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Contributor

Re: 3406B losing prime

I swapped out the hand primer, let it sit over the weekend, and it fired right up like normal this morning. Thanks for all the help! Now my operator can stop complaining!

Super Contributor

Re: 3406B losing prime

The hand primer pump contains 2 check valves which are easy to inspect. The valves cannot easily be replaced but the hand primer pump is easy to remove and install.
Contributor

Re: 3406B losing prime

Ok, swapped the fuel transfer pump. fired it up, then let it sit overnight. took 7-8 seconds of cranking to start. perhaps that was not the issue? The hand primer feels kind of floppy when priming the system. Possible problem?

Contributor

Re: 3406B losing prime

Ok found it. I'll swap it out and see how it holds after. Thanks for the help!

Super Contributor

Re: 3406B losing prime

It's a piston pump on the bottom of the injection pump housing just behind the mounting flange. There will be some oil spilled when you remove the pump.
Contributor

Re: 3406B losing prime

Do you have to clock or time the pump? Also, the engine is crammed into this thing and im having trouble locating said pump.

Super Contributor

Re: 3406B losing prime

Transfer pump isn't hard to replace. 2 bolts (1/4") and 2 fuel lines to remove. They are not difficult to rebuild but the reman isn't expensive and you are certain it's assembled correctly. Get new seals for the fuel line fittings and mounting.
Contributor

Re: 3406B losing prime

Is the fuel transfer pump difficult to replace? Are they worth rebuilding?

Super Contributor

Re: 3406B losing prime

It's probably the check valve in the fuel transfer pump. The easiest way to repair it is to install a reman transfer pump.
Contributor
Accepted Solution

3406B losing prime

Hey, guys. I'm running a 3406B mechanical in an old P&H crane. Recently, if it sits for a few days, I have to pump up the hand primer to get it to start. Once it starts, it runs great. No loss of power and not acting like it's sucking air. I don't smell fuel in the oil. I'm thinking a bad check valve in the system is letting fuel drain back to the tank. I've changed both primary and secondary filters and the problem persists. Any ideas on where to start? Is there a check valve in the hand primer that could have stuck? Any thoughts are welcome. Thanks