civic ignitor question

anyone know the ecu switching voltage for the ignitor?

i want to test one out of the car. i've read this:

formatting link
from graham woods excellent rover 200 web page. the only info it doesn't give is what signal voltage the ecu gives the ignitor - and that would allow me to rig up a dry test. i'm guessing it's 5v as the ecu is old skool electronics, but anyone know for sure?

any help much appreciated!

Reply to
jim beam
Loading thread data ...

Not sure exactly what you're up to. Are you just trying to see if this ignitor has failed or not?

For ignitor electrical tests, see pages 16-50 (fuel injected) and 16-51 (carb'd) of

formatting link
.
formatting link
's free repair guides describe the same or similar tests under Engine Performance and Tune-Up Procedures, PGM-Ig (sic) ignition system, diagnosis and testing.

If you have access to a working ECU in a Civic: The pin number in the ECU which provides output to the ignitor (white wire) could be any of several, depending on the particular model of car. Electrical diagrams at both of the above sites do list pin numbers. E.g. For the 1988-1991 Civic LX, ECU pins C8, B8 and B9 are white wired and go to the distributor. At the autozone site under chassis electrical, wiring diagrams, see Figure 20.

Also maybe worth skimming for more detail on the ECU pins is:

formatting link
formatting link
(note especially turbogixxer'spost here about 5/8ths of the way down on the site) For very detailed electrical information, the guys at the above two sites say get the Helm manual for the specific vehicle and go to the electrical section.

I'm still thinking this may be on the net somewhere. Will post back if I find the voltage.

"jim beam" wrote

Reply to
Caroline

It's me!

Make up the LED test device as described in the zip file and use that and the text instructions and the f/finding diagram.

Voltage signals are the wrong concept since the devices work by current like 74 series TTL does. If you uncouple the signal] wire to measure it on voltage alone, the lack of current may lead you astray!

If the ECU can 'suck' a milliamp or two through the LED, making it flash, then things are working.

HTH

Reply to
Graham W

excellent! great to hear from you graham!

yes, i'm familiar with the old 74 series ttl - long time back, but hopefully not all the neurons have decayed.

regarding the test, what i have is a working honda, and either a non-working coil or a non-working igniter. i replaced both coil and igniter after getting stranded one time. now i want to chuck out whatever doesn't work. i've tested the old coil & it seems ok, but i'm not confident that's an absolute result in service, hence now i want to dry test the igniter. and i want to try this without stripping the working car back down again because i have a broken finger which makes for a little bit of a dexterity problem!

any thoughts?

Reply to
jim beam

Reply to
jim beam

74 series TTL came with totem-pole output and open collector output. 7400 is an example of the former, 7401 of the latter. I gather you mean the ECU output is open collector.

I would hook it up as follows (terminal numbers pr.

formatting link

0V: = 0V (ground) T1: = leave open T2: = 1 k ohm resistor to +12V T3: = +12V T4: = Leave open for now.

Then measure the voltage at T4. If the ECU is open collector (or likely open drain) the ignitor would need to have a pull-up device. You should see either about 12V or about 5V with T4 left open. If you have a function generator, set it to a square wave, 25 Hz, negative peak to 0V, positive peak to whatever you measured at T4 when it was left floating. Hook the function generator to T4. This simulates the engine running at

750 RPM.

Now you should see square waves at both T1 and T2. You can also hook up the coil (short the secondary to avoid painful surprises!) and measure if you still get a square wave at T2 with the actual coil in the system instead of the 1 k resistor. The resistor is a much lighter load than the coil.

Reply to
Randolph

perfect - can measure t4 open & use that. thank you!

Reply to
jim beam

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.