A4 Runs fine for hours then gets rough

[jkenan]

I've been following other posts here on similar issues of rough running, and think there is some great feedback/responses here. My issue seems unique (at least in posts I've found) since the engine runs strong for a substantial period - a couple of hours at least - and then starts to run rough with misfiring, rough running, and even stalling on occasion. I can always restart the engine after stalling, and sometimes it runs great after restarting, but not always. And the symptoms always come back, eventually. This issue has persisted for years, and I have not been able to resolve it regardless of any measure I take.

Some background: Late model A4, completely rebuilt in 2006 with most upgrades from Moyer (and some from Indigo) - FWC, Ignitor EI, Facet Electric fuel pump, crankcase ventilator, and this year new wires, plugs, rotor and EI cap. Also added a new coil with ballast resistor from Indigo. I have zero overheating issues - the engine runs consistently at 180 degrees. I have cleaned the carb, but really found no issue there. During the latest episode this past weekend, I suspected the flame arrestor (the circular one Moyer used to sell but don't see it available currently) may have become too clogged with crankcase vapor so I 'loosened' it thinking air intake was the issue (even tried running the engine with the compartment cover off), but still no improvement. I use ethanol free gas, with appropriate MMO added.

Some things I have not done (and now that I'm home and three hours away from the boat I realize I should have done): Replaced Racor Fuel filter (2 years old now), drained water from racer filter, replaced inline fuel filter between fuel pump and carb.

My gut tells me it is an electrical issue, but what is causing it eludes me. It also feels like it could be sticking valves (but why stick after 2 hours of running fine?) or water in the fuel (but why would water get introduced after 2 hours of running fine?). Why would it run fine for hours, well beyond the engine/compartment coming up to temp, and then run badly? I also feel it could be a temp issue, where some electrical component becomes compromised after enough exposure to a 180 degree engine. Could a compromised wire/connection/component run fine for a while, but become compromised after a couple hours exposure to an engine running at 180 (that's why I replaced the coil, and am tempted to replace the EI too, but already too much $$$)? I'm at a loss, and would appreciate any feedback.

Thanks in advance,

John

[ndutton]

Two thoughts John

. . . and they are unrelated.

Have you replaced the wiring harness? I know you said new wires but I interpreted it as spark plug wires. If the harness has not been replaced, it's at least 30 years old with the possibility of any variety of corrosion/high resistance/poor connection problems.

Try running next time with the deck fill cap removed (maybe compromised tank vent).

[tenders]

How's your oil pressure when the engine gets good and warm?

A guess: your oil pressure switch gets flaky when the engine gets hot and the oil pressure gets lower, erratically starving the engine of fuel.

[Dave Neptune]

Agree

j, Neil & tenders hit on a couple of possibilities. I'd have a jumper wire ready to "hot wire" the ignition next time this "missing~rough running" happens. If you clip it on and the engine smooths out it's the wiring and or possibly the OPSS. You can check for voltage at the resistor for proper voltage while running as well. If you see fluctuations it's the wiring.

I doubt it is fuel or carb related from your info so far.

Dave Neptune

[jkenan]

Thanks for the replies - I think these are all good suggestions.

The wiring harness is only a few years old. I did a total refit on the boat back in '08-'09, and replaced all electrical. I didn't use Ancor wire, but a less-expensive wire I found online at bestboatwire.com. All tinned wire, and manufactured to same specs as ancor. Terminals all still look good, so don't think that is it. The EI is almost 10 years old now, so perhaps the wires there are beginning to short out? The cap and rotor are brand new. I will definitely try the jumper when it starts acting up again - great suggestion.

Oil pressure is solid, and has been. I hate to admit it, but I have bypassed my OPSS, so fuel pump is running directly from the coil. If jumper corrects running performance, then it is definitely wires in the harness, and I'll buy Ancor wire next time.

Fuel vent is definitely something I will check next time I'm down. I suspected oxygen starvation and so removed the flame arrestor, but didn't consider fuel starvation. That would explain why it starts misbehaving after a few hours running.

It will be a couple weeks before I'm back down, and will update this group if these measures identify the culprit (and if they don't!). Thanks again.

[ndutton]

The wiring harness is only a few years old. I did a total refit on the boat back in '08-'09, and replaced all electrical. . . . . . . so don't think that is it.

It's funny how once you think something can't be the cause, hundreds of dollars and countless hours later it turns out to be exactly that. It's like the assumption jinxes you.

Go ahead and look elsewhere but keep the wiring in the back of your mind, just in case. Don't discount it completely just yet. It's only assumed good, not fully determined to be good. Wiring means components too (ign switch, buss bars, fuses).

Based on the symptoms I don't think it's a wiring issue either but that's not conclusive. This post has more to do with assumptions during troubleshooting.

[romantic comedy]

i wonder if it is something stopping fuel flow.

A clogged vent. Something in the tank that gets sucked over the pick up?

If it starts right up, the traditional Spark? Fuel? compression? does not really work.

[Marian Claire]

Do you have a squeeze bulb in the fuel line? Dan S/V Marian Claire

[tenders]

John, now I'm remembering the refit of your 29 that you described on the ericsonyachts.com website as you were doing it...wow.

This guy is not messing around.

[sastanley]

It's funny how once you think something can't be the cause, hundreds of dollars and countless hours later it turns out to be exactly that. It's like the assumption jinxes you.

Go ahead and look elsewhere but keep the wiring in the back of your mind, just in case. Don't discount it completely just yet. It's only assumed good, not fully determined to be good. Wiring means components too (ign switch, buss bars, fuses).

Based on the symptoms I don't think it's a wiring issue either but that's not conclusive. This post has more to do with assumptions during troubleshooting.

This is certainly a possibility..I removed all the engine wiring and replaced with tinned wire and bus bars two seasons ago...turns out I had a loose screw terminal powering my coil. The engine fired right up for 15 seconds, the vibration of the engine caused a short, and the coil could not stay energized. A digital meter never picked up the fluctuations in voltage, so I kept chasing a fuel problem to the tune of a new carb before I tightened that terminal and solved my issue..that new carb is nice and shiny though.

However, I am also in the possibly clogged vent club..after a couple hours there is a vacuum in the tank and the pump can't maintain fuel pressure...a $13 fuel pressure gauge at the carb could confirm or deny fuel delivery.

[Loki9]

I had a coil failure a couple of years ago that showed similar symptoms. The A4 ran fine for 2-3 hours and then started missing. The missing would get worse until the A4 quit altogether. It would usually start right back up but wouldn't run for very long before quitting again. After a long cool down, it would be back to normal. When motoring less than 2 hours, no issues. A new coil from Moyer solved the problem and it's been fine ever since.

[hanleyclifford]

Vent lines should be reamed out at the beginning of each season. Bugs and mud daubers and such like to build nests in them during the lay up season.

[jkenan]

John, now I'm remembering the refit of your 29 that you described on the ericsonyachts.com website as you were doing it...wow.

This guy is not messing around.

Thanks Tenders! The refit was a great project. I learned a ton, and the end result is a boat that is joy to sail for my family and me! I actually renamed the boat 'Carried Away' because the project started as just a bottom job, but then...

[jkenan]

No bulb installed. I will check fuel vent lines for blockage, and am leaning towards thinking this is more likely the issue given the solid performance for a while and then deteriorates. I thought the coil was the issue - the old one had some hairline cracks in it (engine had some overheating issues at one point) and had been in service for years. I replaced it this season, but that did not resolve anything. I have double row terminal strips in the engine compartment, and have sprayed those down with an anti-corrosion spray in the past. May be time to do it again. Have not heard anyone suspicious of the EI - are there any components there that should replaced? I know Don sells a magnetic ring for that unit. As mentioned, I will try jumper. Should I jump battery positive to coil positive only, or should I also jump battery negative to coil negative?

[ndutton]

As mentioned, I will try jumper. Should I jump battery positive to coil positive only, or should I also jump battery negative to coil negative?

No, non, nein, nyet, negatory.

The coil '-' terminal is not a ground and should not be grounded - - EVER!! It is the terminal that receives - - and I'm being very careful NOT to call it a ground - - the signal from the EI (or points). Connecting a ground wire to it will defeat ignition function and ultimately damage the coil.

I really wish the terminal was called something other than '-'. It's a frequent source of misconception.