I have a 1990 F150 4x4 with the 4.9 300-6. Just wondering if anyone has knowledge on how to get timing correct on it when the engine is not yet able to start. The timing set is correct because that it what lead me to my current situation. I have not been able to get it to fire over since shanging the two gears. I have played with the distibutor and wires but still now firing over. It just chugs and then back-fires.The starter and battery are fine too. Any suggestions would be greatly appreciated. Particularly if it Starts it. Just some more fyi it was running just not good when i replaced the gears.. I have spent a few months on and off working on it very slowly. This is my first project truck so i am learning alot along the way .

 

You need to go out and buy a Haynes manual for your truck. I'm not familiar with the big 6 cyl but it sounds like you're just out of time. Hopefully the gears are lined up right and maybe the distributor is just in the wrong hole or the plug wires aren't in the right spot.

 

Thankyou for the suggestions, Unfortunately I have tried all of them already. I Have both a Haynes and a Chilton's and I replaced the gears so i know they are lined up perfect. I Lined up the distibutor and wires, cap to the rotor at tdc and I still have problems. I am condidering pulling the engin out and rebuilding it to make sure it will work. Unfortunately I really don't have the resources at hand.

 

It shouldn't be necessary to pull the engine out.

Go back to first principles. How does a 4-stroke engine work?

Intake - compression - power - exhaust

Pull off the valve cover.

Take out the spark plugs.

Turn the engine over by hand, or bump it over with the starter solenoid. Feel the position of the #1 piston through the spark plug hole with a piece of copper wire or some other soft but non breakable object.

Bring the piston up towards TDC, turning the engine in the normal direction of rotation (clockwise looking from the front of the engine). Feel through the spark plug hole for the piston to reach TDC, or at least pretty close. Check the timing marks. They should be lined up, or at least close. If they aren't, you have a problem. Be aware that the 6 cylinder has more than one timing mark on the balancer. By using an independent means to find where the piston actually is, we can figure out which one is which, and whether the balancer is on correctly. Let's assume we've found a set that line up, and that the piston really is at TDC. Call this point #1 (see later).

Continue to turn the engine clockwise. You will either be on the intake stroke, or the power stroke. Look at the valves for #1 cylinder. If the intake valve begins to open as you turn the engine, it is the intake stroke. If not, turn the engine 180 degrees until the timing marks line up again.

Now we are at TDC of the intake stroke. As you keep turning the engine, you should see the intake valve open fully, and then begin to close as you reach BDC (the harmonic balancer mark will be exactly opposite the timing tab). Keep turning the engine. Now you are on the compression stroke. Both valves should be closed. Bring the engine back up to TDC (feel through the plug hole). The valves should stay closed. The timing marks should be lined up. Now look at the distributor rotor. It should be pointing to the spark plug wire position corresponding to #1 cylinder. If not, the distributor is installed incorrectly. Lift it out and re-index the distributor gear so that the rotor points at the #1 tower.

Keep turning the engine. You should see the valves staying closed during the power stroke. The exhaust valve should begin open as you reach BDC. Keep turning it. The exhaust valve should open fully, then begin to close as you reach TDC again. You are back to where you started.

Rock the engine back and forth through a range of about 20 degrees centered on TDC on the exhaust stroke. You should see the exhaust close and the intake open in a symettrical fashion. This method is good enough to detect a "one tooth off" mis-alignment of the camshaft gear.

If the valves do not operate in a manner that makes sense with where the piston is, then you have mis-indexed the cam gear. If the valves and crankshaft are playing together nicely, it is time to double check the distributor.

Go back to #1TDC on the compression stroke. By this time you can tell compression from exhaust, right? Back the engine off to about 10BTDC. Look at the rotor position. It should point at #1 plug tower. Look down into the distributor. Identify the blades of the reluctor (the slotted thing that passes through the gap in the pickup coil). One blade of the reluctor should just be entering the gap in the coil (in the direction of normal distributor rotation). Turn the distributor body if this is not so. You should not have to turn it terribly far -- you should be able to get the blade of the reluctor to be just entering the gap at the same time as the rotor is pointing towards number one plug tower. If you can't make it work, pull the distributor up, turn the rotor to re-index the tooth by one gear, and try again. Once you get the distributor looking visually right, the timing should be close enough to allow the vehicle to start.

If it still won't start, verify that you have spark with a timing light, and check the timing with the light while the engine is cranking. It helps to have another vehicle to keep the battery charged while you do this.

 

Thanks, it sounds close to what i have been trying to do, but much more clear on what to do than what i have been trying to do. Again this is my first project vehicle. Again thank you