A surprise peterol leak

[roy mawbey]

Guys,

The last time I removed the top on my 356A fuel pump was about 4 years ago. I put a new gasket on the top and under the 10mm bolt. Its been perfect ever since till this week.

We have temps up to the high 80 degrees over here and after a run my temp gauge was in the middle verticle. don't see that so often. Came home turned the fuel tap to off and messed about in the garage. After about 15 minutes the fuel started to boil in the carbs. It happened the same last year I ignored it.

Came out the following day for another run. Turned the fuel tap on and I pulled the car out by hand from the garage. Looked down to see a stream of fuel from under the car as I pulled it out. ( None before I turned the fuel tap on )

The petrol was flowing out from the gasket on the fuel pump. Made sure the top 10mm bolt was tight and took it for a run. Same temps as the day before same middle position of the temp gauge. On returning home all dry but this time I did not turn off the fuel. Waited for the boiling that did not happen? When cold I then turned it off.

Tell me guys, the boiling, the expansion when hot, the fact I was unlucky the gasket was just not compressed enough?? Do you tighten the 10mm bolt often? Hell, the fuel drips straight down near the muffler.

I was lucky I pulled the car out of the garage not drove it out, I would not have noticed!! Odd eh???

Roy

[JTR70]

Very strange thing to happen Roy. Are you sure the fuel leak was originating from the fuel pump gasket and not higher up? So all things being equal you left the fuel cock open this time until it cooled down and no leaks?

[roy mawbey]

Justin,

The leak was for certain from the 44 mm? diameter gasket under the cap of the fuel pump. The petrol was running down the side walls of the pump. Everything else was dry.

It seems okay now but I had to compress that gasket quite a bit with the top 10mm bolt. Strangwe it was fine for 4 years till the this latest hot weather and the fact I had the fuel connections off recently but not the pump cap.

Roy

[JR]

Roy,
Just a thought-how is your rubber gasket around the engine tin?
If hot air from the exhaust system gets up to the area of the carbs that might also cause some of the boiling.
I was wondering after you worked on your starter some of the gasket might have gotten disturbed, since you haven't seen this issue before.
Just thinking here at the beach in North Carolina!

Dick

[roy mawbey]

Dick,

Thanks for your thought. Double checked the rubber shrouding after I did the starter job. All okay. I renewed a lot a while ago. You are correct any heat directed to those carbs would not help. I have had the boiling happen last year as well and seen comments by others who have had it happen.

It does seem to stop it happening you wait and you turn off the fuel tap when the engine has cooled down. Its almost as though the gravity fed fuel pump will allow some fuel to get past the carbs fuel inlet needle valve to fill a rapidly evaporating fuel chamber?

It only ever happens when the engine is really hot. If you start the car when its boiling then the problem goes immediatly.

Roy

[Jack Staggs]

Roy, MMW had a thread on "Engine tin & other" a few months ago where this was discussed, I think around page 9 on that topic.

[roy mawbey]

Jack,

I just went back and read the comments by Mic and yourself on that thread. You are so correct never touch that fuel pump bellhousing unless it does leak!

Some years ago I had the pump off and decided against putting a new diaphragm in I had with the rebuild kit. Its still running with the original. I did though flatten the bellhousing top a little to make it really flat. Your comment about the 44mm? diameter gasket drying out made sense and actually 4 days with no fuel in the bowl and high temps might just have caused that to leak. I seem to remember the original gasket was cork and the new one a rubber neoprene? type.

Since my starter repair job I not only had in stages to tighten the top 10mm bolt to the pump's bell housing but also double check a few times and tighten the fuel pipe and carb connections.

Its perfect now, but I am surprised that the 10mm bolt had to be tightened quite a bit to stop the leak. ( I did not want to deform the top again !!)

I wonder when professional's do a fuel pump and carb overhaul do they advise the owners to double check the connections after the first longish run to make sure they don't all need a tweek with the spanner? Or do they really apply more force than I do

Roy

[Stormin]

Roy,
Perhaps the cork gasket dried up with the fuel turned off and then expanded after a bit and stopped leaking.
In 50 some odd years I've never turned off the fuel except when removing the engine. That said the gaskets in the fuel tap have to soak up in the new position.
Norm

[JR]

Norm,
I never used to either-until a 65 SC was brought to the shop and the engine wouldn't turn over!
Pulled the plugs and the cylinders were full of gas!
Seems like the fuel siphoned thru the carbs into the cylinders making a hydraulic lock.
I now shut off the fuel valve each time the Roadster is shut down!
I will have owned 88971 for 50 years on 10/23/14.
Dick

[Stormin]

Dick,

I switched exclusively to electric pumps.
Worst that happened with the stock pump was when the pin fell out and disappeared on the road.
After pondering I took the dipstick out and managed to twist it into the pump and drove happily home. Didn't really mar the dipstick much either.

Norm

[Jack Staggs]

Dick,

I switched exclusively to electric pumps.
Worst that happened with the stock pump was when the pin fell out and disappeared on the road.
After pondering I took the dipstick out and managed to twist it into the pump and drove happily home. Didn't really mar the dipstick much either.

Norm

MacGyver!

[JTR70]

Dick, the old man typing on the computer GIF is a classic!

[roy mawbey]

Hey all,

So many good points above. Electric pumps ah yes!!! Getting the most out of PC's even if you feel like pulling the white hair out of your head at times ah yes... And I still like cork gaskets although Norm the last one that caused the leak was not cork but some form of rubber.

Like you never turned off the fuel for over 35 years, never saw the need even though I had the same experience as Dick with a dodgy needle valve on a 356C.

Then.... One morning got in the car, drip drip drip from the petcock.Lucky I had driven it the day before all okay. So the puddle was not that much. Rebuilt the fuelcock and I attach a photo of the then 47 year old cork gasket. It resembled hard wood

So, that now has a similar rubber gasket as well. Maybe, the neoprene? gasket will last longer though will I still be around though in 2053 to establish that fact



Roy

[JR]

Thanks Justin,
I have a few of those that I rescued!
Dick

[JR]

Hey Roy,
Regarding the fuel cock: I replaced mine a few years before the restoration when the short stand pipe (reserve) plugged up after some 40 years of usage.
My arm was small enough to get thru the fuel tank fill opening and really clean the tank out before I installed the new fuel cock. There was some sand etc in the tank that must have bypassed the gas station filters.
Now when I am out driving the Roadster I occasionally switch to the reserve position on the fuel cock for a few miles and let fuel pass thru that standpipe also.
I still have the old standpipe stored in a box.
Seems like I never throw anything away!
Cheers,
Dick