How Does it Work ?

[Cherp]

Here's a wierd one. I changed a fuel filter on an md2040 Volvo on the engine. It has a little toggle lift pump nearby and I pumped that for a while. Couldn't get any back pressure to indicate it had filled the filter. Tried to start it and it went first go. There is a primary filter not mounted on the engine. The majority of the fuel is in a tank higher than the engine, so there's a gravity benefit. Still, either this toggle pump doesn't indicate when it has done the job by back pressure, or the air in the filter mysteriously disappeared all on its own. I had not cracked an injector. Any clues?

[daddle]

You pumped the air into the tank via the return line. As a proper diesel should not need anything bled.

[Astrid]

http://extension.usu.edu/files/publi...heet/fm-01.pdf

[shakey doug]

You will feel nil resistance at the pump actuator if the if the motor has stopped with the cam lobe holding the diaphram in the depressed position.

[Cherp]

All three replies useful. Thanks.

[Ex-Calif]

I crack the banjo nut on the top of the spin on fuel filter and pump the lift pump until all air is out. Then I tighten the banjo nut.

I crack the fitting on the injector pump until fuel comes out. Then tighten that one.

Then I crack one injector fitting and crank the engine. Fuel will "pump" out the fitting. Tighten the fiting and the engine will start to run. Maybe "poorly. crack the second fitting and do again. Repeat for more cylinders.

The lift pump has never built up any back pressure.