A frozen Injection pump Fuel Rack, what to do?

I remember MJ McCarroll telling me about the folks who worked on fuel injection pumps in his part of the Midwest, “They’d pull down the shades before they worked on a pump, it was their bread and butter, and they didn’t want you knowing how they did it.”
washed out Bridge

washed out Bridge

Below might lie some trade secrets, and this pump is so similar to all the rest!

No doubt, a frozen pump is about as useless as a washed out bridge, but if you know a few tricks, you might fix it in less than an hour. On the other hand, you can apply just a little too much pressure to that rack, and you’ll need a box of parts to fix it, if you can find them.

It wasn’t that long ago that a Friend pulled a brand new diesel engine from a box and attempted to start it, he lubed it, fueled it, primed it, and no go.. soon he found a frozen fuel rack!

I welcomed him to the club, and told him how common this is, there’s a video on the ‘georgeutterpower’ YouTube pages showing a method to verify rack is free  on the Yanmar and  Yanmar clones when you find the engine wont start, don’t pick up a hammer! Read to the end, it may save you days and dollars, it has others..

The probability of seeing a frozen rack increases if you live in areas with a lot of humidity, and where the air temperature can rapidally rise leaving metal surfaces a lot cooler than the surrounding air. If you live in the Desert, you’ll see troubles like this less often.   There are other causes, but a microscopic amount of moisture between the plunger and the barrel is a leading cause. Keeping your pump full of clean dry fuel is key! If they’re left in the shipping box, there’s a chance they are less protected from moisture.

Injection pumps found in small engines are normally pretty simple, but never confuse  simple with a lack of precision, because any pump that works well is a precision piece of equipment, with tight clearances, so when you take a pump apart, you best make every effort to find a clean and well lighted area to work.  I’ll assume you know that just soaking a part doesn’t make it clean, a scrubbing action  is normally required on small parts, and those who have experience with ultrasonic parts cleaners learn this.. using a small brush, or even the smashed end of a wooden match can make a scrubbing  tool to help clean a small part. Follow up the scrub with a rinse in gasoline or similar and then dry the parts and drop them in a small jar of new diesel fuel till you assemble them. I like to work on white printer paper, I have no idea what the pros do..

Taking the pump apart is usually a lot more difficult when the rack is stuck, knowing not to apply a lot of force to the rack is the first thing to know, the second is to learn that the barrel normally drops in from the top of the pump, and the plunger is put in from the bottom, so when the plunger becomes seized inside the barrel, there’s a disassembly problem.

I have written other articles, most are on the utterpower CD… including disassembly and re-assembly of a common Lister Style 6/1 pump, you’ll be surprised how similar they all are, and at the center of these pumps are two very common elements that make them work.

One element is a plunger (like a piston), and a barrel, (like a cylinder), but there’s an additional bit of near magic, and that is a ‘helix’ cut up the side of the plunger, this is cut like the stripe on a barber pole, (a spiral like groove.



Above: Plunger in foreground, and Barrel behind it. Notice the helix cut spiral around the plunger, also note that piece down a bit from the left end, this tang slips into a slot on the ring gear and it turns the plunger and adjusts the position of the helix to alter the pump stroke, (amount of fuel delivered per stroke of the pump). The rack drives the ring gear.

If you follow along so far, you can see that a stuck plunger will result in a frozen rack, but it may not be all that obvious that any banging or hammering on the rack is loaded onto a single set of teeth on the rack and ring, and permanent damage is normally the result of forcing the rack.

Above:  Here’s the ring gear around the plunger end, you can see that tang is inside the ring gear slot.  Visualize the rack seen to the left engaging the ring gear, and note just how few teeth will take any pounding you do on the rack, the normal result are teeth broken clean off the ring gear.

The location of this helix grove has everything to do with the pump stroke, and the amount of fuel delivered per stroke.   The rack turns the ring that rotates the plunger.  The rack of course is normally tied by linkage to the governor, and depending on the engine design, all or part of the complete fuel control and governor system (RPM control) can hidden from your view.

Reading an article like this can be helpful, but only hands on experience can transfer the complete picture to you. I’ll give you more of an example here.  My DIYer friend who called me about this pump asked me how to take it apart? I told him, let the whole unit set in warm penetrate for a while, and diesel fuel works pretty good for that. After you run out of patience waiting for the pump to loosen up,  you use kinetic energy to take the pump apart. Remember that plunger is normally stuck fast inside the barrel, and we need it to come out.

Here’s where the knowledge transfer gets cloudy, Just how do you apply this kinetic energy and how much?

My answer is you need know how the components go together, and you need apply the kinetic force ‘in line’ with the plunger, and from the end that will move the plunger in the right direction.

But first… above I talked about two main elements inside a pump and mentioned only one.  The first was the plunger and barrel, the second is the delivery valve that sits right on top of the barrel end that is precision machined flat.

175-fuel-delivery-valve-and washer

175-fuel-delivery-valve-and washer

The delivery valve is two pieces, the valves’ machined flat surface sits right on top of the Barrel’s flat top, and the smaller valve piece is found in the center, and is hidden by the large flange nut that the high pressure line attaches to. there’s a spring under this cap that holds pressure on the valve center.

One thing you need to know, that copper composite washer gets crushed a bit and holds the valve body in tight, and about the only way you can remove it IS with kinetic energy. strip all the parts off you can, and set up a piece of hard wood.. like a piece of fire wood on end and on a cement floor, so it’s dead as possible.  Put a leather glove on, and hold the injection pump body tight, and lower the body flat on the valve end of the pump body.  A really good smack might be necessary to loosen the washer and the valve body behind it.

Once you have removed the delivery valve, you will be able to see the plunger inside the barrel, is it full of mud, rust, or what? normally, it’ll look fairly clean, but still stuck, the problem can be so microscopic, you might not see a cause with the naked eye even after you get it apart.

Next is to assure you have removed as much as possible from the plunger side of the pump, this is the side that the injection pump cam follower runs on, you’ll have a roller, a pin, a retainer clip, and possibly more you’ll strip off, and put into your parts to be cleaned bin.

175-plunger is locked to this part

175-plunger is locked to this part

You’ll see this part on the left when you look at the last part you couldn’t disassemble from the cam follower end. There’s a spring, and possibly a spacer or cap, behind this part, and the reason you weren’t able to remove it, is because there’s a slot that locks the end of the plunger and this part together!

With this understanding, you now check your pump for loose parts again, put your glove on again, and hold the pump with the plunger end (cam follower end down).  Raise the pump body high and come crashing down on that wood! Bang! Now look inside, and see if it’s moved any in your favor? If not,do it again!

Note all of the above was understood by my DIYer friend  who sent me this pump I am writing about and still no joy, so I’ll add some more.. and caution you on where a lot of people screw up on this style of pump, and remember, most Chinese horizontals and many more are just like this one!

When the pump arrived here, it was still stuck of course, and the owner had reassembled it to assure a nice neat package.

I soaked it, I added some heat, just enough where it was too hot to hold, I then stripped it, and rounded up my favorite piece of fire wood, and glove. BANG! Didn’t seem to move.

I looked around the shop and was looking for a kinetic energy multiplier, it was the only game left to play save using a punch to drive out the plunger, and I didn’t like that option. I saw one of my 3 foot long clamps up on the peg board, I thought of the injection pump as being similar to a hammer-head, all I needed was attach a long handle so I could increase the velocity of impact!  I clamped the injection pump tight between the jaws of my clamp, aligned my swing towards the block and with both hands, and a wood splitting swing down onto the cam follower end stripped of parts far as I could go. BANG! Yes, the plunger came free from the barrel, and complete assembly was now possible!

Here’s where I may help to calibrate you mind regarding your swing.  You won’t bend the pump body, that’s for sure, and you need think about the mass of the stuck part you are attempting to move, the smaller the part, the harder you need swing. It might be a lot like comparing the effort necessary to pull a .22 cal bullet versus a 30 caliber with a kinetic bullet puller.  As a last thought, if you can’t get the pump apart, then it’s junk anyway, so swing harder!

With this pump all apart, there was no staining or marks of any kind visible to the naked eye on the plunger or inside the barrel, with just a little wiping down with acetone and a light scrubbing with a paper towel, then soaked clean, the plunger runs free in the barrel, adding a little diesel makes it slide tight, and smooth as silk, the clearances are so tight, that we’d likely need 30 power or more to see a spec of what had it bound up, micro rust from condensate is what it usually is I think, but for all I know China might put some glue in their anti rust compounds, I don’t want to leave you with the thought I know for sure what did it!

As I examine the rest of the pump, I see the ring gear has two slightly peened over looking teeth,  someone attempted to put just a little too much force on the rack to move it, and that’s a VERY common thing, don’t do it!

In this case, a jewelers file can do a little clean up, and the pump will function correctly, but cosmetics will be less than perfect.  Just a tiny bit more abuse would have forced us to replace the ring gear, and that part may be difficult to get all by itself.

There are a few things to learn the hard way about this pump, and I have spent some time trouble shooting a few problems that seemed deep and dark mysteries at first.  I was once offered an engine for about half price from a friend that said he was through fooling with it, in his words he had more important thing to get done. I took him up on the offer and bought an engine that sooner or later had enough diesel in the lube oil, that it needed to be drain and replaced. After some study, I decided it was time for the paper towel trick, wipe everything perfectly dry, and keep running your finger across parts looking for the weep of fuel! In this case, the hunt included removal of the injection pump, and study of how the fuel went through it as well.

Pay Attention!

Above,  Here’s one of the larger sources of trouble in this pump when it comes to assembly, and disassembly. The screw you see fits into the slot you see on the injection pump barrel, this is the barrel the plunger rides in. This screw is inserted from the outside of the pump body, and you must take care to assure the end falls into this slot. There’s another hole directly opposite of this one, don’t even think of aligning the screw with that hole!  That copper  washer you see needs to seal well, if it doesn’t, gravity from the fuel tank will weep through this hole, and since the pump end is inside the engine, it’ll go unnoticed by you untill you pull the dip stick one day and find you’re a quart or two over full!

The real danger comes when you half understand what’s going on here, I have seen many screws mushroomed on the end, the owner knew it need be tight, but missed the fact that the end of the screw needed to drop into this slot. In the case of a stuck rack, one can easily remove this screw, and then spin the stuck rack and barrel as a unit and move the slot out of alignment from the hole un-noticed!  When the owner attempts to replace the screw, he notices the screw doesn’t feel tight yet, he thinks he needs to seat it hard into that copper washer, and all the time he’s mushrooming the end of this screw, it really take less effort than you’d think to mush room the end!  Once mushroomed, it’ll never fit into the slot again without being taken down with a file. Look close and you’ll see that this one has been well worked over as it was mushroomed out severely.

Test fit your screw into this slot on the barrel before you drop the barrel into the housing whenever possible. Make sure the screw is tight >AFTER< you know it’s found the right home. Many if not most Chinese pumps are exactly like this one!

This is not a complete guide to this pump by any means, there are exploded diagrams here and there, and even some on my CD,  what I attempt to share in this article is how to take the pump apart when the plunger is seized, and put it back together again without damage.

Remember to keep diesel fuel in your pump if possible, if you have a spare pump in a box, best you store it indoors in a heated room if possible.

Your questions or comments can help improve this article, thank you in advance for any constructive participation. remember, if you live in the NW, you fight this kind of stuff far more often than you do in the Desert 🙂

for any diesel engine in service, a full tank of fuel is a very inexpensive insurance policy.

George B.



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20 Responses to A frozen Injection pump Fuel Rack, what to do?

  1. Harold says:

    “… had enough diesel in the lube oil, that it needed to be drain and replaced.”

    This one small phrase above sure did get my attention. About four months ago I lost an old friend that most people would call an Oliver 550 diesel tractor, about 1952 vintage. I bought “Old Ollie” from the local Ford / New Holland dealer about 23 years ago.

    After getting used to the unorthodox gear shift pattern and placement and the unconventional size rear tires I became comfortable with and pretty fond of that old tractor. I came to really like how the four cylinder engine timidly sipped diesel fuel. The “office” layout was conducive to a quick exit in case any confusion arose about which side ought to be up on one of the rather intimidating hills I routinely bush hogged. I wish I could say the same about the replacement.

    Everything started to unravel when I came in from cleaning up a downed apple tree and noticed several oil spots under the engine, all steadily growing. I grabbed the dipstick, to see if there was any oil left and to my surprise the crankcase was running over. I had already replaced the primary pump with an electric one, years ago, because OEM was not available even then. There was only one other option and with zero experience on injector pumps I decided to find help.

    No local shop would touch it or offer any advice except to tell me where they ship their pumps for repair. I did get the names of three top notch Oliver mechanics, all retired, who might have advice. Two had already passed away and the other was terminally, very ill. I guess there are disadvantages to old equipment no matter how reliable.

    Long story short, I spent two weeks researching, cleaning off and aligning timing marks (three of them) and removing access panels and accessories. I would fix this sucker. After all, how hard could it be? Then as I was waiting for the courage to remove what I was sure was the offending pump a man rang my doorbell and asked if I had an Oliver for sale. He needed one. I told him the situation as best I could. He made an offer on the stipulation I put it back together in running condition so he could load it, which I accepted and which I did.

    A few weeks later my brother saw an old green tractor he thought he recognized as he shopped the 400-mile-long “Rollycoaster” yard sale. The owner was asking more than twice what I got for mine and he told my brother the injector had bad seals and cost more to fix than he expected. It had a couple of shinny new high pressure lines too.

    Question: did I do good or not? I guess I’ll never know. One thing for sure; I still know very little about injector pumps and that can’t be a good thing.

  2. George B. says:


    Good story, I’ll make an effort to answer your question. The old Mechanical injection pump in your Oliver was likely made with four sets of pump elements very similar to what I show here. The key to finding your pump problem is knowing that the fuel is running into the lube oil sump.

    There are two possibilities, but it’s a fair bet it’s leaking from the low pressure side of the pump, if it were from the high pressure side, it’s probable it would cause a miss, smoke, or some noticeable performance problem.
    With this understanding, you could remove the pump, put it in a jig upright, squirt some fuel into the inlet, and watch where it runs out.. wick it dry with paper towel first and watch it under good light. It’s a good bet you’ll see the leak, and maybe you will be luck and find a copper washer that needs to be ‘fattened up’.

    I once asked Master DIYer McCarroll about his 8 cylinder ‘Stanodyne’ injection pump rebuild, he said.. “George… you can’t believe how easy it was, just 8 sets of the simple stuff you find in a one cylinder pump. MJ does have a complete understanding of clean, and what kind of torque a thread or flange needs to stay tight and not leak, he also knows not to use stuff that scratches a part when cleaning it.

    Those high pressure lines, the two main reasons they fail is over tightening the connection at pump or injector end, or allowing the line to move excessively, like having a missing support bracket on the line. A note, if you have a long line that vibrates when running, add a center support!

    Clean and dry fuel Is key to longevity. Keeping the tank full of fuel at all times so condensate is less of a problem, and there’s a fair chance that an Oliver diesel could out live it’s owner.

    The few Olivers I saw were gasoline rigs, and had weird shift patterns too, they had road gears that allowed you to go about twice as fast as any sane man would want to drive a tractor!

    I’d bet breakfast that those lines were replaced because someone over tightened an end when they attempted some maintenance work, maybe checking or cleaning an injector?
    Might be worth saying that a lot of diesel savvy people have been pouring in a bottle of ATF per tank full of fuel for countless years, they are strong believers that this adds lubricity to the fuel and protects the pump. This is now a growing concern, as our Government pushes to reformulate the hydrocarbons into something very different than it was when these simple pumps were designed. Low sulfur fuel is said to have far less lubricity according to folks that know the topic and the chemistry, some add that B5 solves the problem, as this fuel has even greater lubricity than our old diesel at the pump.

    In the old days, Diesel fuel was a product of the cracking tower, in the more modern processes, you can take a wide range of hydrocarbons and bend them into the types of fuels in demand at the time, near magic I think, but if you read the federal laws as it pertains to diesel fuel, it was far more vague than Gasoline. There was a clause in there that the supplier and distributor would agree on the cetane rating of the fuel.

    There’s enough doubt in my mind as to whether the new fuel is good for old pumps that I’d add some two stroke oil, or other fully approved and EPA reccomended additive. We wouldn’t want to do anything a rabid activist like Lisa Jackson would object too. For now, best thing an owner can do to protected an old friend like vintage diesel tractor is keep the tank fuel, and make sure you add a water trap, and primary filter. Remember those old gasoline station pumps we saw as kids, you pumped 20-30 gallons into a big glass carboy, so you could see what you were buying?

    One more thing about injection pumps, a friend of mine cleaned a gasoline carb, and when done, the machine ran great but it would not idle! We took in back apart, and I passed a numbered drill thru the main jet and removed a good deal of varnish, this would likely have caused this air cooled engine to run a lot leaner than designed, and since you need twice the volume of ethanol to flow in order to get the same fuel air ratio in the engine, you are already flowing a fuel about 5 percent lower in BTUs than what the engine was designed for, and you will have a leaner fuel mixture with the fuel you are normally forced to use!
    With this understanding, you want the main jet as clean as possible, as there is a possibility of damage under heavy load as it is. There is even a case to fatten that main jet one step up with a numbered drill, but I leave that decision to people who know more about carbs than myself. In this carb, I found enough dirt in the idle circuit to plant a tomato seed in, and once we cleaned it, it ran like a top. I take time to share that an injection pump needs even more attention as per clean, but you don’t have a seriously corrosive and poorly designed fuel working against you! There are so many advantages to a diesel, one being it is a far more efficient engine that can under the right circumstances burn a wider range of fuels. What we call diesel fuel at the pump today is actually a wider range of fuels than we think… at least that’s what a few petroleum engineers tell me.

    A small book of a comment it was..


    • Harold says:

      Thanks for your comments. Considering those along with your original article I am convinced if I would have attempted the repair myself it would have ended in disaster. Probably, one of my worst omissions has been not keeping the tank full. Also, I never suspected I would need to put a lubricant in diesel fuel. Now that I think about it I used to put a gallon of diesel with a fill-up in an old Ford I owned once.

      First, there were two errors in my post:
      It was not the injector that had bad seals it was the injector pump.
      The tractor was not a 1952 model but a 1960. Here’s the data I sent out or carried to prospective shops:

      Tractor Oliver 550 Year 1960
      Spec. # 45-0057 Ser # 85022-519

      Need replacement or repair of injector pump / pump head.
      American Bosch P/N PSB4A-70V-S4081 A1 500-2000 rpm.
      Oliver P/N 101406-ASA
      Pump Hydraulic head P/N HD4742A

      Tractor runs OK. Diesel fuel fills the crank case. I replaced the primary pump with an electric fuel pump sold to me by the last White / Oliver dealer in Glasgow KY as a suitable replacement.

      Can you repair, replace or provide a repair kit for this injector pump and if so what is the approximate cost?

      As I said before there were no takers.

      The pump to injector lines that were replaced lived in a pretty congested area and included several supports. That the tractor was a compact arrangement is one reason I liked it. As best I could figure the lines would have to be removed not just disconnected. The manual included a note that some mechanics preferred to disconnect at the injectors and remove the lines with the pump. I suspect they were damaged during pump removal or replacement.

      The “Pump Hydraulic head P/N HD4742A” was what made this setup different from anything I had seen before—or since. Actually it was a distributer; not something I would expect on a diesel. The top was round; maybe ½” thick with four lines coming out much like what you would see on a four cylinder gasoline engine distributor.

      The governor was “timed” to the crankshaft; the cam driven pump was “timed” to the governor and the hydraulic head (distributor) was “timed” to the pump which was a single plunger affair that sent fuel to the head which then directed it to the appropriate injector. The governor, pump cam and rather long push rod up to the plunger, which sat under a healthy spring, was lubricated by crankcase oil. I suspected the plunger.

      My manual included a pretty good breakdown on the governor / pump / head assembly but was obviously intended to be used as a “remove and replace” guide not for pump overhaul. The head was pictured only as a removable unit.

      Yep, I’m pretty sure my overhaul / repair attempt on this critter would not have ended well. The guy who owns it now was at least gutsier than me and probably a better mechanic, after all he liked Olivers.

  3. Quinn Farnes says:


    Thanks for posting that. Injection pumps are an area I’ve never looked into. Your pics and thorough explanation helped me understand what’s going on in there. Thanks again for your help.

  4. Russ Davis says:

    Hey there George, nice right up.

    And now my question. Do you think placing the whole assembly in an ultrasonic cleaner, maybe filled with diesel/ATF could possibly make disassembly easier?

    Just spitballing an idea.


    • George B. says:

      Russ, there’s certainly different amounts of ‘stuck’.

      I’d assume that a little heat, a soak in Kerosene, Kroil, or similar that has earned a place on your shelf of proven rememdies is a help, ultrasonic cleaners? I’m not os sure they’ll do much, but can’t see how it would hurt.

  5. Greg says:

    After pounding mine on a board for a while, I gave up and soaked the thing in some 200 degree used veg oil. it just squirted right out on it’s on.

    That warming up also seems to facilitate the subsequent cleaning with gasoline.

  6. roger cole says:

    Hello–I have the fuel pump of the petter AC1 in pieces.I have taken out the copper washer with some difficulty.Whats behind the copper washer is what looks like a sleeve with a bevelled top but it looks like part of the whole casing–is this a separate sleeve which comes out ?Tanks Roger

    • George B. says:

      Roger, your words don’t paint enough of a picture.. you may be talking about the high pressure side of the pump? Here you find a percision valve, the copper may be part of the high pressure seal here. Typically, there are separate pieces on the high pressure side, a spring, a valve, and part of the valve body typically wedged in by that seal.. if someone over tightens this fitting, it can be hard to get the valve out.. did you search on the internet for a drawing of your pump?

  7. Gordon W Emms says:

    Great write up and help.
    However, what is the procedure for setting up the rack gear and does the plunger get installed with the slot facing the inlet port or the other side during reassembly.

  8. James says:

    Hi, I got a Komatsu PC15 mini excavator and I rebuilt the 3D68E engine in it. It works, but I am not comfortable with it. It has a Denso diesel pump like you describe in your article. I got a hard time starting it each day and I have to heat the glow plugs for 15 seconds and five times to eventually getting the engine running. When I was assembling the diesel pump I took the toothed rack off, but wasn’t sure where to match it to each fuel delivery unit. There is a small notch on one of the toothed gears on each single pump unit, but where should you actually set these when matching the rack to the pumps. Your picture is a bit blurred, so I cannot see it well. I cannot find this information anywhere. I set mine to the right of the pump as it seemed the correct place to put it, but this was after I examined the pumps delivery system. There are a couple of marks on the rack, but it is hard to determine where to match them as well. Any info would be appreciated.

  9. Reginald Fletcher says:

    Hi, I am in the UK, I have an Oliver 55 with a PSB4A Fuel injector pump with a broken piston plunger, I have a local machine shop that can make one for me but can anyone help me with the exact length of the rod as mine has not broken off cleanly. Any other help would be appreciated. Many Thanks Reg

  10. Reginald Fletcher says:

    Hi, I am in the UK, I have an Oliver 55 with a PSB4A Fuel injector pump with a broken piston plunger, I have a local machine shop that can make one for me but can anyone help me with the exact length of the rod as mine has not broken off cleanly. Any other help would be appreciated. Many Thanks

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