Hubby has a 79 F150 with an inline 6 (300). Was running fine until we decided to change the valve cover gasket. Nothing major, right? Well now it wont start. We have replaced the plugs, wires, distributor cap, rotor, the distributor, voltage regulator, the ignition module and the coil. He even redid the carburetor. He is at his wits end! There is plenty of fuel getting to the carburetor, and a voltage meter shows that everything has got spark. And yes everything is set to top dead center on the number 1 cylinder! Any advice would be appreciated considering he is ready to torch the truck!

 

"Was running fine until we decided to change the valve cover gasket." So, what happened between then and now? That is where you will find the solution. Probably something very simple but easily overlooked...that is kinda the way those things go.

 

Welcome to the forum, Mrs. farrmb71! Sorry for the problems.

If an engine has compression, fuel [and air] and spark [at the right time], it should fire. Replacing the valve cover gasket should not have caused problems, but many small [old and brittle] wires and vacuum hoses are in the same area and may have been disturbed.

And now, many things have been done to correct, which opens other possibilities. "Everything is set to top dead center on the number 1 cylinder"... are the sparkplug wires properly placed? [1-5-3-6-2-4].

Take a sparkplug wire loose from the sparkplug and substitute a known good one and let the base of the sparkplug rest against the engine block. With someone turning the key [be very careful; neutral or park and brake on!!!], watch the gap for a strong blue spark.

Take the distributor cap off [set it aside with wires attached] and again, crank the engine. See if the rotor is turning?

Just some random ideas.

 

Did you unplug the distributor vacuum lines to get the valve cover off?

 

Me again... TDC on #1 cylinder might be 180 degrees off? [Exhaust vs. compression]

 

We keep hearing that phrase of "180 off". Can someone please explain that in plain English. We have no idea what it means.

 

Yes we did remove the vacuum lines and replaced them with new lines.

 

On a 4 stroke motor the crank shaft rotates 2 times for every one rotation of the cam .. So 2 rotations in the case of a 4 stroke motor = 360* on the cam or one full circle/rotation .. So one rotation of the crank = 180* on the cam or 1/2 of a circle .. to ensure you have the cam in the compression phase for #1 cylinder take the #1 spark plug out and have one person hold their thumb or finger over the spark plug hole and rotate the crankshaft until they feel pressure against their finger or thumb .. continue rotating until 0* mark lines up with the pointer ..

Note: before removing a spark plug shop vac around it's base before removing so no debris falls into the cylinder .. The motor will rotate much easier with all plugs removed .. Some times the timing marks can be off on the harmonic balancer because the outer shell has spun on the inner to get the absolute TDC use a piston stop in the #1 cylinder .. If you need further explanation of how to do this just ask ..

Piston stop (needs to be same thread as spark plug) about $8

 

If you removed the distributor, it means you may have put it in backwards. The rotor will be facing the opposite direction of where it should be (180°).
This happens if you install the distributor to top dead center when it's on the exhaust stroke instead of the compression stroke.

The firing order is 1 - 5 - 3 - 6 - 2 - 4

If you have it 180° off, it's going to be trying to do the opposite, which is:

6 - 2 - 4 - 1 - 5 - 3

The rotor will always be pointing in exactly the opposite direction of where it needs to be.
IF this is the issue, bring the motor to TDC, remove the distributor, turn the rotor 180° and put it back in. (Taking care to be sure everything is properly lined up of course).

 

Well said, AbandonedBronco!

 

So what's the latest on your distributor gear pin issue?

 

This sounds a lot like my problem. Same issue, checked most everything and its all good. The rotor is facing the #1 distributor point (top right) at TDC. I still havent figured it out.

 

On my engine the #1 on the distributor is facing straight forward toward the front of the engine.

 

Ok. Distributor might be wrong then. Ill try switching it. Toward the front left?

 

Sooo I took the cap off the distributor and watched the rotor as it was cranked. How fast should the rotor spin?
Mine was veeery slow.