Lucas CAV pump mystery

[Gordon Gould]

I have a Cummins 239 in my dozer. The fuel system it has a lift pump, a spin-on filter, and a Lucas CAV pressure pump. If the fuel tank is full the fuel level in the tank is above both pumps and filter. I have discovered that the pressure pump leaks a steady drip from around the throttle shaft (pretty sure anyway), but only when the engine is shut down and only after I either change the fuel filter or move the throttle. Also, I think that I have only seen this happen with a full fuel tank but not sure. Once it starts to drip it wont stop until I start the engine. As soon as she starts the drip stops. Then when I shut down it will stay dry forever unless I move the throttle or unscrew the filter.
Does this make sense ?
Is there something I need to fix ?
If so, is it something an OK backyard mechanic can do ?
Thanks.

 

[TraderMark]

Hey Gordon,

Sounds like you need a throttle shaft seal and/or bushing in the top of that pump.
I'm no Lucas expert so I'd take it to a diesel shop myself. If it was a Roosamaster/Stanadyne, I'd just do it myself.
We have a forklift at work with a Ford engine and the Lucas pump. It leaks in the same place yours does, only it leaks CONSTANTLY. It will drain a tank of fuel over a long holday weekend. So yours is going to get worse, not better.


Hope this helps,
Mark

 

[Gordon Gould]

Mark, Thanks for your insight. Based on your comment I did some checking which I should have done first. Apparently it is common for Lucas CAV pumps to develop a steady leak at the throttle shaft. Most seem to blame it on low sulfer fuel ???
Anyway, so much for my wishful thinking. Thanks again for the early warning it makes it easier for me to schedule and get it to a shop for rebuild at a good time.

GG

 

[banjodunn]

G'day Gordon if you search the forum for cav leaking pump/throttle shaft you should come up with a few different threads. The basic layout of the CAV DPA type pumps is the same for 3/4/6/8 cyl engines and the repair you need to do is not that hard you just need to be careful AND clean!!
If you do a search for it i'm sure you will find what you have to do and I know over here he top cover kits are avail on ebay so i'm sure they will be over there.

Good luck

Jon

 

[Gordon Gould]

Well I found a couple of good threads and received some encouraging info from another TBN member. So it is looking like a fix that I will be able to attempt myself.
If anyone knows where I can find some specific instructions or has any words of advise on this I would appreciate hearing it.

Also found this online manual someone might find useful
http://www.fujiyachts.net/manuals/CAV DPA Pump Rebuild Manual.pdf

Thanks GG

 

[BuckeyeFarmer1994]

There are several manuals available at the following link, including a service manual for the Lucas CAV Pump......hopefully this helps:

Index of /manuals