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MG MGA - Vapour lock or what

I went for a 20 mile round trip this morning air temp 80 deg F, on the way back home I stopped at a junction and the engine died, engine temp was 180 F had a job to start again, this happened a few times. When I eventually got home lifted bonnet (hood) and noticed a carb damper was hanging out of one of the carbs, guess this was the problem?

Thanks
Dave
1500
Dave Swinburne

Dave - having a damper hanging out might be the problem, but hard to start is common on hot days due to vapor lock, especially with fuels containing ethanol.

See if it reoccurs with the damper properly installed. If so and it becomes a real headache, think about installing a bilge fan as many of us have done.

Barney G. has a page on it here:
https://mgaguru.com/mgtech/carbs/cb208.htm

I did a simpler installation with the bilge fan mounted in the engine compartment side of the carb duct.

- Ken
KR Doris

Thanks for the advice Ken, I have tightened both dampers so hope this does the trick.

Dave
Dave Swinburne

Dave
I agree with Ken.
My dash pot damper caps, do come loose from time to time, but i am afraid I’d be surprised if that was the reason you couldn’t start the car.
It sounds like classic vapour lock to me.

Just so you are prepared, you may also find that you drive the car quite happily, stop somewhere for 5 minutes or more, and then find the car just won’t start. Once the engine has been switched off, because the cooling system also stops, you will notice the temperature gauge climbs quite quickly. It’s quite normal.

As Ken says, the bilge blower may help. I have one. But first I’d check the regular stuff. In particular do you have the heat shield fitted?

Good luck. I’m assuming it’s this hot weather that is not helping.

G

Graham V

I made a double layer metal shield, doing away with the old asbestos(?) pads.
No problem hot starting even with engine at 200 and air at 90.
Art Pearse

Art
What metal did you use, and are the two sheets tight against each other, or is there an air gap?
I’m sure you’re right that a good heat shield will make a big difference.
Graham V

Graham, don't remember the actual gauge, but thin steel. And separated by about 1/8" with I think metal washers. It is only one layer thick in the region of the carb intakes.
Art Pearse

Thanks Art
Graham V

My problem with the engine dying at junctions etc seems to have gone away at the moment, I have raised the idle revs to 800rpm and the air temp has dropped to typical English summer 70 deg. I also turn my old Kenlowe fan (was fitted to my Mk2 Capri 1976) on earlier if I stop in traffic keeps the engine temp to 190 at idle, works better than the modern fan fitted direct to the rad. Also fitted an old computer fan to the air duct in the wing, every little helps. No mechanical fan fitted.

Cheers
Dave
Dave Swinburne

Photo's





Dave Swinburne

Dave,
great idea to fit the computer fan to the vent, it has to help with the under-bonnet temps.

Just take a look at your Kenlowe fan when it starts up to make sure it spins in an anti-clockwise direction (when looking from the front), because your fan blades are curved to work best in that direction. If the fan rotates the other way, they will not push air too well.

(If you need to reverse the rotation, your fan can probably be run in either direction by reversing the polarity of the wiring, but I would check with Kenlowe first to make certain of this.)

I also removed the engine driven fan on my MGA and tried running with a single 10" Revotec electric fan mounted in front of the rad.

I found that the engine ran quite a lot hotter than with the engine driven fan and the single electric fan really struggled to keep the temperature below 200 degrees in hot weather.

So I swapped to using two Davies-Craig 9" electric fans fitted onto the front of the rad and these control the temperature beautifully.

They only switch on when the car is stood in traffic and quickly bring the coolant temperature down to 185 degrees.

They also fit perfectly onto the front of the rad and they look as if they were made for the MGA.

I have posted a picture of the twin-fans fitted which below, also shows the Revotec 10" fan on its brackets.

I am always slightly irritated when I see how messy the wiring is.
I had made up some special looms for both fans and I planned to run the wires vertically down to the duct panel, and then horizontally across to make a really neat looking installation.

I rather foolishly let someone else who is a qualified electrician do the wiring and he used his usual cost-cutting method of saving wire by running the wires at an angle!
Its on my to do list to tidy it up!

Cheers
Colyn



Colyn Firth

I just installed pair of "Koozies" to insulate the fuel bowls and have fuel line insulation on the way. The "Koozies" are available from Joe Curto of British Superior here in the U.S.

https://www.britishsuperior.com/

Never had vapor lock in 42+ years of having my MGA; recent heat & humidly levels changed that. Vapor lock would only occur when car was driven for a long time and then engine turned off; upon restart after about 15 min, the engine would not run right for several minutes until engine temps started to decrease. This new insulation is in addition to other efforts to increase air flow and redirect heat away from the carbs & the fuel lines.

As for fuel, gasoline today is designed for modern cars, and there's little appetite from the major brands to create gasoline which would be more compatible with 60+ year old cars (Shell may be an exception with their V-Power NiTRO+ Premium fuel), and then we have a mandate in the U.S. that ethanol be made part of the mix. Ethanol causes "phase separation" as it absorbs moisture from the air around it, and then separates into two distinct layers during storage: gasoline on top and water/ethanol on the bottom; not good if you fill up with gasoline that's been stored for a long time. Modern fuel is a contributing factor in vapor lock, especially in older cars.

Gasoline is a blended product, and has no one single boiling point. Lighter compounds start boiling out as low as 90-100F and as more and more of these components successively evaporate, the liquid temperature of the remaining gasoline increases, until finally, the heaviest components start to evaporate in the 300-400F range (ethanol boils out at 178+ F).

About the only thing we can do is to keep the car in proper tune, buy reputable brands (fingers crossed), and do what we can to allow for proper air flow thru the engine bay and minimize the effects of heat.







Nick Kopernik

Nick
Love those koozies - never seen them before

Dave
As you say, the current English summer temperatures will have made a difference. But I do like you computer fan. I remember reading that someone said that at speeds, those vents suck more than release the hot air out.
My local petrol stations are now selling what I think they call E10 petrol, with higher ethanol content, which we need to avoid
Graham V

Hi Colyn, my old Kenlowe does spin in an anti-clockwise direction (when looking from the front) and it really pushes air through the rad so much so you can feel it blowing through the open vent, the vent with the computer fan blasts the air out very well. The cheap electric fan I fitted mounted direct on the rad, air flow did not seem to penetrate the rad very well and some back blow could be felt. Nick I did see this on ebay Fuel Line Heat Shield Thermal Sleeve Insulation https://www.ebay.co.uk/itm/203526533640?hash=item2f63207208:g:My4AAOSwvl9g8I87. Graham take your point about sucking vents, I only switch both fans on (both wired together) when the car is stationary, I also bought some octane boost, not used it yet.
Dave Swinburne

E5 and E10 should be clearly labelled on pump and nozzle. -

https://www.gov.uk/guidance/e10-petrol-explained#availability

"Labelling
At the filling station
At the petrol station, a circular ‘E10’ or ‘E5’ label will be clearly visible on both the petrol dispenser and nozzle, making it easy for you to identify the correct petrol to use.

The ‘E10’ and ‘E5’ labels look like this:" -



Nigel Atkins

The fuel line insulation I ordered is as per pic; its made by Design Engineering to help combat vapor lock. Made of glass fiber and polyester, its laminated to an aluminum outer layer that is self sealing (peel & stick) so you can easily wrap it around existing lines without having to disconnect anything. Here's a pic:


Nick Kopernik

An old boy fairly near to me runs a 1600. He was working on his car today so I stopped to have a look and a chat. I noticed what I thought was an in-line fuel filter on the firewall shelf. He informed me it was a broquet tube and that it was brilliant. He reckons it's improved his fuel combustion, fuel runs cooler and no vapour locks. He made the point of WW2 Spitfires we sent to Russia. They used broquet pellets with their poor quality fuel to get extra performance.

I don't have an opinion. Just thought I would mention the conversation.

Steve
Steve Gyles

Steve, I love Spitfires had a fly in one last month.
Dave
Dave Swinburne

Dave

Yes. Nice machines. Flew one up at Duxford with one of my ex Lightning colleagues a while back. As a pure jet jockey I was more fascinated by propellor pitch, engine boost and rpm than the handling which for me was nice but nothing startling. Ailerons were a tadge heavier than I was expecting. Rudder was light and quite sensitive. But overall well balanced controls for its era. Did a few slow rolls and loops etc.

Steve
Steve Gyles

Steve,

You can get broquet pellets on ebay and they quote "The fuel catalyst is a tin amalgam and follows very closely to the original Royal Air Force receipe which was developed to combat poor quality and low octane fuel." a spitfire must be tame for you after flying supersonic jets!
Dave Swinburne

Steve/Dave
By coincidence there is a very recent posting on another MGA site about broquet. A response to that posting described it as BS and referrred to a decision by the Advertising Standards Authority
www.asa.org.uk/rulings/d-lock-associates-a15-303926.html
Graham V

This thread was discussed between 21/07/2021 and 20/08/2021

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