Carburetor Problems

Even in good condition they often cause problems (Cue John C :0))

Goading me now are you Tony?
Now back in circulation, I have to say, I have had no real problems with mine..... yes, they do appear to be complicated, but really they are not, as long as jets, small vacuum hoses are in good condition, all pivots are not sticking, and the accelerated idle part is working, all should OK.
The choke however can be troublesome,.... but yes, in this case,... (if it is in fact the choke causing the flat spot) ... it could be the wax actuator causing the problem, but there are a couple of other things which can cause the choke not to operate correctly which should be checked first before trying to source a new wax actuator.
It is a pity this thread has gone underground so we dont know what is going on, so I am reluctant to put my tuppence worth in.

[johnb]

It is a pity this thread has gone underground so we dont know what is going on, so I am reluctant to put my tuppence worth in.

I'd be interested in anything related to carb set-up/experience as I'm still on the learning curve with the A310.

I would also like to hear as the choke on my A310 hasn't worked properly for the 7 years that I have had the car, even though it has had a new wax thing before I purchased the cat.
Rob

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I'd be interested in anything related to carb set-up/experience as I'm still on the learning curve with the A310.

Does that mean you have got it running then John?

Regards,
Martin

[johnb]

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Does that mean you have got it running then John?

Sort off but not really.

Haven't done a lot in the last few weeks, since the starter motor problems, as I was away from the middle of November to early December. When I came back I removed the starter and the solenoid worked fine but the motor wouldn't rotate. I've had it rebuilt/refurbished and it now works as it should. Exhaust system back on and have had several attempts at starting. The only variation each time being how much I manually opened the throttle whilst operating the remote start switch.

During these attempts it would run with a stutter so long as the starter was still rotating. Plenty of bangs in the exhaust and finally one big backfire through the front twin choke carburetor. The flames shot up about a foot (air filter and housing not in place) and ignited the vapour coming out of the float chamber breather hole. Fortunately it was easy to extinguish. It did this when I'd held the throttle at near full opening and also manually holding open the two butterflies on the twin choke carburetor. These would never be open normally on starting as they are opened by vacuum from the single choke carburetor once the engine is running. This left an unobstructed flame path from the inlet manifold up through the carburetor. I had noticed previously that it was backfiring through the carburetors as well as the exhaust but the backfire products was just unignited vapour when the two butterflies were not held open.

What I'm going to do is check again all the mechanical things that cause the sparks to be in the right places at the right times, e.g. the distributor position relative to the camshaft, the plug lead orientations at plugs and distributor, the contact breakers connected to the correct coils, static timing correct, etc, etc. Hopefully I don't have to recheck the timing chain set-ups but may have to if I find the sparks are occurring at the wrong times and that all the electrical side is clear. There's plenty on my check-list to keep me busy for a while.

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John, I would just do some quick and dirty diagnosis, if you feel you are getting sufficient atomised fuel from the main jet of the carb- as you are opening the chokes, then loosen the distributor and advance it a bunch, sounds like you are well off and retarded . Then simply give it another go, you will soon find out, and much quicker than trying a bunch of technical stuff - just see; mark your original position before move off. Have you got a nice electronic strobe that will tell you what timing you have?

Martin

[johnb]

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John, I would just do some quick and dirty diagnosis, if you feel you are getting sufficient atomised fuel from the main jet of the carb- as you are opening the chokes, then loosen the distributor and advance it a bunch, sounds like you are well off and retarded . Then simply give it another go, you will soon find out, and much quicker than trying a bunch of technical stuff - just see; mark your original position before move off. Have you got a nice electronic strobe that will tell you what timing you have?

Martin

Merry Christmas to everyone.

Yes Martin, I'll give that a go first.
I'll do a static timing test and double check the points connections to which coil first. When I bought the car the coils were connected opposite to what was shown in the MDR so I changed the connections to as they are shown in the MDR. This needs rechecking as it may have run as originally connected unless the coil king leads had been changed over later. It's worth me rechecking this first as I may have introduced out of phase timing although the static test when I set the distributor originally was OK.
I have a very old strobe light only.

This plate I had set previously at TDC on the firing stroke of cylinder no 1 using a drill through the block into the hole in the crankshaft web with cylinder 1 on the firing stroke.

Hi John,
Seeing as you have your starter running again and your recent experience with trying to start your 310..... a question I wanted to ask some time ago but decided against it for fear of getting a reply..... "what do you take me for" re:- lawn mower fuel...... Only joking John ,..... but regarding the above quote, you used a drill through the block to find the TDC.... no problem there, but what other indicator did you use to identify that the TDC you had located was in fact the one for the firing stroke of No. 1 cylinder.
Sorry if you find this a silly question but it has been at the back of my mind since you posted it, but now that there is obviously a serious timing problem, I would like to eliminate that as a potential problem.
Cheers
John

[johnb]

but regarding the above quote, you used a drill through the block to find the TDC.... no problem there, but what other indicator did you use to identify that the TDC you had located was in fact the one for the firing stroke of No. 1 cylinder.

Hi John, thanks for your continuing interest.

When I set the timing plate on the timing chain cover the rocker covers were off and I knew cylinder 1 was on the firing stroke, when the drill was inserted into the crank web, because I'd turned the engine over so that the rockers on cylinder 1 both had clearance, i.e. both valves were closed. Thinking about it though, it wouldn't have mattered whether it was on the firing stroke or 360 degrees away from firing as the crankshaft would have been in exactly the same position relative to the block with the drill in the crank web.
Before I set the timing plate I'd set the timing chains/crank position/camshaft positions to the book with cylinder bank 4,5,6 150 degrees 'behind' bank 1,2,3 (odd fire engine). Hopefully I did this setting correctly after helpful input from Martin Faulks via email at the time.
If you have any other observations John, they'd be welcome.

John

[johnb]

with cylinder bank 4,5,6 150 degrees 'behind' bank 1,2,3 (odd fire engine).
John

Just to qualify the above and be specific:
- with cylinder 6 150 degrees behind cylinder 1 for the firing stroke of each cylinder.

Thinking about it though, it wouldn't have mattered whether it was on the firing stroke or 360 degrees away from firing as the crankshaft would have been in exactly the same position relative to the block with the drill in the crank web.

Yes... Thats fine John,.... but...... I remember you saying that you had removed the distributor, therefore my next question is...... was the crank turned to the TDC of the firing stroke when you replaced the distributor by lining the rotor up with the mark on the distributor housing ?
If that checks out and you are comfortable that the crank and distributor are correctly aligned....... the next thing is.... with the two coils.... does your manual show which coil king lead goes to each of the distributor king lead inputs, and which coil 12v goes to each of the set of points..... as I am sure you know, any cross wiring in this area will lead to incorrect timing.

One other quick aside..... when trying to start the engine by the method I suggested, leave the twin choke buterflies at rest.... the car will fire and run on just the single choke carb.... by opening the twin buterflies at cranking speed, too much fuel could be sucked in causing flooding and most possibly the cause of your flashes of flame.

John

[johnb]

Yes... Thats fine John,.... but...... I remember you saying that you had removed the distributor, therefore my next question is...... was the crank turned to the TDC of the firing stroke when you replaced the distributor by lining the rotor up with the mark on the distributor housing ?
If that checks out and you are comfortable that the crank and distributor are correctly aligned....... the next thing is.... with the two coils.... does your manual show which coil king lead goes to each of the distributor king lead inputs, and which coil 12v goes to each of the set of points..... as I am sure you know, any cross wiring in this area will lead to incorrect timing.

One other quick aside..... when trying to start the engine by the method I suggested, leave the twin choke buterflies at rest.... the car will fire and run on just the single choke carb.... by opening the twin buterflies at cranking speed, too much fuel could be sucked in causing flooding and most possibly the cause of your flashes of flame.

Yes, the distributor was removed and new points fitted. The answers to your following questions are 'yes' to each point. However, these are the things I'm going to recheck in case I did, for example, cross the coil LT wires.

You're probably correct about the backfire because the inlet manifold was fairly wet with petrol (looking down the twin choke carb, just before the backfire. It was so short-lived it didn't do any damage.

Not the best of weather for working on the car at the moment because the car is on blocks, nose first into the garage. I have to work on it with the door open as there's insufficient room behind it to work with the door closed. Need a unit like clee.

When I was attempting the starts I had my camera recording video. These are two adjacent frames of the backfire. It was so short-lived it didn't do any damage.

You're probably correct about the backfire because the inlet manifold was fairly wet with petrol (looking down the twin choke carb, just before the backfire.

Wow !!!!! impressive pics..... good job you were not looking down the chokes when it actually backfired or you might be less your eyebrows now
Well clearly, all my queries have been addressed but there is some wrong adjustment/wiring/fitting somewhere for the type of problem you have. If you have any queries that you think I might be able to help you with when you are checking everything through, don't hesitate to make contact.
Good Luck
John

[johnb]

..... good job you were not looking down the chokes when it actually backfired or you might be less your eyebrows now

Fortunately, because the car is blocked up and high, it's a stretch to look down the carbs so that kept me at sufficient distance. I won't get any closer in future either.

When I brave the weather outside I'll come back with what I find. Hopefully it will be wiring/distributor position related and not timing chain related.

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Oooo nice flames John I know I said tune for maximum smoke, but ....