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MG TD TF 1500 - Engine problem during first drive after six years

Hello.

After six year of restoration, my TD is again ready to go on the road. I have done all the preliminary checks and during the last weeks I have tried to drive a short distance around the block, just to check steering, brakes, etc. However, in every test drive, I have had the same problem.

The first 100 meters or so, the engine pulls rather reasonably, but after that time, it starts hesitating, and even in neutral it does not rev up. I can hear explosions in the exhaust, and all sort of mechanical noises. After leaving the engine idling, or stopping it, but leaving the fuel pump working, it suddenly behaves properly, with normal acceleration and power. Then again, after a short distance driving, the same problem happens. After arriving to the garage with difficulty, I looked at the engine, and nothing seemed to be loose or malfunctioning. When engine is malfunctioning, and opening the carb throttle by hand, I have observed some back sputtering from the rear carb.

I suspect some problem with the fuel system, and am inclined to believe that the carbs run out of fuel after a short driving distance.

I have tuned the carbs (flow rate, damping oil, etc.) although they need probably a fine tuning, since they are running still to rich, since exhaust CO level is too high.

The fuel pump, which is brand new, and the appropriate model from Burlen, is ticking all the time. After installing the pump some years ago, I did a check, and noticed that it had some difficulty in priming, and when gas came out, the flow rate was very small.

Do you have some hint on the cause for this problem?

Thank you in advance for your assistance.

Jesus
J Benajes

Were the fuel lines replaced, or blown out with air? Certainly sounds like fuel pump related?
gblawson(gordon)

I installed a new copper line and cleaned the petrol tank and the filter mesh in the tank.

I am thinking of making a driving test by gravity-feeding the carbs from a bottle with petrol or by any other alternative method to exclude the pump and tank.

But first, I wanted to get some feedback from the friends.

Jesus
J Benajes

Hi Jesus,

I suspect you'll get a lot of help with this but from what you say it does sound like the place to start is by checking for fuel starvation.
Have you checked that all of the filters are clear, in the pump and the carbs? Also, if the tank has been laid up for some time it might be worth checking that the filter in the tank is clear, (do this as a last resort as you'll have to drain the tank). If you haven't found that filter yet, it's part of the outlet union at the bottom of the tank. It's a long metal gauze filter.
You might also check that the jets are clear and that the inlet needle valves in the float chamber lids are not stuck closed or worse partly open and that the floats are free.
You say that the pump is ticking all the time, is that a steady click every couple of seconds or so, or a fast continual click? If it is fast, then this would indicate that fuel isn't reaching the pump.
Disconnecting the connection at the first banjo union with the pump on,(making sure that the exhaust manifold isn't hot!), will give you a good indication of fuel flow to the carbs.
With the engine idling, if you tap the fuel pump fairly firmly does it start clicking fast then settle down? If it does then perhaps the points need re-setting?
Anyway I hope this helps a bit.

Mike.
Mike Christie

Easy way to tell: Drive it until it starts sputtering, shut it off immediately. Pull the float chamber lids and see if there is any gas. Also, the pump should fill the carbs and then stop clicking. If it is clicking continually, there is a blockage or air leak or something. George
George Butz

Jesus
It could also be a air leak in one of your connections. Dose the fuel pump always have the the same rate of ticking. Always steady, steady then faster or steady then slower. Also check to see if your gas cap has been 100% sealed. Just trip the cap lock and test drive.
John

(good point John)
gblawson(gordon)

Jesus, if the carb bowls are full, check your timing. The condenser could be at fault along with other related ignition problems like points, bad distributor cap or weak coil.
Jim Merz

Thank you all for your interest in helping!

As far as the fuel pump, it clicks very fast (about once or twice per second) and it does not stop clicking. Even with the engine at stop, it took a very long time to slow down clicking. Perhaps the gas cap vent could be a problem, since I renewed the seals there. However, the tank level is very low, so I guessed that it would take longer to create vacuum there as to influence the suction power of the pump.

I will make the checks you suggest.

Jesús
J Benajes

Jesus - John has hit the two very real possibilities - air leak on the inlet side of the pump or a clogged vent in the filler cap. A can of fuel beside the car, with a hose from it to the inlet side of the pump and another hose from the outlet side of the pump into at least a 2L container. Run the hose clear to the bottom of the container. Turn the ignition on and watch the fuel in the outlet container, it should not have any bubbles in it and should pump at the rate of 1.3 pints (US) per minute. Let the pump run as long as possible without overflowing the outlet container to see if it stumbles at all. The next test would be with a fairly large outlet container, reconnect the inlet line from the tank to the inlet of the pump and again turn on the ignition and let the pump run as long as possible. If it starts to stall, loosen the filler cap. If that cures the stall, the vent is clogged. The vent is around the center rivet that holds the center portion of the cap in place. The center portion is spring loaded and puses up along the rivet. If you had the tank sealed, the sealer may have gotten onto the cap, clogging the hole around the rivet. If y have a full tank of fuel, a vacuum will form in the tank quite quickly, producing the symptoms that you are having. Of course, the problem could also be on the ignition side, but I am betting on the fuel side. Cheers - Dave
David DuBois

With my engine running, my pump will click about once every 5 or 6 seconds...maybe a little longer. Of course it clicks quickly until the float bowls fill up...?
gblawson(gordon)

Jesus,

Did you at any time, replace the gasket in the gas filler cap. There must be (air) leakage around this so that a vacuum doesn't build up in the tank.

Try running the engine with the gas cap open.

Gord Clark
Rockburn, Qué.
Gordon A. Clark

How old is the gas in the tank? Old fuel does not perform as well as fresh fuel and may cause problems. Insure that the fuel used is no more than a month or so old.
John Masters

Jesus,

I you have retained the tickler pins in the float chamber lids, you could test the level of the floats.
If you have fuel statvation one or both floats will be low. Do this once you have experienced the problem, just cut off the ignition and do the test.

John
John Scragg

Thank you all for your useful suggestions.

The fact is that until now I haven’t been able to make any check, due to a very busy period. And now my TD is in an exhibition hall, in company of other 39 European sports classic cars, like Bugatti, Delahaye, Pegaso, Aston-Martin, Lagonda, Lamborghini, Ferrari, etc. There it will sit until mid of September, so I had to postpone any work on the engine until then.

In September, I will come back with this issue to this forum, commenting the outcome of the checks I plan to make on the pump.

Jesús
J Benajes

(Bugatti, Delahaye, Pegaso, Aston-Martin, Lagonda, Lamborghini, Ferrari, etc.)

Good to see they have put the above cars in good company!!!!
gblawson(gordon)

Jesus, you are a very patient man. It would drive me batty to finally finish my car, have some things I want to trouble shoot, and then give it up for two months or more.

Congratulations on having your car participate in the display. Please post a photo if you get a chance!

warmly,
dave
Dave Braun

Here you have a photo of my TD close to a TC with a Bentley in the rear.

Dave, it is not a case of patient, but simply some very busy weeks…and the need to bring the car to the exhibition hall on a given date.

Regards.

Jesus





J Benajes

Jesus:

WHAT A WONDERFUL TD! I thought mine was nice but you trumped me. Congratulations.
Dick Thomas
TD13583
Wooster, Ohio, USA


Dick Thomas

Jesus,

Great looking car! Is this the one that was white and brown?

warmly,
dave
Dave Braun

Thank you for your compliments. The result has been possible to a great extent to this wonderful forum, and to the assistance of all the friends here.

After six years working (and extremely enjoying) regularly on the car, the effort/results ratio is very high, indeed. I have kept a meticulous diary of all the time and task spent on the car, plus a record of every single cent expended. You can understand that I don’t dare to make the final addition...

Well Dick, I wouldn’t bet with my TD against yours … . Mine bears also some concessions to originality, like chrome door hinges, radiator slats in body colour, veneer dash board or slightly different colours of interior side panels and seat leather. The top and side curtains have still to be installed, too.

Yes, Dave, when I got he car, it had been painted in cream with brown fenders/wings.

Jesús
J Benajes

This thread was discussed between 30/06/2008 and 14/07/2008

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