Modified starter circuit, what did I screw up now?

Topic: Modified starter circuit, what did I screw up now? (Read 1289 times) previous topic - next topic

Modified starter circuit, what did I screw up now?

April 15, 2011, 06:57:15 PM

I am having issues troubleshooting this problem, hoping some fresh eyes will be helpful.
Car is an 87 TC with manual trans. Battery is in the trunk, and I am runnin a PMGR starter from a 93 Ranger. The wiring changes to accommodate this starter are a large gauge "hot" cable to the starter from the trunk and the signal wire extended from the original relay location. In order to keep from having a live cable runnin the length of the chassis all the time, my "hot" cable also has an additional relay in the trunk near the battery. The signal for this relay is tapped off the R/LB that runs to the neutral safety switch jumper.
This modified circuit worked flawlessly for about a month then started to hiccup once in a while, especially on warm/hot restarts. I could hear the rear relay click, but nuthin doin up front. I assumed the starter itself was pin out. Wednesday, the car decided not to start at all. Same deal, click from the rear relay but nuthin up front.
Checking the wires on the starter, I get 11.9v on the large lug but only 4.6v on the signal lug. Battery voltage is 12.2v. Jumper the starter with a wire from the large lug to the signal lug and it works fine except that it runs on due to being PMGR.
Working backwards thru the signal circuit(R/LB) I found 10.7v at the clutch switch as well as the ign switch and the rear relay. If I disconnect the signal wire from the starter I get 10.7v there as well, but connected to the starter I only get 4.6v again. Ground thru the solenoid case, starter case, transmission bellhousing to wherever shows good continuity, and I added a couple large gauge grounds running between the chassis and drivetrain when I moved the battery to the trunk.

What am I overlooking?

Modified starter circuit, what did I screw up now?

Reply #1 – April 15, 2011, 07:07:24 PM

Can you trigger the starter and check the voltage at the battery had a similar issue with factory wiring and the result was a simple junk battery

Modified starter circuit, what did I screw up now?

Reply #2 – April 15, 2011, 07:32:11 PM

Battery voltage only drops to 11.1v with starter circuit engaged.

It actually started once while I was trying this test for you; scared the bejebus outta me. Just once though, right back to not starting for the second two attempts.

Modified starter circuit, what did I screw up now?

Reply #3 – April 15, 2011, 08:14:41 PM

I am thinking the solenoid must be too large a load for the R/LB signal wire. Probly need to add another relay.

I can put another stock fender mount relay in the stock location. I currently only have a large stud to power up the harness in that location since moving the stock relay to the trunk. Get another fender mount relay, put the harness and charge wiring on the hot side, put the R/LB back on the signal terminal, and run my starter signal off the switched side of the relay.

Modified starter circuit, what did I screw up now?

Reply #4 – April 15, 2011, 08:50:08 PM

I am planing on doing a set up like you and was told that the stock relay the distance for the draw was to long. Check my battery relocation thread in miss tech. There a link on the relays there. I'm using the phone so I can't post a link. I'll check back later.
Hope this helps

Modified starter circuit, what did I screw up now?

Reply #5 – April 15, 2011, 10:15:12 PM

Fixed.
Not sure why I thought I could run both the factory relay and the new solenoid off a circuit Ford designed to trigger a relay. Reinstalling a fender mount relay in place of my power point allowed a full 12v to the starter solenoid and put the R/LB back to simple signal duty(now triggering two relays, but thats a whole lot less load than a solenoid).