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Discussion Starter #1
I have a leak on my 1977 335 industrial on the injection pump at the shut-off valve. The screw that the shut-off cable is attached to moves down when I push it from the top, I think there must be an o ring inside that is missing. Has anyone dealt with a problem like this? A friend just took in his John Deere tractor for an injection pump leak and they charged him $1000 to rebuild the pump and reinstall...I sure would like avoid that on this old tractor!
 

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You are quite right, there are o-rings on the shaft that need to be replaced. You need to remove the top cover from the pump in order to renew the o-rings. You can do this with the pump on the tractor, but you need to clean the pump thoroughly and it's surroundings before you take anything apart. When you have cleaned everything, clean it again. Nothing is allowed to get into the pump.

Renew the o-rings on both the stop shaft and the throttle shaft, all four o-rings (two on each shaft) are the same. You need a new gasket for the top cover as well.
Examples of o-rings and gasket kit:
https://injectionpumps.co.uk/product/lucas-cav-dpa-diesel-injection-pump-top-cover-gasket-throttle-shaft-seals/
https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=CAV+DPA+Gasket+O-Ring+Kit&_sacat=0

This site has some good information, for instance an interactive parts diagram, just click on a part or a number and you get a picture of what the part looks like:
https://injectionpumps.co.uk/interactive/interactive-cav-dpa-parts-diagram.htm
If you click "80", you get the stop shaft:
https://injectionpumps.co.uk/product/cav-dpa-stop-shaft/
If you click "86", you get the throttle shaft:
https://injectionpumps.co.uk/product/lucas-cav-dpa-diesel-injection-pump-throttle-shaft/

There are lots of videos on the Tube about the CAV DPA pump. I think this is a very good one, a bit blurry though::
You have a spring arrangement on the throttle arm, that he does not have. That is no problem, just study how it works and how it is attached and it will not give you problems at disassembly or reassembly.

When you put the levers back on their shafts, be careful that the elongated holes on the levers seats properly on the shaft's shoulders. You can by mistake push the shaft down when you put the nut back on, and that can make the lever pop up from the shoulder and then the lever will not act properly on the shaft.
 

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Discussion Starter #6
This gives me hope not to worry about a full rebuild and timing. Many thanks HåkanTh. I will let you and all others know how it goes.
 

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Discussion Starter #7
Well, I watched a few videos. Looks like there are things that could fall into the bottom of the pump when I take it apart so I am a bit discouraged doing the reseal without removal. Someone told me that I should not take it off though because somehow taking it off and putting it back could mess up timing and it is difficult to fix later. Is it true?
 

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Yours should have the CAV rotary pump. You can't mess up the timing on one of those, as the gear under the front cover that drives the pump has a hole and the front hub of the pump has a metal dowel that goes into that hole, so it can only go back together one way and as long as you remove only the pump, and not the drive gear, the timing can't change. The Simms in-line pumps were a bit more complicated to make sure that the timing was correct when re-installing, but the parts site doesn't show the 335 ever using a Simms pump. Definitely do not remove the pump unless you have a service manual. Both the Ford factory service manual and I&T after market service manual have the prodcedures for both, and if you follow the procedures then it should be in time when you re-install.
 

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You can adjust the timing by turning the pump. It is probably correctly timed as it is, and therefore you need to put it back in the same position as it is. There is a scribe on the pump and markings on the engine like in the attached pictures. Make sure you note, or mark, the position before you loosen the screws that holds the pump.

It is good to have the pump number in order to identify it. There are numbers on an ID plate (see attached picture). Remove the yellow paint chemically, do not use sharp tools or any abrasive material. The numbers are stamped, but the plate is made of thin aluminium, be careful.


I advice you to get a repair kit for the pump, like this:

It contains parts that you will not need for this work, but it has new nuts and o-rings that you need and it is good to use new copper washers for the fittings. It also has plugs to cover the openings. A kit can be found on ebay, for instance. Look for "CAV DPA repair kit".

In a repair kit you will also find a plastic filter and some other parts. See 9, 10, 15 and 19 in the diagram:
These go into the pump inlet and it is a good idea to take the inlet apart, clean and replace the parts. Be careful when you take it apart (springy things...) and watch the order.

pump_2.jpg cav_dpa_timing_mark.jpg
 
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