I have a 351m in a 78 ford f-150. New in the truck- Starter, starter selenoid, battery, distributor pickup, spark plugs.
When I turn the key the starter engages and turns the engine over, but slowly. If I do this a couple times it might make a big pop out of the exhaust or it might not, it is very random. I had the coil and ignition module tested and were said to be good. It just sounds like its not getting any spark. I checked the underside of the distributor cap and no scorch marks or carbon marks. The rotor also seems to be in good condition. Is there something I am missing that should just be so darn obvious to me? Thanks for your help!

 

Timing way off?

 

When I set the timing i brought cylinder one up to TDC and pointed the rotor toward number one plug one the top of the distributor cap like the haynes manual says, is this right?

 

Just checking:

Cylinder #1 is the frontmost passenger side cylinder (differs from other makers)

Piston is at the cylinder on its compression stroke as opposed to just having pushed exhaust out of the exhaust valve.

Pardon me, just checking for an obvious error.

Have you checked to see if you are getting spark at the spark plug while cranking?

The last troubles I had with starting were caused by an intermintent bad magnetic pickup inside the distributor.

 

what is the safe way to check for spark? I replaced the magnetic pickup inside the distributor today and it really didn't seem to do anything. Thank you for taking time to reply to my posts, I was excited to get the truck running this weekend but right now its not looking too promising...

 

Sounds like you have the rotor 180 degrees off. You'll need to find TDC on the compression stroke of cylinder #1. Usually you'll want the rotor pointing at about 1 o'clock.

Make sure the spark plug wires are going where they should as well.

Josh

 

How do I know what is the compression stroke, without any fancy tools?

I installed the distributor with the rotor pointing at one oclock(pointing towards the drivers seat when facing the engine). Could I have installed it
on tdc of the exhaust stroke?

 

Get a remote starter switch for your solenoid so that you can observe your engine while cranking it. They are cheap. Lay the spark plug onto part of the engine that is ground, (away from gas fumes) , so that the threads are grounded, crank and observe whether the plug is sparking.

If you pull off your valve cover, identify which valve is lined up to your intake manifold runner and which one is lined up with the exhaust port. The intake valve opens on the downstroke prior to the compression upstroke. If you pull all the plugs, you can rotate the engine much easier. I have a large breaker bar with a large socket on it to use to rotate the crank. Rotate the crank and observe the opening of the #1 intake valve, when it closes, the piston is on it's way up for it's compression stroke. The TDC mark should be lined up with the timing mark when it's at the top.

Remember that 351/400's have a firing order that differs from other Ford V8s.

Number your cylinders from passenger side front to rear:1-2-3-4 and driver side front to rear: 5-6-7-8 The proper firing order for the 351/400 is: 1-3-7-2-6-5-4-8

It doesn't really matter where your rotor is pointing so long as it points at #1 and the firing order is sequential around the circle, and the rotor is at #1 while #1 cylinder is roughly TDC on it's compression stroke. When I take my distributor out, I make note of where #1 plug wire is, and make sure the rotor is pointing at it. So when I drop the distributor back in, I'm in the general neighborhood of timing enough to start the engine and fine tune it.

 

is there any way to test the spark plug wires to make sure they are working properly?

 

another double check.

The rotor goes counter clockwise around the distributor. Make sure your firing order is counter-clockwise

Unless the wires are old and abused, they probably are fine. Mechanic shops have electronic analyzers that can catch plug wire problems.

 

Another related question. If I have the crank at TDC on #1 with the distributor out, can I put the distributor back in the block in any position so long as I place the cap with the #1 plug wire lined up with wherever the rotor ends up?

 

Still no luck with getting the truck to start. I think i'm going to check the compression to make sure its okay. Any other suggestions that I might try? Please HELP!!!

 

I had a problem with my magnetic distributor pickup working dependably. The star shaped (8 pointed) wheel just above the floor of the distributors advance mechanism pass's by a magnetic pickup that tells the electronic ignition to fire the coil. (I'm assuming you don't have points). You might try this test: Pull the distributor out, Pull the coil wire out of the top of the distributor and arrange it near a ground (needs to be a small gap) so that it would arc and create spark if triggered to. Ground the outside of the distributor (its usually grounded to the block) using a jumper cable. Spin the distributor gear with your fingers with the ignition switch on and see if it is prompting the coil wire to spark. These magnetic pickups can fail or be intermintent. The air gap between the sensor and the passing points of the 8 point star need to be correct. If this component isn't working you'll never get spark.

 

Holy crap that would be a ton of work. Here is a simplified procedure for your idea.

Bring #1 cylinder to TDC, loosen the distributor hold down, turn the key to "run" and hook up a timing light to #1 wire and then twist the distributor back and forth. It should fire the timing light.

Josh

 

I tested the compression and it didn't even move the needle on the tester. Blown head gasket maybe? Could it be that the timing chain loosened a little and the cam and crank skipped out of time with each other?