US 1980SC Fuel leak from distributor

[andino]

Hey all,

I'm in the process of replacing my airbox due to a crack. I'm at the point where I'm testing for leaks on the fuel system since the new airbox has passed my smoke tests. During my fuel testing, I found that I have a pretty decent sized leak coming from the bottom of the FD into the airbox. It seems to be pooling first in the valley of the arm for the airflow meter so my guess is the maybe an oring on the bottom of the FD has let go from sitting around for so long.

I'm wondering if anyone has an idea of what could be leaking. I have the oring labeled #2 in the diagram below but I wasn't able to get the FD off the metering base plate with my slotted screwdriver. I have some bits coming that will hopefully get a better fit onto those flat head screws but I'm not sure if I should just consider sending the whole FD to be refurbished somewhere. I also read somewhere that there's an oring for the fuel mixture screw as well but I couldn't find a diagram that showed that oring.

[$yncro]

Have you looked at the back side connectors maybe the leak is coming from there.
There is a small O ring in there.. maybe just send it to Tony. He's good he'll prob
bench test it first maybe just a simple O ring fix. Good luck.

[Ltanderso]

O-ring #2 in the image doesn’t seal a fuel path. It prevents air leaks. That won’t be the source of your leak.

[Funracer]

There are 12 fuel related ports to the FD, 7 on top 5 in the rear and the plunger cylinder inserted into the bottom of the FD from inside. Check the O ring seals in the pressure regulator. Rebuild kits are sold on PP and easy DIY. If you are sure the FD 12 top and backside fittings are dry maybe the O ring that seals the plunger barrel to the FD body has failed. See minute 8:30-10 here:
https://youtu.be/O07KlxiUbDY?si=HGq_p9hCgnfcNNj3
If you think this is your leak I suggest sending it to a professional for rebuild.

[andino]

Thanks for the replies everyone!

I didn't see any leaking externally from the fuel ports but I'm going to test again today or tomorrow to confirm. But my suspicion is I'll likely be pulling the FD and it's going to need a refurb.

Funracer - the pressure regulator orings are the ones referenced in the diagram posted as #4 and maybe #5? Or am I mistaken which part is the pressure regulator?

[boyt911sc]

Originally Posted by $yncro

Have you looked at the back side connectors maybe the leak is coming from there.
There is a small O ring in there.. maybe just send it to Tony. He's good he'll prob
bench test it first maybe just a simple O ring fix. Good luck.

There are several sources of fuel leak in the fuel distributor. But there is one particular o-ring inside the fuel distributor that could be replaced without taking the FD apart. First determine the source of the leak. It could be from the fittings, around the seam, fuel injector/s, or from the bottom (barrel).

The test takes only several seconds using a test jig to determine the culprit. The test is FREE to members of this community. Just send the FD with a return shipping label preferably UPS. Remove all the fuel line fittings and place the FD in a zip lock bag to prevent from losing the micro filters. Happy New Year!

Tony

[Funracer]

Originally Posted by andino

Funracer - the pressure regulator orings are the ones referenced in the diagram posted as #4 and maybe #5? Or am I mistaken which part is the pressure regulator?

That is correct

[E Sully]

Part 2 is only to seal for air leaks between the fuel distributor and air metering plate. The fuel pressure O-rings 4 and 5 would not cause a fuel leak, they control the system pressure. Part 6 is the copper sealing washer that could cause an external leak.
If the leak is from the bottom, small chance it's the plunger, which you could remove and check for scoring. More likely an internal O-ring, shown in this video at about 1:05.
https://youtu.be/GMSxahS239A?si=pckgjw3JaYXGDw_G

[andino]

Thanks for the info and videos. I don't see any external leaks on the FD so once some slotted bits arrive tomorrow, I can see about taking the FD off to determine if the piston is scored but its looking more and more like a rebuild of the FD is in order.

[boyt911sc]

Originally Posted by andino

Thanks for the info and videos. I don't see any external leaks on the FD so once some slotted bits arrive tomorrow, I can see about taking the FD off to determine if the piston is scored but its looking more and more like a rebuild of the FD is in order.

Andy,

Before you decide to have your fuel distributor rebuilt, I will give you an opportunity to use and test a newly rebuilt FD-077 without any obligation to purchase. You are NOT buying it just borrowing it for the test. Send it back to me if you don’t want to keep it. No question asked. If you are interested, PM me where to ship the FD. And you take care of the shipping expenses. Think about it.

Tony

[andino]

Originally Posted by boyt911sc

Andy,

Before you decide to have your fuel distributor rebuilt, I will give you an opportunity to use and test a newly rebuilt FD-077 without any obligation to purchase. You are NOT buying it just borrowing it for the test. Send it back to me if you don’t want to keep it. No question asked. If you are interested, PM me where to ship the FD. And you take care of the shipping expenses. Think about it.

Tony

Thanks Tony. I'd really appreciate that. I'll send you a PM about it now!