1gm bleeding fuel line.

Herrick18911 · Jun 4, 2015

Typically, there are 2 fuel pumps on the engine; an electric lift pump who's job it is to lift the fuel from a tank that sits lower than the engine and then a high pressure mechanical fuel pump that is mounted on the engine which supplies fuel to the injectors. The electric lift pump is on when the key is turned on but the mechanical pump operates only when the engine is turning. The mechanical pump sometimes has a hand pump built in.

When bleeding the engine, the electric fuel pump should be adequate to suck fuel and push it to the filter where you can open the bleed screw until it stops making bubbles. It is possible for the engine to run without a functioning lift pump and I suspect this is so in your case. The mechanical pump often has enough suction to draw the fuel up from the tank but not easily.

I don't believe it possible for the engine to run if the reverse was true, the lift pump functioning and the mechanical pump not.

Tod

Benny17441 · Jun 4, 2015

The GM1 just has a mechanical lift pump and the fuel injector high pressure pump. The mechanical lift pump is a very simple mechanism. 99% of the time when these fail it has to do with a ruptured diaphragm with the loss of suction and a fuel leak. Look under the pump for any kind of leak and also check your engine oil to make sure no leaking fuel is raising the oil level and diluting the oil. Further with the number of hours that we usually motor these pumps tend to last for decades so it is not likely, absent a leak, that your pump may have failed. If you are having to pump the bulb at every startup you likely have an air leak in the system. Check the lines, banjo connectors and bleed screw seals. A clogged fuel tank pick up tube may obstruct fuel flow. Does your tank sit lower than the engine? Is the fuel fresh and in good condition? make sure your tank vent is clear with no obstructions. Can the engine run without the assistance of the lift pump? It probably could at least for some time but it would not be either way a clear indication of the condition of the pump. I believe whoever installed the manual bulb pump may have placed it there to simplify bleeding the fuel lines. The lift pump is not really very efficient for the task. I would gather your engine has more than a few hours on it so to help start it open up the throttle all the way and make sure the starter is turning the engine at a fast enough speed to allow compression build up in the first 3-4 revolutions. Be ready to drop down the throttle lever once the engine catches. Hope some of these info helps.

kloudie1 · Jun 4, 2015

A note: The lift pump is driven by a cam in the engine.. When the engine stops, sometimes the cam has the lift pump fully or near fully compressed and moving the finger lever does not push fuel.. The cam is driven at half engine speed, so try rotating the engine a half turn at a time and testing the finger lever.. You will feel the full travel against the internal spring when the cam is fully retracted.. It may feel like thee pump is shot, but it may be the cam keeping the travel of the lever in an ineffective place.

Alan Gomes · Jun 4, 2015

jfschena said:
Went out to my oday 26 this afternoon to bleed the fuel system and run the engine prior to splashing.

The procedure I used last season was: pump the bulb until fuel goes from the tank to the bleed valve at the high pressure filter, then actuate the lift pump manually, until fuel comes out the bleed screw at the high pressure pump.

Today, I Pumped the bulb style hand pump, and yet, was unable to draw any fuel out of the tank to the primary filter on the side of the tank. I suspected the bulb pump had failed. I could hear fuel agitating in the tank when I squeezed, I just couldn't move any fuel.

I replaced the bulb and was able to get fuel into the primary fuel filter and out the bleed screw of the high pressure filter. However I wasn't able to get fuel out the high pressure pump bleed screw using the lift pump. I bled to this point using the squeeze bulb.

I started the engine anyway. It started very hard, it took 3 or 4 attempts. It did start. I ran it 10 minutes. It archived full rpm.

I suspect my lift pump is broken. I'll probably encounter hard starting the next time I start.

What do you think about this. Will an engine start and run to full rpm without a lift pump?

Thanks

Joe

FWIW, when I first bought my E26-2 (which also has a 1GM), the surveyor made the following note: "Remove the 'squeeze ball' type priming pump from the fuel line. This device is not approved for use below deck or with diesel fuel." So out it came!

Also, the advice Claude gave you about rotating the engine and checking the throw on the lift pump lever is spot on.

Alan Gomes · Jun 4, 2015

jfschena said:
If I remove the squeeze ball, how do Prime the engine after drawing the lines? Thanks

I'm not sure how to answer this other than to say that I've always been able to prime the engine after changing filters using the lever on the lift pump. But then, I've never done anything radical like removing and replacing a line to the fuel injector that might require more extensive priming than what I've found necessary.

You might find this link helpful, especially since the engine he uses in this tutorial happens to be a 1GM10: http://www.onboardwithmarkcorke.com/on_board/2009/01/bleeding-a-diesel-engine.html

Alan Gomes · Jun 11, 2015

jfschena said:
This is exactly what happened. I confirmed it right after the new one arrived .

So with the lift pump situated properly with respect to the cam, are you now able to prime everything OK?

kloudie1 · Jun 11, 2015

Great!