I was doing some electrical troubleshooting on my new to me 4020 and I pulled the fuel pump fuse so I wouldn't drain the battery. Forgot to install the fuse and the tractor started and ran just fine. Is the fuel pump only for priming?
My 4020 runs with the fuel pump fuse pulled: What gives?
- Thread starter hammick
- Start date
- Views: 5612
4570Man
Super Star Member
- Joined
- Apr 7, 2015
- Messages
- 18,495
- Location
- Crossville, TN
- Tractor
- Kubota M59, Kubota L3800, Grasshopper 428D, Topkick dump truck, 3500 dump truck, 10 ton trailer, more lighter trailers.
I doubt it'll run very long. My older Kubotas will continue to run with the key off. After a few minutes they burn the fuel already in the system and die.
LincTex
Silver Member
There is a small gear pump in the fuel injection pump, but it isn't strong enough to be used as a "lift pump".
If the fuel tank is above the engine like in my Yanmar, the fuel will gravity feed through the filter & pump, and it'll run fine.
If your fuel tanks are under the floorboards like on my 3510i, then you won't run for very long.
BTW, electric fuel pumps are designed to "push" fuel, not "suck" it.
Branson engineers really screwed up by mounting the elec. fuel pump way up on the back of the firewall.
The life of the electric fuel pump will be improved *dramatically* if it's moved down near the fuel tanks.
If the fuel tank is above the engine like in my Yanmar, the fuel will gravity feed through the filter & pump, and it'll run fine.
If your fuel tanks are under the floorboards like on my 3510i, then you won't run for very long.
BTW, electric fuel pumps are designed to "push" fuel, not "suck" it.
Branson engineers really screwed up by mounting the elec. fuel pump way up on the back of the firewall.
The life of the electric fuel pump will be improved *dramatically* if it's moved down near the fuel tanks.
Cougsfan
Veteran Member
- Joined
- Sep 10, 2008
- Messages
- 1,568
- Location
- Eastern Washington State
- Tractor
- Ferguson TO35, Branson 4720CH
Out of curiosity, could you expound on what you are saying? I would agree that all pumps push better than they suck, as cavitaion can be a nemesis for any pump, some designs more so than others. I would agree that mounting the pump with a flooded suction is theoretically better, but question the real world problems of a little suction lift.
Gear pumps are fairly well suited for fuels and better than most designs for cavitation resistance. But lifting a couple of feet seemingly shouldn't be that big a problem for any fuel pump. I can see what you are saying being a problem if you repeatedly run your diesel tank out of fuel, which is hard on a lot more than just the fuel pump. But most people are smart enough to never do that more than once. What is the mode of failure that is avoided if you move it closer to the tank? Does failure happen a lot?
DavesTractor
Elite Member
I think this has been pretty well answered. As mentioned, the FIP on the engine will pull a little fuel, but is not adequate in most situations with a low mounted tank. But if your tank is full and you are not running the tractor hard, it might very well run for a long time without the electric lift pump. But a FIP that is well supplied with generous amounts of fuel from a lift pump (or a high mounted tank) has less problems. Cavitation is an issue if the pump is struggling to get enough fuel, and that will lessen the life span of the FIP.
But it certainly is not like a car that relies on an electric pump to bring gas to the injectors. Shut off that pump and the car shuts off quickly.
But it certainly is not like a car that relies on an electric pump to bring gas to the injectors. Shut off that pump and the car shuts off quickly.
LincTex
Silver Member
Inside of the little electric fuel pumps is a "shuttle" that is forced one way ("home" position) by spring pressure, and is sent the opposite direction when a coil of wire is energized, just like an older GM starter solenoid plunger. When fuel is used, the spring pushes the "shuttle" towards a set of electrical contacts. When the pump is empty and the contacts made, the electromagnetic pushes the shuttle against the spring and the cycle repeats as necessary. Inlet and Outlet check valves are on each end.
The higher you lift the pump, the less effective the spring is inside (it isn't very strong in the first place) to "pull" the shuttle against the fuel. As you get higher, this spring works harder. The typical Bendix/ Facet/ Carter pump was never designed to make rated fuel pressure while "pulling a head".
I don't necessarily say this makes the pumps "fail", but it will make them "fail" sooner - - in as much as, as they wear- their output will decrease prematurely.
An electric fuel pump that quits working when mounted high above fuel level will often miraculously "come back to life again" when moved down to where the inlet is more easily fed. We found this out with our old IH 503 combine - it "ate" an electric pump almost every year until my grandpa finally moved the pump down well below the fuel tank.
DavesTractor
Elite Member
LincTex, that's a great explanation, and I agree. The pumps on the older Branson's fail often enough that we always keep a few on the shelf for customers. Haven't seen it much on newer units, but that is perhaps just because they are newer. It's a pretty light duty pump, because it has a light duty job.
We often will find crud in the pump that makes it stop working. The pump is before any filter, so whatever junk is in the tank gets pushed through the pump into the filter and then into the FIP. I'm not suggesting another filter, but perhaps a more robust pump that can move insect parts and little pieces of oak leaves or whatever gets into a tank.
I bet if we had the specs for the pump, it is well within it's range of lift capability, but that does not mean it wouldn't do better if mounted low.
We often will find crud in the pump that makes it stop working. The pump is before any filter, so whatever junk is in the tank gets pushed through the pump into the filter and then into the FIP. I'm not suggesting another filter, but perhaps a more robust pump that can move insect parts and little pieces of oak leaves or whatever gets into a tank.
I bet if we had the specs for the pump, it is well within it's range of lift capability, but that does not mean it wouldn't do better if mounted low.
LincTex
Silver Member
Hard to believe some sort of screen isn't standard equipment.
It doesn't need to be as "fine" as a real fuel "filter" is.
DavesTractor
Elite Member
Many of the Indian built Mahindra's have a screen inside the tank at the outlet. We get calls from customers that the tractor won't start, or starts and then dies above idle, or barely runs and misses. Almost always it is the little screen in the bottom of the tank is clogged.
If there is a screen of sorts, it needs to be easily accessible and cleanable. I know they do make inline screens that look like inline filters, but it a mesh instead of a paper element. And they are cheap, maybe that is a good solution. Probably $10 instead of over $100 for a lift pump.
Of course we all ought to keep our feel clean, but somehow crud gets into tanks, even with folks that are super careful.
