Can Wet Plugs Fire?

Ed Martin · Oct 1, 2019

My 68 383 RR cranks but does not fire. I replaced the coil, cap, rotor, ECU and verified a good spark at coil and at one cylinder. Tried to start it several times during replacement of the above parts (a week or two apart each try) over a period of several weeks. At first I thought it was a fuel problem and initially could get it to start if I cranked long enough and at the same time pumped the pedal 2 or 3 or more times. Now I'm replacing the plugs and they are wet from all the rich mixture (building up, I guess) when trying to start.

Questions: (1) will wet plugs prevent firing?, and (2) assuming the problem is a wet combustion chamber, will new plugs be able to fire if there is left-over over-rich mixture left in the combustion chamber or is there anything else I should do first?

Please give me any comments or suggestions.

toolmanmike · Oct 1, 2019

Not usually. Wet plugs need to be replaced or cleaned and dried. I always spin the engine over to blow the fuel out. Wipe the fuel off the paint under the hood and on your fenders right away and don't forget to pull the dipstick and smell it for gas in the oil. Change oil and filter if it is overfull and/ or smells like gas.

PurpleBeeper · Oct 1, 2019

See above from toolmanmike....good advice

beanhead · Oct 1, 2019

If the plugs are getting gassy then the engine's getting fuel. If you saw spark, that's good BUT it doesn't mean it's happening at the right time....next thing I would do is verify TDC and that the distributor is not 180° off, and that it's advanced enough for the engine to run. (These checks are free and just take a few minutes

) Verify correct plug wiring order as well.

WP29440SE · Oct 1, 2019

I would be making sure you don't have stuck/dirty needles and seats allowing a fuel dump to the point the plugs won't fire in the first place.

beanhead · Oct 1, 2019

WP29440SE said:
I would be making sure you don't have stuck/dirty needles and seats allowing a fuel dump to the point the plugs won't fire in the first place.

That's a good one too. That, and proper float setting.

Ranger16 · Oct 1, 2019

Don't overlook a misadjusted choke either. If it is clamped tightly closed, it will not start and WILL wet the plugs.

oldbee · Oct 1, 2019

Ranger16 said:
Don't overlook a misadjusted choke either. If it is clamped tightly closed, it will not start and WILL wet the plugs.

Wet the plugs? Yeah, pretty quick too.

oldkimmer · Oct 1, 2019

Was any work done prior to this happening? Kim

Don Frelier · Oct 1, 2019

I've had Cases where the choke didn't close and the car wouldn't start. In that case it's also possible to flood it from too many accelerator pump shots. You get past the desired mixture for firing without starting. Successive pump shots flood it.
I usually get a sixth sense that it isn't acting right and find the problem before it's flooded.

Ed Martin · Oct 2, 2019

toolmanmike said:
Not usually. Wet plugs need to be replaced or cleaned and dried. I always spin the engine over to blow the fuel out. Wipe the fuel off the paint under the hood and on your fenders right away and don't forget to pull the dipstick and smell it for gas in the oil. Change oil and filter if it is overfull and/ or smells like gas.

Thanks toolmanmike. This is good info. You're talking about spinning with plugs removed -right? I wonder by cranking without taking the plugs out (and not hitting the pedal), if that would push any gas out the exhaust or if that would even be a good idea?

Ed Martin · Oct 2, 2019

oldkimmer said:
Was any work done prior to this happening? Kim

Thanks everyone regarding carb/choke/etc. Prior to this problem (I forgot to mention this), I had re-installed the original manifold (had been running an Edelbrock Torker) and put on a new Holley carb so I assumed float level was ok and choke seemed to be closing the right amount (what opening should there be vs "tightly closed"?). Looking back I realize I was flooding it by pumping too much. Is spinning the engine the only way to dry out the combustion chamber?

Don Frelier · Oct 2, 2019

You should be able to just pull the plugs and leave them out for a day.
Or if you are in a hurry, then still with plugs removed open the choke and throttle and crank it for 10 seconds at a time, maybe 3-4 tries should do it.
You can hit the plugs with a heat gun or even a torch.

Ranger16 · Oct 2, 2019

Ed Martin said:
(what opening should there be vs "tightly closed"?).

Closed chock should be .100 open. 7/64" would be close enough.Use a drill bit to measure it.

P.S.
This is per the Edelbrock manual, but I doubt Holley would be much different.

Ed Martin · Oct 2, 2019

Don Frelier said:
You should be able to just pull the plugs and leave them out for a day.
Or if you are in a hurry, then still with plugs removed open the choke and throttle and crank it for 10 seconds at a time, maybe 3-4 tries should do it.
You can hit the plugs with a heat gun or even a torch.

Thanks Don. These are great ideas!

Ed Martin · Oct 2, 2019

Ranger16 said:
Closed chock should be .100 open. 7/64" would be close enough.Use a drill bit to measure it.

P.S.
This is per the Edelbrock manual, but I doubt Holley would be much different.

Thanks Ranger16. I'll have to check it. It seemed to be snapping closed with a small movement of throttle under the hood. As I remember, the opening was not "much" (that doesn't seem very technical, does it?).

toolmanmike · Oct 2, 2019

Check your choke operation after the engine sits for hours and cools off. (best overnight) Depress the accelerator to the floor one time to set the choke. The choke butterfly should close fully with slight tension. As soon as the engine fires the choke should open slightly and continue opening with time to prevent stalling. If it doesn't open fast enough it can stall the engine with too rich of a mixture. Pumping the gas will just aggravate the problem. Without seeing the choke for myself it's hard to tell what it's doing.

miller · Oct 3, 2019

toolmanmike said:
Depress the accelerator to the floor one time to set the choke.

That's exactly how the choke should work...as long as it's adjusted correctly.
If it's 'snapping' into choke, could be adjusted wrong. That's something you need to determine, going by what type of choke it is.
Once the engine is warmed up, the choke should fully open. Carb handbook will tell you how to adjust it.

Yep, check your oil, to be sure it's not loaded with gas!

John Dwyer · Oct 9, 2019

Ed Martin said:
My 68 383 RR cranks but does not fire. I replaced the coil, cap, rotor, ECU and verified a good spark at coil and at one cylinder. Tried to start it several times during replacement of the above parts (a week or two apart each try) over a period of several weeks. At first I thought it was a fuel problem and initially could get it to start if I cranked long enough and at the same time pumped the pedal 2 or 3 or more times. Now I'm replacing the plugs and they are wet from all the rich mixture (building up, I guess) when trying to start.

Questions: (1) will wet plugs prevent firing?, and (2) assuming the problem is a wet combustion chamber, will new plugs be able to fire if there is left-over over-rich mixture left in the combustion chamber or is there anything else I should do first?

Please give me any comments or suggestions.

Old Mopers … gotta love 'em. If it ain't choked right, you'll crank ALL DAY.

John Dwyer · Oct 9, 2019

John Dwyer said:
Old Mopers … gotta love 'em. If it ain't choked right, you'll crank ALL DAY.

I got to a place with my '68 383 where I installed a manual choke …. starts right every time. I'm pretty sure it has something to do with creating a vacuum in the carburetor to get the fuel flow moving properly.

Can Wet Plugs Fire?

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