When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
Hey guys, I'm looking for some electrical expertise.
On my 1986 Trans Am I am running a FiTech throttle body EFI system which requires a 12v signal from the ignition circuit via a white 'key' wire. Recently I had issues with the FiTech failing to prime and began diagnostics by jumping the 'key' wire directly to battery. Connected directly to battery it worked perfectly. The battery itself is brand new and tested 12V/600 CCA, alternator is brand new, and new distributor. I used a multimeter to test the voltage from the pink wire that comes from the ignition switch and connects to the 'BAT' terminal on the HEI distributor and found the reading to be between 8-9V with key ON despite the reading at the battery terminal being 12V. I believe this is why my FiTech has been having issues, but I am not certain where to go from here. Anyone have any thoughts?
Pink wire visible coming from Ignition Switch. White wiring is for the FiTech 'key' signal
The power from the ignition switch should actually be via a pink wire w/black tracer. This is not a resistance wire, as was found in older designs. It routes directly from the ignition switch through the C100 connector and to the distributor, and thus should be at full battery voltage. Resistance at the switch, connector, or Duse Link "B" could be causing the lo voltage.
The power from the ignition switch should actually be via a pink wire w/black tracer. This is not a resistance wire, as was found in older designs. It routes directly from the ignition switch through the C100 connector and to the distributor, and thus should be at full battery voltage. Resistance at the switch, connector, or Duse Link "B" could be causing the lo voltage.
Excellent, thank you. It is always a good day to learn something new.
I have accumulated diagrams over the years, and cannot recall where most of them were hosted. Is this an original carbed '86? If so, I can probably load up the diagrams a few at a time.
I have accumulated diagrams over the years, and cannot recall where most of them were hosted. Is this an original carbed '86? If so, I can probably load up the diagrams a few at a time.
Yes, it is. 1986 quadrajet 305 with the 5-speed T-5 gearbox.
does it have battery voltage when you disconnect it ??? or is this with it hooked up ?? if you check it with a load on it, you probably will see a voltage drop. but if you disconnect it, and you know nothing else is spliced in with that circuit, and you're only getting say, 8.7 volts or something, then there is something eating up voltage. as old as these cars are, i'd think someone has probably robbed a hot wire for something else and that device is either eating up voltage, or has shorted out and causing a pathway to ground. hope this helps
does it have battery voltage when you disconnect it ??? or is this with it hooked up ?? if you check it with a load on it, you probably will see a voltage drop. but if you disconnect it, and you know nothing else is spliced in with that circuit, and you're only getting say, 8.7 volts or something, then there is something eating up voltage. as old as these cars are, i'd think someone has probably robbed a hot wire for something else and that device is either eating up voltage, or has shorted out and causing a pathway to ground. hope this helps
Well, one of the POs did attempt to wire a bass speaker into the rear hatch at one point, and there are some sketchy looking wires around the fuse box..
Quick update. I tested voltage to the Ignition Switch and got a reading of ~11 V, which is consistent with the reading across the terminals of the battery using the same multimeter. Now beginning to suspect the Ignition Switch itself..
The same voltage on both the male and female sides of the connector?
I measured the voltage at the red wire indicated by the arrow, and the pink wire. Both tested at a maximum of 11V. I also ended up replacing the ignition switch itself, but this did not solve the problem..
Not yet. I was out of town for a week, but will continue to work on it as weather permits. Because the ignition switch was not faulty and the fusible links appear to have been replaced at some point using crimp connectors and electrical tape, I figure it might be worth soldering in new link wire and heat shrinking the connections properly. I will keep you all updated.
Well, I am happy to announce that the issue has been finally resolved. After replacing my ignition switch, rewiring my fusible links, hours of multimeter testing and chasing wires, the problem turned out to be.. a bad switch.. Yes, the PO wired in a kill switch under the center console that had burned up. Always something isn't it.
Nevertheless, thanks for all the help and invaluable information!
There is nothing more frustrating than aftermarket and/or customized systems that aren't documented. The word "hack" comes to mind. I've done full-on EFI conversions for people from '57 Bel Airs to '70s Chevelles and F-bodies, and handed the owner full sets of documentation, parts lists, and schematics for future reference.
02-08-2024, 04:15 PM
