86 F250, 5.0 L, No Start

[discnik]

Here's the scoop: 1986 F250 5.0 L Vin "N" 4X4 Dual Tank

Complaint: No Start

Additional: Someone cut the front tank filler neck in order to siphon fuel from the front tank.

Vehicle suddenly started stalling, barely made it back to their house. Vehicle would not start afterwards.

Had weak spark, orange, in spark tester, the glass type.

Cap, rotor, wires and plugs had seen better days so they were replaced.

TFI module failed 80 % of the ohms tests, so it has been replaced.

Ignition coil secondary windings were an infinity reading, so replaced.

Compression was 120 - 150 psi, except for # 7 / 80 psi.

Double checked TDC mark, # 1 plug out, and rotor positon it's fine.

No evidence of a sheared drive gear pin

Have not had a chance to test pick-up coil.

Fuel pressure KOEO 45 psi.

Still have a weak spark at tester & No-Start condition.

Have I missed something ?

Any suggestions greatly appreciated.

[Torch]

The 80psi reading on # 7 shouldn't keep the engine from starting, it might vibrate a little have have a lower power output than it should but the other seven cylinders should be able to compensate for that but I would have it looked into, it might be a valve rocker out of adjustment or something worse that you probably really don't want to know about.

Orange spark is a bad sign, that color means that it is a very cold temperature spark, check the primary voltage at the ignition coil's POS or + terminal using the battery's NEG terminal for your multimeter's ground, you should be getting something close to battery voltage.

If that checks out fine the electronics in the distributor are probably the problem and are not giving a large enough output signal to fully fire the ignition coil at it's highest voltage, in old school terms think of it as the points being out of adjustment and go from there.

[discnik]

Sorry, should have updated remedy sooner. Come to find out the timing chain had jumped two teeth.

By advancing the distributor as far as possible I could get the engine to POP.

Pulled the timing cover, the chain was actually trying to walk off of the Cam gear.