F134 fouling plugs after rebuild

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portajon
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F134 fouling plugs after rebuild

Post by portajon » Tue Aug 27, 2019 11:14 am

Thanks in advance for any advice offered and thanks to the forum administration.

1956 Willys CJ5. Pulled the engine a couple months back for a rebuild. Professional shop did the rebuild. Blue Mountain Motors in Lagrande, Oregon. Engine runs well after installed. Did have a bit of a trick with timing, but it is properly timed at 5 degrees BTC and runs out OK.... for just about half a day. The plugs carbon foul VERY quickly. New set of R45 plugs. New points, button, cap, wires... dwell and gaps all set.

I THINK the carburetor may need rebuilt. Maybe.... but what other tweaks might I be missing that would cause black, dry, carbon fouling that quickly?

Thanks again.

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Re: F134 fouling plugs after rebuild

Post by Scoutpilot » Tue Aug 27, 2019 12:20 pm

You need to advance your timing a bit. Carbon is building up because the spark plug is firing late. This causes an incomplete burn. If you have access to intake manifold vacuum, use a vacuum gauge to tune it.

some light reading for you; http://oldjeepcarbs.com/thread/29/time- ... ming-light
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Re: F134 fouling plugs after rebuild

Post by artificer » Tue Aug 27, 2019 3:04 pm

+1 & a good hard run.
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Re: F134 fouling plugs after rebuild

Post by Joe Gopan » Tue Aug 27, 2019 4:41 pm

Check to see if the Intake Valve Seals are properly installed-and correct.
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Re: F134 fouling plugs after rebuild

Post by artificer » Tue Aug 27, 2019 4:51 pm

The OP wrote:black, dry, carbon fouling
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TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: F134 fouling plugs after rebuild

Post by portajon » Tue Aug 27, 2019 5:23 pm

Took her out for a "good hard run" this afternoon and it certainly helped. How much should I advance the timing? Maybe just get it right between the two marks?

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Re: F134 fouling plugs after rebuild

Post by artificer » Tue Aug 27, 2019 6:59 pm

Make sure point dwell/gap is correct before doing anything.

Between the two marks is retarding the ignition & we need to advance.
Halve [guesstimate] the distance between the 2 marks & reset that far outside/before the 5° mark to get about 8°.

Rick suggested to set with a vacuum gauge & I agree.
These are about $15 from HF & hook into manifold vacuum below carb throttle plate/butterfly level.
The timing is set on 5° @ idle or just above idle on a new engine [with vacuum advance plugged off if vehicle has].
Advance spark by rotating distributor until best vacuum reading is obtained then back off 1-2" of mercury or about 1/4" movement @ the outside of the distributor.
Clamp & road test to ensure no knock/pinging. No matter what adjustment method is employed.
Most likely will be fine, but if evident gradually retard until knock is no longer evident.

FI: If the spark plug heat range is correct ~
dry black sooty plugs are indicative of fuel burn &
wet black sooty plugs relates to oil.
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: F134 fouling plugs after rebuild

Post by Wolfman » Wed Aug 28, 2019 5:33 am

Could just be a new engine and todays gas.
Compression on a new engine is usually a little low until it gets " run in".
Wait & see is an option.
With todays gas, low compression equates to poor fuel burn and black dry carbon on the plugs.
I like the idea of bumping the timing ( advancing) a bit. Have had good results with this myself. No spark knock under load !!
Even after the engine is " run in" and up to par, it is still lower compression than engines that todays gas is mixed for.
If the only driving you are doing is, around the neighborhood, you might try a hotter plug. R46 instead of an R45.
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Re: F134 fouling plugs after rebuild

Post by Joe Gopan » Wed Aug 28, 2019 6:42 am

Reminder, why did cars and trucks of the 40's-60's run so good on Unleaded 100 Octane AMOCO White Gas?
I've workrf on a pile of Jeeps since the CJ-2A thru CJ-5 days and same for M-38/M-38A1 and have always set timing @ 5BTDC and they always ran like they were jet propelled including my present MB and M-38A1.
It is not that uncommon for Intake Valve Seals to be an issue on fresh build F-134 Jeep engines. Worn intake valve guides and valve stems along with improper seal installation will result in considerable oil consumption in the F-134.
Did the shop have to do anything to the Intake Valves?
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Re: F134 fouling plugs after rebuild

Post by portajon » Thu Aug 29, 2019 10:09 am

artificer wrote:
Tue Aug 27, 2019 6:59 pm
Make sure point dwell/gap is correct before doing anything.

Between the two marks is retarding the ignition & we need to advance.
Halve [guesstimate] the distance between the 2 marks & reset that far outside/before the 5° mark to get about 8°.


FI: If the spark plug heat range is correct ~
dry black sooty plugs are indicative of fuel burn &
wet black sooty plugs relates to oil.
Hmmmm..... This bent my brain a little. If we want the spark later in the ignition cycle, wouldn't we want the sparked advanced closer to TDC and not farther away? Seems like moving it to 8 degrees would give us a spark even earlier in the compression stroke.... I don't quite understand how this would be "advancing" the timing.

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Re: F134 fouling plugs after rebuild

Post by portajon » Thu Aug 29, 2019 10:13 am

Ben Dover wrote:
Wed Aug 28, 2019 6:42 am
Reminder, why did cars and trucks of the 40's-60's run so good on Unleaded 100 Octane AMOCO White Gas?
I've workrf on a pile of Jeeps since the CJ-2A thru CJ-5 days and same for M-38/M-38A1 and have always set timing @ 5BTDC and they always ran like they were jet propelled including my present MB and M-38A1.
It is not that uncommon for Intake Valve Seals to be an issue on fresh build F-134 Jeep engines. Worn intake valve guides and valve stems along with improper seal installation will result in considerable oil consumption in the F-134.
Did the shop have to do anything to the Intake Valves?
I know there was a burnt exhaust valve, head gasket was blown, crank was turned. Suppose to have been a complete rebuild so I presume the valves were seated.

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Re: F134 fouling plugs after rebuild

Post by Joe Gopan » Thu Aug 29, 2019 10:21 am

And maybe not. The OEM seals are a special square sided O-Ring. There are aftermarket Umbreller seals that work tho. It iis easy to see if the OEM Seals were installed wrong as they will be resting on the head and not installed under the valve stem keepers.
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Re: F134 fouling plugs after rebuild

Post by artificer » Thu Aug 29, 2019 10:52 am

Mike W offered a sensible suggestion, for an irregularly used vehicle.
portajon wrote:
Thu Aug 29, 2019 10:09 am
Hmmmm..... This bent my brain a little. If we want the spark later in the ignition cycle, wouldn't we want the sparked advanced closer to TDC and not farther away? Seems like moving it to 8 degrees would give us a spark even earlier in the compression stroke.... I don't quite understand how this would be "advancing" the timing.
Advancing ignition timing to get better 'complete burn' is what was offered.
Splitting between the 2 timing marks is retarding the ignition & will exacerbate 'incomplete burn'.
Advancing is for earlier spark & higher octane fuel~
Retarding is for later spark & lower octane fuel~

Getting side tracked/led astray/confused?
If the valve stem seals were not or incorrectly fitted there would be a totally different spark plug scenario/appearance/symptom/s & a smoke screen. Something not mentioned to date.

If the vacuum gauge was employed, as suggested, we'd be done, dusted & not getting confused.
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: F134 fouling plugs after rebuild

Post by Joe Gopan » Thu Aug 29, 2019 11:34 am

Jeeps with the F-134 have beem running on 80 + Octane fuels since the F-134 came out around 1951 with no issues, Jeep Service manuals and Army TM's have listed 5 Degrees BTDC from that time thru 1971 when the CJ-5 w/F-134 went out of production. Many have tried advancing timing to cure Jeep engine ills only to discover their engine pinging after fiddling with advancing the timing.
Both my M-38A1 and MB with fairly new engines run perfect on 90 Oct Ethanol Free and have no issues but would if the timing on them were advanced. Not bragging or grand standing here, just trying to demonstrate what Jeeps can do when maintained using factory procedure and schedule.
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HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
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Re: F134 fouling plugs after rebuild

Post by Wolfman » Fri Aug 30, 2019 7:06 am

You have to take your thinking up to " Light Speed ", Portajon.
It is hard to imagine how fast a piston is moving up and down in the cylinder.
To begin, fuel does not explode, ( or shouldn't ). It burns at a steady rate. Although this is really fast.
Higher octane fuel burns "slower" than lower octane fuel and compression pressure has an effect on the burn rate, what ever the octane.
The perfect world would be, start the fire ( spark ) so fuel burns at an optimum rate, as the piston is rising on the compression stroke and cylinder pressure is increasing so you get the best burn rate without compressing the fuel to point it self ignites from the pressure. Spark knock.
To get this best burn is a combination of compression pressure. Fuel octane and ignition timing. We are going racing now !
Back to the jeep engine.
With a stock jeep engine the compression pressure is set. You add higher octane fuel, which burns slower. So to make up for the slower burn rate, you advance the timing. Start the fire earlier. Kind of like cheating. By starting the fire sooner, heat expansion from the burning fuel causes the cylinder pressure to rise quicker, Before reaching TDC, from heat expansion and the higher octane fuel burns faster from the increase in pressure, giving you ultimate performance. Or in this case, looking for the same performance with the higher octane fuel, you get from using lower octane fuel. Not going racing. All about variables. 8)
So, back to your question. Advancing the timing is having the spark occur sooner or more degrees before the piston reaches Top Dead Center ( TDC ) on the compression stroke.
Example. Advance timing to 10 degrees Before TDC instead of the listed 5 degrees. Which is the safe way to go.
If you make the change, go for a drive and with the engine under a load, you do not want to hear any spark knock !!!
How much advance ?? Your call. I would not go past 10 degrees TDC. ( For non racing situations )
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