Keywords for non members outside the forum to find this post,( Lister CS 6/1 fuel pump service repair strip clean and rebuild repair )
Today I decided to take a better look at the fuel pump. I had concerns over this unit as I couldn't move the rack which governs the speed of the engine. Essentially it was seized.
I have scoured the net for info over the last few days and although there is information out there, none of it is very clear to a novice like myself. I even found the manufactures exploded diagrams somewhat misleading and still didn't explain how to actually strip and service these units.
So, the best way to learn is to strip the unit down and do some exploring....
However, armed with little information it has taken me all day and evening to strip clean and re-assemble this unit. Now I've done it, and figured out how it does it's job it would be a fairly simple matter to tackle this again in under an hour or so.
Having seen many, far too many, questions on this subject on various engine forums "ALL" of which gave little help and no pictures I have decided in the Madmodder spirit to put a post together with lots of pictures. We like pictures here, but in this case I'm hoping that it may save someone the grief of going at it blind.
If you are not into engines (yeah right!!) then the rest might bore you,
My Seized Lister fuel pump....this is a Bryce BOAB unit, yours may be a CAV unit but from what I can tell they are very similar.
On the bench, this is a back view showing the piston cylinder locating screw 4
Manufactures exploded diagram, Refer to this for part no's
First things to take off are the top fuel pipe fitting 20 followed by 21,17,19,16, (note, 16 it two parts making up a none return valve, be very careful not to drop and loose the smaller part) and the circlip 14 at the bottom along with the bucket 13. The rest should fall out, be careful and try your best to note what goes where. Best to take lots of pictures for reference.
However, if your unit is anything like mine all the internals will be stuck fast and you'll have no idea which bit to tease out first. This makes disassembly rather difficult for fear of breaking something. As I said earlier it took me hours to get all the bits out. Not because any of them were difficult, but more because of fear of damaging something.
These bits should fall out the bottom, in this order, collet retainer 12, spring 11, and spring seat 10.
Followed by these, pinion 9 and piston 3. This is where the manufactures diagram becomes really misleading as item 3 is actually two separate parts. The piston which has a helix machined into it and the piston bore which has the fuel delivery bore in it. One comes out through the bottom and the other comes out the top. The piston bore does not move and is fixed in place by a locating screw 4 at the rear of the casting. The piston and bore have a very close tolerance and therefore subject to seizure at the slightest provocation. This is what was seized on my unit and not the rack 6 and pinion 9 as originally suspected.
This is why you should not force the rack side to side with a hammer or some such implement in an effort to free things up.
If these bits do not fall out, or can't be easily pulled out then you need to remove the non return valve item 16 next. This might not be easy as the sealing washer may be holding it a bit tight. But it should come out. Be careful not to damage the internal bore of this item or you may have problems in keeping pressure at the fuel injector when running the engine.
Once this out out you will be able to see the piston inside the bore. They look like one unit but they are not. You can now push the piston out of it's bore from the top using a drift pref a wooden dowel. Do not use metal. It you damage the bore your pump will be ruined and not longer serviceable.
If you can't remove the non return valve to gain access to the piston top you will have to remove the piston from the bottom.
Remember, if this is the case the spring and retainer will still be in place making access difficult. You will have to flip the spring retainer with a screwdriver. This is fairly easy to do, but try not to score the casting. It's not critical, but best be careful all the same.
After removing the retainer, spring and seat, you should be able to pull the piston out. Remember, this is the bit that is seized, mine was really tight and took some effort.
Here you can see the piston with the machined helix. Note which way this fits into the bore. Get it 180 deg out and your engine will be spinning at full pelt with no way of slowing it down. The governor will not work at all. The manufactures instructions state the two items (piston and pinion) are marked for orientation. Yep, mine was, only both ways....really helpful I must say.
If you look at the helix and the hole in the piston bore the two should line up when reassembling. That is the helix should face the front of the pump housing.
Indecently mine was back to front, suggesting someone had stripped this before at some time. I've yet to run this engine, so a good job I found this !!
So, now the piston is out, the pinion will fall out too along with the rack 6. Watch you don't drop it !!
That's it, all disassembled.
It turned out that my unit was only gummed up with fuel residue/varnish. A simple clean and reassemble and all was well with everything working as it should.
Ready to go back on the engine
Hopefully that didn't send you to sleep
and helps someone sometime.
I could write a re-assembly with how to line it all up, but it's not that hard with a bit of common.
