump before jumping to that conclusion. You never know, but keep a detailed log book on your equipment of repairs/parts, use it even for filters and fluid changes. You know that the filter just might be plugged with something that took out the fuel pump in the first place. You might need to clean the fuel tank, check fuel lines for deterioration.
 

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Discussion Starter #20
I would try the fuel pump before jumping to that conclusion. You never know, but keep a detailed log book on your equipment of repairs/parts, use it even for filters and fluid changes. You know that the filter just might be plugged with something that took out the fuel pump in the first place. You might need to clean the fuel tank, check fuel lines for deterioration.
I definitely plan to try the fuel pump first before even touching the injection pump, considering my fuel pump is gone so it’s a good place to start. On a side note, I’d like to try pressuring the line to the injection pump to see if the pump can start with fuel pressure. Do you think that there is anyway to do that before buying a new fuel pump? I’d rather not buy a $60 pump just to have it turn out that it wasn’t the problem and that I’m still screwed.
 
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