weird fuel leak from the sending unit on 69

[Michael L.]

Guys,

I recently did some work replacing the rear bumper mounting hardware on my 69 coupe. Prior to this my fuel sending unit had never leaked. This is a total resto with a new tank and sending unit. I had decided to remove one bolt at a time in order to not disturb the alignment of the bumpers. As soon as I removed the very first bolt the fuel sending unit started to leak. After replacing that bolt the leaking slowed significantly but it hasn't stopped. I'm not really sure what to make of this. I'm guessing I need to maybe pull the sending unit and replace the gasket? Is there a gas tank stop-leak that I could try? My concern is that somehow removing the bolt resulted in some kind of deformation of the tank that resulted in the leaking and will a new seal help this if the tank is now deformed? Is there a sealant I could use on the gasket prior to install in order to try and ensure it seals? Appreciate your thoughts on this.

Mike

[Richard M.]

Re: weird fuel leak from the sending unit on 69

Very strange. Never heard of that.

Exactly which bolt? Photo of inside area if possible.

Rich

[Mark M.]

Re: weird fuel leak from the sending unit on 69

Michael is the sending unit a repro ? The c2 sending units lately have been coming from overseas from a number of sources and of course some are questionable in quality. I'm guessing the same sources make the c3 units. One of the repros lately is prone to leak at the electrical connection stud with the gasket. A local friend had a c2 going for pv and it leaked just as the car came off the trailer at that connections gasket. I believe this style has a riveted type of stud instead of oem threaded type. These are dangerous leaks. Also there have been discussions on the replacement o-rings as being thinner. My guess is the leak was just starting and you are fortunate to catch it early. Can you get a picture of the sending unit?

[Michael L.]

[Michael L.]

Re: weird fuel leak from the sending unit on 69

Just got back into the shop and attached are the pics of the bumper bolts I replaced and the fuel sending unit. After a closer inspection, as unlikely as it seems it appears to be leaking from not only the seal but also around the outer collar that the locking cam locks into. Far as I can tell this is spot welded to the tank. I have wiped it several times and the fuel continues to leak from around that area of the tank. After surmising that the tank got deformed from my loosening of the bolts when they were swapped out, I decided to loosen the tank mounting bracket bolts to see if relaxing the tank would have any affect and it seems to have slowed or stop the leak from the seal, but it is still leaking from the space between the collar and the tank. What are my options at this point? Pull the tank and have my local radiator shop solder that collar (if they're willing to do it, and will no doubt need to be tanked first for safety reasons)? Or just order a whole new tank? Has anyone else had this problem???

Another option I just thought of is I still have the original tank which is in decent shape. I guess I could have that tanked out and swap in the sending unit from this one. I only replaced it for aesthetic purposes. Appreciate your input.

Mike

fuel sending unit.jpgfuel sending unit BB.jpgbumper bolts.jpg

[Richard M.]

Re: weird fuel leak from the sending unit on 69

Michael,

I don't think your tank is defective. I think the seal is the problem and fuel has worked its way up to the joint.

After seeing your photos, I'm surmising that in the process of removing those bumper bolts, your wrenches disturbed the hose leading to the sender outlet pipe, putting a strain on a marginal seal between the sender and the tank. Hard to see, but is your lock ring fully locked? It looks like it may not be.

I'd drain the tank, acquire a new (properly sized)o-ring, soak it in oil overnight, then reinstall the sender with o-ring using a new lock ring, ensuring it is fully locked and seated.

I'd also check the sender terminal seal nuts for tightness. Those repros can be suspect in that area.

Then add a few gallons and check again.

Rich

[Michael L.]

Re: weird fuel leak from the sending unit on 69

Thanks Rich I'll give that a try. the lock ring is definitely fully locked.

[Keith W.]

[Michael L.]

Re: weird fuel leak from the sending unit on 69

Yes I ordered a new seal and the sending unit tool. I looked at my original tank, which I still have, and realized the spot welded collar doesn't seal the tank at the sending unit. 100% of the seal is the O-ring.

I guess what surprised me about all of this was that the seal is relatively new, just 4-5 years old and it has been in place with fuel in the tank for several years and never leaked until I removed the first of the bumper bolts that I was swapping out. Really strange. Even stranger, when I replaced the old bumper bolt with the new one, the leak slowed, but never stopped entirely. I guess I'll just change the seal and hope for the best. If not, I did send my original tank out to get cleaned out at my local radiator shop, so if worst comes to worst I can replace the tank, but I'm hoping it won't come to that.

Is there any kind of sealant I can use to help with forming a seal? I think pretty much everything dissolves with gas but figured I'd ask.

Mike

[Michael L.]

Re: weird fuel leak from the sending unit on 69

OK so I drained the tank and replaced the o-ring as well as the locking cam and it is still leaking. I noticed when I installed the locking ring that it was remarkably easy to turn to the almost fully locked position with just my fingers. I did get the special tightening tool but I hardly needed it. What are my options now? I did have my original tank cleaned and painted so I could put that in if it comes to that but I'm just surprised I'm having so much difficulty with this. Thanks for any input you can give.

Mike

[Richard M.]

Re: weird fuel leak from the sending unit on 69

Mike, It appears your new o-ring may be out of spec. Can you measure it and compare to the one you removed, using a dial caliper.

Rich

[Patrick B.]

[Michael L.]

Re: weird fuel leak from the sending unit on 69

Thanks Patrick! I'll PM you my address!

[Mark M.]

Re: weird fuel leak from the sending unit on 69

Michael, after all that's been said here, I checked a number of original and replacement sending units, rubber o-rings and locking cams here on an original tank. What stands out are the locking cams (ring). There are 3 raised areas that are bent from the flat part to match up to the tangs on the ring spot welded to the tank. They lock into the tank ring when turning the cam. Laid flat these 3 bent spots measure .12-.14" on original locking cams and 4 of 5 repros here measure .075-.085. The original rubber o-ring and most of the repros here are around .24-.25. The original cam needed the tool to install. The repro cams with smaller locking bends with the one o-ring here thats thinner (.235), could be installed by hand. If you can install the locking cam by hand, in will probably leak. Measure the 3 locking bends on your cam. They may be too flat on your repro to compress the rubber ring enough. You can make the bends bigger with a few hand tools on the bench. The only thing left is to compare the o-ring seat area to spot welded ring tabs on your repro tank to the original tank. I believe these tanks all come from Canada and I haven't heard of any issues with them. If you need a locking ring(cam),I'll adjust one and send it.

[Harry S.]

Re: weird fuel leak from the sending unit on 69

If the gasket is the same as a 63, here are some measurements.

Just took some measurements on the gasket

NOS Thick .2385 ID 1.868 OD 2.377

Rerpro Thick .2270 ID 1.789 OD 2.277