Weak spark, no power = pick-up coil
 

My truck has been running me crazy trying to figure out what was wrong with it. I had completed a 460 swap (replacing the 300 wheezer, don't get me started on what a disappointment that motor was) 2 weeks ago, but the BBF just did not seem to have the suds it should have. The first 1/3 of the throttle was great, but after that, there wasn't much there. It started and idled fine as well.

Long story short, after swapping many parts, it was the pickup coil in the distributor making the spark kinda weak, but not so weak that it had any trouble starting, which is kinda odd I thought. I searched and read many threads about weak spark, and they all either didn't start at all, or were hard to start. Mine was not like that. Also it did it hot or cold, which also seemed unusual, generally the pickup coil will start to falter when it gets hot.

Anyway, after swapping lots of parts, some new (like plugs and wires and cap and rotor, which it needed anyway) and some used, thanks to a generous friend with a supply of old Ford trucks, tonite I got it when I swapped the distributor out.

Now it runs like a 460 should, certainly more power than that old truck has ever had in it's life. I put a lot of time and money and busted knuckles into this deal, maybe now I can get some payback. I'm putting it right to work - I've got a 20' trailer to pull about 100 miles on Sunday.

I didn't know you did a 460 swap on your 300 truck. Thats cool that its running right now.

What was wrong with the 300, just old and worn out?

I gotta pull a trailer for the prison ministry I am in, it weighs about 7000# or so loaded and the Six was not up to that at all. It only had 175K on it but it was getting tired, it didn't even like the 1500# trailer I pulled for my church a few times. Mileage had also dropped - it used to get 18 but was down around 14-15 lately. I had been shopping for an F250-350 for the trailer work but then decided, hey, why don't I just drop a 460 in this truck?

I was all excited and tried to drive it to work today, but I smelled gas about 10 miles into the commute and pulled over, #7 injector is leaking, had to go back home. Euphoria delayed again...

Sounds more like you were out of time with old distributor. The PIP sensor (there is no pick-up coil in EEC IV distributors) is just a trigger for the ICM and has nothing to do with how much spark you get.

Being out of time would not make my spark from the coil be orange, tho.

Maybe if you had a bad ground inside the distributor?

http://i54.photobucket.com/albums/g9...tionSystem.jpg

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Maybe, don't know, I swapped the whole distributor, just figured it was the PIP sensor, it's working now, so not gonna mess with it. :-)

Replaced injector o-ring tonite, crossing my fingers I can drive it tomorrow for a whole day without something letting go. This has been more of a fiasco than I planned for - I don't think my truck is very happy about giving up it's original engine.

Hi Everyone,

Reviving old post. I actually have the exact same issue with my 460 1990 tfi-iv. Truck has an orange spark, but cranks, and runs just fine under no load or at idle. At 3k rpm or under load it bogs down something awful. I ran checks, dizzy ground came in at 1.2k ohms should have been near 0. in the diagnosing procedure outlined in Haynes manual (I know, I know) it led me to believe the PIP stator had failed. Subford, assuming it is the ground, is there a way to repair the distributor ground without replacing the entire distributor?

Alternatively, is there another way to confirm that the pip is working? I'm getting spark with the SPOUT plugged in, although the spark is orange. According to Haynes, they said turn over the motor KOEO with my DVOM attached to battery negative and the other end attached to the spark out pin on the harness. It said set dvom to AC volts and crank and should read between 3 and 8.5 volts AC. I got maybe .03 volts AC. According to my DVOM a resistance check of the harness side leading back to the ICM passed.

Thanks,

Thomas

The ignition ground is from the screw in the PIP sensor through the distributor housing to the distributor hold down bolt to the block. The block is grounded by the large NEG cable from the NEG post of the battery.

This is the ground for the whole ignition system from this screw all the way back to the ICM and PCM computer.

I do not know where you took the ground reading point but it should be zero ohms ~ from the screw to the NEG post of the battery.

You might also want to view this video. I know it is for a newer truck with the ICM mounted on the fender but it still works and is wired the same except for the IDM and start wires for trucks after 1994.

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Run a heavy jumper ground wire to the distributor body. Orange spark = Bad. Ignition system draws what, maybe 10 amps? You can't really measure straight ohms resistance for this, (although should be low) it has to be measured under load, for voltage drop. But we know the spark is bad already, so it's even money that might be it?

OK. I've attached a few photos below. Here's where I got the 1.2k ohms reading:

While using the Haynes manual, I was also using a TFI IV worksheet I found on rangerstation.com, I just noticed that their layout of the TFI connector and the Haynes book's layout of the TFI connector are inverted. So when I was following the TFI worksheet it said "Check TFI module to distributor ground at pin 6." So when I plugged into pin 6 on the TFI connector, according to the worksheet, it was the ground wire, but according to haynes, it would have been the PIP Out wire. In the photo of my connector it looks like the light green/yellow wire on the far end.

I rechecked resistance from the TFI connector ground (according to haynes) this time the black/tan or black/white wire and got zero ohms.

I also plugged in all the connectors and and clipped my alligator clip to the bright brass screw next to the green wire inside the distributor near the PIP (was that the correct mounting screw?) and then clipped the other end to the battery terminal NEG post and also got zero ohms. I also checked ground from the distributor body to battery NEG and got zero ohms.

I am using my DVOM with alligator clips and t pins inserted into connector from the front side, and I am using the straight alligator clip to clip it to the shaft area of the distributor case.

Finally, the PO had told me that someone at some time swapped out the motor of this truck (a 1990 f250 4x4 460) with a '92 460. My wiring harness seems to match the scheme of the 1990 wiring harness, except that the SPOUT Wire is pink on mine. FWIW, I also have a fender mounted TFI, mine is the gray push start unit which mine is a manual trans so that should be correct.

Thanks for the link to the video. I've watched it a couple times before. May need to go back and revisit it.

Thanks for your help.
https://cimg4.ibsrv.net/gimg/www.for...339a094590.jpg

Illustration of TFI ICM connector on TFI flow chart.


https://cimg7.ibsrv.net/gimg/www.for...1e2f07cbc0.jpg

Haynes Manual wiring diagram for 1990 7.5 vin G


https://cimg8.ibsrv.net/gimg/www.for...be7cce6b98.jpg

Back side of my actual TFI Connector


https://cimg9.ibsrv.net/gimg/www.for...6bd9832a5a.jpg

inside of distributor


https://cimg0.ibsrv.net/gimg/www.for...035191ac34.jpg

Haynes illustration of layout of Distributor connector and TFI connector


https://cimg1.ibsrv.net/gimg/www.for...9b2f5c7cba.jpg

My actual distributor connector and harness side distributor connector


https://cimg2.ibsrv.net/gimg/www.for...25bbed69ab.jpg

wire color of distributor side connector


https://cimg5.ibsrv.net/gimg/www.for...b661db7d74.jpg

wire color of harness side of distributor connector

Also, I noticed that the distributor side harness connector has seven wires and the harness side connector has 5 wires. nothing leads me to believe that this is wrong because the truck ran fine before, but just an observation.

The 7 & 5 wire distributor systems:
http://i54.photobucket.com/albums/g9...pskx8z8uqj.jpg

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The 1990 7.5 Ignition:
http://i54.photobucket.com/albums/g9...psqgbpebtj.jpg

1992 Ignition:
http://i54.photobucket.com/albums/g9...psbyjjqtd7.jpg

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