A4 Runs fine for hours then gets rough

[Marian Claire]

Cool. I have anchored in Smith and Greens Cr many times. Sending E-mail. Dan S/V Marian Claire

[hanleyclifford]

Happy memories of Smith and Green Creeks - I see a future RV on the horizon...

[Marian Claire]

Hanley aboard Destiny leaving the raft up on Smith Cr. April 2012. http://neuseriversailors.com/photogr...r_041412_1.jpg
He then spent the following week helping PT 26 install a "new" A-4.
Dan S/V Marian Claire

[Dave Neptune]

Loose plugs

John, a loose plug or plugs can give enough resistance to interfere with the "spark". this can cause a weak fire in the cylinder and sooting up at idle or mid ranges would be an indicator of a weak spark at the tip! It could also be timing and a carb running to rich.

It all works together!!!!!

Dave Neptune

[jkenan]

OK, so here's a photo of the brand new plugs with about 1 hr run time on them (lined up cylinder #1 - #4 left to right).

I cleaned the plug seats, and no smoke was seen coming from #1, but it is interesting that #1 is still the sootiest. Engine temp ran at 140 for about 5 minutes under load before it got up to 180, and stayed there until I killed the engine for a sail yesterday. Then I started up and motored back for about another 1/2 hour, with same temp curve.

I also checked voltage, at the coil + terminal (this coil is new, and has an external ballast resistor), and it was around 7V which is what it should be with the external resistor.

I think I definitely have rich fuel mixture here. Choke seems to be working properly. Time to install the adjustable carb? What else could be causing sooty plugs?

BTW, thank you all for your interest here. I really appreciate it!

[sousou]

Only chiming in hear to say that you're not alone. A few months ago I went on a shakedown run and several hours into the trip, the A4 started 'stumbling' as you described. Even after shutting it off for thirty minutes the problem persisted. After 10 or so minutes (and lots of throttle adjustment) it eventually cleared up and I was able to motor home.

My fuel pump died a few weeks later, but I'm not sure if the two were related. It seemed like something was sticking as you originally suggested.

I haven't had a chance to go on a long run after replacing the fuel pump, but I'll report back since you're holed up for the rest of winter.

[hanleyclifford]

The7 volt figure for coil+ is highly suspect. The A4 cannot run below about 9 volts.

[jkenan]

Hanley- I'll call Tom at Indigo tomorrow and ask about this. I seem to recall that he advised when I purchased the coil w/external ballast resistor that it would regulate voltage around 7V or so, controlling coil temperature and therefore premature coil burn-out. I don't disagree with what you are saying. I'll let you know how that conversation goes.

Also worth mentioning that the problem presented itself with an older coil that had been in service for a few years with no external resistor. I did not check voltage at coil +, but upon inspection, there were many hairline cracks in the plastic top of the coil, which was suspect. The replacement coil from Indigo did not resolve the issue.

[67c&ccorv]

A weak spark can well be the cause of "sooty plugs"...I would check that ballast resistor/coil combo like Hanley said.

[ndutton]

Hanley and 67 are all over this. Previous testing on a running engine with a variable resistor ahead of a generic coil showed engine performance dropped off noticeably when the coil input voltage dipped below 9 volts.

Your source of information on an Indigo (or anyone else's) product should be Indigo themselves but I will comment that I've always felt their resistor product was on the aggressive side and in an attempt to offer a one size fits all product (understandable) they ignore variations from boat to boat in system voltage and internal coil resistance if the coil involved is not one of theirs. Both of these values are important for a well balanced ignition system.

Like Hanley said, the 7 volt number is a concern. Looking forward to reading Indigo's response.

[JOHN COOKSON]

$0.02 Worth

Maybe the wire to spark plug #1 is not conducting properly and\or the end connectors are not working properly which is resulting in misfires or weak firing of the plug. Also are there issues inside the distributor cap?

As far as the shutdowns go, since you feel it might be electrical (post #1), try bypassing the boats wiring by running a jumper from the large cable on the back of the starter to coil + and see if the shutdowns go away.

TRUE GRIT

[jkenan]

I spoke to Tom at Indigo, and he corrected my recollection on the voltage of the coil at the + terminal downstream of the ballast resistor - he said it should be at least 10V if also running electric fuel pump and EI, which I am running. He also reinforced a concern brought up by many of you here, which is that I am suffering significant voltage drop somewhere in the circuit, and as the engine runs for a while, the engine box builds heat, and the wires themselves increase heat, the snowball effect kicks in which may explain the poor performance after running fine for a while. So my next foray into this beast of an issue will be to re-run wiring, look at ignition switch, etc, until I see at least 10V at the coil + terminal (and then continue to inspect the rest of the wiring & connections just to be sure).

Won't be until March that I'm back down. Thanks everyone (and Tom) for your feedback. Will continue to check for further posts in the meantime, and look for a thorough update from me then!

Best regards to all.

[Michael Edwards]

Hey John,
we are just a little north of you on Jordan Creek, near Belhaven, NC.
Look at your ground wire conections too.
Two things caused problems on AnnaDor, were a loose crimp connector and old rusty bolts on the the transmission that were used for ground connections. I replaced the cover plate bolts with stainless steel and discovered the bad crimp was my problem(a faulty ground).
I also agree that sediment in the fuel tank can get stirred up. We had the engine stall in a storm on the Albermarl Sound after taking down the sails and were motoring to Edenton, when silence ... from the Atomic Bomb...it started up...ran for a while then died again... and again...
In short all of this points to "Touch Erverything in the system".
The fuel pump hasn't been mentioned.
Like you, we have many Indigo Electronics products, that have truly improved our experince with the A4, but clean fuel and good connections have proven to be of upmost import.
Our motor runs great! But.....its always a concern.

[hanleyclifford]

Clean fuel is indeed "of the utmost importance" and it only happens when we take a proactive approach now that we are consigned to live with ethanol which as John mentioned on the other thread is cleaning our fuel tanks and depositing the contents in our carbs, if we let it. If you can empty a tank and clean it that is first prize but even if you do a serious filtering system should be planned and implemented.

[HalcyonS]

So ethanol and additives are here to stay. And they will foul the carb, it seems. And afaik, they are dissolved so they don't filter out.
So what are we to do?