Fouled Spark Plugs Cause No Start

Classic Car Carburetor Foul Spark Plugs

Episode 498
Autorestomod

The F100 is not happy. It is fouling plugs. We look at how the carburetor can percolate the gas out of the carburetor and cause it to be rich on start up.

[Spaceplant]

Bought a 72 f250 with a 390 last year. (My first truck ever) so I could actually work on it and get my learn on. You guys have been super helpful. Keep it up baby!

[robkallok]

Well done guys - making excellent use of your thinking caps. It’s so hard to not jump to conclusions in cases like this.

[CopCat]

We placed a spacer on my wife's 1965 Mustang, 289 4V, and it helped out immensely. We also have an aluminum intake manifold.

[rocketsock]

☕️😋That bronze paint really makes me want to sip another coffee. Great content again!

[yeboscrebo]

This exact thing is happening to me! I took a look at my carb and someone has plugged all the vents? My truck starts right up in the morning but after even a short trip I’ll go to start it again and I’ll have to mash down on the accelerator to get it to go. Love to see what happens when you put the spacer on there.

[AndrewWallacelive]

I snarfed my coffee just a wee bit this morning when I awoke to this video since I almost called you yesterday about my own Autolite 4100 carbur-tater problem. Like yours it runs way too nicely to be most of the major stuff, but it likes to spontaneously overfill the back bowl if I happen to over-enthusiastically enter my driveway, which means it then proceeds to trickle/pour gasoline onto the secondary throttle plates. Having checked and rechecked float level, wet, with the engine running, it’s something I’m still worrying through. Sometimes that’s just what you gotta do!

[mattshansen]

I love you guys. I'm a ford guy but I have a 1969 AMC Ambassador and a 1979 Jeep Cherokee. Love the videos. 👍❤

[mark]

I had this exact issue decades ago with my 360 FE. Summer time was the worst, you 
would have to literally wait for ever for it to cool down before even attempting to restart it.
It would start right up on a cold morning and run just fine otherwise.

[welder]

Had this problem before fixed it by putting a 4 core radiator in to help with cooling. Also changed the fan.

[waynep]

JEFF and KAM. I have been FIXING THIS issue since 1983.. the fix is a 10 micron fuel filter before the mechanical fuel pump.. disconnecting the fuel line to the carb.. extending the fuel line into a clean clear soda bottle. disconnect the power to the ignition coil.. get somebody to crank the engine for 15 seconds while you watch the pulses into the bottle.. you should have equal pulses.. do this 3 times.. each time for 15 seconds.. hook the hose back to the carb and you are fixed..

WHY.. sediment in the fuel pump check valves reduces the suction from the tank and the pressure held in the fuel line to the carb.. it also gets into the needle and seat in the carb.. what happens.. when you shut off.. your needle and seat is leaking and overflowing the bowl and fuel is dripping out of the booster venturi's. causing the carb to flood the cylinders.. but eventually the fuel in the line is exhausted and whats left turns to vapor and vapor starts pouring out of the carb.. down at the fuel pump the partially open check valves allow gravity to allow fuel to drain back to the tank.. taking some out of the float bowls as the needle and seat level is below the normal fuel level..

the 10 micron filter before the pump works with flushing the pump with filtered fuel..

don't believe me.. pull the fuel line off the carb.. and try blowing into it.. you should NOT be able to blow bubbles in the fuel tank.. still don't believe me.. extend the fuel line with some clear vinyl hose and hang it over the hood latch.. crank the engine with the coil power disconnected until you get fuel in the clear hose.. notice how long it takes to get fuel from the tank and thru the pump into the hose when you have fuel in the hose stop cranking.. watch the fuel vanish backward thru the fuel pump as the check valves are now partially open..

i use either a 1984 corvette fuel filter as it has 3/8 inlet and out let or a 1994 ford probe fuel filter as it has 5/16 inlet and outlets and those are both 10 micron rated filters. it is the only fix and i have been fixing cars for a living since 1979.. after a year of automotive trade school.. not just a guy with a bucket of tools..

there are other issues the 10 micron fuel filter fixes.. Hot vapor lock coming to a stop or idling in heavy traffic.. the engine will start to run rough then stall and won't crank .. this is the fuel in the pump and the line to the pump not having enough pressure to stop from boiling and turning to vapor the liquid fuel is pushed back to the tank thru the partially open check valves in the fuel pump .. the engine running on vapors leans out. the pistons and rings expand beyond normal and grip tight in the cylinder walls preventing the starter from being able to spin the crank.. this is why after 10 minutes the engine can be cranked but it takes a while of cranking to get the fuel from the tank.

[brianwaskow]

I have a Weiad triangle shaped air filter on a 289. The bottom plate is flat and allot smaller than a stock air filter.

[victormartin]

Jeff, please do a follow up. My 71 F100 390 has been doing that for about a year now. Aluminum intake, spacer under carb, fires great in the after running, not so much. Going to switch to non ethanol gas to see if it clears up. May end up putting in heat extractors in the hood to cool it down a little more. These FE's sure put out the heat!

[johntripp]

I bought one of these, same color, new in 1974. I replaced the stock carburetor with a Holley four barrel and it went. That was in Vancouver where winters can get cold allowing the Ford to show its nature (Not a cold start engine usually) another problem fords have is the fiber gasket on the intake manifold. Nice truck but I don't miss it.

[johnwalters]

Greetings! I think I remember you saying that you thought you had a 390GT. All the "S" code 390 engines came from the factory with a 1/4" Phenolic spacer. The original carb was usually a Holley 4150. I think such a spacer would really help. BTW thanks for the great video on the F100 Mirrors! I was able to get the parts you suggested and the job went smoothly. Thanks for all the great videos. You guys rock!

[jimgee]

i will email you when i get the chance to have free time to open up the carb if need be xmas is around the corner so most likely early january neighbor told me to throw in a set of platinum plugs in my 1970 engine with a pertronix ignitor in the dist the carb issue what do you think about platinum plugs in a 1970 engine have a great channel i love it, soon yall will have 100k subs and a silver plack on the wall, ,,bravo ..

[bigdsnuffy]

Definitely going to have to deal with heat issues on my 289. Here in the southwest with temps in the summer topping 115° to 118°.

[scottmartinetti]

Love seeing that guy talk straight. Not acting like he does most of the time. I can respect that much better.

[TheKeymaster]

Definitely would like to see the result of the phenolic spacer. I have a 77 F150 with the 460 and have been dealing with this issue since getting the truck back on the road in 2018. I always have to give a couple of pumps as least for the truck to start. Of course, it's always worse in the summer and after driving it for more than 30 minutes, stopping and then restarting, I usually have to pump it a lot to get it restarted due to the gas boiling out of the carb. I can't run a phenolic spacer right now because I still have the original spreadbore manifold that the Motorcraft 4350 used to reside on. I now run a Holley with an aluminum, spreadbore to standard bore spacer under it. I bought a phenolic spacer to try to fix my issue but the carb ended up sitting so high, the kickdown for the transmission wouldn't line up. Luckily, this isn't my daily driver so I tend to just deal with it best I can. But I'd like to upgrade to an aluminum intake down the road and then I could use the phenolic spacer instead of the aluminum adapter. I enjoy ya'lls videos, thanks.

[anthonysantiago]

Good Diagnostics, would like to see an update on this issue..

[gregvanderboom]

If I don't use a spacer due to clearance issues, I like to use the 3/8 thick flange gasket to insulate the carb a little. I remember International Harvester used a thick gasket that extended out just past the fuel bowl that was supposed to keep the fuel in the bowls cooler.