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MG TD TF 1500 - Sudden Failure to Launch

I've had good success with previous attempts, so I return with another question for the gods.

Yesterday, I tried to start the car up (52 TD), and it just would not. It had run the day before, no problems. The only thing I had done was to install a new speedometer cable. Though stranger things have happened, this seems an unlikely culprit.

The starter is cranking the engine nicely. It just doesn't want to go. Not even a bit (no coughing, no rough start then fail). It just turns and turns, but no fire.


I've checked the usual suspects (spark - all four plugs
show good spark, fuel - pump clicks, checked float bowls and they look good). Checked the pistons in the suction chamber, and they are moving well.

Short of bell, book, and candle, if anyone has a direction to sail, I'd really appreciate it.

DWB

Spark at the plugs means your points are opening and closing so you should get a sputter or two IF you have fuel. You mentioned your fuel pump was clicking...does it stop, indicating that the float bowl is full?

Sounds like a fuel problem...if you have starter fluid (or brake cleaner) spray some in the carb while someone cranks the engine (key on). See if it will catch then...
Gene Gillam

Hi Gene:

that's the darndest thing. Up to the float bowls, there is no apparent fuel problem. The pump will fill them, then stop (as it should). Removing the top of the bowl, there's fuel in the float chambers. And spark in the cylinders. Problem is somewhere between A and B.
DWB

Check timing...it's an quick and easy thing to do and will make sure nothing happened to your distributor to move it.

If that's good then, while cranking the engine put your hand over the mouth of the carburetors (one at a time)...is there suction?

Take the top off one carburetor and pull out the piston/needle. Can you see fuel in the jet? Should be visible, depending on how your float is set, about an 1/8th of an inch down or so. If you see the gas then you know you're getting fuel (or something that resembles it) that far at least.

If there's suction and fuel (and a good spark) then try starter fluid if you haven't done so yet. You don't have an enemy who would have put water in your tank, do you?
Gene Gillam

How much spark? Under normal pressure a spark should be able to jump a good 1/4". Perhaps you have 'spark' but it is not doing its job. The coil should read about 3.2 ohms across the terminals, the condenser should ramp up the reading on a volt meter set on ohms to infinity (one lead on the case of the condenser, one on the pigtail, disconnect the condenser first), and when reversed, should decrease the reading.

Carburetors rarely suddenly fail... but electrical things do.

Hope this helps,
dave
Dave Braun

One of the things I have learned from this site is
If it was working prior to doing something on the car, before you go tearing into anything else, go back to what you did and see if it is causing the issue.

In this case, is there something along the path of the speedometer cable route that would affect the starting?

How about a wire under the dash? I agre, it is a bit of a mystery in that it has spark, it has fuel, SO what else might be the issue that would have been changed by the work you did?

Bruce Cunha

Any chance you somehow shorted the tach drive cable against the dizzy?
Like Dave B said "how much spark?"
David Sheward

When you checked the plugs, were they wet or dry ???
STEVE WINCZE

Just a thought....Using a heavy glove, and with #1 plug wire held about 1/4" from the plug , have someone crank the engine...I know it's silly, but sometimes, that will cause the engine to fire off...
If that works, look for a problem with the coil or condenser. (weak spark).
Edward
E.B. Wesson

Same thing happened to my wife the other day, trying to start her TD.

Rolled it over and over and over, no fire.

I told her it helps to turn the key on! (no joke)
Jim Northrup

Hey Jim, been there, done that. Sometimes the brain switch does not work right. In such cases the car does not start. Glad I ain't the only one that has done that..
Tom Maine (TD8105)

All -

thanks for the comments. The spark is pretty strong, so I do not think that that is the problem. I did not have a lot of time, but did some checking.

1) Removing the air intake manifold, I can detect a very weak suction from the carburettors when turning over the engine. It's not much, but can be felt.

2) The butterfly in the front carb was stuck, the throttle is not opening properly.

BTW, the question about who might be an enemy motivated to put water into the engine is a good one. The only one I know who might be sufficiently angry at the car to do that (the wife) would have to know that such an action would result in MORE time spent with the car, not less...
DWB

David...with your hand over the carburetor intake there should be a quite a strong suction when the engine is cranked, not a weak one. Something isn't right...intake valve stuck open?
Gene Gillam

Agree with Gene. Take off the rocker (valve) cover and look for a bent rocker arm.

If you're queasy about rebuilding your carburetors, let me know.

Warmly,
Dave
Dave Braun

I second all of the advice above, starting with Bruce's advice- the problem is most often a result of what you just worked on. The other guys are right on as well of course. If you don't see any visible damage with rocker cover off, spin the starter and make sure the valves are opening and closing properly. Did you try what Gene said earlier- spraying some starting fluid or brake or carb cleaner into the intake and cranking? If no start, that pretty much means compression or ignition problem. There is also the old time rule of always trying new (not cleaned) plugs in any no-start engine. Also good to try in light of possible weak carb suction- pull the plugs and test compression. George
George Butz

It Could be flooded, also. Too much of a good thing...
The timing could be way off. The distributor on my late TD has no clamp to hold it in place ( I just read yesterday that they changed to some tapered bolt arragement to lock it in place)
The compression check is a good idea, with all the cranking it should take care of a flooded engine, too.
Chuck
cj schmit

This thread was discussed between 13/05/2011 and 20/05/2011

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