Power Loss Again - The Mystery Deepens

[egsj]

Hello. I posted here a few weeks ago about my Traveller suddenly running out of power and I collected many useful suggestions which I've worked through with my local moggie specialist. But the problem persists! My last conk-out was on a large multi-lane roundabout with a juggernaut up my chuff. (Well, it was Friday the 13th!)

The car takes a few slightly juddery seconds to stop, it doesn't misfire, and as often as not I can get it going a few minutes later - though it will conk out again after a while if it feels like it. I've been through three fuel pumps in the past two months. The current one's working fine: on breaking down, I unscrew the hose and turn the ignition one click, and out chugs the fuel at a good steady pace. So all's well there. What particularly stumps me is that the last two fuel pumps did fail on me, thereby suggesting a clear cause (though it's odd that two in a row should be duff) - and yet the problem is exactly the same with a working pump.

This is where I've got to with troubleshooting so far:

I've had the coil, distributor, rotor arm and even the pipe from the fuel tank to the fuel pump changed.

The filter in the pump is not revealing any muck from the fuel tank.

The float chamber next to the carb has been cleaned, and air's been blown down the jet assembly.

The carb has been checked and cleaned. It's not icing up (the power loss was occuring in warm weather last autumn, anyhow) and the piston in the carb, though not moving perfectly, is apparently not bad.

There's no vacuum developing in the petrol tank from a blocked filler-cap breather.

A problem on the electrical side is unlikely, isn't it? It can't be points-related as I have electronic ignition, and it can't be the electronic ignition because the power-loss was happening before that was put in. The plugs were changed last January and seem fine.

My mechanic doesn't think it's a brake sticking on. I have discs and a servo fitted. But, I must admit, I keep forgetting to try de-clutching (as someone suggested before) to see if the car runs on freely when the problem occurs. So I can't yet eliminate that from my enquiries. I'll try that next time...

Any more ides out there? I want to go on holiday in three weeks' time, she's my only car, and I don't feel safe driving her out of city limits. Conking out on a dual carriageway on Christmas Eve certainly wasn't fun. I don't want to do that again in a hurry!

Jamesy

[PSL184]

Jamesy, you say the piston in the carb is not moving perfectly - It should be !!! It should rise and fall without any roughness or sticking at all - If the piston sticks, even slightly, it will give the symptoms you have described (and as you have eliminated everything else it points in this direction). Strip out the dashpot and needle assy from the carb. Very carefully clean both the piston and the dashpot. Check the needle is not bent (even slightly) and reassemble. Make sure that the piston falls with a solid clonk when its all back together again. f any doubts about the needle or jet, replace them !!!

[simmitc]

And brakes are still a possibility. If the de-clutch allows the engine to race but the car still slows down then you've found the problem. It will occur only if the master cylinder was not modified when the discs were fitted. Normally I'd say that you would notice the build up of heat, but if you're only in city limits most of the time, it's quite possible to stop the car without the brakes getting too hot. Happy hunting and good luck.

[kennatt]

have you checked the valve inside the carb float chamber,the one atached to the float,if this is sticking,although you have petrol pumping at the pipe it might not be getting into the float chamber,Next time it stops, switch ignition off coast to the side and before trying to start take off the top of the float chamber and see if there is petrol inside,,this needle valve and seating can be cleaned up but better to replace,cheap and easy to do worth checking if you havent done so allready

[egsj]

Thanks to all... I'm pretty sure the valve inside the float chamber is fine, and that the master cylinder was modified correctly on the switch-over to discs - that was done by the previous owner a few years ago, and the power loss problem has only surfaced in the last few months. So it sounds like the carb needs further investigation, as per the first reply.

Will get on the case. Any other theories welcome, of course...

[andyjack]

Don't even know if you still have one with electronic ignition but in the past I have had similar symptoms whith faulty condensors.

Also many years ago a freind was suffering similar problems and that turned out a piece of debri (think it was a bit of masking tape) floating around inside his petrol tank. It would occasionally block the outlet but as soon as the petrol pump stopped it would fall away, allowing the car to run as soon as the fuel supply resumed. Due to the random and unpredictable nature of the fault every time the fuel supply was checked it all appeared fine.

I know it is a long shot, but the pump running dry could also explain why it is eating pumps.

[charlie_morris_minor]

You say that you have discounted the carb icing up as it occurs in warm weather, my carb would ice up what ever the weather.. my understanding that icing of the carb is more a function of accelrating hard and sucking in lots of air through the carb.

I had a 1300 fitted with a K&N and overdive gearbix and would happily run at 80 - 85 all day long. However there was a hill on the way home from work that if I tried to accelrate from 70 to 80 the carb would ice up and I was lucky if i could do 50 whilst the carb warmed up again. Might be worth trying to accelrate hard up a hill to completely discount icing up.

Are you always going around a corner/roundabout? I seem to recall a story in the owners club mag about a manifold that was not bolted down correctly and when going around a corner the manifold moved slightly and let in air and would run badly / almost stall. i would have thought your moggy specialist would have checked the manifold though.

[Leo]

Jamesy
Are the fuel pumps you are using the electronic type? If so they must match the polarity of the car. If they are connected the wrong way round they will be permanently damaged and prone to overheating and sudden failure, only to work perfectly again after a few minutes.
Also it may be worth checking the carburetter float for leaks or sticking as this can cause these problems

Leo 69 Traveller

[egsj]

The current pump's electronic (I think!), and working fine, so is presumably connected corrrectly. I believe the last one wasn't electronic. But I'll double-check this - and run through all the other useful suggestions here -with my specialist some time in the next few days and let you know how I get on. At least this is a good way for a newbie to begin learning what's what under the bonnet! And I'm sure the answer to the mystery can't be far off...

Jamesy

[bmcecosse]

You seem to have covered most of the possibilities - could be loose wire breaking the ignition - the sticking carb piston is not good - clean/polish it - and finally the idea of something floating about in the fuel tank is unusual but not unknow.

[MuNNzY]

i have just had some problem 2 day and come on to post about and found this lol, i have cleaned the carb piston (dash pot) fingers crossed. if not new condensor and coil me thinks.

[bmcecosse]

Coils are very reliable - although they can have loose connections - worth checking. Condenser - just change it anyway!

[Declan_Burns]

Could very well be the condenser-I had exactly the same symtoms and it turned out to be the condenser in the end. Mine once conked out in the same manner on a motorway brige across the Rhine-at least I had a nice view if not somewhat scarey!
-as BMC says replace it.

Declan
(DEC 1964H-formerly HMP 960 B)