I have a 91 f150 with a 300 straight six with the TFI IV ignition system. The truck recently quit running on me. First it started to sputter and buck like the timing was completely off. We changed the ignition module which is mounted on the distributor and it ran again the next day. I took it out the road to give it a test run and it quit on me. We changed the ignition coil and the module again. Still wont run. Any ideas?

 

Barring a plugged fuel filter, probably the stator(PIP) in the distributor. I would check to see if you are getting spark through the plug wires when it quits and won't start.

 

I am getting spark but its acting like its out if time. Also the tach spins backwards when im cranking the engine

 

Did you pull the distributor to replace the module?

 

A few thoughts.

You might try pulling your distributor cap to make sure that everything is rotating smoothly and there's no slop. The drive gear is fiber and it could get damaged.

Also, if you pulled the distributor originally, recheck the position. Get #1 to TDC on the compression stroke and check that the rotor is pointing at #1.Takes a little screwing around, but it can be done. I used to mark a line on the side of the distributor.

The PIP could be screwed up ( and may have been part of your problem originally). It's a magnetic sensor that reads the position of metal ring inside of the distributor.

As for the ignition module, make sure that you use the heat grease, and make sure that you tighten the screws -- I believe that one of them is a ground. Also, they come in black and gray -- and I think that there's a difference.

Good Luck,

hj

 

No i did not pull the distributor to change the module and the distributor was changed about two years ago

 

I would go down the fuel road before ignition. Put a pressure guage on your system and verify pressure. If your dead set on ignition, the Haynes manual has an excellent testing procedure which is preferable to throwing parts. If you find your pip is actually bad, it's easier to just change the distributer.

 

Its deffinately getting fuel. We're pretty sure it's ignition. Any ideas why tach would rotate backwards

 

IIRC, Tach uses a pulse signal from the TFI. If the pulses are funky, then the tach might do that. On my truck, the tach has stops, so I assume it is also spinning forwards at some point. And the 2 different color TFI's are different, DO NOT SWITCH COLORS.

Also, if any of the TFI input signals are wrong, the module would put out something wacky. Your old units (I see there have been 2) might have been killed by an overvolt input signal. Did you pull codes AND check sensors/modules/etc. with a multimeter?
And did you reset the dizzy? They sometimes rotate on their own.
-Mike

 

Yeah we bench tested the tfi modules and all test good

 

How about everything that plugs into it?
-Mike

 

It plugs into the distributor and the wiring harness. Wiring tests find which leads back to the pip

 

Changed distributor. Truck runs now but idles rough

 

Now check plug wiring, plugs and gaps.
-Mike

 

Also distributor rotates when loose