C

Colthebrummie

Well-Known Member
I don't know if I'm going senile or what but I can't get Compo to start. It's been parked up for about 4 weeks and it was fine last time I used it. I've had the battery out and on charge but now Ive put it back it refuses to fire. It turns over a treat but won't fire so I checked for a spark, nothing, changed the lead, nothing, changed the coil, nothing. A year or two back I replaced the points with an electronic module, so my suspicions rested on that. At least with the old points they would let you know when there was a problem but I imagine an electronic module just fails without warning so I thought about buying a new one but for the extra cost I decided to buy a whole new electronic distributer instead. I've just fitted it and the b@stard still won't start. There is now a faint spark at the plug, not very impressive at all but even a weak spark should make it want to start. I've removed the air filter and dribbled some petrol down the throat of the carb but still nothing. There is petrol visible in the fuel filter. I know the timing will be a bit out but not enough to make it not at least cough. What else is there to try other than stripping the carb. Carbs just don't stop working when they have been perfectly good. 40 odd years of tinkering and this makes me feel like an idiot. Help!

Col
 
rob1miles said:
Try a good 12v supply to the live side of the coil.
Click to expand...
I measured the volts at the + side of the coil with the ignition on and got the same as the battery, 12.5 volts. Although I will hot wire the coil in the morning, I'm running out of ideas, I don't want to take the top off the carb unless it's a last resort.

Col
 
swisstoe said:
What carb is it Col ?
Click to expand...
Zenith, it's the original carb. It's been running as sweet as a nut until now, newish filter, petrol seems to be getting as far as the filter. There is no smell of petrol though, you'd think there would be after several spins of the starter with full choke and blipping the throttle. I haven't had any of the spark plugs out yet to see if they are wet, I'll do that tomorrow.

Col
 
Colthebrummie said:
Zenith, it's the original carb. It's been running as sweet as a nut until now, newish filter, petrol seems to be getting as far as the filter. There is no smell of petrol though, you'd think there would be after several spins of the starter with full choke and blipping the throttle. I haven't had any of the spark plugs out yet to see if they are wet, I'll do that tomorrow.

Col
Click to expand...
Dirty fuel line causing blockage. Try removing in line from carb and fill a small empty water bottle with the fuel as you kick start. If okay reattach then try from return line to the tank.
 
saxavordian said:
Dirty fuel line causing blockage. Try removing in line from carb and fill a small empty water bottle with the fuel as you kick start. If okay reattach then try from return line to the tank.
Click to expand...
The transparent fuel filter is literally 2 inches from the carb with fuel in it, so I'm confident fuel is getting to the carb.
Mingus said:
Check your coil....could be fubar if a weak spark....oh and engine earth strap
Click to expand...
The coil is only about a year old and the spare is about the same. I bought a new Accuspark coil when I fitted the electronic ignition module, the leads are also relatively new. The earth strap is worth exploring, although the starter spins really well. The weak spark might be due to the quality of the plug I was using to test it, it was an old one I found lying about, also it might not have been getting a good earth where I was holding it whilst the missus turned the engine over. The only thing I can think of is a blocked carb jet, I hate mucking about with carbs, it never goes well for me.

Col
 
A bit of petrol down the throat and it would have fired if it were just a carb problem. Get a good plug on a lead [ one from the engine is fine ] and recheck that spark.
 
Trick I have used to great effect over the years to prove if the High tension side is working,
Take of the Distribution cap clips and turn the cap up, put the rotor arm on your finger and inside the cap and get some one to spin it over,
Straight away :) you will know if you have a faulty rotor arm, you should see if their is any tracking inside the cap and the strength of the HT spark, it’s shockingly simple and quick to do but will show up any problems with your spark,
Putting fuel straight down the carb throat eliminate fuel starvation so you are left with wet plugs or low compression that’s unlikely as it was running a few week back,
 
since it could still be fuel or electics there's only a few thigns you can try:
12v hot wire to coil as it could be low voltage due to dirty connections
Fuel down the carb to see if it fires, if you can keep it running like this then rev it and put your hand over the carb for an instant, it can pull the dirt through and save time. alternative is to loosen the dizzy and turn it back anf forth to make it spit back and blow the dirt out the jet, mark the timeing first!
Take the HT leads, cap and arm off and leave them in a low oven for an hour.
Try all at once since you may have 3 faults!
 
One more thing...had a brush cutter with 1 year old petrol which wouldnt start, fuel had gone stale, drained the tank and new fuel started first pull.....how olds the fuel in the tank?
 
I've got it going. I rechecked all the HT side of things and everything seemed ok so I turned my attention back to the fuel. Yesterday, I dribbled some petrol into the carb but it didn't have any affect, I tried the same today but still nothing. I disconnected the fuel pipe from the carb and put it into a glass jar to pull some petrol through to repeat the petrol in throat trick but when I spun it over, no petrol came through. I have a second fuel tank under the driver seat so I switched the supply to that and plenty of petrol came out. I know there was plenty of petrol in the back tank when I last used it and the guage is reading a quarter of a tank but when I dipped it there was nothing in it so either I have a leak, which I doubt cos I'd notice a puddle underneath, or some scrote has syphoned the fuel out, I don't have a locking cap. I now need to get a Jerry can of petrol to put in the back tank to see if there is a problem with it. Thanks for all your suggestions, it helps knowing people are offering help.

Col
 
Nice one...and other than lost fuel and getting a lock a cheap fix....i once couldn't get a series 2a petrol started for hours until i noticed i'd disconnected the fuel cut off switch...doh!
 
Well at least you now know the problem and a small petrol leak can evaporate over time leaving no trace. Cheers, John.
 
But :) if he had put in a cap full off fuel down the carburettor Venturi at the start he could have saved himself a lot of work and hassle,
 
That’s crap, I have been in the motor trade 50 years and never once had a blowback fire wise of any significant,
Every time you press the throttle down you are injecting a squirt of petrol,
 
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