Engine won't restart after running for awhile

[Mr. Close Reach]

This has been a consistent problem with my A4. It's a Moyer rebuild (via previous owner) that runs like a champ in all other respsects.

The typical scenario is I motor 30 minutes or so into the fuel dock, pumpout etc, then shut her down for 5-10 minutes, then try to restart to be on my way. She'll turn over just fine but never starts. I've tried opening the throttle all the way, thinking maybe it wasn't getting enough something but that doesn't seem to do it. If I only run the engine for 5 - 10 minutes it doesn't seem to be a problem.

After a certain amount of time it will finally start right up and run fine again. Any ideas?

[hanleyclifford]

Have a look at your points. Are they clean? Check the gap to be between .018 - .020, maybe a little more if you have a Delco. Check dwell next time the engine is running.

[David Masury]

I think that it may be as simple as a new coil or condensor.... heat and time make of those weak and will fail after a 30 minute run

David

[domagami]

Coil or...?

I'm curious about this one too.

Two questions about conditions:

1) Do you have this problem after running only 5 minutes? 10 minutes? Or is it always after running for 30 minutes?

I would think that after you get it up to temperature (10 minutes), it won't matter if it's 10 minutes or 110 minutes. True?


2) How long can you run the engine? That is, will it fail on it's own after an hour? Or is it only in trying a restart?

[Mr. Close Reach]

Thanks guys.
To clarify, it will run continuously for as long as I want it to - hours and hours. It's just the restart that is a problem. And yes 10 minutes seems to be about the magic number. Once it has run that long, it is difficult to restart. Less than 10 minutes and it's not a problem.

I'll check the points, probably time for new spark plugs anyway.

[Marian Claire]

Do you run your fan when the engine is running? Long shot here but could the coil stay cool enough to work when underway but when the engine is shut down, no natural air flow, no fan, no water flow. I realize the engine is not getting any hotter but maybe the heat is just migrating to all parts of the engine compartment, coil etc. FWIW. Dan S/V Marian Claire

[jacques debauche]

No restart

The next time this happens, pull the lowest sparkplug (#4) and see if it has water on it. I had the same symptoms as you are experiencing, and it turned out that water was getting into the manifold after the engine was at low idle (e.g. approaching a dock). There evidently wasn't enough exhaust pressure at low rpm's to lift the cooling water from the lift box to above sea level, and on shut-down water flowed back into the manifold. If I shut down immediately after high rpm's there was no trouble restarting. Replumbing the exhaust system so that water was injected into the exhaust after the exhaust had been brought above sea level cured the problem.

[breweraz]

similar experience

When the motor will not start, pull the lead wire off the coil, hold it about a 1/4 inch from the top of the coil and try turning the motor over. You should be able to arc a sparc. If no spark than I sugest the following:

There are three things I ended up replacing, but in my case, one at a time so it was frustrating. If I ever have the problem again it will be all three.

Assuming you have a points system:

1 . Replace the coil - if you go to a parts store, as opposed to ordering through Moyer make sure you look closely at the specs. The coil must be a 3 ohm resitantce or more. There is a popular coil used in older tractors that looks very similar. The parts store guy looked at my coil, grab one off the shelf and told me 'this was it" . It looked similar but was only a 1.5 resistance. That coil will run for a little while, heat up and stall the engine proably burn out more if I tried to run it any longer.

2. Replace the condenser. If you were going to pick a starting point and only do 1 item it would be the condenser. When the coil is going bad it ususlly only runs till hot and quickly gets worst to the point it will not start at all. But since each condition and motor is different there are no absolutes.

3. Check all your wires off the coil especialy the wire from the neagtive terminal of the coil to the distributor. In my case the wire from the coil to the distributor looked good from the outside but at the connector was broken down to the last few strands.

After getting the right coil, back to the store for a condenser and the last run to get the right connectors, she has run great. None of these parts are difficult to change and not very expensive. So go for it all at once and save yourself some grief.

I know the frustrating feeling when you do not have confidence in the motor. But I can tell you when the A4 is dialed in it is a great motor.

Tim

Tim

[domagami]

1,2,3

Agree with Tim's excellent post.

(And that little wire off the negative of the coil is easy to overlook, but don't)

Please do provide an update to this one when you sort it out.

[perchance]

hot restart

I am wondering if it could be vapour lock. In an enclosed engine compartment the temperature can rise due to heat soak causing vapour lock especially if your fuel lines run a long distance and are on the small side. A high ambient temperature makes it worse.

[tenders]

Vapor lock is theoretically possible I suppose but I have never once seen an A4 problem that ended up being vapor lock. I doubt this will be the first one -- the A4 doesn't get hot enough under normal circumstances, and certainly in the circumstances we know about this case, to vaporize fuel in the lines and the carb preventing the carb from doing its job with liquid fuel.

[rheaton]

My engine wont start if warm, and choked, even slightly. You might want to just verify your choke is off, and adjusted correctly.

[ArtJ]

This sounds somewhat like a fuel related shutdown due to a leak or
problem with the fuel delivery or pump or vent.
Check numerous postings for further details.
Do you have a outboard type rubber bulb installed in your fuel line?
If so, try pumping it. Also possible air getting in fuel line.

try bleeding fuel line at carburetor via main jet passage plug.

Could also be clogged fuel filters.

[Mr. Close Reach]

thanks for the tips

Ok thanks, I hope to find some time to check these suggestions over the weekend. I'll post an update!