Fuel Tank Problems

[mike.perry]

I was adjusting the back brakes on my Traveller when I noticed that the back of the fuel tank was wet. I cleaned the area and saw petrol seeping down the tank. Fearing the worst (rusted tank) I retrieved my spare tank from the store.
After drilling the heads off several bolts I managed to remove the left floor panel to reveal petrol lying around the rim of the tank which I had filled up on Friday evening. A cleaning up session identified the leak coming from the sender unit so I swapped it over with the spare. It still leaked, apparently from the gasket.
Question:- Is there a sealant that works on a petrol covered surface or is there a gasket available?
I have an MOT this week. Do I go for a drive to use up a couple of gallons of petrol then clean up the tank and hope the tester does not notice?
Why does my fuel gauge (1098 gauge) still read 3/4 full when full even though I have changed the sender unit? Is there any adjustment on the gauge?

[MColes]

When I had a crack in my tank I used Petro Patch. I found that the putty type was better than the fabric/paint on type.

[mike.perry]

Thanks, I'll try to get some in the morning. (It might have to be Halfords)

[MColes]

Can't find it on their website but they may have it in-store.

It's just like sticking blu-tack to the tank when it first goes on but it goes off really hard. I had a small hole in the bottom of my tank which I patched with it. Been on their a few months now and the tank has been filled to max and had no problems with it. You don't need to use much.

Which reminds me my brother still has over 3/4 of a tube of mine which he "borrowed" for 5 minutes well over a month ago

[David53]

I have the same problem as Mike with the sender unit leaking. Only happens when I fill right to the brim so now I just put a medium amount in when I fill up

[mike.perry]

I cleaned up the surfaces and applied a layer of silcone sealant to the surface of the sender unit, allowed it to dry a bit and bolted the unit in place. Topped up the tank and waited. No leaks!!
MOT 1400hrs tomorrow.

[David53]

Good luck with the MOT Mike!

Was it a special silicone to cope with the petrol?

[bmcecosse]

I was going to suggest silicone - but expected to be 'howled down' by an angry mob! And you all know I don't like controversy

[MColes]

[mike.perry]

Yep, it worked and passed the MOT. Nearly didn't as the tester found a rust hole on the top of the rear inner wing near the seat belt mounting. Solved the problem by removing the seat belt as it is not a legal requirement!

[swithland]

I have a fuel leak at the moment. Initially I identified it as coming from around the sender unit when the fuel tank was full, so I changed the gasket and it still leaked. Then I used some kitchen silicon sealant and it seemed to be OK for a while. Now ive discovered paint coming off the back of the fuel tank underneath and I can smell petrol again when the tank is full.

Ive also discovered today after a drive through town in very slow traffic that the engine was a bit erratic. Ive topped up the damper on the carb and its still erratic. It was a hot day today....about 30 degrees centigrade !! Probably hotter in the Central Hong Kong traffic. I noticed some air bubbles coming through into the filter ( fitted after the pump ) and suspect that the leak may in fact now be coming from the connection between the tank and the copper feed pipe. I did notice going up hill the engine seemed to starve a bit and the pump was clicking like mad ( and that was on a 3/4 full tank ).

Going to have a proper look tonight. I received some Blue Hylomar from ESM yesterday which is non hardening and petrol resistant, so will reseat the fuel sender unit with that and check the copper pipe connection to the tank. All the connections on the pump are tight and the fuel pump is pretty much brand new. Will also check that there is enough ventilation through the fuel cap.

Does anyone have any other ideas while I am at it ??

Cheers
Charles

[mike.perry]

The ticking is probably a sign of fuel vapourisation. Try fitting a rubber sleeve over the fuel pipe where it passes near the exhaust. Never driven a Minor in 30 deg C but the pump can tick rapidly even in British hot weather

[swithland]

The ticking is probably a sign of fuel vapourisation. Try fitting a rubber sleeve over the fuel pipe where it passes near the exhaust. Never driven a Minor in 30 deg C but the pump can tick rapidly even in British hot weather

Mike, Ive been down to have a look, and firstly, there was a drop from the connection between the tank and the feed pipe. I loosened off the pipe and put some ptfe round the threads then tightened up. Whilst tightening, the head of the 14mm brass connecotr snapped off. Woops ! But the pipe appeared to be well locked in place, so I cleaned up the tank, gave it a coat of hammerite where the paint had come off through the dripping, and put plenty around the pipe joint to try and ensure there could be no air sucking in through the joint. Then tested. The fuel filter filled right to the top ( never had that before ) and there were no bubbles going through the filter. Then I took Daisy for a half hour spin around town. When I got home, there were bubbles again going into the filter.

I am going to put some silicon sealant around the pipe joint to the tank to ensure no air can get sucked through tomorrow once the hammerite is hard. But....I think you are right about the vapourisation. It is really getting quite hot here now, so will use a length of heater hose to clip around the fuel pipe as you have advised. Will also cranck her up tomorrow evening to see when the engine bay is cold if there are any bubbles......

Many thanks for the advice

[fsk658]

Hi I had the same problem when I fitted a new 9 1/2 gallon tank. As I usually fill my tank to the top, it still leaked after several gaskets and different sealants. I found the petrol was seaping up the fixing screws that fix the sender unit in the tank.I made some gasket washers to fit under the heads of the screws with a hole punch. Fit with gasket sealant also on the threads dont overtighten the screws as this sqeezes out the gasket.It may seem fidley but I have had no more leaks since. John

[swithland]

Hi John
I filled up last night and there were no leaks from the sender, so based on the bare paint patches under the tank just below the copper pipe connection to the tank that must have been the problem. Going to recheck again tonight that my fix did the job.....

[bmcecosse]

The fast ticking pump is probably 'the vapours' due to high temp - only permanent cure is to fit the fuel pump low down in the engine bay - so it has flooded suction.

[swithland]

Yes I would agree its boiling in the pipe. Going to try lagging the pipe first.

[swithland]

Lagging the pipe has worked ( using some rubber heater hose ). Im going to buy some of that Kevlar heat tape for the exhaust pipe thats exposed inside the engine bay too. Daisy is fine out on the open road, but sitting in traffic for long periods is not a lot of fun !!

[rayofleamington]

I've just read the old thread about gasket woes.

A decent cork gasket should work fine - it did on mine a few years ago. I used blue gasket gue on the screws, as the originals appeared to have had some kind of sealant. Are these leaking gaskets made of cork?

Initially I hand made a gasket from gasket paper when I was replacing the sender - this was useless as standard gasket paper isn't ok for fuel (as i later found out).

For adjusting the reading - you should be able to bend the float arm a bit.

[swithland]

a decent cork gasket should work - it did on mine a few years ago. I used blue gasket gue on the screws, as the originals appeared to have had some kind of sealant.

Initially I hand made a gasket from gasket paper when I was replacing the sender - this was useless as standard gasket paper isn't ok for fuel (as i later found out).

For adjusting the reading - you should be able to bend the float arm a bit.

Bending the float arm is a good idea. Had not thought of something as simple as that, but whilst its not now leaking.....I am going to leave well alone and always fill up when the meter hits half way !!.