cgunnr

Alright, so, Having a crank/no start issue on my '86 FC. The car runs fine off of ether, but fuel doesn't get past the rails. Have essentially replaced the whole fuel system at this point, from pump to even getting new primary injectors, and confirmed operation via testing. However, despite the injectors having power, I believe they have no signal. Though they click on a test rig, they won't click when cranking. I believe it's down to some kind of electrical issue, but don't have any ideas on what it could be at this point. My only lead right now is a mystery connector located on the engine harness just off the ECU in the passenger footwell (attached). It looks like the wiper connector, but is in a weird spot right off the ECU bundle, has colors that aren't the wiper connector, and also isn't my wiper connector because my wiper connector is plugged in and works. Worth noting that previous owner installed some weird stuff and i've previously had to fight electrical shenanigans caused by that. I'm running out of things to test, so all ideas on what could be wrong are welcome.

mystery connector

Cardinell

Have you checked the anti-theft system?

cgunnr

Not installed in my car, to my knowledge. Previous owner did, however, have an aftermarket alarm installed, which i had to uninstall and bypass, as the control unit for it was dead and was cutting off my fuel pump and spark (both of which now work after removing it).

Cardinell

Understood.

Have you checked for voltage at the connector while cranking? If you don't have voltage, obviously the injector won't fire. If you do have voltage and still no click, i would try checking the injector driver circuit at the ECU. If you have a spare known-good ECU, it may be easier to swap that in and see if the car will start



Edit:
Since you have an 86 that means your injectors are low impedance. Check the resistor pack under the air box per the FSM. If it's out of wack it could also cause an issue

cgunnr

Okay, so update: when unplugged from the ECU, injectors fire constantly. I guess the issue is signal wires. Somethings getting lost between the ECU and the ECU and the injectors

Cardinell

Do you have a known good ECU you can swap in to pinpoint whether it's the unit, or the wiring?

cgunnr

unfortunately, no. Is there a way to test direct signal from the ECU pins? I know that the signal wires essentially just ground the injectors so I have no idea how to test if there’s actually signal

cgunnr

Okay so update, more PO wiring shenanigans. Any ideas what these wacky splices do?

Cardinell

So I dug through the FSM and found a couple things for you. One thing is the FSM suggests checking the CAS of the injectors don't fire. That is below:





If that isn't the issue, then I also found the pins you'd want to look at on the ECU. Screenshots below:






Pins 3E and 3C are the ones that give the primaries their signal. Check those while cranking





I'm looking through the wiring diagrams a bit further to see what those splices are about.

Cardinell

Just wanted to clarify on those splices a bit. One of them it's clear what wire is spliced (red). The other one I can see pretty clearly but it's hard to tell from the picture (yellow).





The red one appears to just be a ground.







The yellow one (if I'm referring to the correct wire) is a part of the boost sensor circuit (in our case, air pressure sensor because no boost). Not a ground. Not sure why it would be spliced

WondrousBread

Those splices are probably from an AFC installation, or possibly one of those old eBay "speed chips". Not sure if those are a thing anymore.

Anyways, the injectors firing all the time suggests that something in that circuit may be grounded when it shouldn't be. The injectors receive a constant 12V and the ECU pulses the ground to fire them.

I would try testing the injector wires at the ECU with a multimeter to see if they have any continuity to ground. If they do, work your way up the harness in the footwell for each wire and look for signs of tampering.

EDIT: Also, there are factory splices in some of the grounds near the ECU.

cgunnr

okay just want to update this thread. Got the injectors firing. It ended up being split wires deep in the engine harness. Issue now seems to be lack of spark, which is weird because it used to run fine in ether and now it’s stopped doing such and will just flood

cgunnr

I think the AFC theory has some merit to it, as this car clearly has a bit more of a rich history than I thought when I picked it up, presuming it was an old guy’s daily. Had a bunch of mods from the early 90s like a period correct radar detector, streetported irons, and an 18lb flywheel. Having an AFC installed would make a lot of sense really

FührerTüner

iTrader: (5)

Lack of spark or no spark? Theres a black check connector on the leading coil harness near the leading coil. With the ignition in the run position, check for 12v. If you have 12v, you have a trigger issue.

cgunnr

Just thought I'd update the thread; Everything's good now on the FC! Thanks for all your help everyone!

FührerTüner

iTrader: (5)

You gonna tell us what the issue was orrr.....