if you added a fuel return to the tank

[sujitroy]

My second set of carbs I rebuilt seems to have resolved my stalling issue with my 1st Stag. It's an auto. But unfortunately, my hot start issue has gotten worse in that previously I could leave my car for about 30 mins. but now I cant start it after around the 15 min. mark. I did not replace the float valves. Based on everyone saying its to do with fuel pressure and fuel getting passed the valves, I'm thinking of teeing off the supply back into the fuel tank. I have a Fed. Stag and there are so many pipes in the tank that this is will be a simple modification. For the tank return what size hole should I drill?
I'm really not fixing the issue as my other Stag doesn't have this problem. Alternatively, would investing in good quality floats valves work? I currently have a cheap pressure regular in the fuel line. Unlike my other Stag where the clear fuel filer is about 2/3rd full, this one is about 2/3rd empty. If the fuel pressure went up due to a hot non running engine, wouldn't the filter fill up with more fuel? I don't see this happen. Another experiment I plan to try is to switch off the fuel pump before shutting the engine off.
Sujit

[MikeParker]

Sujit,
I was under the impression that the hot start issue was related to ignition - mainly coil break down. I have a standard fuel pump, no pressure regulator and no electric fan and have no problems with hot starting at up to 37C with E10 fuel. I do get vapour in the fuel line but it starts on the button every time. Best to fix the issue or you might introduce more problems.
Mike

[Wheelz]

Perhaps it is still related to the carbs? Just because they have been rebuilt, it does not necessarily mean they can now be ruled out? Have you checked that the vent valves are working properly? I think you can disable the vent valves to always vent to atmosphere, which might then reveal something?

To confirm it is the coil, when the problem occurs next, put a cold wet cloth on it (or some freezer spray) and see if it then suddenly starts.

[sujitroy]

Based on swapping the carbs and the heat start problem has gotten worse, I'm assuming it is the carbs. Coil in newish as that took care of a miss fire when hot however, with quality that doesn't mean much. I have Lumenition. Vent valves were checked when I rebuilt the carbs. I checked them by blowing air through them.
Sujit

[022Dave]

Based on swapping the carbs and the heat start problem has gotten worse, I'm assuming it is the carbs. Coil in newish as that took care of a miss fire when hot however, with quality that doesn't mean much. I have Lumenition. Vent valves were checked when I rebuilt the carbs. I checked them by blowing air through them.
Sujit

Do the easy bits first, and only do one thing at a time; don't launch into several potential points at once. Change the ignition coil, and see if that effects an improvement. Coils are not infallible; I was speaking to Dave Taylor (DJT) yesterday, and he has been plagued with coil failures, all of them 'quality' brands. Where is your coil mounted? Is it absorbing heat by being in contact with the engine block?

Dave

[stag8manod]

The Stag tank already has a return line fitting as it's the same tank as the P.I. Estates
Cheers Ian A

[jbuckl]

When you have found ‘quality float valves’ let us know

[MikeParker]

Another car stopper is one of the carb pistons sticking up. The test is to unscrew the dashpot and then push down. If stuck, you hear a clunk as the piston drops. Cure is to polish the piston shaft. Could be cleaning the carb parts caused some corrosion?

If the vent valves are working, you can see petrol condensing in the tube when the engine is hot. I use transparent piping for this, and run the combined vent outputs forward through the front bulkhead past the rad and then down to below the car. It does absolutely stink of fuel when very hot and with the engine stopped. One reason I think of getting EFI is to cure this. Can you buy anything to absorb this fuel? What did the US carbon canisters do? Can these be bought here?

Mike

[Wisey]

I think carbon/charcoal filters are only good in gaseous situations. I think the amount of liquid in the vent lines you describe would saturate the carbon. If the vent line/s went a catch pot that had a carbon filter in it's vent, might be a solution. But then the condensed fuel in the catch pot would need to be recycled back into the fuel tank/system. Just a thought....

[trunt]

Can you buy anything to absorb this fuel? What did the US carbon canisters do? Can these be bought here?

Mike

The Federal engine carbon filter has that carb vent line going to it and seems to handle it, even though it can get quite bit hotter here!

The canister is also connected to the line from the camshaft venting line to the strombergs so the fumes are drawn into the engine. The carbon canister is actually open to atmosphere at the bottom. Any fuel/Vapor that makes its way there is held by the carbon and as it evaporates is drawn into the engine via the carbs. The third line to it is the vent for the fuel tank.

You could reproduce that, even though I got rid of some of the federal stuff I left that stuff in place as it made sense to me..

Rimmer sell the 3 tube type, (very expensive)but there is a 2 tube version for Mk1 that may suffice. Perhaps Tony White has a few from the federals he has dealt with? You can apparently open them up and replace the carbon if it’s bad (feels too heavy)

Terry

[trunt]

When you have found ‘quality float valves’ let us know

Indeed.. I got a pair, zenith branded, that cost a lot carefully checked the floats and their angles and still had issues even at 2.5 psi . I took the fuel pressure down to 2psi and it’s been fine since.

[MikeParker]

The Federal engine carbon filter has that carb vent line going to it and seems to handle it, even though it can get quite bit hotter here!

The canister is also connected to the line from the camshaft venting line to the strombergs so the fumes are drawn into the engine. The carbon canister is actually open to atmosphere at the bottom. Any fuel/Vapor that makes its way there is held by the carbon and as it evaporates is drawn into the engine via the carbs. The third line to it is the vent for the fuel tank.

You could reproduce that, even though I got rid of some of the federal stuff I left that stuff in place as it made sense to me..

Rimmer sell the 3 tube type, (very expensive)but there is a 2 tube version for Mk1 that may suffice. Perhaps Tony White has a few from the federals he has dealt with? You can apparently open them up and replace the carbon if it’s bad (feels too heavy)

Terry

Thanks Terry. That explains how the petrol from the carbon gets removed again. I think that would be a good addition even here in the UK as my car does stink out the garage after a run on a hot day. There are these things on Ebay which are cheap enough. I presume they would do it?

https://www.ebay.co.uk/itm/324915805429?hash=item4ba67dbcf5:g:NM4AAOSwSodhpI8u

Mike

[elvimto]

The Federal engine carbon filter has that carb vent line going to it and seems to handle it, even though it can get quite bit hotter here!

The canister is also connected to the line from the camshaft venting line to the strombergs so the fumes are drawn into the engine. The carbon canister is actually open to atmosphere at the bottom. Any fuel/Vapor that makes its way there is held by the carbon and as it evaporates is drawn into the engine via the carbs. The third line to it is the vent for the fuel tank.

You could reproduce that, even though I got rid of some of the federal stuff I left that stuff in place as it made sense to me..

Rimmer sell the 3 tube type, (very expensive)but there is a 2 tube version for Mk1 that may suffice. Perhaps Tony White has a few from the federals he has dealt with? You can apparently open them up and replace the carbon if it’s bad (feels too heavy)

Terry

You can open the canister take the charcoal and put it on a flat baking tray and outside use a blow torch to burn off the gasoline and rejuvenate the charcoal, also use a water spray bottle to keep it from burning and use scotch brite cut to size for the pads. It does work I did mine and it helped I have a MK1 Federal car.