Lift pump prime not moving fuel

[micshr]

My 1981, 720 started one morning, ran a bit on maybe two or three cylinders and quit.
I replaced the primary fuel filter. I could suck fuel up into the plastic( Old school) and the filler cap is off the tank.
I re attached the fuel lines and tried to prime the IP. No luck.
I put the intake tube in a cup of fuel. the pump did not drag the fuel in.
I put the output tube into the fuel cup. One pitiful bubble even with a lot of pumping.
I squirted fuel into the bleed screw holes and pumped. no fuel was forced back out.
How far into the pump must I go to find the diaphram?
Can I fix this without removing the pump from the bock?
who rebuilds these things?

I will try to add a photo of the IP. It is missing a few niceities, like a altitude adjuster and shut off device. (some one installed a hand cable for shut off).
I am having trouble reading the part numbers on the IP. It is an inline
type bosch with two bleed screw ports.?
Oh well, I don't know how to attach photo. [/img]

[philip]

My 1981, 720 started one morning, ran a bit on maybe two or three cylinders and quit.
I replaced the primary fuel filter. I could suck fuel up into the plastic( Old school) and the filler cap is off the tank.
I re attached the fuel lines and tried to prime the IP. No luck.
I put the intake tube in a cup of fuel. the pump did not drag the fuel in.
I put the output tube into the fuel cup. One pitiful bubble even with a lot of pumping.
I squirted fuel into the bleed screw holes and pumped. no fuel was forced back out. -SNIP

1st: a couple of canned replies:
See Lift Pump and Fuel Filters and review in their entirety.
2nd: what about the larger secondary filter?
3rd: on the Lift Pump's fuel inlet side slip fitting, there is another little wire filter screen. Remove this banjo bolt to get to the screen. Pretty hard for this to clog but if the rubber lines are old, it could be obstructed with flaked rubber.
4th: The Lift Pump is secured to the injection pump by three nuts on studs. I've changed my lift pump without removing the whole injection pump from the engine. But you will need tiny fingers to get the nuts back on.
5th: sniff your engine oil. When one of these lift pumps fails, it is possible for raw fuel to contaminate the engine oil.

[asavage]

My 1981, 720 started one morning, ran a bit on maybe two or three cylinders and quit. I replaced the primary fuel filter.

Just so we're talking about the same thing: the Primary filter is the translucent plastic one on the firewall -- the $10 one.

I could suck fuel up into the plastic( Old school) and the filler cap is off the tank.

So no major restriction back to the fuel tank pickup. Good!

I re attached the fuel lines and tried to prime the IP. No luck.
I put the intake tube in a cup of fuel. the pump did not drag the fuel in.

Hmmm. I was going to jump on the Secondary filter (the largish metal can, see the fuel filters thread, but if you pulled the intake line off of the lift pump and didn't get any output, that does sound like a failed lift pump. Though a clogged Secondary fuel filter is a lot more common!

How far into the pump must I go to find the diaphram?

It's a piston pump, no diaphragm involved (unlike on the LD28's VE IP). See the Lift Pump thread.

Can I fix this without removing the pump from the bock?

Likely. However, removing the lift pump from the IP is pretty easy, if you do need to remove it. Removing the IP itself from the engine is not recommended except as a last resort, because you have to remove the timer assy cover and timer assy, and that's not fun because done right it requires a tool that most don't have.

I will try to add a photo of the IP. It is missing a few niceities, like a altitude adjuster and shut off device. (some one installed a hand cable for shut off).

That's a common modification. The stock IPC works well when it works, and has the benefit of turning off the engine if the oil pressure fails, but it's a fairly complex system, and the FSM is really required to troubleshoot it.

Oh well, I don't know how to attach photo.

The problem here is that this forum software does not (yet) accept uploaded pictures. In order to post a pic, it has to be hosted somewhere else. This is going to change soon, but for now you can send me the pic and I'll host it manually, or use a photo-hosting service.