CAV problem

The inner part of the hydraulic head of my 1980 Series 3 diesel rotates freely when it is out of the body but when I replace it, mating with the spindle, it just moves a bit then stops. I imagine that the whole device from spindle to head should rotate easily but I cannot think of what is stopping it. Any explanation or advice as to how to rectify the fault greatly appreciated.

Perhaps this might help , I’ve never took mine apart
http://www.diydieselshop.com/113109996
You could also post some pics showing the issue

Thanks Steve. I'll try to include a picture of the head. It is the central bit with the vanes which should rotate freely At least I assume it should and I don't want to find that I put it on the LR and the quill or something else breaks.

CharlesY would have known the answers but not been on here for a few years now, you can search on here to see what’s been asked previously, I did find a post saying the vanes only go in in a certain way,
I assume you can turn the bottom shaft freely that works of the camshaft without the vanes in but not with the vanes connected?

Agreed, check the centre spins without the vanes in then double check how you have the vanes.
Attached is manual.
.

rob1miles said:

Agreed, check the centre spins without the vanes in then double check how you have the vanes.
Attached is manual.
.

Click to expand...

Thanks for the input and link.
It doesn't spin with or without the vanes.

steve2286w said:

CharlesY would have known the answers but not been on here for a few years now, you can search on here to see what’s been asked previously, I did find a post saying the vanes only go in in a certain way,
I assume you can turn the bottom shaft freely that works of the camshaft without the vanes in but not with the vanes connected?

Click to expand...

Even without the vanes it will move only a fraction - about the travel of the bolt in the ring on the advance retard device.

Just checked mine which is on the bench and the bottom drive spins easily, have you had a search on you tube
CAV DPA pump brings a few videos up

if i the hydraulic head turns whilst it is removed as an assembly but will not turn when installed it must be the pumping plungers and or shoes/rollers are stuck

adrian hogg said:

if i the hydraulic head turns whilst it is removed as an assembly but will not turn when installed it must be the pumping plungers and or shoes/rollers are stuck

Click to expand...

Thanks Yes This is the conclusion I've come to from having a look at diagrams, but I am wary of dismantling lest I upset the calibration. Any suggestion s as to how to do this without cocking everything up would be greatly appreciated.

Once the head and rotor assembly is removed from the pump body you can unscrew the cross rotor that turns the blades in the transfer pump then slide the rotor assembly out of the hydraulic head. Find a piece of steel which is a good fit in the slots (at a push you can use the oval side plate off the pump but make sure you insert it as deep as poss into centre of slots and turn with a good adjustable spanner big enough to hold the full width of plate as close to the transfer rotor as poss. and hold the rotor across the two bi-hex pins in a soft jaw vice Be careful as the SHOES CAN BE PUT IN BACK TO FRONT they contact the fuel adjuster plates in the max fuel position with a concave profile
Dirt even in tiny amounts is your enemy if you dismantle the rotor from the head, running clearances are only a couple of microns so nothing abrasive is welcome especially if trying to clean parts use copious amounts of clean diesel or paraffin. I will gladly talk you through it if you send me a pm Iwill give you my mobile number

Pistons could be gummed, if so worth trying some penetrating oil. If there's a tiny bit of corrosion I have polished out with brasso but as said above, dirt is your enemy.

Thank you both very much for your advice. I'll have a look at it tomorrow and see what I can do. Thanks for the offer of a phone call. The problem is I am rather deaf and cannot hear anything on the phone so if you don't mind I may contact you again when I get stuck.

hi faber have sent you a text, feel free to call me if you get stuck putting it back together

I forgot to add, if its ever been run on biodiesel or veg oil and there are traces in the system it really gums up these pumps.as they are fuel lubricated with tiny clearances. The veg oil sets if left standing - it polymerises over time - and will completely glue the moving parts together. Penetrating oil and some heat will get the parts to move, once moving you can flush it out.

Thanks. I have never run it on Biodiesel despite attempts by a farmer friend to sell it to me cheap!

Thank you everyone for your help. I removed the slotted top bit and seeing that the plungers were seized tried to tap them out with a chop stick. This didn't work so I made a couple of short dowels out of hard wood and both popped out. I've cleaned them up, bathed them in diesel and put them back. Everything now rotates freely.

Nice one hope it’s starts ok