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.
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.
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.
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.