car dies intermittently, advice on what I've found

boboli

New Member
Jun 12, 2010
22
0
2
Tucson Az
First i would like to say hello. I haven't owned a mustang in nearly 10 yrs. I was spending too much time and $$$ on them so I bought a nice foreign car with a really long warranty. Well the warranty is now up and I decided to pickup a 1989 mustang LX 5.0 conv I found. It has been a project so far but its biggest problem is an intermittent dying problem.
I had to change the trans (aod) because someone either left the TV off by mistake or on purpose to cover up a trans prob. The car ran when I got it but not when I started the trans swap. After the swap it still didn't start. It would fire up just enough to make you let go of the key but would never actually fire correctly. It seemed to have spark but no fuel pressure. The pump had been noisy, it still primed with the key, but it trickled out of the schrader valve. There was 12.25 volts to the pump when it was jumpered to run. The car would also run fine on carb cleaner so I changed the pump. The car started and ran fine. I was busy filling the aod and setting TV pressure, maybe 5 mins, when it died. It turned off like you had turned the key off. I went over and tried the key again and it started right up. then dies about 2 mins later. It started again but died quickly. Then it wouldn't start, just crank a lot.
I have been following the cranks and no start checklist and I used a noid light at the spout connector. I also put a spark test light on the coil. When you crank the car, th pump primes with the key but there is no noid light flashing and the coil wire doesn't have any spark. I did try another used ford TFI and also a tested the TFI with a test light to the coil wires ( no illumination at all) but the problem has not changed. I also tried another used coil I Had.
If I am following the checklist right, I believe that the pip in the distributor is bad because there is no noid light illumination. Is there something before that in the system I can check to see if it is loosing power before it gets to these. I have a feeling that this car was sold because of this problem. The ignition switch is changed, inertia switch has cuts in the insulation on both sides, tank was out, and on. I think someone was looking for a problem and couldn't find it.
Please any help would be greatly appreciated as i don't need another parts car.
Thanks
Boboli
 
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You have already diagnosed the problem. The PIP sensor in the distributor is bad.

The PIP is a Hall Effect magnetic sensor that triggers the TFI and injectors. There is a shutter wheel alternately covers and uncovers a fixed magnet as it rotates. The change in the magnetic field triggers the sensor. A failing PIP sensor will often set code 14 in the computer. They are often heat sensitive, increasing the failure rate as the temperature increases.

The PIP sensor is mounted in the bottom of the distributor under the shutter wheel. In stock Ford distributors, you have to press the gear off the distributor shaft to get access to it to replace it. Then you drive out the roll pin that secures the gear to the shaft. When you go to press the gear back on it has to lined up perfectly with the hole in the gear and shaft. I have been told that the hole for the pin is offset slightly from center and may require some extra examination to get it lined up correctly.

Most guys just end up replacing the distributor with a reman unit for about $75 exchange

Spark with the SPOUT out, but not with the SPOUT in suggests a PIP problem. The PIP signal level needs to be above 6.5 volts to trigger the computer, but only needs to be 5.75 volts to trigger the TFI module. Hence with a weak PIP signal, you could get spark but no injector pulse. You will need an oscilloscope or graphing DVM to measure the output voltage since it is not a straight DC voltage.

See http://www.wellsmfgcorp.com/pdf/counterp_v8_i2_2004.pdf and http://www.wellsmfgcorp.com/pdf/counterp_v8_i3_2004.pdf for verification of this little detail from Wells, a manufacturer of TFI modules and ignition system products.
 
Thanks for the help jrichker
i figured it was the pip, but thought I would see if there was a possibility of another problem. I also don't like to throw money at repairs so i figured it can't help to ask for some knowledgeable advice.
I am familiar with the hall effect triggering as I have a dodge omni glh turbo that uses a similar system. It is much more fragile than the mustang's but just sits between the distributor and the rotor under the cap so its easy to change.