2.9L TFI Weird Issue

[Uncle Gump]

It's been awhile.... but I'll try.

The tach wire between the negative side of the coil and TFI allows current to flow from the 12volt positive side of the coil... through the primary windings in the coil to ground at the TFI. It's hard to see "pulsing" 12v to 0v on that wire... unless you have an oscilloscope. The update rate on a DMM isn't fast enough to show that 12 to zero change... it will typically display a varied voltage which would be half of battery voltage... depending on crank speed.

 

[BoomTexan]

It's been awhile.... but I'll try.

The tach wire between the negative side of the coil and TFI allows current to flow from the 12volt positive side of the coil... through the primary windings in the coil to ground at the TFI. It's hard to see "pulsing" 12v to 0v on that wire... unless you have an oscilloscope. The update rate on a DMM isn't fast enough to show that 12 to zero change... it will typically display a varied voltage which would be half of battery voltage... depending on crank speed.

I figured that it would do that, the VAC to VDC conversion typically hits like 12/1.414, but in that case, I should be seeing like ~8V, not 4 like it is currently. For this sawtooth, I'd expect 6, but I'm not hitting that either.

Just to see if my logic makes sense, does this statement make sense to you: the coil just isn't activating at all for some reason anymore, and given that I've cycled two known good TFIs through it, the only failure point should be my new distributor, right? (especially given wiring diagram linked below)

Of course as soon as I get the motivation to get outside and work on this, it starts raining.

 

[Uncle Gump]

You have to remember or consider what battery voltage is while cranking. That signal line should be roughly half of battery voltage.

 

[Uncle Gump]

The fact that you can see a voltage in that tach wire other then battery voltage tells me that the hall effect is triggering the TFI.

I also read that you said ballast resistor. Where is this ballast wired in?

 

[BoomTexan]

Ended up replacing the new distributor with the old one and it fires off now. My theory is the pickup coil was actually shot.

Anyways, it's firing, but it's running rough and rich and doesn't want to idle. Don't think it's a timing problem, though it might be. I might try and rotate the spark plugs one over and see if it'll help, because when I retard timing it gets better and nearly idles.
Put it in at the correct orientation (to the best of my knowledge). There's only 3 positions that the distributor can fit into, right? It has that weird tooth thing at the bottom that I could only get to fit into the gear in 3 positions at least. If that isn't the case, then rotating the wires one over should get me to a 60 degree adjustment. The hall sensor has 6 poles too, so it should be able to fire at all points. There's a good chance that this thing was screwed with in a weird way before I got it, and I just never changed the spark orientation.

Anyways, questions:
1. Does the red wire go into the left or the right side of the ignition coil? With the spark prong facing you and the plug at the bottom? The plug fell completely apart so I just have the two prongs. Not sure if it matters to be honest, but I don't really want to put it to chance.
2. I can run this without the O2 sensor plugged in when it's cold, right? Just broke it free from it's exhaust manifold prison and need to JB Weld it back in, so I can't run it for ~24 hours after while I wait for it to cure. Would like to get it ironed out today before I put the JB Weld on tonight.

 

[Uncle Gump]

You have to get the coil polarity right...

That distributor should drop in in many different positions. Only one is correct. Ti get it fully seated... not only do the gears have to align... but the distributor also drives the oil pump. It's a hex shift and sometimes you have to turn the engine over slightly to get the next to align... then the distributor drops into position.

If it were mine... I would put the engine at TDC of compression on number one cylinder. Then drop the distributor in with the rotor pointing to number one on the distributor cap. Make it run... pull the SPOUT... time the engine properly... tighten the distributor... connect the SPOUT.


You can rewire the cap if the distributor is of a tooth or 7... there is no signature signal... if all the hall effect vanes are the same size. But why... take a minute and install it properly.

 

[BoomTexan]

Ah, that's good to know. Will do on the distributor, sounds easier than timing it again anyways. Was just so confused why it wasn't lining up in a way that would fire correctly.

So, to answer my question, which side does the red and the green wire go on? Any idea there?

 

[gaz]

@BoomTexan
Hello,
You have more than one thing going at once, so knock it down to 1 thing at a time...
TIMIMG:
1) if you are 180° out it most probable that your #1 cylinder TDC is 180° out, an easy mistake. Verify that your #1 cylinder is at 0° TDC first. This whole thing works better with the #1 plug on the distributor in close to the correct place (passenger side towards the firewall as marked on the distributor cap). To accomplish this I remove the passenger side valve cover, while rotating the engine clockwise from the front to rear view, watching the valves move until they are in the only position that 0° TDC on #1 can be.


2) once certain that your engine is at TDC on #1 cylinder, perform the 50/50 test to conclude whether you have a fuel or electrical fault; if you have a fuel issue it will start on starter fluid, if you have an electrical issue, it WILL.NOT START on starter fluid.

Once here, you should have more information to share or have it resolved.

NOTES
• I would have unbolted the manifold connecting ("H" pipe on an 86) as opposed to sawing off. New bolts are a good thing and those pipe sections are like gold in the wild.
• once you do get it running, relocating your ignition module to either behind the front grill (in the airstream) or the passenger apron are both great places. More important is installing the wire shielding.
*** no matter what, after installing a different distributor, the timing must be verified (I only make that adjustment at normal operational temperature with all engine loads on...lights, A/C, stereo...)

 

[BoomTexan]

@BoomTexan
Hello,
You have more than one thing going at once, so knock it down to 1 thing at a time...
TIMIMG:
1) if you are 180° out it most probable that your #1 cylinder TDC is 180° out, an easy mistake. Verify that your #1 cylinder is at 0° TDC first. This whole thing works better with the #1 plug on the distributor in close to the correct place (passenger side towards the firewall as marked on the distributor cap). To accomplish this I remove the passenger side valve cover, while rotating the engine clockwise from the front to rear view, watching the valves move until they are in the only position that 0° TDC on #1 can be.


2) once certain that your engine is at TDC on #1 cylinder, perform the 50/50 test to conclude whether you have a fuel or electrical fault; if you have a fuel issue it will start on starter fluid, if you have an electrical issue, it WILL.NOT START on starter fluid.

Once here, you should have more information to share or have it resolved.

NOTES
• I would have unbolted the manifold connecting ("H" pipe on an 86) as opposed to sawing off. New bolts are a good thing and those pipe sections are like gold in the wild.
• once you do get it running, relocating your ignition module to either behind the front grill (in the airstream) or the passenger apron are both great places. More important is installing the wire shielding.
*** no matter what, after installing a different distributor, the timing must be verified (I only make that adjustment at normal operational temperature with all engine loads on...lights, A/C, stereo...)

Thanks for the help here! I'm 100% certain that the #1 TDC is not 180 degrees out, I was careful to install the new distributor at the same orientation as the old one, and think I just jumped some timing when reinstalling the old one.

I'm 90% sure that it's a spark issue, but I'll dump some ether in there just to check. It's running very rich but there is a decent chance that the new fuel filter I installed may have created some pressure issue.

I actually have relocated the ignition module to the passenger apron already, did the Aerostar heatsink module with the dummy unit. Haven't had any problem with the wire shielding so far, but when I get all the electrical stuff together and start doing wire cleanup, I'm planning to get some shielded cable runners.

Unfortunately I put an impact on it to try and get it off, but it just would not break free. Spent a good hour or so trying to get 2 bolts off and decided I was just going to have to bite the bullet and saw it off. I didn't want to do what I did either. Have just been fighting this O2 sensor off and on for about 6 months and it was impossible to progress with it in its current orientation.
Actually thought about reattaching it in a more replacable orientation (doing what Ford should've done from the start lol), which would've required the sawing anyways.

edit:
3rd time today I've gone outside to work on this thing and made it barely 5 minutes before it started raining again. Will post updates tomorrow.