matts86fc3s

ive done everything, replaced everything, my secondaries just arent firing. so i heard if your car was built before the middle of 87, that the secondaries had resistors or fuses or something. there under the airbox. mine is an 86. i just heard about this on nopistons.com, so now im asking, how do i test them and how many ohms should they have going through them? or volts or whatever i need to do. thanks -matt

matts86fc3s

im talking about for the resistors no the actual injectors

richardfc3s

Is it a TII?? There should be a soleniod resistor that runs between your ECU and injectors. I think that's what it is that your looking for. Now there are other components that activate your injectors (secondary) so there could be other problems. I not sur of the impediance of the injectors though. There either 13 ohm or 3 ohm

matts86fc3s

no its an n/a. there looks to be 2 resistor or junction boxes under the air filter box. thats what im asking about. guy i talked to said hes seen more than a few go bad on peoples cars... and this car sat for 3 years soo... i just want to know how i can find out if theyre bad. everything else has been ruled out...(new secondary injectors, new computer, added grounds...ect.) thats the last thing i have yet to check is those resistor boxes or whatever they are

HAILERS

One lead on the center pin and then touch one at a time each of the other four pins should result in a reading of SIX (6) ohms each. Jpg attached.

P.S. the jpg that shows the plug is wrong as far as FP, FS, RP, RS go. Ignore those callouts and go by wire colors on the emissions harness that plugs into the Solenoid Resistor.

After ohming out the Solenoid Resistor and coming up with 6 ohms each, the sensible thing would be to ohm out from the connector to the small plug on the ECU. Wire colors are available in the fsm. The resistance from the solenoid REsistor plug to the ECU pin for each circuit should be around nine to ten ohms IF I remember right. Subtract the resistance value of your meter leads from whatever figure you get.

matts86fc3s

im getting 6.2 ohms on each prong. i dont get it. my secondaries just arent firing. i mean i hit 3800 and it will not go past 3800 rpm. thats as high as it will go. it just hangs at 38k rpm and boggs down forever untill you let off. it doesnt "stumble" or "buck" it just boggs like you could floor it and it stays the same rpm and low deep sound. i grounded the cpu, fuel pump... replaced the secondaries... replaced computer...what the else could it be? my pressure sensor maybe? i have straight exhuast no muff. no cat. 5th and 6th ports are wired open....

HAILERS

So? You now go to the female side of the connector. You look at the color of a given sockets wire.

Let's say the color is brown/red. You put a lead off the meter on that socket. Now you go to the ECU small plug and find the Light Green/Black wire in socket 3C. You put your meters other lead in that socket and the meter on ohms should read something like 9 or ten ohms. That would have been the circuit for the Rear Primary circuit.

Now you do that for the other three wires on the Solenoid Resistor plug and they should read the same as the one above.....9-10 ohms.

The reading you got on the plug in your post is good. Six point two is just fine.

Another way to do this is to connect the plug on the solenoid resistor and the one on the ECU. Put the meter on volts and back probe the pins 3C, 3E, 3F and 3H. You should see 12vdc on each.

If you see 12-13vdc on each, that's good. So go for a drive with the meter lead in the back of pins 3F or 3h. Those are the secondary injector pins. Do just one at a time.

The voltage should be approx 12-13 volts as you drive. Now stomp the pedal at say 3000 rpm. The voltage will stay at 12-13 volts til you get over 3500 rpm. Then the voltage will drop like a rock to some lower figure. Like maybe 7 volts give or take. The specific figure won't matter as long as you get a very large drop from the steady figure of 12-13 vdc that you saw below 3500 rpm.

IF the figure drops below the steady figure of 12-13vdc, then the injector/driver is working. IF the figure does not drop.......probably a bad ECU.

Do the same with the other secondary injector pin.

You might be able to do this in the driveway. PUll the vac hose off the boost sensor. Plug the vacuum line. Start the car. Each time you rev the engine over 3500-3800 you should see/hear the engine stumble a bit. IF your looking at the voltage on either pin 3F or 3H the voltage should make a drop as you rev over3500-3800 rpm. Unfortunaltly it won't drop nearly as much as if you were actually driving the car under load over 3500-3800 rpm.

Personally I'd check it while driving. Note: the engine must be under a load and over 3500-3800 rpm for this to work. No load means they won't come online. Gotta stomp the pedal.

The pins 3F has a Light green/Red wire and pin 3H has a Light green/White wire at the ECU small plug. Just FYI.

I would not buy a new ECU unless the voltage at those pins was not approx 12vdc normally and the voltage did not drop when you had the engine under load over 3500-3800 rpm.

A note here. In order to access the ECU plugs easier you should unbolt the ECU so you can raise it up at an angle to access the pins.

HAILERS

IF you idle the car and the engine is warmed up, you should be able to backprobe pin 2B on the ECU middle plug (Brown/Red wire) and the voltage should be approx 2.3 to 2.7 vdc. That's at idle and for a turbo sensor. A non turbo sensor will read 3.5 to 4.0 vdc.

NOTE: I forgot, you have to remove the vacuum hose off the boost sensor and plug that line when you read pin 2B. Actually if you just have the key to ON and engine off the reading should be about the same.

I assume your injectors are stock 550's and not some 720 or 1000 cc injector.