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MG TD TF 1500 - Starting problem revisited

I wrote the other day about the problem I have had with my 54 TF starting after getting hot. It will start fine originally, then after a good drive it refuses to start. Much of the feed back said it was probably vapor lock. If that is the case is there any thing you can do to stop it. It's gets frustrating not knowing if you are going to get back home. The last time it happened I waiting about 20 minutes and finally had to push it off.

Thnaks for any help.
Bud White
S.A. White

As an experiment, you might bring a plastic bag , filled with really wet, rags , with you....
Drive the car till hot, and when you stop, if it won't restart, take the wet rags, and wrap the carb bodies...Leave the rags on for a couple of minutes, and see if the car starts....If it does, then vapor-lock is your problem....
Are your fuel lines shielded?...If not, that may help.
On "B's" , the problem was solved with an asbestos-lined shield, and bakelite standoffs, for the carbs...
Since you probably don't want to have to make carb shields for your T, then You might think about having your exhaust manifold, ceramic coated....This will reduce the temperature dramatically, and may stop the vapor lock.
Edward
E.B. Wesson

bud, i have not thought through all that happens to make this work..but i choke it after a sit and she fires right up..coughs and sputters a bit. when it stops the sputtering..10-15 seconds..choke off and away i go.
just to keep from over looking another source of the problem..do you have a good spark at all plugs when she is hot and won't start?
a variation of what edward posted...back in the day they used to just dump water over the carb body/fuel pump on my '35 terraplane.

regards, tom
tom peterson

Bud, this problem, which is vapor lock is caused by heat soak and as such, a heat shield doesn't help much. What is happening is that when the engine is shut off, there is no air flow to carry the heat out of the engine compartment and it soak into everything in compartment, including the carburetors. While a heat shield will keep the carburetors from getting too hot while the car is moving, once the car stops and the engine is shut off the block and exhaust manifold act like the heating element in an oven. The problem area is the channel between the float bowl and the carburetor jet. As the fuel in this channel heat up, it boils and forms a bubble in that channel. The bubble puts back pressure on the fuel in the carburetor, shutting the needle valve off hard so no fresh fuel can be pumped into the float bowl. When you try to start the car, it may start initially, but soon run out of fuel. Pulling the choke out usually disrupts the equilibrium causing the bubble to move a bit and allow fresh fuel to enter the float bowl and after a few minutes, with air moving through the engine compartment and fresh fuel entering the float bowl, the carburetors will cool down a bit and this settle out. With our TD, I find that just propping the hood open while the car sits will usually prevent the heat soak and ensuing vapor lock from happening. I have toyed with the idea of installing an electric fan on our TD that is heat controlled to prevent this problem, but have not done so yet. This issue has been discussed to great lengths on the MGA BBS. You might want to take a look at their take on the situation. The discussion (quite long) can be reached at: http://tiny.cc/hokqh Cheers - Dave
David DuBois

I have been through many problems this summer. Now, this item is the only remaining. I am going to install a heat shield, which, as David states, will be of help when the car is running. Then I shall install a second fan, one that I can start with a button on the dash. This is not that easy with a TD, since there is very little space between the grill and the radiator, but there is one type that goes in. A friend of mine, who had the same problems, says since he did this, no problems any more.
See my thread about this further down, many persons had much to say about this item.
















Raymond Wardenaer

Bud,
Just so we have an exact sequence of things happening,,,, you said "The last time it happened I waiting about 20 minutes and finally had to push it off."
Do you mean push it off the road? or Push it to start it? (as in pushing it to get it rolling and then let the clutch up while it is in gear)

SPW

STEVE WINCZE

Mine does this but the choke trick works, so I see this as no big deal really. A very simple work around that always seems to do the trick.

Just part of owning a T series.
L Rutt

I had the exact same thing happen this weekend on a warm uphill long drive of about 30 miles. I didn't know the choke trick at that time but for some reason I pulled the choke out a little (panic/desperation perhaps?) and she started right up, sputtered a bit, then off we went. This post makes me feel much more secure knowing why it worked!
Ed
efh Haskell

I learned the choke trick the hard way too but it has definitely worked for me as well.
A. R. Todd

Hi Bud,

All good advice above but I hope you're not running as per WSM, ie static timing at TDC! This is almost guaranteed to lead to overheating - see Archives, but around 1/4" ahead of the CS pulley notch is about right. I've also insulated the float chambers, and now no problems with vapour lock etc.

PS electric fan will make little difference unless you run in a lot of heavy static traffic.

Good luck,

John
J C Mitchell

My instant cure for vapor lock (which only happens on hot days when briefly parked) is to hold down the tickler pins for a couple of seconds with the key on, to release the gas and 'prime' the carbies.

Matthew.
Matthew Magilton

a couple of tidbits to dwell on to fight vapor lock...

when you can't start a hot engine, and the fuel pump is clattering away like crazy, it is trying to pump gas vapor, usually in vain.

All above mentioned suggestion are good advice, so I won't repeat popping the bonnet, water/wet rags, choke it, MGA http://tiny.cc/hokqh, piss on it...

Ussally, I whip out a small adjustable wrench and crack the fuel line to the carb until the pump reprimes and squirts some gas, but remember to barely crack it and not hose the hot exhaust down with raw gas.

a full tank of gas on a hot day makes all the difference in the world. The high location of the pump promotes vapor lock because not only is it trying to pull gasoline up at the boiling point, it has to raise it a vertical height which actually lowers the boiling point. An empty tank has a big handicap of better than a foot of vertical draw, whereas the gasoline level of a full tank is within a couple of inches of the pump.

push it to a slope where it faces downhill,

Insulating the fuel line up to the pump is not a bad idea; it will make a margin of difference but not eliminate the threat completely.

Alcohol aggravates vapor lock. I learned back in the 1980s with gasahol, the alcohol was desirable in the winter for "drying" moisture/condensate from the gas, but in hot weather, my fuel injected SAAB would die on the highway above 85F!

I relocated the fuel pump to the rear of the car, below the gas tank so it has plenty of feed and it then pushes the fuel to the carb, not pull it the length of the car and uphill. (also added a new Facet for backup).
Jim Northrup

John,
I just wonder; why wouldn't a fan help when the car is stationary?
Raymond Wardenaer

Hi Raymond,

Yes an electric fan will help when stationary, as when in heavy urban traffic, start-stop etc. However most Ts are used nowadays for recreational driving, not commuting, and an electric fan is not easy to fit in our cars, for marginal benefit.

The main reason for overheating, and to be tackled before other measures, is retarded ignition, based on the outdated advice in the WSM re. static timing at TDC! See Archives on this subject.

Cheers,

John
J C Mitchell

John, my friend here in Oslo has such a fan, and since he installed that, he has never had a problem. The chairman of the MG club in Norway has a company selling fans, and he has found one that can be fitted between the grill and the radiator. It is a very tight fit, but it can be done.
Also, the TD is my only car and I use it all summer. In winter I rely on the buses and trams, since I live in central Oslo.
Raymond Wardenaer

I had a 77 MG midget that would start vapor locking as soon as it got warm outside. I ended up with the same solution as Jim and installed a pump back near the tank and never experienced the problem again. Someone told me to stop vapor lock you can clip woodent clothes pins to your fuel line but that is probably just an old wise tale.
Richard Taylor TD3983

One other possibility: if you have the original points/condensor, the condensor could be having a hot-soak issue. That used to happen back in the 70s with other cars. You can also put a small cooler in the car with a couple ziplock bags of ice. If you get the no-start, just ice down the bottom of the carbs and float bowls and give it a try. George
George Butz

Hi Raymond,

You must do what you think is best, but I do hope you are not running on TDC static timing and/or the timing profile is not retarded!

Cheers,

John
J C Mitchell

Hello John,
since I am not very good with engines, I don't even understand what you mean by your last post. Sorry.
Raymond Wardenaer

Hi Raymond,

Don't worry, we all had to learn over the years! The Archives are a good place to start on any topic, but what I am saying here, is generally accepted as correct. There is a notch on the crankshaft pulley, which can be aligned with the pointer on the timing cover indicating top dead centre, (TDC) when no 1 piston is on it's firing stroke. With current petrol etc it is normal to make a mark around 4mm in front of this notch giving approx. 5 degrees before top dead centre (BTDC) as the basis for adjusting the distributor so the points are then just opening.

If your static timing is as per the workshop manual (WSM)on TDC you will be running retarded, the major cause on any make of engine for overheating, fuel vapourising etc, as well as poor fuel consumption. What I am saying is before doing anything else to control fuel vapourising, check, or get a mechanic to check the static timing, aiming at around 5 degrees BTDC. Heat shields, better fans, insulating fuel lines and float chambers will help, but get the timing right first!

Hope this helps,

Cheers,

John
J C Mitchell

Thank you John,
the mechanic, a very experienced one in old British sports cars, has gone through everything during the two months they had the car. I hope he did the things you suggest, too.
Raymond Wardenaer

Hi Raymond,

I hope so too ! Good luck,

John
J C Mitchell

This thread was discussed between 21/08/2011 and 25/08/2011

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.