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  #1   IP: 108.6.52.2
Old 08-23-2012, 01:22 PM
Mr. Close Reach Mr. Close Reach is offline
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Warm engine won't restart...compression issue?

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.
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Old 08-23-2012, 01:53 PM
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Could very well be. If she has spark and fuel and is getting air it should go. The only thing left really is compression. So I would get a gauge and check the compression. I would think, however, that if it starts cold it should start warm as well. Others may have more to add.

Do you have lots of power when driving the boat? Will she do hull speed or do you notice the engine revs just don't come up?? Typically, if she has lots of power under load she has the ability to put out some horse power...that would suggest that she does have some compression. Certainly worth a check and then you know.

All that said, I be making sure there's a nice blue spark from the wire when checking fire...if not, it could be coil or something else in the ignition system.
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Last edited by Mo; 08-23-2012 at 01:55 PM.
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Old 08-23-2012, 01:56 PM
Dave Neptune Dave Neptune is offline
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Question ?

Mr, are you using the choke when trying to restart warm? How is the idle, smooth, rough surging etc? What temp does the engine run at?
From your post I asume you did check for spark(??).

Dave Neptune
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Old 08-23-2012, 02:17 PM
Mr. Close Reach Mr. Close Reach is offline
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Thanks guys. Yes the power seems fine, no problem to get the engine to hull speed assuming a clean bottom/prop.

I will check the spark again today, it was strong last season (I've had this problem for years) but probably worth another look. Yes I do re-start with full choke, to no avail. The engine seems to run cool - plenty of cooling water (that comes out hot). Can't remember the temp I usually see but will take another look at that as well.
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Old 08-23-2012, 02:22 PM
JOHN COOKSON JOHN COOKSON is offline
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2 Questions

Does the engine ever shut down while it is running perhaps longer than 20-30 minutes?
Or does it just not start when you turn it off after running when it is well warmed up?

TRUE GRIT
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Old 08-23-2012, 02:27 PM
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Sounding a lot like the overheating coil problem.

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Old 08-23-2012, 02:38 PM
Mr. Close Reach Mr. Close Reach is offline
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John - no, except yes. The previous three seasons it never shut down on me, whether I was running it 20 minutes or 4 hours. However, this seaon it has shut down on me twice. Once after running for just a few minutes (in that case I was able to start it right back up) and one after running for ~25 minutes, woud not restart that time.

67, that occured to me but wouldn't that cause a shut-down, rather than just a restart issue?
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Old 08-23-2012, 02:45 PM
Dave Neptune Dave Neptune is offline
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Lightbulb Checks

Mr, time to possibly look at the ign switch itself. Next time it occurs check spark immediatly and then run a "hot wire" to the + side of the coil and check again or do a voltage reading at that terminal. Coils are usually a bit consistant time wise regardoing intermitant failure if comporimised but the switch can screw up anytime and even supply a weak voltage.

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Old 08-23-2012, 06:41 PM
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This caught my attention:
Quote:
Originally Posted by Mr. Close Reach View Post
Yes I do re-start with full choke, to no avail.
I don't need any choke restarting a warm engine. In fact, every engine I've ever had in my life didn't need choke when restarting warm. That covers any manual choke gasoline engine you can imagine - inboards, outboards, lawn mowers, generators, motorcycles, chain saws, weed whackers, you name it.

Using choke in these cases virtually guaranteed a [fuel] flooded condition.
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Old 08-23-2012, 11:38 PM
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Lightbulb

Mr. CR..I am with Neil...and I've had trouble here too...with a warm A-4, choke does not help it start...if the engine is off for 20 mins (fuel dock/pumpout etc.) if I apply choke (out of habit) it will not start.

I find that leaving the throttle at idle and no choke and just spinning the starter, and she magically fires.
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Last edited by sastanley; 08-23-2012 at 11:40 PM.
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Old 08-24-2012, 08:28 AM
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I also agree,as my engine starts without choke after an initial warm up and will continue to do so for up to 2 hours or so unless air/water temp is very cold .
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Old 08-24-2012, 10:10 AM
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Sometimes when my motor is warm it takes some throttle to get it to fire.
Seems like the warm manifold maybe warms the carb body and causes it to spill some fuel or vapor and makes a rich condition that needs some extra air to fire.
(This is not always needed, but noticed it on the hot days of this past July)
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Old 08-24-2012, 10:27 AM
Mr. Close Reach Mr. Close Reach is offline
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Thanks; I have tried every permutation of choke/no choke/throttle/no throttle.

Hoping to check the compression this weekend.
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Old 08-24-2012, 12:15 PM
JOHN COOKSON JOHN COOKSON is offline
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A Momentary Digression

Quote:
Originally Posted by Ball Racing View Post
Sometimes when my motor is warm it takes some throttle to get it to fire.
Seems like the warm manifold maybe warms the carb body and causes it to spill some fuel or vapor and makes a rich condition that needs some extra air to fire.
(This is not always needed, but noticed it on the hot days of this past July)
+1 on this.
I've noticed the same thing - the warmer the weather the less choke I need to start the engine. This is true when the engine is warm or cold. Maybe this is because gasoline is more volatile at warmer temperatures???

Side note to Mr.CR R\E post #7 last sentence:
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.

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Old 08-24-2012, 12:23 PM
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Another option is to close the valve on the gas tank when you think you might have difficulty restarting the engine. Then reopen it, just after the engine restarts.
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Old 08-24-2012, 01:55 PM
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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.

Last edited by Kurt; 08-24-2012 at 05:06 PM.
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Old 08-24-2012, 04:11 PM
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Quote:
Originally Posted by JOHN COOKSON View Post
...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.
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Old 08-24-2012, 06:51 PM
Sony2000 Sony2000 is offline
 
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Yes he may have a weak coil, and giving it full throttle to start wouldn't hurt, and is worth a try.
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  #19   IP: 107.0.6.242
Old 08-24-2012, 11:11 PM
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Quote:
Originally Posted by Mr. Close Reach View Post
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.
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Old 08-25-2012, 12:42 PM
Dave Neptune Dave Neptune is offline
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Lightbulb 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
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Old 08-25-2012, 03:13 PM
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+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.

Last edited by marthur; 08-25-2012 at 03:22 PM.
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Old 08-25-2012, 03:34 PM
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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
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Old 10-14-2012, 11:05 PM
Mr. Close Reach Mr. Close Reach is offline
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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.
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Old 10-15-2012, 12:27 AM
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Smile 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.
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Old 10-15-2012, 01:21 AM
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Quote:
Originally Posted by Mr. Close Reach View Post
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.
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