Ford 3910 Injector Pump removal/install

[ovrszd]

The Injector Pump on my 3910 has been seeping fuel since I bought the tractor two years ago. It got worse last Summer, to the point I would shut off the fuel when parked. Primarily was leaking from the O-ring that connects the two pump body parts. When the weather got cold it was so bad that fuel would pour from it when first cranked. So I hauled it to my warm shop for repair.

I talked to a good friend of mine that has a repair shop and primarily works on AG tractors of all types. Joe said "I never take a pump apart, I remove it and take it to a local shop for repairs". After I looked at the parts diagram I decided I wasn't going to take it apart either......

Removing the pump isn't extremely difficult. But attention needs to be paid!!!!! Particularly in the timing of the pump. Two things time the pump. The gear that drives it and the position of the pump. The three bolt holes that mount the pump to the engine are slotted. I carefully marked the pump housing and the engine case so I could get it back in the same spot.

Unhooking the various linkages and injector lines was pretty simple. Joe suggested removing the starter to make this process easier. Fortunately for me, I needed to replace my starter so it was coming off anyway. He also said it's easier to get the front cover off to expose the gear drive if the lower radiator hose is removed. The block drain petcock is right by the injector pump so I drained antifreeze until it was low enough to remove the upper end of the radiator hose without dumping.

 

[ovrszd]

For me, the next step of removing the drive gear from the pump was most critical!!!!!

I removed the upper end of the radiator hose and tied it out of the way. This allowed me to access the 5 bolts that hold the gear cover on.

Once the cover is removed you are looking at the pump gear and the gear that drives it. I rotated the engine until the timing dot on the drive gear meshed with the pump gear, no mark. I rotated several times looking for a marked tooth on the pump gear. There was none. Joe had said I should find a mark on each gear and when they are together that's where you want to stop turning and take it apart. That makes it easy to realign the gears when assembling.

I called Joe. He said rarely you will find a gear that isn't marked. A detailed shop manual might describe using characteristics of the gear as a guide. Such as "align the dowel pin on the pump gear with the timing mark on the drive gear". He said to not pay any attention to something as vague as that. He said turn engine until the drive gear timing mark is meshed with the pump gear. Then use a sharp punch and mark the pump gear tooth that's meshed with the drive gear. That's what I did. I was very concerned about this procedure. So concerned I never unmeshed the gears. Removed the three bolts that allowed the pump shaft to separate from the gear and left the gear sitting there meshed.

The pump gear has a dowel protruding out the pump side of the gear. The pump shaft is slotted to accept that dowel. So the gear can only go on the pump one way.

 

[ovrszd]

I don't know about you guys, but here's how my projects go.

I removed this pump to fix an O-ring leak. No big deal......

Couple days after dropping off the pump Bruce (pump guy) called me. "Hey we got a problem, the Cam Ring and Rear Cover on this pump are shot. That's why it's leaking". Okay, do whatever. "Well it's gonna be around $675 to repair it". Okay, do whatever..........

If you look carefully at the pic of the Cam Ring you can see the lobes built into the ring. This is a part of the process the pump using to squirt fuel at the proper time to the proper location. One of the lobes had started coming apart. Chunks of it's surface are missing. Was just a matter of time until it clogged the system with debris.

Because of this possible clogging he also suggested having the Injectors rebuilt. I said let me make sure my pump problems are solved and financially recover first. He said "Okay, whatever".

I didn't get a picture of my rebuilt pump before I painted it. Sorry bout that. I don't know what type of cleaner Bruce uses, but, this pump appeared as good as new. Only way I could tell it was my old pump was by the manufacturing tag on the side. He replaced every seal, bushing, washer, o-ring on this pump. He charged me $200 labor. The expensive part was the two worn pieces that had to be replaced. The Cam Ring was $250.

So I put a good coat of paint on the pump.

 

[Birdhunter1]

Going from memory from when I had a leak fixed on mine I thought the pump only matched to the gear one way and the timing marks on the plate the pump attaches to had to align with the 0 mark on the pump. But I've only done it once and followed book procedure, which spelled it out well and after reassembly the tractor runs as good as it did beforehand.
I think I was able to take it off and put it back on without draining the antifreeze and moving the hose, I think I unbolted the radiator and moved it slightly without draining it, but I am kind of a contortionist anyway. One thing I did was I unhooked the battery so that the engine could not be cranked and moved and misalign something.

Either way, great pictorial of how its done.

 

[ovrszd]

Again, I stress the importance of timing the pump. I was very paranoid about this process. Using the picture that I previously had taken of the pump shaft position, I turned the shaft until it was in that same position. This would make it easier to align the gear dowel into the shaft slot. My patience and diligence paid off. The pump gear aligned onto the shaft first try with no hassles. I quickly put in the three gear bolts tightened finger tight. Then put in two of the pump case bolts thru the slotted holes. Using my timing marks that I made before disassembly I felt confident the pump was in time. Finally breathed a sigh of relief.

 

[ovrszd]

Going from memory from when I had a leak fixed on mine I thought the pump only matched to the gear one way and the timing marks on the plate the pump attaches to had to align with the 0 mark on the pump. But I've only done it once and followed book procedure, which spelled it out well and after reassembly the tractor runs as good as it did beforehand.
I think I was able to take it off and put it back on without draining the antifreeze and moving the hose, I think I unbolted the radiator and moved it slightly without draining it, but I am kind of a contortionist anyway. One thing I did was I unhooked the battery so that the engine could not be cranked and moved and misalign something.

Either way, great pictorial of how its done.

Yes, the pump shaft is slotted and the gear is doweled. Issue is timing the pump gear to it's drive gear. If you happen to dislodge the teeth and get off a tooth you got problems.

Yep, draining antifreeze and moving the hose was a convenience thing, not a necessity. Made removing the front cover MUCH easier.

Yep, first thing Joe said was unhook the battery and remove the key. DO NOT risk the engine being turned while the pump is removed!!!!

 

[ovrszd]

So, after installing the pump and hooking up all the linkages and fuel lines it's time to bleed the system. My Operator's Manual described this process very clearly with pics.

There's a bleeder valve on the top of the filter head, start there. Loosen the bleeder and turn of the fuel at the tank. Let it push all of the air out. I let mine run pure fuel for several seconds.

There's also a bleeder valve on the side of the barrel on the pump. I loosened this bleeder and let it run until pure fuel had ran for several seconds. My manual said to use the starter to turn over the engine to purge the air out of the pump. I did that and didn't appear to get anymore air.

Lastly you bleed the Injector lines at the Injectors. Loosen all three lines and turn the engine over with the starter. Make sure fuel shutoff (manual knob) is in the run Position. Also make sure the hand throttle is in the Wide Open Throttle position. Manual says to not turn over engine more than 30 seconds without pause to prevent overheating starter. I only turned it over for about 5 or 6 seconds at a time. Took half a dozen attempts before fuel started squirting out of the loosened Injector lines at the injectors. Tightened the lines and it cranked right up.

Starts easier. Sounds more confident when it starts. Doesn't appear to smoke as much. Appears to be money well spent. Now gotta save up for Injector rebuilds.

In my pics I used the tip of a white ziptie to point at the bleeder on the filter head and the pump case.

Also, in this first pic of the front cover, you see that the top bolt is still loose? That bolt holds the engine crankcase breather tube. This old engine doesn't use a PCV valve. I note this because that cover has an indention pressed into it for that tube bracket. Make sure you install the cover with that indention at the top so the tube will fit.

 

[ovrszd]

Another thing Bruce the pump guy suggested is to use a quality fuel filter. His eyes glazed over as he went into a 5 minute discussion on the merits of various fuel filter brands. He even had a parts store brand filter disassembled and laid out on the bench, alongside a disassembled Delphi filter. There was 4 times as much filter media in the Delphi. And he explained in terms far above my mentality curve the difference in media.

I bought a Delphi filter from him for $5.50. He convinced me of the value of clean fuel.

So, she's all buttoned up. No fuel leaks. Runs great. $700 later.

 

[Jerry/MT]

Thanks for a great description of injector pump removal and replacement on 3 cylinder 10 Series Fords!

 

[ovrszd]

Thanks for a great description of injector pump removal and replacement on 3 cylinder 10 Series Fords!

You are very welcome. I hope you never need it for reference.