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MG TD TF 1500 - cuts off at times
|Several months ago I purhased my first MG, a 52 TD. Since I am a novice with this car, I need help with two items. First the car temperature runs between 80 and 90 degrees. Is this to hot or should it be 70 degrees? To lower the temp, what route should I take: thermostat, radiator, etc.|
The second item is after running for approximately 20 minutes, the car acts like it runs out of gas (temp approximately 85 degrees). After letting the car sit for approximately 5 minutes, I can turn the ignition back several times and the fuel pump will begin clicking like it normally would and the car will start. Is this vapor lock or the beginning of a bad fuel pump? How do I check it?
|Jeff, Your problem is with the fuel in the float chambers overheating and vapourizing at the top of the float chambers, pushing fuel in the chambers down and into the carburators. Carburators run cold when an engine is running because of the heat needed to vapourize the fuel but heat up as soon as the engine stops by conduction/radiation from the engine. With the engine stopped this displaced fuel runs into the inlet manifold for as long as it takes for the system to cool down, or the float chambers empty - which would be several minutes. Fuel will not ignite if the mixture is to rich which is why the engine will not start - when this situation arises. This being the case, the car will not start again until the fuel has vapourized out of the manufold or turning the engine over to get the rich mixture out. When the ignition is turned on again the fuel pump, pumps fuel in again as they have been emptied.|
The correct temperature is 85 deg (for a "TF") so a TD would be the same. Your operating temperature therefore is ok. Some put in an aluminium heat sheild between the carburators and the inlet manifold but I have not done this preferring the keep the original appearance. The problem of overheating fuel should not be as bad with a TD because of the extra space around the engine compared with a TF. Some put in small electric fans directed to the carburators to keep things cool.
The first thing to check is if the overflow/ventilation tubes are fitted to the top of the carburators because so long as the petrol vapour can escape then the problem will not arise.
Your fuel pump would not be a problem.
|Jeff, Just to add to what Peter has said - with the fuel pump mounted on the bulkhead, you can generally hear it ticking quite clearly with the engine running - if it stops and needs tapping to restart, or ticks slowly, it may be on the way out. Fuel vapour locks on TDs and TFs is quite common - it has happened on my TF several times (and not necessarily on particularly hot days)- so I fitted a heat shield from Brown and Gammons. This is a neat unit that does not detract from the period look of the car and has done the trick for me - I can recommend it to anyone. AB|
You said "after running for approximately 20 minutes, the car acts like it runs out of gas" Is this running at an idle, or actually driving ??
1) If you are sitting still ideling, watch the pins that stick out of the fuel bowls,, they should stay relativly high out of the top of the fuel bowl as the engine is running. If they start to go down, and the engine begins to quit, your problem is with the fuel pump... at this point, tap the end of the fuel pump to see if you can get it pumping again,,(kind of like knocking on a door with your knuckles) If it does start pumping again, you will hear the pump ticking, and the pins (ticklers) will start to rise indicating that the bowls are filling, and the engine should run smooth again..
2) If the engine stops after driving 20 minutes, Imediatly turn off the ignition, and safely pull off the side of the road, and check the position of the pins (ticklers) again, if they are down, your pump has stopped.. Most likley it will be the points in the pump that need cleaning ..
80 90 degrees isn't too bad for a TD,,, adjusting distributor points and timing could bring it down a bit,,
Keep You Stick On The Ice,
|My current 1953 TD runs contentedly at 85-90 degrees C here in Florida. Even in stop and go driving I have never experienced vapor lock. May be a difference in the evaporation rate of fuel from one place in the world to another.|
My earlier 1953 TD owned in the late 50's did exhibit the engin stopping problem which was caused by dirty or incorrectly adjusted points in the fuel pump. Until you get the points fixed dropping a wheel into a pot-hole will usually jar the pump into operation without stopping and raising the bonnet.
|J. M. Haskins|
|I had a similar situation when I first bought my car about 6 years ago. The car would have to sit for quite some time before starting again-perhaps an hour. I reset the float levels, cleaned the tank, cleaned the fuel lines, etc. Nothing helped. It turned out to be a bad coil!|
|Comment to Steve in Canton Center, CT.|
While I certainly believe you are accurately describing the operation of your tickler pins in the top of the fuel bowl there are several problems here.
First, the pin should have a spring that keeps the pin pressed to the top of the fuel bowl lid. The pin should not rise and fall with the float inside the fuel bowl. The design is for the pin to be pressed down temporarily, to lower the float so additional fuel comes into the fuel bowl. Releasing the pin should cause it to spring back up against the fuel bowl lid.
Second, although I have described the "correct" operation of the tickler pin as designed by the factory, this operation presents a significant safety hazard and should be corrected. The pin does not provide a liquid tight seal against the fuel bowl lid. If the valve in the fuel bowl sticks open gas will overfill the bowl and come out where the tickler pin goes through the lid. This will spill gasoline onto the hot exhaust pipe below, risking an engine fire. (Note that the opening in the fuel bowl lid the pin goes through is BELOW the level at which the overflow pipes would drain gasoline away. What were they thinking???)
This problem has been discussed in the archives. I solved the problem on my 52 TD by taking the pin assembly out of the fuel bowl lid, cutting down the brass pin so the visible portion plus about 1/4 to 3/8 inch remained, then bedding the pin in epoxy putty that I pressed into the bottom of the hole in the fuel bowl lid. From outward appearance the top of my fuel bowl lids look correct and a factory design problem has been corrected. (Sometime after our TD's the factory removed the tickler pins entirely.)
Have you checked your point gap? If the points are marginally opening when cold, they will not open as heat builds up, making it seem like a fuel feed problem. After adjusting, make sure the adjusting screws are as tight as you can make them, otherwise the points will just slip closed again.
|Greg Van Hook|
I agree with your comments re fuel overflowing up through the tickler pin holes. My TF originally had the float lid tickler pins which sometimes leaked fuel down over the starter motor (fire risk when starting), so I replaced them with lids without the pins, but had previously discarded the overflow pipes a couple of years earlier as the pipes appeared to be useless for the reasons you have pointed out.
With this new setup, leaking fuel was not a problem but as the float bowls were not vented, the car suffered from the problem that Jeff raised at the start of this thread, erratic running after a long fast run. Fitting new overflow pipes solved that problem but I still find that the car idles somewhat slower after a fast run due to the effect of the hot exhaust maifold on the fuel, as I have previously stated.
Your solution of the modified tickler pins is to be commended... originality and fire safety.
|The other possibility is that someone has altered the gas tank cap so that it is no longer vented. As you drive and use up fuel, a lower pressure develops in the tank overcoming the fuel pump suction. From a similar experience on my MGB, it takes about 10 - 20 min. to stop the car under normal driving. |
To test, drive with the gas cap open and see if you stall.
|A common problem with old SU fuel pumps is that the varnish insulating the windings on the solenoid coil degrades with age and stops insulating.This is not so bad when the coil is cold but with 20 min to 1 hour of running the coil heats up and the internal pressure on the widings starts to short out the coil. The flow of fuel reduces and/or stops. This may explain the running out of fuel feeling. Sitting for a while allows the coil to cool and start to operate again.|
I have heard this problem called the "1 hour from home" syndrome. A quick check woiuld be to change out the fuel pump for younger one an see if it still happens.
|Do not overlook the distributor capacitor. I had a similar random situation off and on for a year and I looked at and adjusted everything without results. Finally I replaced my 48 year old capacitor with a $2.50 one and the problem was solved.|
I believe that we attempt to attack the SU carbs as the source of all evil on these cars and yet I have found that once they are adjusted properly they run trouble free for years. The same goes for the Lucas electronic components.
I have a 1951 TD and I am facing roughly the same problems with the water cooling.The running temperatrure around 80 degré C is perfect but you have to check this temperature in hot summer, in mountain climbing. What I have done on my TD: first to modify completely the radiator with a modern honneymoon structure. I have suppress the mechanichal fan and I have installed an electric one. I have suppress the by pass system in the water piping, and I have reinstalled
a thermostat which starts to open at 74 degre C. That works perfectaly well. Concerning the fuel pump I am also facing the same problems, the best thing to do is to foresseen a second pump, put in serie, in the fuel sytem this pump should have a switch. But if your pump seems not running correctly, use an hammer it helps.
Good luck Georges.
Also consider the coil and/or HT lead. I had similar go/stop problems on my TF, and only in quite hot conditions. Diagnosis started at the fuel end but finished smartly at the electrical end when a replacement coil and HT lead fixed the problem straight away.
Yikes... so many answers to one little question!
I can well relate to this problem....had the same a few years ago...go back into the "archives" of this BBS and look for "vapor-lock" thread.
One little trick I did discover (after having the car towed home several times only to have it start right up when I got home)....Go to the local drug store and purchase some "cold packs" (the ones you "snap" to activate). When she dies on you...snap a couple of these and put them on the carbs...if this rapid cooling of the carbs lets her start right up again...then vapor lock is a good bet. I still carry a couple of these with some small bundgie cords in my car...but haven't had to use them for several years.
All the advise on this thread has been good...just a matter of figuring out what one is causing your problem! So how did I "cure" my problem?...well you might not like the answer....but:
I had some pretty bad overheating & vapor-lock problems back then.
I changed so many things at once it's really hard to tell what really cured the problem
but my TF has run cool & strong since. The list includes:
Installed 6 vane "bruno" water pump
Now run about 60/40 H2O/anti-freeze with water-wetter
Re-built the carbs....they were a mess
Re-built the fuel pump
Replaced rubber fuel lines with stainless steel
Had exhaust manifold "Jet-Hot" coated (inside & out) Best $100.00 I ever spent on this car.
New coil, plugs, plug wires, points & condenser.
( I run Bosh platinum plugs with a pertronix ignitor and Lucas sports coil now)
I guess, in "hind sight" it would have been wise to do these one @ a time...but I was really getting sick
of being towed home only to have the car start right up by the time I got it home!
Cheers & Best of luck,
David 55 TF1500 #7427
|Thanks to all for all the suggestions. I went for a ride this morning and after about 20 minutes it acted like it was running out of gas. I pulled off the road let the car quit and shut off the ignition. I then turned the ignition back on and began tapping the fuel pump. After 5 taps the pump began ticking again. The car was notturned off for more than a minute. Now it points to the fuel pump. Since I am a novice, buy new fuel pump or rebuild? Also any suggestions for adding electric fuel pump?|
Thanks to all
|A few years ago, I experienced the indentical problem. I rebuilt the pump with a kit and installed a second fuel pump on the frame above the rear axle. I bouught it at Auto Zone and is the same one as shown in the Moss catalogs except a lot less money. Buy the low pressure model. |
I connected both pumps to a three position switch mounted in a hole I drilled in the steering column support. I rewired the original pump to the forward position of the switch, the center position is off (poor man's anti-theft device)and the rear pump to the rear position on the switch. The rear pump will push fuel right through the inoperative SU and the SU has no problem pulling fuel through the auxiliary pump.
From time to time, I change the switch from the forward position to the rear and let it run a few miles. This confirms its operation and exercises it as well. No more pushing due to a stubborn SU!
The rebuild is not difficult. Much cheaper than a new pump -- go for it! For what it's worth, my car did the same thing last summer. Annoying, but an easily solved problem.
|Rebuild your own pump, or buy one of the new electronic SU's. Maybe I have been lucky, but since dad bought the TD in the mid-70s it has never quit due to the fuel pump. I rebuilt the one that came in the car about 10 years ago, and clean the points every couple of years.|
|Join The New England MGT Register. Buy a workshop manual, & a few other books on the car. Inspect the fuel pump points, make sure they are of the double point construction, not single. Replace them if they show wear.Join the club, buy the books, find a local repair shop that knows these cars, & pick thier brains. Mechanics take bribes, coffee, dougnuts, etc.|
P.S. remove the float bowl covers & floats to inspect for dirt,[rust], r/r the fuel pump screen to clean, r/r the tank supply line to remove & clean the screen in the tank. Happy MotorinG
This thread was discussed between 20/05/2003 and 01/06/2003
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