FUEL EVAPORATION OVERHEATING CARBURETTOR

For TA 14 and TB 14 cars
Faylen
Posts: 10
Joined: Wed Jul 22, 2015 4:02 pm
Name: Terry Grange

FUEL EVAPORATION OVERHEATING CARBURETTOR

Postby Faylen » Mon Aug 31, 2015 5:45 pm

I HAVE RECENTLY PURCHASED A TA 14 AND THE FUEL IN THE CARB EVAPORATES ONCE THE ENGINE GETS HOT, CAUSING MISFIRE AND EVENTUALLY STOPPING ALTOGETHER.
I HAVE HAD A HEAT SHIELD FITTED, BUT IT HAS NOT HELPED, ARE THERE ANY OTHER WAYS TO SOLVE THIS PROBLEM?

johnlayzell
Posts: 151
Joined: Mon May 21, 2012 2:44 pm
Name: John Layzell

Re: FUEL EVAPORATION OVERHEATING CARBURETTOR

Postby johnlayzell » Tue Sep 01, 2015 2:41 pm

Don't know much about TA14's, but here is how I resolved vapour lock on my 12/50:

HP 9877 cruises fairly happily at 45-50 m.p.h., but initially proved to be a little unhappy with South Florida's 90o F+ (32o C+ ) degree summers. Frequently, on the way home from an outing when stopping at a toll both or red light, the engine would suddenly die as a result of vapour lock or fuel boiling in the carburettor. Often the coolant would also boil in heavy traffic. Modern high octane fuel is apparently the primary culprit, about which much has been written elsewhere. The addition of an 11 inch electric fan, which can be removed in 8 minutes if necessary, and use of distilled water with WaterWetter, a cooling system heat transfer agent, completely cured the coolant boiling, but not the vapour lock. One by one, I experimented with the various remedies proposed by members in both The Alvis Register and Alvis Owner Club Circulars and Bulletins, but it was not until all of the following steps had been taken did I achieve success:
• fuel filter bracket to distance the filter from the manifold
• aluminum and rollboard insulation heat sink between manifold and fuel line
• aluminum heat sink between manifold and carburettor, with 1/8” gasket
• exhaust pipe blanket wrap in engine compartment
• fuel line insulation sleeve, from petrol tank to carburettor
Finally, now added to the standard US 89 octane unleaded fuel is a liberal cocktail of Marvel Mystery Oil, fuel stabilizer and lead substitute, all of which have resulted in no vapour lock, boiling or engine dying in over ten years or about 4,000 miles.

First thing I would try is the fuel line insulation sleeve:
http://www.ebay.co.uk/itm/Heatshield-Pr ... 35ac09610c

Good luck!
1925 SC12/50
1937 SP25 VDP Saloon
1970 Peking to Paris Rally VW Beetle

RichardWallach
Posts: 346
Joined: Mon May 21, 2012 10:14 am
Name: Richard Wallach
Location: Melbourne, Australia

Re: FUEL EVAPORATION OVERHEATING CARBURETTOR

Postby RichardWallach » Wed Sep 02, 2015 9:52 am

Terry,

My two bobs worth for what it is worth.

Is the shield an identical copy to the original and fastened as such? I am trying to eliminate a shield that is failing to play its part as planned?
I own a TA21 with a single Solex and it was originally fitted with a thick heat insulating gasket between the carburettor and inlet manifold. Over time this was replaced with a standard gasket resulting in fuel boiling in the float chamber. To that end is a thick gasket fitted to the TA14? If not try an thicker one. I know that an old 1960's gasket kit that I have for my TA21 also included a pair of thick mounting gaskets for the later fitted twin SU's.

With respect to the motor in general do you feel that it is running hot? Where is the temp gauge sitting? If side engine flaps are fitted are they open?
Is the cooling system up to spec? Is the timing correct? All these things can result in reaching a tipping point where the below bonnet temperature causes havoc.

Regards
Richard
Melbourne
Last edited by RichardWallach on Wed Sep 09, 2015 11:12 pm, edited 1 time in total.

OldBodger
Posts: 1
Joined: Thu Sep 03, 2015 4:13 pm
Name: John Edward Jolley

Re: FUEL EVAPORATION OVERHEATING CARBURETTOR

Postby OldBodger » Thu Sep 03, 2015 5:15 pm

Maybe I can contribute.
Having last year returned a TA14 to the road, this year I have had fuelling issues over the summer. I have been hard put to decide if they were due to blockages or vaporisation, I suspect both! I have been blaming much of this on the ethanol now added to our petrol which I believe loosens old sediment causing blockages and also lowers the vaporisation temperature, I don't know if it is true but I was informed that old 4 star used to vaporise at around 100 degrees centigrade but modern 2 star does so at 50.

So this is what I have done:
Flushed out the petrol tank with Marine Clean from Frost.
Replaced the fuel line.
Fitted an aluminium heat shield between the manifold and the carburettor.
Wrapped the exhaust manifold and downpipe in fibreglass tape insulation.
Fitted an HP (pusher) SU fuel pump at the rear of the car next to the fuel tank and removed the one on the bulkhead. The theory here is that a higher pressure in the fuel line, especially within the warm engine bay will reduce the chance of vaporisation. The set up is thus like that on an MGB among others.
Changed to using "super unleaded" which I have been informed has less or even no ethanol.
Also in the interest of good cooling I have flushed the radiator and block and opened the bonnet side vents.

Things do seem improved though the bulkhead filter is still trapping some crud from the tank and I will keep an eye on that.
If things stay OK I will revert to the LP (sucker) pump on the bulkhead and see how that behaves as I would rather have the car as Alvis intended.

It may be of interest to note that at about the same time this year my daughter's Morris Minor started to show just the same symptoms and I tried out much of the above on that car first, in particular the heat shield, exhaust wrap and disconnecting the SU pump on the bulkhead above the exhaust and using a HP one next to the tank instead. It was the fact that I had the same problems at the same time time with two cars which made me suspect the increased ethanol as the underlying cause.

johnlayzell
Posts: 151
Joined: Mon May 21, 2012 2:44 pm
Name: John Layzell

Re: FUEL EVAPORATION OVERHEATING CARBURETTOR

Postby johnlayzell » Fri Sep 04, 2015 2:44 pm

Is ethanol free, or "recreational" fuel available in the UK? It is in the USA, in many States, particularly near marinas, as boats use it exclusively.

I use recreational fuel whenever possible in my old cars.
1925 SC12/50
1937 SP25 VDP Saloon
1970 Peking to Paris Rally VW Beetle

RichardWallach
Posts: 346
Joined: Mon May 21, 2012 10:14 am
Name: Richard Wallach
Location: Melbourne, Australia

Re: FUEL EVAPORATION OVERHEATING CARBURETTOR

Postby RichardWallach » Fri Sep 04, 2015 11:55 pm

As an aside, a 10% ethanol blend is available in Australia. I think the octane is around 95. I deliberately don't use it preferring the lowest grade which is 91. We also have 95 and 98 RON available too. The TA21 was designed for "pool" petrol back in 1950 so the car runs quite happily on 91 octane petrol. Summer temperatures are regularly in the high 30's and the Alvis shows no sign of boiling either with respect to water or fuel. I really feel that the thick gasket between carburettor and manifold made all the difference.


Richard
Melbourne

Faylen
Posts: 10
Joined: Wed Jul 22, 2015 4:02 pm
Name: Terry Grange

Re: FUEL EVAPORATION OVERHEATING CARBURETTOR

Postby Faylen » Sat Sep 12, 2015 6:10 pm

Thank you all for your vary useful advise and comments.


Return to “TA 14”

Who is online

Users browsing this forum: No registered users and 1 guest