CAV injector pump

gas987

gas987

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Hi, Having trouble with my CAV DPA pump. Engine is a Perkins 4108. Finally worked out that the shaft driving the pump is moving forward in the drive hub and disengaging from the pump. Does anyone know how this shaft is supposed to be held in position, should it just 'fall' out of the fuel pump or should it be attached somehow? I have the pump and timing gear cover removed but can't see anything obvious. Cheers.
 
gas987 said:
Hi, Having trouble with my CAV DPA pump. Engine is a Perkins 4108. Finally worked out that the shaft driving the pump is moving forward in the drive hub and disengaging from the pump. Does anyone know how this shaft is supposed to be held in position, should it just 'fall' out of the fuel pump or should it be attached somehow? I have the pump and timing gear cover removed but can't see anything obvious. Cheers.
Click to expand...

If you take the pump off, contact Alan Darby of http://lynxdiesels.com and he will be able to sort it for you.
 
Thanks Tom, I have the manuals for engine and pump already and am aware of how to use a search engine. I was just wondering if anyone here had some 'hands on' experience....Thanks also Ianj. The pump works fine, the problem is with the quill shaft / pump drive hub somewhere. The engine runs for a while then the shaft seems to work its way forward out of the drive hub. Thanks again for your comments / links.
 
gas987 said:
Hi, Having trouble with my CAV DPA pump. Engine is a Perkins 4108. Finally worked out that the shaft driving the pump is moving forward in the drive hub and disengaging from the pump. Does anyone know how this shaft is supposed to be held in position, should it just 'fall' out of the fuel pump or should it be attached somehow? I have the pump and timing gear cover removed but can't see anything obvious. Cheers.
Click to expand...

Does it look like you have the correct quill shaft and it is making full engagement in the drive hub on the engine. Is the spline in the drive hub a blind spline or open right through?

The manual suggests the quill shaft just sits in the pump which would suggest that when the pump is assembled on the engine it is trapped in place???
 
The quill shaft is the original, the drive hub is open right through into the timing gear case, nothing looks broken or excessively worn. All was fine last year when the boat came out. The engine is in my garage at the moment as I was changing the head gasket and repainting it. After reasssembly I couldn't get fuel to the injectors. I eventually removed the pump to find nothing apparently wrong with it. I refitted it and the engine ran for a while before cutting out. I removed the timing gear cover to find the shaft had moved forward out of the hub splines..Cheers for your reply.
 
gas987 said:
The quill shaft is the original, the drive hub is open right through into the timing gear case, nothing looks broken or excessively worn. All was fine last year when the boat came out. The engine is in my garage at the moment as I was changing the head gasket and repainting it. After reasssembly I couldn't get fuel to the injectors. I eventually removed the pump to find nothing apparently wrong with it. I refitted it and the engine ran for a while before cutting out. I removed the timing gear cover to find the shaft had moved forward out of the hub splines..Cheers for your reply.
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You have to have wear in the drive hub. Strip out the hub and take a look at the bearing, all the tolerances are in the workshop manual. Have to say that there has to be a gut busting amout of wear in the hub bearing for the the fuel pump quill shaft to become disengaged.

You do not mention if you have mechanical or hydraulic DPA. Are you saying quill shaft is moving forward though the hub and losing drive?? Curious to know how you re-timed the engine after this happened.........

If quill shaft came forwards right through the hub as I understand it, simply tugging the pump shaft has to result in forward movement.

Hope you have mechanical DPA.
 
Hi Latestarter, yes the quill shaft is moving forward through the hub until it completely disengages, you can pull it forwards through the middle of the fuel pump drive gear.
It's a mechanically governed pump. Re. the timing there are master splines on the quill shaft, it only fits into the drive hubs one way. There are a few degrees of adjustment on the pump body itself, a scribed mark ensures the pump is aligned as it was when it came off.
As you say I suppose the next step will be to remove the hub for further inspection, just wondered if the quill shaft was supposed to be just sitting in the drive hubs with nothing to stop forward movement other than the tension in the gears.
Cheers.
 
gas987 said:
The quill shaft is the original, the drive hub is open right through into the timing gear case, nothing looks broken or excessively worn. All was fine last year when the boat came out. The engine is in my garage at the moment as I was changing the head gasket and repainting it. After reasssembly I couldn't get fuel to the injectors. I eventually removed the pump to find nothing apparently wrong with it. I refitted it and the engine ran for a while before cutting out. I removed the timing gear cover to find the shaft had moved forward out of the hub splines..Cheers for your reply.
Click to expand...

Is there a groove in the quill shaft at drive end for a circlip????
 
It sounds like the pump drive hub is moving foward, this could be the circlip is missing from the back, or the bronze bush (alloy on late engines) it runs in is worn or lose in the block.

If the drive hub is moving it will afect the injector timing, if not I would look at the pump and see if the drive shaft has a lot of play.
I do have a good spare mechanical type pump if you need one.
 
macnorton said:
It sounds like the pump drive hub is moving foward, this could be the circlip is missing from the back, or the bronze bush (alloy on late engines) it runs in is worn or lose in the block.

If the drive hub is moving it will afect the injector timing, if not I would look at the pump and see if the drive shaft has a lot of play.
I do have a good spare mechanical type pump if you need one.
Click to expand...

The drive hub locating circlip is all present and correct. Pretty sure the hub is OK, the timing marks on hub and drive gear are still aligned correctly. The problem definately seems to be the quill shaft moving forwards out of the drive hub as there is nothing to stop it. Engine runs fine until this happens. Puzzled as if something had broken you'd have thought there would be bits of it in the hub. Looking at parts drawings everything seems to be there. Thanks for you replies.
 
Well the drive hub is out and looks OK. There is a groove machined in the inner bore of the hub a couple or three millimetres forward of the splines, looks like there should be a circlip in it but there was no evidence of one on strip down. Has anyone stripped down this hub before, should there be something in this groove to retain the quill shaft?
 
gas987 said:
Well the drive hub is out and looks OK. There is a groove machined in the inner bore of the hub a couple or three millimetres forward of the splines, looks like there should be a circlip in it but there was no evidence of one on strip down. Has anyone stripped down this hub before, should there be something in this groove to retain the quill shaft?
Click to expand...

About 30 years since I looked inside a 4.108.......Certain you should have a circlip in there.
 
gas987 said:
Well the drive hub is out and looks OK. There is a groove machined in the inner bore of the hub a couple or three millimetres forward of the splines, looks like there should be a circlip in it but there was no evidence of one on strip down. Has anyone stripped down this hub before, should there be something in this groove to retain the quill shaft?
Click to expand...

Normaly on a marine engine there is a drive for the water pump in the hole

pumpdrive.jpg


I can't remember there being a cirlip there.
 
Latestarter1 said:
If you have a shop manual look at J9, if not PM me and I can send you a copy.
Click to expand...

That circlip I have! It fits into a groove on the outside of the hub and holds it and its drive gear in position.
Engine all together now and running fine so I'll just have to inspect periodically to make sure nothing's amiss.
Appreciate your suggestions, thanks.
 
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