Primer bulb on Yanmar Diesel

[Sailor 99]

Originally Posted by bact0ee

I have a primer bulb on my Yanmar diesel (54 hp) and after about a hour or so it will collapse when running at 2500 rpm. When it collapses it shuts off the fuel and the engine dies. I recently tried running at 2000 rpm and the problem went away.

Has the bulb wore out to where it cannot handle the suction at this rpm or is there another culprit.

Appreciate any thoughts. Thinking of removing this bulb from the system. It is between the fuel tank and the racor.

I understand why you have the primer bulb. Useful for re priming the system after a fuel filter change. I had a fuel filter on my first boat that was really hard to change the filter and ensure you had a good seal. The lift pump on the engine is never going to over come an air leak.

That said you have a blockage in your fuel line between the primer pump and end of the pick up tube in the tank. I had the same thing happen. I had used Ultra Black to seal the inspection lid and used too much. A blob fell into the bottom and hardened and then got sucked up the pickup tube. Engine fuel pump sucked that primer bulb flat.

You might also have a kinked fuel line. Either way same thing. Fuel flow is being restricted.

[Sailor 99]

Originally Posted by Snore

Check racor, it is likely clogged. High ROM needs more fuel, racor cannot supply, injector pump pulls vacuum, bulb collapses. When you see it you assum blurb, but real fault is clogged filter, or other impediment to fuel flow.


PS I HATE primer bulbs below deck! Spend $100 and wire in a lift pump. It should turn on with ignition. This will also make changing filter much easier.

OP says primer is between tank and fuel filter so it is not a clogged filter it is a blocked fuel line.

[Sailor 99]

Originally Posted by Snore

Check racor, it is likely clogged. High ROM needs more fuel, racor cannot supply, injector pump pulls vacuum, bulb collapses. When you see it you assum blurb, but real fault is clogged filter, or other impediment to fuel flow.


PS I HATE primer bulbs below deck! Spend $100 and wire in a lift pump. It should turn on with ignition. This will also make changing filter much easier.

If this electric pump is going to run all the time it must be after the water separator. Parker says a fuel pump will cause any water to be emulsified by the pump and the water separator will not be able to separate the water out.

[sinnerman]

My neighbor has a Yanmar with a primer bulb between the tank and the Racor.

For those of you who say it is not needed, you must find enjoyment in "diddling" the mechanical fuel pump lever for extended periods when bleeding the system. This is why people install a primer bulb..

Since fuel flow is small on these diesels, if it the bulb is collapsing it is probably because of a restriction upstream.

Possibilities:

- Plugged fuel tank vent (wasps etc. in the vent)
- Algae sludge in the tank plugging the fuel tank pick up tube
- Algae sludge from the tank plugging the tank shutoff valve - or- the check
valve in the squeeze bulb inlet (highest probability)
- Old fuel lines with collapsing inner diameters.

cheers

[bact0ee]

Update on my primer bulb collapsing. I have now run the engine for three straight days (10 hours/day) at 2500 rpm with no problems. I did this with the diesel fill cap off allowing the tank to vent through it. This appears that the regular vent has some problem I need to address. Thanks for all the input.

[Khaos13]

Yeah! Glad you solved it. I've seen the screen across the vent opening corrode to the point of total blockage. This was on multiple Morgan 41's in a VI charter fleet. I just installed a Larand primer bulb on my boat and have yet to try it out. These are supposed to be the best out there but we'll see. The primer bulb makes perfect sense to me.