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MG TD TF 1500 - vapor lock advice?

Running my TD in a rally last weekend, I had to stop several times because the engine started cutting out from lack of fuel. I suspect I am experiencing vapor lock, since this always seems to happen on hot days, and the problem goes away if I let the car cool down for 30 minutes.

I've heard of several fixes people use for this problem on various cars. I wonder what methods have been successful on TDs. What has worked for other people?

Moving the fuel pump?

Thick gaskets between carbs and intake manifold?

Placing heat shields between the float bowls and exhaust manifold?

Move the fuel line to the opposite frame rail so it doesn't run right alongside the exhaust?

Thanks in advance for your suggestions. I always seem to get good advice here.

Ted
Ted Preston

The problem may not be a vapour lock. A common problem with cars with SU fuel pumps is that the varnish used to insulate the windings on the pump solenoid breaks down with age and when the pump heats up (hot days, long runs) the pressure of the expanding copper wire coupled with the aged varnish causes the pump to cut out. 30 mins sitting allows it to cool down and off you go again. The easiest way to teel the difference is that if the problem is a vapour lock the pump will be clicking at a very hihg rate compared to noemal operation. No clicking indicates a faulty pump.
Phil Stafford

Ted,
Had this problem with my TF last year! I changed so many things at once it is hard to tell just what cured it. Got a lot of good advise from here ...and took some of it.
First of all depressing the overflow "pin" on the floatbowl should clear any air out of the line to get you going again..(make sure you know where the overflow is routed to first!). My TF had rubber fuel lines that seemed to heat up quicker than the stainless steel ones...a good cheap place to start. Check those float bowels to insure they are clean also...mine were really nastie and were sticking. You will no doubt get some mixed feelings on "heat-shields".....for me after rebuilding the carbs and changing the lines I had not needed them. If your exhaust manifold is rusted and nastie you might want to consider getting it jet-hot treated....it will look good and my car runs cooler with the "slippery" treatment to the inside of the manifold. (cost about $100). Last time I opened this for discussion it started a bit of flack on the old BBS...but I still feel it has helped.
Best of luck to you.
David 55TF1500
David Sheward

Ted- My TD can be driven really hard on a 95 deg. day here and has never even sputtered (restarting after sitting 10 min is another story altogether!) TDs have lots more room underhood than TF's, so something is wrong. Check that no fuel line has been moved against the exhaust, etc. Advice on the pump above is correct. Did you check for spark? Seems years ago that a bad condenser would do this when really hot (coil too). SU frequently gets blamed when the Prince of Darkness rears his ugly head! If you have electronic ign. I would check that also.
George Butz

I'm guessing, based on your observations above, that my problem is vapor lock. When I attempt to restart the car, the fuel pump clicks away at a fast pace, but can not seem to pump any fuel. I have clear plastic fuel lines between the pump and the carbs, so I can see that there is no fuel in them.

I often solve the problem by using the pins on the tops of the float bowls to release the air and get the fuel flowing again. Unfortunately, this fix is often short-lived, since the car will start to cut out again if I keep it under load. (If my memory serves, each time I experienced this "cutting out" problem, I was driving up long hills, with the water temperature up over 100 celcius.) If, on the other hand, I can crest the hill and start down the other side, thus taking the heavy load off the engine, I do not experience any further "cutting out".

Ted Preston

Ted,

A couple of comments. One is to ask your fuel supplier if they have alcohol in the fuel. Conoco and Total both use it and it is more prone to vapor lock. Phillips, Exxon and a few others do not use it. The alcohol causes problems in older cars that do not circulate the fuel past the injectors.

Another possible solution is to add an auxiliary fuel pump near the bottom of the tank where the head pressure is the highest. You can get the low pressure versions at auto stores for about $30. Switch them on when necessary but don’t run it continuously. Be sure to wire it to the part of the ignition switch that is off when the key is off.

Good luck,
Bill
Bill Loubiere

Ted - It sounds to me like your vapor lock problem is comming from excessive under hood temperature. I have driven through Wyoming and up some of those long hills in our TD and never experienced temperatures above 100°. One of the things that comes to mind is that your grill slats may be rotated to the point that they are obstructing the air flow over your radiator and through the engine compartment. The other thing that I would ask, when was the last time that the engine cooling channels and the radiator were thouroughly cleaned out? The heat shield and additional pump will both help get you past the occasional vapor lock, but will not cure the problem of excessive temperature in the engine compartment.
Good luck - Dave
David DuBois

I would start with the fuel pump first. I regurly drive in 100+ temps with my car running just under 100 with no vapor lock problems. Make sure that you car is configured as originally as far as routing, fuel line sizes etc.

Now if I could just get the car to run cooler I would be all set. But that is another story.
Chris Couper

Chris,
Drain and flush radiator and block with a good flush compound (Prestone makes one) the fill with plain water and add "Water Wetter", I bet you will run 10° C cooler.
It has worked for me. Also since running cooler, I never get vapor lock. Even when climbing to Neal's Gap and stopping at the top. I run at 85° C in the hottest weather (~ 100° F)
Don Harmer

Been there, done that. I am ready to blame the new unleaded gas since NOTHING has changed on my car in the last 20 years but the gas going into it. If anyone has any emperical data on unleaded gas and engine cooling I would like to see it. Also if anyone has found a gas addititive that lets the car burn cooler then I would like that too. Keep in mind my car runs just great until the outside temp gets about 95+, otherwise it's fine. Even at 100 I can idle the car all day long at about 95C.
Chris Couper

Just came back form GOF Central and ran car at 4000 rpm for several hours in 90+ deg weather and the coolant temp never went above 85 deg. Stops for rest which can heat soak in the engine compartment never caused a problem with a restart.
We have the orig. MG fuel setup. We use 50/50% Prestone AntiFreeze/Distilled Water with a little pump lube. A good clean block and radiator help, but getting the right thermostat really helps.
colin stafford

Don:

<<<snip>>>
e fill with plain water and add "Water
Wetter"
<<<snip>>>

AND a rust inhibitor/water pump lubricant! Straight water does transfer heat better, but some antifreeze raises the boiling temp. A 30% antifreeze solution is a good compromise.

The only way I can get high octane gas for my 9.3:1 CR TD is with gasahol. It doesn't cause any problems with vapor lock unless the car sits alot in traffic or starting after a short shutdown.

You can also use no thermostat in the summer, but expect longer warmups.
Blake J.

With regard to Chris Coupers' interest in emperical evidence on gasoline being the variable. I had the plesure of driving a 55 TF15 all over Europe (mostly Spain/France/Italy/alps.) for 3 years and never had the first heating or vaporlock problem in nearly 40,000 miles. Of course this was 1956/7/8 and the car was new, and the octane was so low you would have to ease up to a building and let the clutch out to stop running on/dieseling. This would seem at least to point at the fuel. Dave/55tf15

To Blake, J.
"Water Wetter" comes both with and without the pump lubricant. Of course add some if it needs it. With "Water Wetter" and pure water the system never gets to the boiling point so increasing it ( and reducing the heat transfer) by adding glycol is not needed. At least that has been my experience.
Don Harmer

FOr what it's worth, Discount Auto Parts sells the Red Line "WaterWetter" for $6.99 for 12 fluid ounces - enough for a cooling system of 12 - 20 quarts. It is advertised to have the following cooling characteristics:

50% Glycol/50% Water - 228F
50/50 + WaterWetter - 220F
Water Only - 220F
Water + WaterWetter - 200F

They recommend at least a 15% antifreeze in the radiator since the WaterWetter doesn't protect against freezing. They also claim it reduces rust, corrosion, and electrolytes as well as cleaning and lubricating water pump seals.

Gene G

Ted,

I had a similar problem to yours several years ago when returning to PA from the Andover, MA GOF when Anders Clausager had Old No. 1 here in the States. We were going through the Pocono mountains in 100 degree temps and the fuel pump couldn't seem to keep up on the long hills. It did tun out to be the fuel pump because after I replaced it, I haven't had that problem since. I do get some vapor lock if after a long run on a warm day, I stop for a short time, perhaps to fill up the gas tank. It will then sputter a bit until it clears out the air in the fuel lines.

Charlie
Charlie Baldwin

Has anyone thought of putting an electric fan beetween the radiator and the grill ? That not only help the vapor lock issue but more eficient cooling in trafic and other nigthmares.
Jose Vargas

I thought about it Jose, but it seems there are lots of folks out there who can drive their TD's without vapor lock problems, so I should be able to get the bugs worked out without altering the car.

But . . . I have a radiator fan from a Fiat Spider that looks like it would fit in front of the TD grill. If I get discouraged, I may give it a try.

By the way, my thanks go out to all of you for your help. I haven't yet made any changes to the car yet, but I did drive in another rally recently. Thankfully the car doesn't vapor lock at night. I wish they held more night rallies!

Here's another question, for someone who knows the properties of metals better than I do. Which metal would make more effective heat shields, steel or aluminum?
Ted Preston

I thought about it Jose, but it seems there are lots of folks out there who can drive their TD's without vapor lock problems, so I should be able to get the bugs worked out without altering the car.

But . . . I have a radiator fan from a Fiat Spider that looks like it would fit in front of the TD radiator. If I get discouraged, I may give it a try.

By the way, my thanks go out to all of you for your help. I haven't yet made any changes to the car yet, but I did drive in another rally recently. Thankfully the car doesn't vapor lock at night. I wish they held more night rallies!

Here's another question, for someone who knows the properties of metals better than I do. Which metal would make more effective heat shields, steel or aluminum?
Ted Preston

Oops!
Ted Preston

This thread was discussed between 25/07/2001 and 29/08/2001

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