Mustang Still Cranks But Wont Start :-(

[Sh3aNz0r]

I followed the checklist on this forum that jrichker wrote, and am a bit stuck. I also have a 92 LX 5.0. The car was running along just fine then out of the blue, died and has not restarted since. I have good spark, because if i spray ether in it will run for about 5 seconds before it runs out of fuel and dies, tested fuel pressure to the rail and pressure is good. Things I have noticed are that with the ignition on, the fuel pump never stops priming, and when trying to crank the car, a Noid light installed on 1 of my injector wires gives no light at all. Is it likely that the problem is the PIP sensor even if I am getting spark? Was recommended to me to replace the TFI, but if the TFI was bad, I would expect no spark, not no injection functionality. Any input would be greatly appreciated. Already have replaced parts that weren't the issue, and with the weather getting nicer, I really want to get this monster back on the road! Thanks in advance!

PS. I know the checklist says PIP sensor could be the issue if injectors aren't firing, but would I also get no spark if the PIP was bad? Or is it possible for it to allow 1 circuit to work but not the other since it is partially responsible for both. Thanks!

 

[jrichker]

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.

To remove the gear, first you drive out the roll pin that secures the gear to the shaft. Then you get to press the gear off with a hydraulic press or puller. When you go to press the gear back on, it has to be perfectly lined up 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 remanufactured unit for about $75 exchange


PIP problems & diagnostic info
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.

 

[Sh3aNz0r]

My issue is that I always have spark, SPOUT in or out, but can not get injectors to fire at all. Can get the car to run on ether without issue, but the injectors just aren't firing. Also still worried about why the pump constantly primes instead of shutting off when it gets up to pressure. Starting to wonder if its not a computer issue. Bought the PIP and the ICM, but don't want to spend the time or money if its not likely that either one is causing the car to have great spark, and have fuel to the rail w/good pressure, but the injectors just will not fire. I get voltage to red on the injector wiring, but like stated before, noid light will not light up, and injectors will not fire.

 

[jrichker]

My issue is that I always have spark, SPOUT in or out, but can not get injectors to fire at all. Can get the car to run on ether without issue, but the injectors just aren't firing. Also still worried about why the pump constantly primes instead of shutting off when it gets up to pressure. Starting to wonder if its not a computer issue. Bought the PIP and the ICM, but don't want to spend the time or money if its not likely that either one is causing the car to have great spark, and have fuel to the rail w/good pressure, but the injectors just will not fire. I get voltage to red on the injector wiring, but like stated before, noid light will not light up, and injectors will not fire.

It is evident that either you did not bother to read or did not understand the information in my post.


PIP problems & diagnostic info
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.

 

[Sh3aNz0r]

I did read through it and I did understand that the PIP sends signal 2 ways to different devices (the PCM and the ICM). So if i understand what i read, it is very possible that the PIP is supplying the signal needed for the ICM to fire the spark plugs, but is not sending the signal needed to the PCM telling it to pulsate the injectors? Sorry if I upset you, I just am trying to be sure because as stated in the welcome wagon, im new to these Ford Ignition systems and want to make sure I cover all my bases. Trying not to replace the distributor if possible.

 

[jrichker]

.

So if i understand what i read, it is very possible that the PIP is supplying the signal needed for the ICM to fire the spark plugs, but is not sending the signal needed to the PCM telling it to pulsate the injectors?

That is correct. If the PIP pulse is less than 6.5 volts, the injectors don't fire. You will have spark but no injector pulse.

Check out the link to the Wells tech article. I think you will find it very interesting.

 

[Sh3aNz0r]

I read through the entire thing and it was a very informative read. Guess I will try replacing PIP next, since the part is only 15 bucks. From what I read, you cant incorrectly reinstall the shutter wheel unless you were to turn it around a full 180 degrees because there is a roll pin that helps realign the shutter wheel. Once again I appreciate all your suggestions and cant thank you enough for your help with this issue. I will check back and update after replacing the PIP. Thanks!

 

[Sh3aNz0r]

quick question before I jump into replacing this PIP sensor in the morning. Read the WellsCP and noticed the differences in the ICM. The car is equiped with a grey ICM, but when I went and purchased a replacement, the replacement is black? Should I try to use it, or do i need to get the grey one for it to work? Sorry if the question seams stupid, just not sure if I should swap it out before getting myself into further issues... thanks in advance!

 

[jrichker]

You need a gray module in a 86-93 5.0 Mustang

b]Diagram courtesy of Tmoss & Stang&2birds[/b]

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring Mustang FAQ - Wiring & Engine Info Everyone should bookmark this site.

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pinout
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

 

[Sh3aNz0r]

decided to just replace the entire distributor after removing the cap, rotor, and shutter wheel, only to find rust and remnants of moisture in it. real quick question before i tackle it this weekend. before pulling the distributor to find out if its steel or cast iron gear, is there any other way to know so I can go pick up the replacement before tearing her apart? As always thanks in advance!

 

[jrichker]

decided to just replace the entire distributor after removing the cap, rotor, and shutter wheel, only to find rust and remnants of moisture in it. real quick question before i tackle it this weekend. before pulling the distributor to find out if its steel or cast iron gear, is there any other way to know so I can go pick up the replacement before tearing her apart? As always thanks in advance!

Roller cam engines use a steel gear. Flat tappet cam engines use a cast iron gear. All the 5.0 Mustangs from 85 on had roller cams as original equipment.

 

[Sh3aNz0r]

I can not thank you enough for your time and wealth of knowledge you have assisted me with in this matter. Thanks jrichker!

 

[Sh3aNz0r]

Well I got the car running! Long story short, everything I had already replaced was fine, but somehow a 1/8 inch rot hole formed in the door jam on the passenger side, and allowed water to drip down onto the computer...
replaced the computer, and re-timed the car now that I had replaced the distributor, and she fires and runs without issue. Decided to throw some stretch wrap over the computer to prevent any further water issue while I repair the rot hole above the unit.

Thanks again for all your help!

Brandon