Warm engine won't restart...compression issue?

[Kurt]

I don't agree with your local "A4" guy about compression. You have lots of good suggestions here. If you can actually start your engine I can't in any way imagine how compression drops to such a low level after running under load for a bit as to cause a shut down. Check out the ideas floated here by the real "A4" guys.

[edwardc]

...A heat damaged coil will cause both shutdown and restart issues. A heat damaged coil will cause a shutdown when it warms up and the engine will not start until it cools down. This will usually occur in cycles. The shutdown cycle will become shorter as the damage progresses.

In Mr CR's case, it's possible that the coil is right on the edge of failing, and that the rise in temp that the engine experiences on shutdown (because there's no longer coolant flowing) further heats it enough to push it over the edge.

[Sony2000]

Yes he may have a weak coil, and giving it full throttle to start wouldn't hurt, and is worth a try.

[hanleyclifford]

Hello,
My rebuilt A4 runs like a top in all circumstances except the following: if she has been running for more than 20-30 minutes and I shut her down (at a fuel dock, for example) she will not restart for at least another 25 minutes or so.

I've posted about this here and also gotten some excellent support from Ken that has ruled out most of the simple stuff (fuel pump, no spark etc). The local "A4 guy" (Tony at Watanabe Marine) said that it is probably a compression issue and I should test the compression on the engine after running it.

This sounds plausible to me, interested in hearing anyone elses take on this.

This condition occurs more often than we think with engines that have oil pressure safety switches wired in the ignition circuit. The hot oil will not develop enough pressure at cranking speeds to close the switch. If you have such a switch try overriding it with a jumper.

[Dave Neptune]

Experience

Guys it is true that a warm engine should restart without the choke. But we are dealing with an updraft carb with no acceleration pump, like on the old carburated cars. Those engines had the carb on top and just a touch of the throttle squirts a shot of fuel DOWN into the manifold~easy start. Two strokes have an abundence of puddled fuel inside the crankcase so just a spin gets plenty to start. In fact when the outboards went to CD type ignition one of the big problems with a warm engine was that if you turned on the key and the crank position was on "throw a spark" the engine would quite often start without the starter engaging , when working as an OB mechanic I heard this a lot.

Now to an A-4 or any updraft carb set up. First there is no acceleration pump so a squirt of fuel is not going to happen. Yes there are fumes within the monifold but they are heavier than air and literally run out of the carb and when shut off a bit of the fuel being delivered falls back down inside the throat. Depending on how warm and how long of a shutdown this fuel will evaporate and gravity will take it away. When restarting an updraft it usually takes a few spins of the crank to get enough fuel lifted to get the engine lit!! Using the choke at this time is not really necessary unless you just like using the starter more. If you engage the choke when warm, it is a must that you disengage it as soon as it starts. It isn't really necessary just easier on the equipment. If you have an A-4 with a properly adjusted idle (lean enough) it should idle all day with no plug issues and be a bit hard to start when it has set a bit while warm! It's just the nature of an "updraft" configuration!!

Dave Neptune

[marthur]

+1 on Dave's post.

I have my mixture leaned out as much as possible consistent with smooth running. My motor will always fire on the first couple of compressions if I use choke and a touch of throttle. It generally doesn't start at all when cold without choke. When warm it will often grind for a number of revolutions before firing if I don't use choke. Sometimes it is a little hard to start without choke, even if warm.

I will also add that I have hand started my motor a number of times. I ALWAYS use choke when hand starting, even when the motor is warm. The choke makes sure that the motor does not have a too-lean condition and backfire. I have never flooded the motor when hand starting and I fear the handle kicking back and whacking my hands or arms. The old guys in my family (now all departed) all had stories about that sort of thing happening with their cars and tractors.

[sailbristol]

what carb do you have ? my old one was cast iron and would get so hot after shut down to cause vapor lock as in actually boil the gas in the fuel bowl. after switching to one of the newer alminium body carbs no more problem

[Mr. Close Reach]

UPDATE! No spark...maybe a coil issue?

Finally got the time to do some more detailed diagnosis here. Those of you who were suggesting a coil issue might be in the money.

I can now confirm that I'm getting no spark when I try to restart the warm engine. Absolutely none. I waited the usual 25 minutes and cranked it again - initially there was no spark but after maybe 2-3 seconds of cranking there was a spark and she fired right up (on 3 cylinders).

So is this maybe a coil or distributor issue? My I have the Pertronix ignitor in my distributor...not sure about the coil but I think it is what Moyer supplied on the rebuild (previous owner).

For the record, I also replaced my very old primary fuel filter/seperator, fuel lines, and in-line filter. And the Facet fuel pump is clicking away as soon as I turn on the ignition, so it's not an OPSS issue. Trying to eliminate as many variables here as possbile.

[Mo]

Coil and external resistor.

You need a coil. There were / are issue with coil overheating and dying a premature death with the pertronics EI. They require a resistor between the distributer and the coil. Ken at MMI will be able to sort that out for you.

Neil Dutton, Hanley Clifford, and Shawn have all gone into great lengths on this issue as well. There was a good read on it here in one of the threads but I forgot to save it. I sure someone will send you the link and steer you in the right direction for a resistor.

[hanleyclifford]

Finally got the time to do some more detailed diagnosis here. Those of you who were suggesting a coil issue might be in the money.

I can now confirm that I'm getting no spark when I try to restart the warm engine. Absolutely none. I waited the usual 25 minutes and cranked it again - initially there was no spark but after maybe 2-3 seconds of cranking there was a spark and she fired right up (on 3 cylinders).

So is this maybe a coil or distributor issue? My I have the Pertronix ignitor in my distributor...not sure about the coil but I think it is what Moyer supplied on the rebuild (previous owner).

For the record, I also replaced my very old primary fuel filter/seperator, fuel lines, and in-line filter. And the Facet fuel pump is clicking away as soon as I turn on the ignition, so it's not an OPSS issue. Trying to eliminate as many variables here as possbile.

If your electric fuel pump starts as soon as you turn the switch to "on", you have an error in your wiring. The pump should only work if you have oil pressure except while cranking if you have an override on the starter "R" terminal. Your engine may have the fuel pump bypassed from the OPSS, but not the coil positive.

[Marian Claire]

I believe this is the thread Mo is referring to, http://www.moyermarine.com/forums/sh...light=resistor
Dan S/V Marian Claire

[JOHN COOKSON]

Job#1: Be sure you have the correct coil with the correct amount of resistance for your EI as previously suggested.

Job #2: Are you getting power to the coil when the engine is in the shutdown mode? Check with a volt meter when shut down to be sure. There could be a wiring or switch problem you haven't found yet. On your boat is the coil wired in series or parallel with the OPSS? Normally the OPSS is wired in series with the coil with the coil first. As Hanley suggested maybe someone bypassed the OPSS because it wasn't working. This may be a "red herring" but it is easy to check.

TRUE GRIT

[nyvoyager]

if you find you still have the same problem after looking at the electrics: you may want to look again at fuel system
I went thru similar for a few years until i disassembled the entire fuel system. 1st it turned out to be a clogged fuel line from the tank. Then it was the sediment in the tank.
agree with Hanley's post: if your fuel pump starts when the ignition key is turned - you have a wiring issue. My boat did the same thing when i first purchased her. It was a modification made from mech to electric fuel pump "back in the day".... on City Island.
Wanntanabee.... we are likely be local to eachother.

[dvd]

Close Reach

I have had this coil issue and the way I first detected it after the engine began stalling out was to simply check the temperature of the coil by placing my hand on it. Be careful because if its the coil issue we are all talking about it will be pretty hot, but you should be able to carefully check its temp by touching it. In my case the coil was really hot and they only way I could get the engine to run again was to put ice on it. Not conventional but it worked until I could get a new coil. I would not have even thought of the coil if it hadn't been for this forum. Luckily I had still had the original coil and that seems to work fine.

Good Luck

dvd