12 A with carburettor won't start, what have I missed?sed?
12-03-23, 04:52 AM
#1
Junior Member
Thread Starter
12 A with carburettor won't start, what have I missed?
New water pump, new manifold gasket. new starter motor, new coils, breakers checked. nice sparks from the plugs, no compression faults. new rotary fuel pump (before it was a diaphragm pump on mine (?)). Well, battery is average but holds better with the new starter which makes the engine cranking faster. But, no way to start.
Well, to be exact, sometimes it starts. Then it works great. No smoke once it's warmed up, very stable idle, smooth and responsive engine... but I don't dare use it for any trip where I have to stop the engine, because I'm convinced it won't start again. What could the matter in your opinion?
Well, to be exact, sometimes it starts. Then it works great. No smoke once it's warmed up, very stable idle, smooth and responsive engine... but I don't dare use it for any trip where I have to stop the engine, because I'm convinced it won't start again. What could the matter in your opinion?
Last edited by IGRIDYX; 12-03-23 at 06:38 AM.
12-04-23, 03:48 PM
#3
Flooding?
When you're trying to start it and it won't fire up, pull the spark plugs and check if they're wet. If so, then it's getting flooded.
You didn't mention if you had replaced the spark plugs, plug wires, dist cap and rotor. If not, that's a good idea. Even if the spark *looks* strong when the plugs are out, that's no guarantee of the ability to generate spark when surrounded by compressed air/fuel mix.
But if it is flooding the best recommendation I can give is new battery cables. They're easy to make and don't cost a lot, but they make a HUGE difference in cranking speed. Cranking at 300rpm after new battery cables I never have flooding issues. Cranking at 250rpm or lower on the stock cables and I'd occasionally have starting issues.
The stock cables tend to corrode inside over time, and they weren't exactly oversized to begin with. Go a size larger, copper cables and connectors. Have the battery tested.
If your cranking speed is good and your ignition is strong you should have a MUCH easier time starting. The only other thing I could think of, but only after you've done the above, is some kind of carb issue.
If the plugs are never wet, then maybe you have the opposite problem from flooding - maybe your carb's accelerator pump isn't working well. So when you pump the gas pedal a few times before/during starting you don't get the squirt of gas that helps it catch and get going. Grab a carb rebuild kit and the carb manual off foxed.ca. Don't adjust the floats (they're factory set and it's a royal pain to get them back to the right spot if you change them) and reuse the stock needles and seats since the ones in the rebuild kits are notorious for being shitty and sticking.
Good luck!
Jon
When you're trying to start it and it won't fire up, pull the spark plugs and check if they're wet. If so, then it's getting flooded.
You didn't mention if you had replaced the spark plugs, plug wires, dist cap and rotor. If not, that's a good idea. Even if the spark *looks* strong when the plugs are out, that's no guarantee of the ability to generate spark when surrounded by compressed air/fuel mix.
But if it is flooding the best recommendation I can give is new battery cables. They're easy to make and don't cost a lot, but they make a HUGE difference in cranking speed. Cranking at 300rpm after new battery cables I never have flooding issues. Cranking at 250rpm or lower on the stock cables and I'd occasionally have starting issues.
The stock cables tend to corrode inside over time, and they weren't exactly oversized to begin with. Go a size larger, copper cables and connectors. Have the battery tested.
If your cranking speed is good and your ignition is strong you should have a MUCH easier time starting. The only other thing I could think of, but only after you've done the above, is some kind of carb issue.
If the plugs are never wet, then maybe you have the opposite problem from flooding - maybe your carb's accelerator pump isn't working well. So when you pump the gas pedal a few times before/during starting you don't get the squirt of gas that helps it catch and get going. Grab a carb rebuild kit and the carb manual off foxed.ca. Don't adjust the floats (they're factory set and it's a royal pain to get them back to the right spot if you change them) and reuse the stock needles and seats since the ones in the rebuild kits are notorious for being shitty and sticking.
Good luck!
Jon
12-04-23, 05:14 PM
#4
That's a good point. There's no easy way to check the water seals without opening up the engine but if it blows white smoke on startup and you have to keep topping up the coolant those can be signs that one of your water jacket o-rings is blown and leaking into the combustion chamber. That is possible but in my mind it's not quite as likely as the other stuff, and since it would take a full engine rebuild to fix you might as well try all the other stuff first.
12-04-23, 05:35 PM
#5
You can check the coolant seal with this tester. https://www.pineappleracing.com/cool...estercspt.aspx. You'll' need to remove the water pump housing and exhaust manifold. You're checking if water is making into the combustion chamber. I'd only check if there was a visible issue like sweet coolant smell/white smoke in the exhaust or the rad getting pressurized and being push through the overflow. Otherwise, I would not bother.
12-04-23, 07:47 PM
#6
That's a good point. There's no easy way to check the water seals without opening up the engine but if it blows white smoke on startup and you have to keep topping up the coolant those can be signs that one of your water jacket o-rings is blown and leaking into the combustion chamber. That is possible but in my mind it's not quite as likely as the other stuff, and since it would take a full engine rebuild to fix you might as well try all the other stuff first.
as for the likelihood of it being the water seals, you're probably right. there are probably other things that are more likely. however, i saw this part:
sometimes it starts. Then it works great. No smoke once it's warmed up, very stable idle, smooth and responsive engine... but I don't dare use it for any trip where I have to stop the engine, because I'm convinced it won't start again.
and it immediately brought me back to a time when i had to drive around on a bad coolant seal. it was pretty much just like he described. the only piece really missing is having to add coolant every few days. i also don't really remember mine smoking too much, but it may have. it was a long time ago.
so i threw it out there. if i'm right, great (not really great for him), and if i'm wrong, even better.
12-10-23, 02:21 AM
#7
Junior Member
Thread Starter
But I have no over-pressurized radiator, no coolant smell nor white smoke at exhaust. Plugs are not wet, but the thing drains my battery high speed. Sometimes starter turns fast, other times lower. I don't know where to point the issue. Could it come from some wiring? (My plugs connectors are as old as the engine)
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