Electric fuel pump wiring & bleeding your diesel
Good advice here. They call 'em "lift" pumps for a good reason, 'cuz some boats have the fuel tanks lower than the engine. For instance, our C34 has the fuel tank higher than the engine, but still has a lift pump for our M25 series and M-35 series engines. The fuel is reported to flow adequately without the lift pump until the tank is half full or lower, due to the routing of the fuel supply hose and the pressure drop through the line and the fittings (engineer-speak) between the tank and the engine's injector pump. Other boats from the same builder have low fuel tanks.
Bleeding without a pump has got to be a chore. I tried it once using the finger pump on the Racor and my fingers STILL hurt and that was 13 years ago!!!
Instead of alligator clips, one could install a simple hard wired setup and install a simple toggle switch.
I've done just the reverse: the fuel pump runs all the time the key switch is on, and when I have to bleed the secondary filter I have to remove the screw to bleed the air out of the sec filter; rather than spilling fuel all over during the time it would take me to go to the electrical panel and turn the main DC switch off, I put in a toggle switch in the engine compartment that I easily reach and turn the pump off when fuel starts to come out of the screw hole.
The newer Catalina and other brand engines have a dual start wiring arrangement where the pump comes on when the glow plugs are energized and then stops until the engine starts AND only resumes when the oil pressure is made. I find this kinda dumb for bleeding, but the engines are supposed to be "self-bleeding." "Self-bleeding" works for the primary filter, but doesn't always work on that secondary filter, which is why it makes me think the concept is dumb. There's another downside to this silly design:
...requiring holding the glow plugs via the keyswitch spring position ON while hitting the start button MEANS that there is a continuous draw on the battery bank from BOTH the glow plugs AND the starter motor. Our C34-group experience is that this INHERENTLY leads to tough & rough starting. The Mark I “trick” has always been to RELEASE the glow plug (button in our Mark I case) BEFORE the start button, so that both heavy amperage draws are NOT on at the same time.
and
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Another interesting sidebar to this whole "when does the fuel pump run?" issue just occurred to me after stumbling over this thread:
http://c34.org/bbs/index.php?topic=64.0 or any other of the many fuel bleeding posts.
IF the fuel pump ONLY works when the glow plugs are held on with the spring switch OR when the engine is running, bleeding the fuel system is a real PITA. To successfully bleed the system, as discussed here and finally summarized by Ken Heyman (
http://c34.org/bbs/index.php?topic=2884.0), it's MUCH easier to run the fuel pump without the engine on, and why would you want to have to energize the glow plugs when you bleed the engine?
Another one of those
UNFORESEEN CIRCUMSTANCES and
unintended consequences as a result of a "design improvement" that makes things worse, not better.
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and:
http://c34.org/bbs/index.php/topic,3347.msg21275.html#msg21275
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Of course, I'm not opinionated about this at all!
In that case, I recommended to our skippers that they re-wire the stupidity out of their systems and just run the pumps all the time.
Here's a perfect example:
http://c34.org/bbs/index.php/topic,5078.30.html
Good luck. You'll love that pump when ya need it!