frequency valve issue - where is test port?

[schumicat]

I don't think my FV is working. Car is an 82 SC (has the FV and 02 sensor). I think it is not working because of the following:

1. unplugging relay under passenger seat makes no difference in idle
2. can't feel or hear FV buzzing (but never really tried to feel/hear when it was known to be working so not certain I could tell.
3. unplugging 02 sensor makes no difference in idle (02 sensor only has 5k miles on it

I have done the following:

1. checked relay under passenger seat - it is working and I can feel it click when engine started. Bench tested it and it is working as designed.
2. swapped the lambda ECU under passenger seat with one from another 82 - no difference
3. measured the resistance at the FV - it measured within spec
4. checked the connector (14 pin?) near the driver side firewall was seated - seems to be ok
5. cleaned ground for the ECU
6. confirmed 15 degree C temp switch (the one on the passenger side cam cover) is open above 15 degree C as it is supposed to be.

I would like to check the FV test port to make certain it isn't working - where exactly is it? Also welcome any ideas about what else could be reason for FV/lambda not working. Thanks

[Scott R]

It's a little barrel shaped connector about an inch long with a rubber cap. You can normally find it under the rear defrost relay after you remove the engine electric cover panel. It's normally just shoved under the panel.

[T77911S]

fuse 18?

[schumicat]

Thanks Scott. Checked at the test port and confirmed no signal getting to it.

It isn't the fuse; as noted in original post the relay has power (works).

Cleaned ground for the ECU and that made no difference either.

The only thing left I can think of is wiring connectivity between the ECU and FV.

[john walker's workshop]

just because the relay clicks doesn't mean it's working. you need to have 12V out of both 87 terminals. get out the test light or volt meter. check the relay plug for corrosion or broken wires. check the multi-pin plug by the top of the left rear shock for corrosion.

[SCadaddle]

I'm working on that same exact issue over in Meridian with my 82. My ECU was declared non functioning by installing it in another car without the issue---the symptoms of the FV traveled with the ECU. So I says "gee, I'm glad my car runs fine now and too bad about yours!" of which the reply was "you can't afford to buy me a new box!" i.e. the ECU from the known car wasn't installed in my car to test. In my case pretty sure it's the wiring between the ECU and FV that caused the fault.
I'm armed with another ECU and plan to work on it today.

[Scott R]

If it comes down to suspecting the ECU, which is a long shot over the relay, check all of the soldier joints on the board inside. These are not difficult to repair.

[schumicat]

update.... I checked all the connections for corrosion and and everything looks ok. I opened one of the two ECUs I have and the soldering all looked fine and is like new inside.

I checked the 12 pin harness (by driver side rear shock) with a test light and pin 10 (blk/red) is the only pin that has 12 volts when the car is running. If I'm reading wiring diagram correctly, one blk/red wire supplies power from the relay to the FV, and the other blk/red wire (pin 6) runs from the FV to the ECU.

Does anyone know whether more than one pin of the 12 pin harness is supposed to have 12 volts?

Does anyone have a pin out diagram of the ECU? I checked the ECU harness while the car was running and 1 pin (about in the middle) had 12 volts. So the ECU and FV seem to be getting power. I would like to see if the FV pin of the ECU connects to the harness at the FV end.

Thanks

[Scott R]

It's a ground on circuit like power windows so I believe that's correct. It goes to ground to fire the "injector."

[john walker's workshop]

jump the 30 terminal on the relay plug to both 87 terminals and see if that gets it going.

[SCadaddle]

Originally Posted by SCadaddle

I'm working on that same exact issue over in Meridian with my 82. My ECU was declared non functioning by installing it in another car without the issue---the symptoms of the FV traveled with the ECU. So I says "gee, I'm glad my car runs fine now and too bad about yours!" of which the reply was "you can't afford to buy me a new box!" i.e. the ECU from the known car wasn't installed in my car to test. In my case pretty sure it's the wiring between the ECU and FV that caused the fault.
I'm armed with another ECU and plan to work on it today.

Update: Spent the day over at Howards' shop. Sorted out the wiring to the FV in my 82 with new leads and connectors between the ECU, relay and FV. Howard started his 83 SC and as normal it ran fine. Then we installed the ECU I bought as a used part in his 83 and it ran like crap--no FV action. Removed ECU and put it in my 82. My car ran like crap (as expected). Removed it once again and installed Howards' ECU from his 83 in my 82. FV runs like a champ.

Snakebit......

[schumicat]

another update. FV started working after I opened the 12 pin harness, checked continuity of various wiring between the 12 pin harness, FV plug, ECU and relay and plugged everything back in. There must have been corrosion somewhere that came loose or a loose pin somewhere. I tried my old ECU and of course it worked fine now...so I wasted $100 on an ECU but I guess I have a spare now. Thanks for all the help.

[SCadaddle]

If you've got a spare functioning ECU and want to get out of it for $100 I can make that happen today!