Rebuilding fuel priming pump

[Columbo]

Last fall when I was completing routine maintenance I noted that the fuel priming pump on my Cat 311B excavator was leaking fuel everywhere when I tried to prime the system after a fuel filter change. Machine S/N is 8GR00401. I pulled the parts diagram below from SIS, are there user-serviceable parts inside the priming pump or should I order a new one (looks like p/n 239-6656 is the current replacement for around $100).

In addition to making a mess when changing filters, I have been investigating a periodic loss of performance issue which I described in another thread. I’ll be checking fuel system pressure this year when I get the machine out of its winter hibernation but could this leaking primer pump contribute to my power loss issue?

Cat excavator periodic slow hydraulics

I’ve noticed a strange, periodically reoccurring issue with my excavator- Cat 311B s/n 8GR00401. Sometimes after I’ve been running for awhile the hydraulic functions will slow down. The problem primarily effects the boom/stick/bucket circuits and not the slew/travel functions. It seems to vary...

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[Columbo]

Pic wouldn’t post in the message above, let’s try again… the part that’s leaking is # 1-7 below.

 

[Delmer]

I'd bet that is common enough across different transfer pumps. It needs the same threads and that's it, it holds the check valve spring down, but otherwise does not interact mechanically with the rest of the transfer pump. The bore and stroke of the hand primer itself aren't critical. It looks like aftermarket replacements are $10-30 so no point in looking too hard for seals, unless it's easy to get the plunger out, then it's probably just an o ring that's worn.

 

[thepumpguysc]

Take down #5.. that’s the one with the filter screen in it..
U can replace just the hp..

 

[Columbo]

Take down #5.. that’s the one with the filter screen in it..
U can replace just the hp..

I’ve cleaned the screen inside the banjo bolt (#8) but I will do it again while I’m there. Are you saying there is a screen behind the plug #5 as well that should be cleaned?

 

[thepumpguysc]

Sorry.. #8..

 

[Columbo]

Sorry.. #8..

Thank you! I’ll clean it again, it was certainly dirty the first time.