Engine starting problem

[MikeJenkins]

Hi folks,

I'm looking for some advice. My atomic 4 ran fine last week, but 3 days later it doesn't start at all not even asputter I have checked feul and seen it pumping into jar at carburator. I remoovded and cleaned out new carburator. There were no obvious fuel delivery problems and I have fresh gasoline this season.

I have spark from the coil to ground of about 1/4" to maybe up to 1/2". I also see a spark at each pulg when removed and held to block. I have tried lots of battery power. I do have an Indigo electronic ignition and note that LED on electronics module is not on even though I get a spark.

I checked compression in each cylinder, all were above 90 psi. I plan to check timing and distributor tomorrow any other ideas will be helpful

Thanks and regards

Mike

[rewell6]

Since you have a gas engine just make sure not a lot of gas fumes are nearby when performing the spark test.

How old is the engine? How many hours? How good was the maintenance?

Step 1 - fuel - Are you sure fuel is leaving the carb into the engine. If you move the throttle does a little gas squirt out into the carb? If you can't take the throttle cable loose and open the throttle you will need someone to open the throttle for you while you look in the carb with a flashlight. You should hear and see a little squirt of fuel. If you see a little fuel squirt out skip the next step.

Step 2 - I bet it's fuel related.
I would do this before checking the timing. To test this you could put some fuel in the carb, just about a tablespoon full. Just drop it in the carb, put the spark arrestor back and try to crank. If it tries to crank just a little then your problem is in the carb. Stuck float or needle, maybe a bad accelerator pump (part of the carb).

Step 3 - spark You already checked the spark at the plugs so that's not the problem. Could be a bad rotor (in the dist) or a bad dist cap. A crack (you probably wouldn't be able to see it) in the cap or rotor would cause problems. Could be the electronic module has gone bad. Did the LED come on before?

Step 4 - You can check the timing but unless the timing chain broke that's not going to be the problem. Engines don't usually die like that. Extremes would be a cracked crank or cam, but I bet it's not that either.

[MikeJenkins]

I think the problem is solved. Thanks for your help "Rewell16" or others responding to this post. I did work on the fuel side for a while even to point of putting a littkle gasoline in each clylinder. I checked timing and then replaced coil. The engine fired up with the new coil. I tested spark with new coil and a blue spark for over 1/2" was noted. The former coil produced only a yellowspark less than 1/2". In future I will know that the health of the spark is important.

Regards,

Mike

[NOLAsailing]

The electronic ignition in the A4 is very tough on the coils. Although the electronic ignition is a worthwhile upgrade, try keeping a spare coil along with your other spare engine parts. When I had an A4, I went through a couple coils a year.

[Twoowls]

Your local auto store has some relatively inexpensive high output oil filled coils that should last for years. The Indigo system has nothing to do with coil life.
The coil fires the same number of times regardless of the trigger system. Look for a good name brand racing coil.

[TommyD]

Any PNs for that racing coil? I have a similar problem & have a spare Indigo sourced coil I didn't think of putting on. I always wanted a replacement on hand .. just have to *think* to put t on. Was convinced also it was fuel.

TD

[Twoowls]

Mallory, Crane and others make really good multi-spark racing coils. No boat engine will ever tax these coils. We run at 10,000 RPM at 14 to 1 compression and they do not fail. No Atomic 4 will reach these numbers. Of course if you use nitro, boost the compression to 14:1, who knows....

[TommyD]

Replaced my coil & I still am trying to get a reliable start. The best I can do is to pour gas into the carb, which works. It's been suggested I either have a poor diaphragm in my fuel pump (electric, 3 yrs old) or I am getting air into the fuel lines & need suction from the running engine to actually draw gas thru the pump. Anyone with similar experiences? I will try tightening all my lines / clamps, bring some spare hose with me before I buy a new pump.

TD

[cardiacpaul]

Tommy,
the A-4 is a simple engine.
Even with the electronic ign. system, you don't need a really high perf. coil. you have a 4 cyl engine, not a v-8, hence, "coil soak time" is not a problem, heat, however is.
Any decent 12 volt internally ballasted coil will work just fine.

from your problem description, and temporary solve(pouring gas in the carb) its fuel related.
Check these things.

Float bowl and needle valve operation. It might be a good time to rebuild the carb. dribbling some gas into the breather keeps fuel flowing, allowing the engine to run, but if you stop, so does the motor. That says fuel supply which is controlled by...
a) fuel pump and pressure. you need about 4 lbs of pressure to keep the gas flowing. thats not a lot.
b) float bowl and needle valve sticking in closed position (or set too low)

Gas is not sucked up into motor by vacuum UNTIL it hits the bowl in the carb. Its pushed to the needle valve by the pump. The float regulates the level of fuel in the bowl via the needle valve. If the needle valve is stuck closed, then no fuel gets to the bowl. (this isn't very common, the fuel pressure "should" be enough to overcome that.)

It may be the gasket between the carb and the intake, but that rarely is the problem, I'd hazard a guess on fuel supply to the carb or the carb being full of gunga munga. (technical term)

DO NOT confuse the nedle valve in the bowl with the "idle" needle screw on some carbs, they're two different things.