I am having trouble getting my son's 70 F100 with a 390FE to start and I was hoping someone here could give me a nudge in the right direction. My plan was to have it running before he graduated from boot camp, but I think I have run out of time.

Prior to leaving, he was out driving it one night and said he hear a loud bang or pop. Of course, he has no other details other than it was running fine then made the noise and then he couldn't get it started. We towed it home and it sat for a while.

When you turn the key to the start position, the engine will spin freely, but it makes no attempt to actually fire up at all. I cannot hear any cylinder attempt to fire/combust.

Things I have checked:

Fuel:

It has a brand new QFT carb on it I had sitting for my highboy project. It is getting a steady 6 psi of fuel and I can physically see two streams of fuel coming out of the squirters when I actuate the accelerator pump.


Air:

I performed a compression test on the engine to make sure it was ok and received the following results:

1 - 180
2 - 170
3 - 170
4 - 170
5 - 180
6 - 165
7 - 160
8 - 175

This was a wet test as I had squirted some oil into the cylinders prior since the engine had been sitting a few months. Even though I could not warm the engine up properly, I did do a leakdown test on the two lowest cylinders (6,7) just to make sure there were no stuck valves or head gasket issues. The only place I could detect leaking air was from the dipstick tube. I am assuming this was due to the larger gap in the cold rings.


Electrical:

I did some of the tests in the service manual to test the electrical system. They all passed but one; however, all the sub test for that test passed so I am kind of stumped. All pieces of the ignition system are new from a few months ago when we first went through the engine: distributor, cap, rotor, points, wires, spark plugs - plugs show a light grey color as they should. I had set the afr with a gas analyzer to make sure it passed emissions.

Spark Intensity Test (Coil high tension lead) - Passed
Battery to Coil Voltmeter Test (4.5v - 6.9v) - 6.40v - Passed
Starting Ignition Circuit Voltmeter Test (drop <= .1v) - 12.40 -> .90 - Failed
Ignition Switch Voltmeter Test (<= .3v) - .230v - Passed
Resistance Wire Voltmeter Test (4.5v - 6.6v) - 5.13v - Passed
Coil to Ground Voltmeter Test (<= .25v) - .116v - Passed

I also checked the spark plug wires and they were within the allowable 1000 ohms per inch. I was not able to perform the spark plug test because I do not have the adapter required to check spark intensity at the plugs.

The Starting Ignition Circuit Voltmeter Test has me a little puzzled. I could have sworn when I performed it a couple weeks ago, it passed. However, when I went out recently to double check all the numbers for this posting it was then failing.

At this point I am not sure where to move onto and hope that someone here can steer me in the right direction. I do have a complete Centech setup here for it I bought quite a while ago when we first got the truck and if this is electrical related, maybe that will be the way to go. Thanks in advance for any help that may be provided.

 

Timing chain jump a tooth?

Advance the dizzy and see what happens.

 

The compression is up so cam timing must be ok.

Noticed you did not list condensor being replaced an if so some Chinese junk don't last long.
Check in side dizzy for any shorting out points or condensor wire rubbing the inner housing rubbing off the insulation shorting out dizzy, also check the ground wire inside dizzy. An rear fire wall to engine ground wire.
Check for side to side shaft dizzy play.

Voltage at coil is on the low side.

What I'd try is hot wiring it by placing a little jumper wire from +side of battery
straight to the +side of the coil an try starting it.

What color is the spark at going to the plugs??

You can work the solenoid with a screw-driver or with a remote push button starter switch for doing so test if you haven't yet.

But do check the timing, best to remove #1 spark plug & dizzy rotor cap mark on the dizzy housing with a felt pin where #1 wire sits then crack engine over while watching rotor an at the compression stroke at TDC go slow so you can check it.
Report back findings.
Orich

 

I did not replace the condensor; it is still the same one that came in the distributor when we bought it (rebuilt Ford autolite). I will try that if the other suggestions do not work.

I already did this. I wanted to make sure the distributor wasn't too far advanced and preventing it from starting. I ended up retarding the timing back to 10 deg btdc because it was a little high.

I will check the rest of the items you suggested tomorrow and let you know how it goes.

 

Ford did a ign switch screw up that caused these trucks to catch fire or hard starting.
That affected the starting circuit.

So this could also be why you have low voltage at the coil.

Ford replaced the ign switch with a flat blade push on plug type switch.
But ford only did this when customers had troubles with them, but it was not recall.

Pictured below shows the bad pin switch and the replacement one.

This is what the new replaced looks like.


This was the failed one, it would over heat one of the small one that would cause the plug terminal to expand making poor contact lowering the voltage going to the coil while in starting mode. Best to inspect the ign switch plug for any sign of Burnt blackish markings of the small terminals.

A replacement new plug has to be spliced into use the newer switch, they can be found at even Auto zone. I got one out of a junk yd truck in great condition and used it. As the replacements do have color coded wires which made it easier to splice in. Remove Battery ground cable first tho.

I got lucky an found a new autolite ign switch on ebay for $12 buck when, I did mine.
Orich

 

Put a timing light on the #1 sparkplug wire and crank the engine over. If the light doesn't flash, the condenser is most likely bad.

 

I actually did this one already, it was flashing. Slowly, but it was flashing.

I believe it may already have the blade style. I will double check when I go out in a few minutes.

 

It does look like it has the blade style installed.





I cleaned off both sets of contacts with contact cleaner and sandpaper, no improvement.

Everything inside the distributor looks good. I had previously put a new ground wire at the firewall before all this started, unpainted surface on the intake to unpainted surface on the firewall.



Unfortunately, this did nothing. There was no change when attempting to start the engine.

I am not sure and not sure how to test this one. The truck has those deep female spark plug boots so I cant get the connector close enough to the engine block to jump the air gap.

Thank you guys for all your help so far, I really appreciate it.

 

Insert a screwdriver or bolt in the plug wire and do it that way. ( Phillips screwdriver with wooden handle works best.)

 

Looks orange, sometimes every couple fires a blue-ish white.

 

Take a screw driver and move both the condensor and the point leadin wires away from the inner sides of the dizzy housing.

As they look like both are touching the housing insulation will be rubbed off from the Vacuum advance movement stall the motor.

Ps did you try to hot wire it.

Harbor freight has the spark plug testing spark lite.
A useful testing tool to keep in one vehicle

Also what it the BLACK mark from on the vacuum advance arm that rotates the points plate??
Look like where a leadin wire got pinched or something.
Orich

 

I will move the wires tomorrow when it is light again outside.

If by hot wire you mean running a 12v lead directly from the battery to the battery side of the distributor as you suggested, then yes I did and it didn't help unfortunately.

Thanks for the heads up on the spark plug tester.

I will also check the black mark tomorrow and see what it is. It could just be black marker. The distributor has some markings inside from the rebuild process, i.e. purple paint pen dots on the screws probably signifying they were tightened/torqued.

Unfortunately, my camera focued on the shaft in the center and the peripherals were out of focus. I didn't know until everything was closed up for the day and I opened the picture up on my laptop.

 

I myself only had one condensor fail on me in 55 yrs of driving.

Plus worked in a couple auto repair shops and one brake shop and have only come across the older resistor blocks the failed.

But since many auto ignition part have been being made by the Chinese known as being made off shore, we here on this site see just about a dozen a yr guys having starting issues that have had one of these off shore made condensers being the issues.

Or one of the inner dizzy wires being the problems.

I find it odd that a dizzy rebuilder would let a dizzy out door with the wires rubbing on the inner dizzy housing as they should have pulled them up some an away from the housing sides where the insulation will be rubbed off an short the points out.

I'd bet the rebuilder is not installing motorcraft points & condensers unless you got it from ford dealer.

The old oem ford Fe's timing gear is another known source for stripping the nylon teeth that cause the engine to jump timing an just enough to not start. any where after a 100k on the clock

Just rambling some!

 

Off the cuff, reset the air fuel screws on the carb. What carb is on it? QFT, wth is that?

 

This was one of the first things I did when I was ruling out the carb, but thank you for the suggestion.

QFT = Quick Fuel Technologies - Holley 4150 clone

I found the problem. When I was moving the condenser wire away from the housing, the wire fell out of the condenser even though it shows in the picture that it is still connected to the condenser. I replaced the condenser and the truck fired right up. Now I just need to get everything reset, run it through emissions, renew the tags and it will be ready for my son when he gets back.

Thank you everyone who helped me out on this one, especially you orich. Reps all around as the system lets me. I do feel stupid for not just changing this at the beginning along with the points.