94 Mustang GT: Voltage Drop Fix

I finally got everything sorted out with Rock Auto.  Their customer service was great, they created a label for the return of the remanufactured alternator with the wrong case.  Unfortunately I didn't get that out until Friday.  So it only shipped on Monday.  Once they received it, another remanufactured unit was sent to me.  It arrived two days later.

In the meantime, I sourced an old stock 3G alternator, rusted from sitting in someone's shed, and one that was on a running car that is known good.  I also still had my original in the car.  Once the remanufactured alternator arrived, I had a total of four 3G alternators.

The remanufactured units don't come with a pulley.  The two alternators that I sourced did have pulleys.  One was stock, the other one is an underdrive.  I also still have the stock one on the one in the car.  I removed the stock pulley from the unit that was sitting in the shed.  I cleaned it up the best I could and hit it with some self etching primer followed by some engine enamel.  It was better than before, but didn't look all too great.  I realized at this point that I was going to need a media blast cabinet to do some clean up work.  More on that in another post!

I removed the stock 245k mile alternator again (I've had practice).  I installed the pulley I had just painted on the Remanufactured unit and installed it in the car.  That entire process took about 25 minutes.  Next step was to take it for a ride and see if the voltage drop was still present.  I started it up to make sure everything was working as expected and noticed the voltage gauge on the dash read higher than it usually does.  This was a good sign!  I shut the car down.

Next I boxed up the rusted old alternator as a core return, got the label on the box and brought it to the FedEx drop off.  After it arrived at Rock Auto, they inspected it and returned to me the 75$ core charge.  Nothing like getting 75 for an alternator that doesn't really work, is rusted and I don't know how many years old.  This also meant that I was into the remanufactured Motorcraft that is installed in the car for 106$ total.

I took the car for a ride and eventually wound up at the same hill where I do my testing and logging.  I did the same exact thing that produced the last few logs that showed the voltage drop.  Once I got back to the house, I checked the log.  Its FIXED!  The minimum voltage was 14.18.  Much better!



I still may upgrade to a 200A alternator.  The way I figure, and since I have another core to use, it would cost me out of pocket significantly less than buying a 200A off the shelf.  All I need is the remanufactured unit, an upgraded rectifier and an upgraded stator.  Maybe a winter project once my bank account recovers!!!

94 Mustang GT: Voltage Drop, Alternator Harness Upgrade, PIP failure

Since I've been logging data with the Moates Quarterhorse, I've noticed a significant voltage drop between 4 and 6k RPM.  Voltage drops from normal down to 12.6, which is just about battery voltage.  If you open the hood of the car with out it running and test the battery, it will be 12.6v.  With the car running, it is 14.4v.  

So far, I have added an 8GA ground wire from the negative post to the factory ground location on the chassis.  The 4GA ground from the negative terminal to the engine was not changed.  I did clean the surface of the ground strap from the motor mount to the frame rail when I did the engine swap.  The log looked the same.  

Next, I thought maybe it's the battery.  So I ran the same test / collected the log while using a 750A battery instead of the 525A stock battery.  Same result, no change.

It has to be the alternator not being up to the task.  Not surprising for a unit that was born in 1994 and has gone through two voltage regulators and one set of brushes.  It was time to replace it!  I ordered a motorcraft remanufactured unit from Rockauto.com.  

Normally, remanufactured units work really well.  That’s typically because they are hand built and tested.  The remanufactured alternator I received looked great at first, until I put the stocker and the reman unit side by side.  Looks like someone used the incorrect front case when rebuilding the reman unit.  I can’t get the pulley to sit right because it hits that shoulder on the case.

After a few emails, I shipped the ‘mis-boxed’ reman unit back to them with a label they provided and I should have the new reman unit tomorrow.  Hopefully that one is correct!  

I did rebuild the stock alternator harness with a 4GA charge wire.  I removed the stock harness - disconnect two plugs on the alternator and the charge wire, then the charge wire at the distribution block by the battery, the 4 pin plug, and the plug for the AC compressor.  I disassembled the harness by removing the wires from the loom.  Then I made a new 4GA charge wire, same length.  I used a hydraulic crimping tool for the 4GA lugs (That hydraulic crimping tool works really well) and used heat shrink tubing.  Then I added it to a new loom and wrapped it all in electrical tape.  It really looks stock.  I went one step further - On the back of the alternator is a bolt for the smog bracket.  I cleaned up the surface area and ran a 4GA ground wire from the alternator case to the engine bay.  It came out really nice!

I took it for a ride identical to the others to see if the graph is the same.  I think that the hard drive protection kicked in on the laptop because I’m missing like 3 seconds of log file data, which ironically is 4k to about 6k RPM.  You know, exactly where I need to see if the voltage drop is still there… That was Friday evening.

Saturday I took it out with intentions to run an errand with my wife and collect a new log.  About 1/2 mile from my house the car stalls, barely starts and is running rough.  I suspected the PIP sensor since the tach was jumping around.  Ran back home (glad I had sneakers on!), grabbed my truck and trailer and got the car home – took a couple tries to get it onto the trailer due to no power / barely running.  Got it back home and pulled the codes.  Code 211 – profile ignition pick-up (PIP) sensor – circuit failure.  

I suspect the Summit Racing street strip distributor has a failed PIP sensor (stator / pickup).  The distributor has 7800 miles on it and is less than 1 year old.  If it is the PIP I’ll know later today after swapping distributors for an MSD 8455 pro billet distributor I borrowed from a friend.  I still have the stock distributor, and a brand new DU-50 Motorcraft pickup.  Next steps will be depending on what Summit says about their failed product.