A10 engine stuttering, coughing and stalling (Read 258 times)

[jonh]

As well as my other overheating issues my engine is now spluttering and stalling  Symptoms including the engine starting but then cutting out after a couple of seconds repeatedly and then when she does fire up and run coughing and stuttering as soon as I try and pull off and most likely stalling again. This happens from cold and if I start her and then leave her to idle and warm up before trying to drive off. I've had it happen a couple of times now, once after stopping for half an hour and the second time after not using her for eight or so hours. The symptoms I've just described don't happen all the time though and sometimes she just starts (with a little difficulty) and then just runs normally, other times she really doesn't want to run at all. I'm not sure where to start investigating this issue. Any suggestions or ideas anyone ?

[gainsb1]

I would try the simple and cheap stuff first. A faulty condensor might cause these symptons. Replace the condensor AND points (use Nissan/Japanese). It could also be a fueling issue with some crap in the carb that is intermittantly being dragged into the jet. This happened to a friend of mine who had a Sunbeam Alpine. The problem with the crap in the jet was cured but then occurred again and again. It was eventually sorted after numerous cleans and replacement fuel filters had been put in to get rid of the stuff in the fuel.It was obvioulsy sucking up the silt/rust on the bottom of the tank, so you might want to take the tank out and flush/repair it. Difficult to see if it's the tank without removing it.

Leigh (Area rep)

[dirtynails]

before you do too much- the very first thing to check is the hot air flap on the air intake (make sure it's to hot all year round).
the second thing is the flexible pipe coming off the exhaust manifold - it's prone to collapsing inside with age - and it smothers the engine.
hope this helps.

[jonh]

Thanks for the suggestions. I'm running with electronic ignition and I have the flap on the air inlet set to summer, the flex pipe is ok.

I found that the fuel level in the fuel filter only reached half way up (half fuel / half air) which was the level of bottom of the filter outlet pipe. Having back filled some fuel into the filter to expel the air the fuel level now sits at 3/4. The engine is starting better now if I've used it recently but if I leave it for a few days the float level in the carb drops down to the bottom and the engine is difficult to start again. I'm wondering if the diaphragm in the fuel pump is leaking and the fuel is flowing back out of the carb under gravity and emptying the float bowl in the carb or something like that. I've taken the fuel pump off and pumped it by hand to confirm that it is pumping but I've no idea if it's pumping at the correct pressure or not. Perhaps the pump is ok but the fact that the fuel level in the float chamber drops after a few days seems suspicious to me.

Any further thoughts ?

[dirtynails]

The pump cant suck petrol back out of the float chamber & what seems to be air in the filter is normal - strange as it seems!. The chamber is empty  possibly because 1) leaked out of the chamber drain plugs (copper washer missing) - or 2) petrol has seeped down in to the engine. I can't envisage how that could happen unless the float chamber isn't vented. ie. building pressure from temp & forcing fuel through slow running or main jet. Very long shot - but is there an electric fuel cut off device on that carb? Might not be sealing properly when engine is not running.
Hope this helps you!!!!
P.S. again from memory - which isn't always right - some of them datsun carbs had a hollow screw coming up from the bottom (carb removed) which might have been for venting. Open to contradiction there.

[jonh]

Since the carb is higher than the pump (and the filter and return line to the tank) I was wondering if the fuel was flowing back out of the carb through the pump and into the filter / tank under the force of gravity. I'd assume there would be a one way valve or something in the pump but if it's faulty perhaps fuel can flow back through it in the wrong direction ? There isn't anything electric on the carb, the only things going to it are pipes and the throttle and choke cables. The gasket that joins the carb to the manifold looks wet (I don't know why or if that's normal). I'll look at the diagram of the carb in the Haynes manual to try and figure out where the drain plugs are. The only bolts I remember on the outside are for the jets.

[dirtynails]

You're right. To remove jets,take out bolts & put a screwdriver through the holes. There should be copper washers on those & some carbs had locking tabs as well. The petrol goes in to the top of the carb through a needle jet operated by the float. The float level setting determines the amount of petrol in the chamber (engine running - should be half way up on the sight glass). The needle isn't submerged in petrol so petrol cannot be sucked out of the carb via the pipe. Think you're on the right path with the damp gasket-that should be dry. Rub it with your fingers & see if it smells like petrol!

[gainsb1]

I have just resolved my 160J spluttering, jolting and jerking by fitting a new distributor cap. Closer inspection showed that two of the outer terminals were blackened and (now) obviously not able to meet the demands of the electrics. Try this and let me know. I've had several weeks of tweeking to sort it and forgot to check the flippin' obvious.

Good luck. Leigh (Area rep)