I posted previously about a crap ton of problems and got some pretty good advice.

I broke everything down, took everything step by step and got down to where I can work on one issue at a time.

As it stands now I have gotten everything to work in the truck as far as I can tell but It wont fire.

1986 F150 4x4
302 EFI
AOD Trans (I bet i can break this pretty fast)

Quick history, when I got the truck it had a wiring nightmare. After many suggestions I was able to get the truck to turn over by key, fuel pump wired to a toggle switch, and it seems everything in the truck accessory wise works now.

I did some testing on the coil, I have 12 volts on the hot wire and 10-ish when cranking. For some odd reason I put the meter on the coil wire it self, it read 12 volts and 5 volts when cranking.

The wire plug going into the TFI is supposed to have 3 wires that should have at least 90% of the available batty power. But Unless I did it wrong, I only have 1 hot wire. (Probably did it wrong.)

I guess I am ignorant as to how I am supposed to test these things...

But as mentioned in the first post (Could not find it, and that could be cause I am tired) The previous owner had a wire from the solenoid, and two wires from a factory harness (They lead to the coil and the Distributer) all wired into a push button switch.

This truly has me stumped. I have chased wires from point A to B looking for shorts all day long.

hope some nice, talented, skilled, educated, expert, pro, or even someone good at faking it can lead me off into the right direction here.

The TFI is supposed to be New (1.5 years old never ran) Can it be tested at Autozone?

What about the EEC, could this be causing my problems and if so is it testable somehow?

Also what amp fuse would be the best fit for the High pressure pump I have wired up to a switch? I am currently using a 30 amp.


Edited - I found the link the the previous thread I posted, if anyone helping needed to read the first cry for help. It can be found here

 

My truck doesn't have EFI or a computer or much of anything electrical and I've
never delved into the ignition to this level so I don't know how much help I can
be but, of what you just said, there is one point that caused me to raise one
eyebrow in a Spock-like fashion:

I'm confused by that statement in that first you have 12 & 10 when cranking
but then suddenly you're at 12 & 5 while cranking, I don't understand why the
difference (difference in the test points?). Regardless, it seems to me that
something is backwards; as I understand it, the ignition should get max battery
power while in START but voltage is reduced while in RUN. Hopefully somebody
else will chime in....

-ct

 

The coil was bad, I replaced it. The difference was in test points. You are supposed to have at least 90% of the available battery power while cranking at the coil. I have that but when cranking the coil itself was hardly putting anything out.

So now I have a new coil and noooo fire to the plugs. I'm wondering if the TFI modal is not bad as well...

But then again, in my supreme automotive electrical ignorance I could not help but wonder what the TFI does... or that little brown modal inside the distro.

So in hopes someone will chime in..

86 f150 302 EFI

Wont fire when cranking. Checking TFI and replacing if needed today. What else should I be looking at if that does not fix it?

And where in the world is the fuel pump relay?

 

fuel pump relay drivers firewall behind coolant tank ect, bypass it and see if it starts but if you have no spark I would look at the optical pickup in the distributor,but check the ignition control module,bolted to dist,and go from there cranking you should have close to 10 volts if you have less than 10v it will never fire cause the ign module is set up that way ,10 volt to the module itself not the coil output of module if that makes sense,those spouts and tfis go bad easy

 

I don't even know what a TFI module is, I don't think I have one ('81 400 carb no
computer).

-ct

 

On most all vehicles, the coil is supplied with 12 volts, or close to it, with the key on. But the coil minus terminal is not grounded, so there is no current flow through the coil, even though you have 12 volts on the + of the coil.

The old points, duraspark II and III modules, HEI, TFI modules, and some of the aftermarket boxes, are all hooked to the minus terminal of the coil, and that's what grounds the coil, and completes the circuit so current flows through the coil. This is no small job, since the coil flows a lot of current when the circuit is first completed.

There is always something that tells the above modules to complete the coil circuit. In the case of points, it's the cam lobes inside the dist. In the case of all the modules, there is a wheel of some kind that tells a pickup to send a signal to the module.

 

Well, the fuel pump kicks on when bypassing the relay by wiring it direct. I know there is a way to test relays but I need to look it up.

Does anyone have a spiffy wiring diagram of the fuel system in 86 f150 302 tfi.

I have one with all the wiring but was looking for something more isolated with just the fuel wiring.



I have 10-11 volts when cranking. The module on the distributor has been tested and they said it was fine. I guess I will change that pickup.

I still suspect some sort of wiring issue or worse... But every day I seem to get a stab closer.

 

yeah its either a wiring problem or the pickup then as long as the ign module is good,hope this diagram post it from a chiltons so Its not the best but it should help identify the wires and chase the to check for opens or shorts I cant get it to post drop me a email a marvinghearing@yahoo.com and I'll shoot it over to ya