Leaking Fuel Pump

[mswyka]

Saw something today that I have not seen before.  Our 78 Intruder needed new carb flanges.  When we brought it in we saw that the fuel was low and there was some fuel around the fuel pump and fuel lines.  We assumed that this was just another leaking fuel line so after changing the carb flanges, we added a few more clamps to the fuel lines.  Fired up the sled and looked again and we had fuel squirting out of the pump through the gaskets.  Pump had otherwise been good and the screws were tight.  Time for another rebuild.

[Vader440]

I am experiencing the exact same thing right now. I thought it was a hair line crack in the side of the pump. What was the final outcome, did rebuilding the pump take care of your problem.

[mswyka]

Turned out that our fuel lines were not tight.  Ended up switching to smaller diameter fuel line for  the older lines and adding clamps for the lines that were not quite so bad.

[Vader440]

I'll check the fuel lines again. I sure seemed like it was leaking right out of the side of the pump. Thanks!

[Truder78]

Same problem here I noticed it was seeping gas when it was running on the second block down from the top there is a pinhole and gas was spitting out. Did a rebuild with the ltd pump kit put the extra hole in the bottom black gasket and it is doing the same thing. all lines are tight. Screws are tight so what did I miss?

[Vader440]

I swear i have a hairline crack in the side of my fuel pump. Took it off, took it apart everything looks good, put it back together and tightened all screws new clamps on fuel line, it's still bubbles out the side by the discharge tube. I'm at the point I'm going to just replace the fuel pump and see what happens.

[Boomologist]

Is the nipple loose or cracked?

[gixxer6]

Could it be a hole in one of the fuel lines? 

[mswyka]

In the top of the pump there is a valve with a diaphragm on both the top and the bottom.  This valve opens and closes with the pulses that come from the engine.  The small hole on the second level of the pump is a vent hole for this valve.  If there is  fuel coming out of the vent hole there is a leak into the pulse side of the valve chamber.  So either one of the diaphragms has a hole in it or one or both of the diaphragms are not sealed tightly to that particular layer of the pump.

[Vader440]

This actually doesn't have the original two stack fuel pump on it. It's a basic round two outlet Mikuni. I tried a new piece of fuel line. I think it could very well be leaking around the nipple or a small crack I can't see. 

[Truder78]

R :)ebuilt the fuel pump for the second time this time all went well and the leak is gone.