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Engine missing fuel pump plunger

Robin8er

Well Known Member
My Lycoming O-360 engine came with a cover plate covering the hole where the fuel pump goes (no fuel pump on engine) I took off the plate to install the pump and it appears that there is no plunger installed. I turned the engine over 1/2 and then 1 full rotation and never saw the plunger, but I do see there the plunger goes.

Is it likely that there is no plunger in my engine? Or would it have to be installed for the engine to work correctly? I just want to make sure I'm not missing something obvious. I bought it used/rebuilt.
 
Mine too

I just custom ordered and received an engine just like this.
I will be making it into a fuel injected engine, with an electric fuel pump.

So the factory (at my request) removed the plunger and put a plate over it.

Sounds like the previous owner did the same here.

If you are putting an engine driven fuel pump on the engine, you will need to install the plunger.
 
Your engine might have simply been made for a high wing plane with no engine driven pump. :)

Yes... the accessory case will have to come off.
 
Fuel Pump Plunger

I likely have a used spare plunger I could sell. And Yes the accessory case needs to come off to install the plunger.

Don Broussard
RV9 Rebuild in Progress
57 Pacer
 
depending on engine model, you may also find that the accessory cover may not be machined for a push rod, or the idler gear is plain & without the lobe to push the push rod. Also if it is a narrow deck, while the accessory cover is off, check that the oil pump AD had been complied with.
 
Your engine might have simply been made for a high wing plane with no engine driven pump. :)

Yes... the accessory case will have to come off.

Many of the high wing engines were also missing a gear with an eccentric on it that is needed to move the rod and run the pump. There is gear without the eccentric that is used on those engines.

With the accessory case off, it is easy to change the gear and fuel pump plunger rod.
 
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Thanks for the reply. I assume I have to remove the accessory case to install it?

The sump will have to come off before you can remove the accessory case.

Chances are the plunger hole has been reamed since the opening was also milled.
 
Well it looks like the engine is missing the correct gear for the pump as well. I was able to remove the left magneto to check. Thanks for the help every one, this should be fun. (and expensive)
 
Not at all

I just went through the same thing and followed the advice of folks here on the message board. Ordered the gear from Aircraft Specialties:

http://www.aircraft-specialties.com/gear-assembly-fuel-pump-idler-ael75072/

As someone indicated previously, pull the sump prior to the accessory case (its actually a very simple job). In my case for the O-320, the old gear slipped off and the new gear back on in a matter of seconds. I would set the #1 cylinder to TDC and confirm all of the gear marks align before removing, and drop on the new gear with the same alignment. The most critical part of the operation is ensuring that the pump arm and rod align perfectly. With a little engine pre-lube on the gear and rod this is easily accomplished.
 
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