Pre-ignition & slight ping at WOT on vacation

[superbenk]

Im on vacation with the boat & I'm getting very slight pinging and some hesitation at high RPM (over 3k). Pulled the plugs and they are stark white & clean which makes me think I'm getting pre-ignition. I didn't bring my timing light or many of my tools. What can I do to salvage the boat for vacation this week? I tried turning the distributor slightly counter-clockwise to retard the timing (that's right isn't it?), which seemed to help but it's still having a problem. Could it be bad gas? Filters are new & only run once this year. Replaced thermostat & temp sits at 110-150? depending on load.

I took the manifold off this spring & inspected/cleaned it. Checked carb float when I put manifold back on. Took anti-siphon off & replaced with straight through without change. What else can I do/check? Remember I have limited tools with me (socket set & Solec manual). I was thinking of getting some octane booster and 93 octane gas (only have a 5 gallon can).

- Frustrated

 

[Bondo]

Re: Pre-ignition & slight ping at WOT on vacation

Could it be bad gas?

Ayuh,... That's My guess,... or Crud in the filters...

Filters don't have a used up date,... Brand New, 'n ya introduce Crud, 'n the brand new filter, is Junk...

 

[Idlespeedonly]

Re: Pre-ignition & slight ping at WOT on vacation

What motor is this?

 

[superbenk]

Re: Pre-ignition & slight ping at WOT on vacation

1980 OMC 140 Stringer (3.0L GM)

 

[Idlespeedonly]

Re: Pre-ignition & slight ping at WOT on vacation

If the distributor rotates CW (which I believe it does), turning ccw is advancing it. This should make it ping more. CW is retarding it. should make the pinging go away.

 

[superbenk]

Re: Pre-ignition & slight ping at WOT on vacation

If the distributor rotates CW (which I believe it does), turning ccw is advancing it. This should make it ping more. CW is retarding it. should make the pinging go away.

I'll double check that. Maybe you're right. Turning it CW made it stumble at idle. Turning it CCW smoothed it out.

The pinging is very subtle and only at high rpm. Couldn't replicate it on the hoist even with the boat in gear (under load & probably not the safest test).

Would carbon build up be a concern? No idea if there is build-up, but I considered getting some cleaner additive.

 

[Don S]

Re: Pre-ignition & slight ping at WOT on vacation

Why don't you use a timing light? (rent or buy a cheap one) It's cheaper than new pistons.

 

[Reinell-BRXL-191]

Re: Pre-ignition & slight ping at WOT on vacation

Normally, an engine that runs good, and with a tight distributor won't develop a timing issue. (unless the timing chain or belt has slipped) - so, more than likely, your issue is actually fuel related, and changing the timing to try and correct it will most likely not fix the problem, and continued detonation will end up putting your rings and piston ring lands in the oil pan...

I would actually be looking for a clogged jet in the carb, or lack of fuel pressure at higher RPM..

 

[superbenk]

Re: Pre-ignition & slight ping at WOT on vacation

Normally, an engine that runs good, and with a tight distributor won't develop a timing issue. (unless the timing chain or belt has slipped) - so, more than likely, your issue is actually fuel related, and changing the timing to try and correct it will most likely not fix the problem, and continued detonation will end up putting your rings and piston ring lands in the oil pan...

I would actually be looking for a clogged jet in the carb, or lack of fuel pressure at higher RPM..

Not sure I could fix (or diagnose) a clogged jet at the dock on vacation. Really don't want to spend the vacation rebuilding the carb (assuming I could even come up with a rebuild kit on short notice). We're only here through the end of the week. Does this sound like a boat that's down for the count this week or is there anything simple I can do?

 

[BonairII]

Re: Pre-ignition & slight ping at WOT on vacation

Put your dist back to what is was....and change your fuel and/or fuel filter and see if that solves your problem.

No sense in making changes in timing etc when it may be as simple as bad gas. If you have a large onboard fuel tank and don't want to throw away what could be "good" gas......then Fill up a portable tank with fresh fuel and run the motor to see if the fuel is the culprit.

 

[superbenk]

Re: Pre-ignition & slight ping at WOT on vacation

For what it's worth, the plugs look like something between #20-23 on this photo:

 

[Bondo]

Re: Pre-ignition & slight ping at WOT on vacation

For what it's worth, the plugs look like something between #20-23 on this photo:

Ayuh,... It's goin' Lean....

An ole indian trick that Sometimes works,....
Start the motor,...
At Idle,... use yer hands to completely cover the top of the carb, 'n Choke out the motor....

Sometimes,... it'll cause the speck of crud to be sucked through wherever it's stuck, 'n free up the carb...

Sometimes....

 

[superbenk]

Re: Pre-ignition & slight ping at WOT on vacation

Neighbor let me borrow a timing light & tach/dwell meter! Timing was way off so I adjusted it back to +4? @ 600 RPM & now it seems to run much better (ping is gone!). However I'm still getting stumbling at higher RPMs. Now it almost seems like its a touch too rich:

I'm concerned my spark is too weak. I ordered a new voltage regulator the other day which should arrive today. The tach/dwell meter read only 9 volts which is obviously really low. The dash meter reads 10-11 volts (still low). Battery on the charger reads 12.6 volts before charging which seems decent. I'm trying to hunt down a multimeter now.

 

[Idlespeedonly]

Re: Pre-ignition & slight ping at WOT on vacation

Problem #1 -Champion plugs
Problem #2 -weak spark would usually be a bad coil
9 volts is where the coil should operate.

 

[superbenk]

Re: Pre-ignition & slight ping at WOT on vacation

Are AC plugs better than Champion? The Solec only lists Champion or AC plugs (AC MR43T or Champion RBL-8). Is there an NGK that would be better?

What about the points? Would an electronic system help? A local marina might have one locally (maybe).

 

[HT32BSX115]

Re: Pre-ignition & slight ping at WOT on vacation

Are AC plugs better than Champion? The Solec only lists Champion or AC plugs (AC MR43T or Champion RBL-8). Is there an NGK that would be better?

What about the points? Would an electronic system help? A local marina might have one locally (maybe).

If you can read PDF's, here's a conversion table. I don't know how accurate it is.

http://wildaboutcarsonline.com/memb...9990350494271/Spart_Plug_Conversion_Table.pdf

 

[superbenk]

Re: Pre-ignition & slight ping at WOT on vacation

Fixed!!! Timing was still off b/c timing marks are rusted & hard to read. Redid it in a different position where I had marked it a few years ago & now it's running perfectly!!! Of course we leave tomorrow

 

[Maclin]

Re: Pre-ignition & slight ping at WOT on vacation

I bet the points eroded and that changed the dwell which changes the timing and also weakens spark. New points, dwell adjustment, and then timing is due probably.

 

[superbenk]

Re: Pre-ignition & slight ping at WOT on vacation

I bet the points eroded and that changed the dwell which changes the timing and also weakens spark. New points, dwell adjustment, and then timing is due probably.

Could be. I'm ordering an electronic conversion kit before the next boat trip.

 

[Kainon]

Re: Pre-ignition & slight ping at WOT on vacation

I believe 9v is normal while running, at the coil or key on, 12V when starting it gets the extra juice through the start circuit.

corrosion on connections will drop the voltage to the dash and that dash gauge can be off by more than 10% ( use a digital gauge to triple check )

check battery voltage at the battery first, then go out to other connections from there to know what you have.