Ignition Timing Issues?
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Joined: Aug 2007
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From: St. Charles, Missouri.
Ignition Timing Issues?
Okay, on my '74 F-250 Super-Cab with a rebuilt 390, a new Edlebrock 650 CFM Carburetor. The truck has been upgraded from points to a electronic solid state ignition. We checked the firing order and position of the distributor and determined that the truck was running 180 out. That was probably why it was running rough. At least 2 of my cylinders were off, so we fixed the firing order. So now the firing order is correct. We put the timing about 10 degrees advanced and it won't start. Why isn't it starting? Even if it the timing was a little off, it should start. It just backfires up through the carburetor. There was an ignition cut-off switch that the previous owner installed which we bypassed by running a wire from the coil to the positive side of the solenoid when the truck was running 180 out, it did run. Did we burn something up in the ignition circuit? After a while, it was just turning over and it wasn't firing at all... I'm thinking I may have a ground wire off or loose.
Any help would be appreciated.
Any help would be appreciated.
Elder User
Joined: Dec 2007
Posts: 813
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From: Up Nort Minnesota
I've never tried to run an fe 180 degrees out, so I just have to believe you.
But every time I've experienced 180 out with other engines, they backfire through the carb, stumble and do all kinds of bad chit, but wont run.
if you pull plug wires, are you making spark??
If you crank and make spark, plus you have fuel, then you must be sparking at the wrong tome or sending the spark to the wrong holes at the wrong time.
How do you know you are at 10 degrees BTDC?
But every time I've experienced 180 out with other engines, they backfire through the carb, stumble and do all kinds of bad chit, but wont run.
if you pull plug wires, are you making spark??
If you crank and make spark, plus you have fuel, then you must be sparking at the wrong tome or sending the spark to the wrong holes at the wrong time.
How do you know you are at 10 degrees BTDC?
Senior User
Joined: May 2012
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Are you sure #1 was at top of the compression stroke when you adjusted distributor rotor position? Have you had a buddy crank the key while you turn the dist? If you know the firing order is right, and you get it to fire up while you're doing this, then you could just get it running and adjust it by ear and feel and take it from there. When you get play in the chain and the lifter system and so on, it can be hard to get it on timing using the marks.
Posting Guru
Joined: May 2010
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From: Alton, MO
How did you determine this? Just because you have the firing order correct does not mean you are in the correct place timing wise. I am with the post saying you are 180 out now. Did you lift the distributor & move it or just move the firing order on the cap? If you just moved wires then you are 180 out. You need to set the crank on 0 & pull the cap. Is the rotor pointed at #1? How did you set timing at 10* when it doesn't run?
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I also think it's a 180 degrees out, given that it's back-firing through the carb (piston forcing air/fuel through an open intake valve). If you want to be sure, do this: Make sure your #1 is at TDC on the compression stroke. Put the cap on your dist, and use a marker or a bit of tape to put a mark on the side of the dist body (the part the cap attaches to) right below where the stem on the cap for the #1 plug wire goes. Now takle off the cap and turn the dist until that mark lines up with rotor. Now, you have the piston at TDC, and the rotor aligned with #1 plug wire. It should start (assuming other systems are OK). Then you can deal with the fine adjustment on the timing.
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Agree j ballan. That's why I don't think it was 180 out before. No way it would run, even roughly. But like I said, usually the simplest thing to do with these old engines is don't over-think it, just put #1 piston at TDC on compression and there rotor at #1 on the dizzy and start her up. Then do the adjustments.
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