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AC5040 Fuel Leak

A

AC16

New User
Hello, I have a 1978 AC 5040. I have a fuel leak when its running on the top end of the motor. I'm not sure what its leaking out of is called nor how to stop it. Any help would be great, Thanks in advance!

I have photos with yellow arrows.

cvphoto4598.jpg


cvphoto4599.jpg


cvphoto4600.jpg
 
Can you post a picture of more f the engine so i can get a reference point of where it is on the top of the engine.
 
That's a dampener for the injection pump, it will work fine without it. On the outside of pump the bleed screw has the same thread size, if I recall a 5/16 NF bolt is the correct thread. If you remove the bleed screw body and check the thread size, find a bolt that will fit where the bleed screw fits, then remove the dampener and install the bolt in it's place with the copper washer. Perkins pumps use a similar dampener too, that sometimes leaks the same spot.
 
Curious why does it leak out of the pin hole though?
Is that pin hole factory and what causes it to do that?
 
(quoted from post at 19:28:05 05/13/20) Curious why does it leak out of the pin hole though?
Is that pin hole factory and what causes it to do that?
Click to expand...

It's a pulsation dampener with a diaphragm in it.

When the diaphragm fails they leak out the vent hole on the "dry" side of the diaphragm.
 
That's a vent hole, so the steel disc inside can "flex" under pressure. There's NO diaphragm, but the steel disc and an O ring to seal it. Over time the O ring gets hard, cracks, and starts leaking fuel then it comes out that vent hole. I've been removing them on pumps I have in for repair, as pumps work fine on the test stand without the dampener. Many other CAV DPA pumps on other engines don't use the dampener anyway..
 
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