86 N/A Electrical Issues
 

Working on a totally stock '86 FC N/A 5-speed that will not start. Here's a list of what I've checked:

-Starter spins up just fine

-Coils are firing

-Compression present on both rotors

However,
-Fuel pump is not turning on. No "whirring" when key is first turned on, no pressure to the fuel lines

-Engine won't fire even with remote fuel pump but will fire up for a second with starting fluid, so I'm assuming injectors aren't squirting

Big red flag (I assume):
-With key in "on" position, dummy lights do not light up in center cluster

So, after realizing that, I confirmed:
-EFI and Engine fuses, and the Room fuse that runs the gauge cluster are fine, trouble-light shows power at all the right locations on these

-EFI main relay works fine, power present at the right spots in the right conditions

-Finally, as was advised in another thread I unplugged the two-prong plug from the back of the alternator and grounded the white/black wire (which is supposed to rule out a bad alternator messing with the ground that the ECU needs in order to turn the dummy lights on) then turned the key and STILL no dummy lights

So with all this I can only figure that the ECU is shot. I'm about to purchase a replacement but the reason I've come to this vast wealth of rotary knowledge first is because I'd like to know if I've exhausted every possible troubleshooting option. If I install another ECU and the EFI system is STILL down, tears will flow. And I'd like to avoid that. So if there's any other fuse, relay, wire, anything at all I can check, please guide me in the right direction.

Y'all have done nothing but help my wife and I in our adventures with her FD, so hopefully this new project of ours sees lots of love (and help) from this forum as well!

Read the thread right below yours.

And go check the Meter fuse as it powers the alternator warning light relay which turns on the idiot lights w/key to on. This is a CPU related issue and not ECU.

This was the buddy that was having problems lol anyways I'll copy your post here. wish i could kill the other thread though now

Thanks for the quick response! Meter fuse is fine (I don't know why I said "Room" fuse earlier), and jumping the fuel check connector with key on does not make the fuel pump run. The circuit opening relay does have voltage at the blue wire, and I'm able to read power at the fuel pump, as well. I'd assume that means bad fuel pump, but I wonder why the engine still wont fire with a remote pump?

The pump would also need "a ground" besides voltage for it to run.

Alright, updates!

Tested the fuel pump outside of the car and it was dead, dead, dead. Replaced the fuel pump, dropped it back in and now the fuel pump DOES run with the fuel check connector jumped.

However, as soon as I disconnect the check connector, the fuel pump stops dead and I lose voltage at the blue wire on the circuit opening relay. Where do I look from here?

The AFM has an internal "fuel switch" that passes a ground from a Black wire connected to the AFM to the Brown wire connected to the AFM. Apparently the "switch" is not working. Perhaps it is dirty and some carburetor cleaner might fix it, but probably not. If that were the case then the fuel check connector would again need to be jumpered. The jumper could also take place inside the car at the Circuit Opening Relay by jumpering the bottom two wires in the relay plug instead of in the engine bay. This would be the solid Black wire (bottom row far left position) to the Brown wire (bottom row far right position). Only difference to jumpering versus not jumpering is the fuel runs w/key to on versus not running w/key to on. If your AFM fuel switch is toast then you don't have much choice besides possibly fixing the problem or getting a workable replacement (different AFM).

I encountered a car that wouldn't turn the pump on because the AFM was seized due to corrosion.
Have you checked that out of Curiosity?

Did some more reading and found that the pump isnt supposed to run with the key in "on", but rather with the key in "start", and the AFM runs it in "on" once the engine is actually running. Is that right? I ask because II got the engine to run for a few seconds by squirting some fuel in the throttlebody, and confirmed that when the engine is running, the pump does run.

If that sounds like its doing what its supposed to do, I'll assume the injectors are bad. Gonna pull the upper manifold when I get some time and check them out. Will update on where it ends up soon, and thanks for all the help!

Correct.

Well, I just got the injectors back from the shop and they check out just fine. I'm assuming it's now time to figure out if the problem lies in the ECU or the AFM. Any advice on where to start poking?

Have you tried starting the car w/the AFM disconnected w/the fuel check connector jumpered? Have you tested the Brown wire at the TPS w/key to on to see if it measures 5 volts. If it is a fair lower then it could prevent the car from starting. Have you measured pins 3E and 3C for battery voltage w/key to on? This validates that the leading injector plugs are secured to the injectors. You could also disconnect the secondary injectors before this to also show that you don't have the injector plugs switched (secondaries on primaries). And you showed that the fuel pump runs w/key to on w/the check connector jumpered but have you proved that the pump runs w/key to start. If it did then the Black/White wire in the top row far left position of the Circuit Opening Relay would have voltage w/key to start and it would cause the Blue wire in the same plug to have voltage as well. You might want to check this aspect first.

If you check for voltage on pins 3C and 3E forget about pulling the secondary injector plugs off.

Took advantage of the UIM being off and grabbed a set of noid lights to test the injector plugs. With the fuel test connector jumpered, I've confirmed that with the key at "start" the injector plugs have a pulse and the fuel pump does run. Will steal a multimeter soon and check the tps and ECU, but does finding a signal at the injectors mean the rest of the electrical is good?

Also, the throttle position sensor's brown wire shows a solid 5V with key on.

Have you checked the timing of the CAS? It should look like the pic in post #9

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/new-13b-first-start-loud-boom-timing-question-978911/.

Also, the car should start and run on just the leading coil so maybe you might want to narrow down the possibilities and disconnect the trailing coil for now. So make sure the leading coil fires at both bores and that both leading wires are going to the lower plugs on both rotor housings.

And pin 2I at the ECU should read 2 to 3 volts w/key to on w/the engine cold. The sensor connected to the pin governs the amount of fuel on a cold start and a warm start so it's important to be getting the right amount of fuel on a cold start which requires more fuel than a warm start.

Coils firing properly, CAS timed correctly, pin 2I showing proper voltage with key "on." I'll tell you what, once we narrow down what's keeping this engine from firing on its own fuel, it'll be nice knowing pretty much everything else seems to be working right!

Perhaps the engine is now flooded from all the starting attempts. If so then disconnect the fuel pump and use the starter fluid a couple of times over and then reconnect the fuel pump plug and start the car in a normal manner. And you might want to start the car w/the fuel check connector jumpered and the AFM disconnected.

And when you confirmed the fuel pump ran w/key to start was this with the fuel check connector jumpered or not as it should not have been jumpered.

IT RUNS.

We just put the fuel injectors back in after having them cleaned, and it fires up and runs like a charm. Apparently when the injector guy said they were fine he was being very optimistic. It runs good and smooth. I'll figure out later why it's smoking so bad and why the temperature gauge doesn't work, just too thrilled right now to worry about anything except the fact that its purring.

That post needs more sputtering fc vids :D

Very soon! Except the videos wont be of a sputtering FC, they will be of a smooth purring FC... that pours white smoke out the exhaust. LOL!

Good stuff :) an coolant leak somewhere?

Oil, I think. At least, it SMELLS like burning oil.