do these engines have a hall sensor for the ecu trigger?

[adam459]

do these engines have a hall sensor to trigger the injectors from the ecu? i can see two wires going into the dizzy (red & blue), could these wires be it? if so does anyone know which one is the input into the ecu for the trigger.
cheers,
Adam.

[GreenV8S]

The dizzy has a pickup inside it which may be Hall effect or MVR, which connects to an ignition amplifier. The ignition amp takes the weedy little pulse from the pickup and thumps lots of current through the coil by pulling the -ve side of the coil down to earth. Hence the -ve side of the coil provides a strong signal that pulses between 0V ish and 12V ish. The ECU and tacho are both connected to the -ve side of the coil. (On mine the tach is connected at the coil end of the wire to the ignition amp, and the wire to the ECU comes off the ignition amp end of the wire. From the electrical point of view it makes no odds.)

Why do you ask?

The wire from the ignition amp to the ECU is usually a solitary black wire that runs along the near side rocker cover, through a dropping resister in the region of the throttle body and then joins the main ECU loom where it goes through the bulkhead.

Edited by GreenV8S on Friday 20th July 17:23

[adam459]

GreenV8S said:

The dizzy has a pickup inside it which may be Hall effect or MVR, which connects to an ignition amplifier. The ignition amp takes the weedy little pulse from the pickup and thumps lots of current through the coil by pulling the -ve side of the coil down to earth. Hence the -ve side of the coil provides a strong signal that pulses between 0V ish and 12V ish. The ECU and tacho are both connected to the -ve side of the coil. (On mine the tach is connected at the coil end of the wire to the ignition amp, and the wire to the ECU comes off the ignition amp end of the wire. From the electrical point of view it makes no odds.)

Why do you ask?

The wire from the ignition amp to the ECU is usually a solitary black wire that runs along the near side rocker cover, through a dropping resister in the region of the throttle body and then joins the main ECU loom where it goes through the bulkhead.

Edited by GreenV8S on Friday 20th July 17:23

thanks for that.
the reason i ask is because i've fitted a megasquirt ecu (just fuel at the moment) and i cant get an injector pulse from it, so i'm wondering if there is a wire wrong?
do you know much about the wiring on these? if i send you a wiring diagram which i've followed would you be able to tell me if it's correct?
cheers,
adam.

[That Daddy]

Have you tried reversing the wires(dont ask another project)i think you will find its a constant energy/moving magnet dizzy(very common in the eighties)and if it is the sensor is polarity conscious works on two wires(the third is just an indy earth for the dizzy) the unit creates a very small voltage(when triggered) that switches the module which in turn energizes the coil ve-,just a thought may be of no use but worth a go

[GreenV8S]

I wired my OMEX straight into the pickup, the input to the ECU in my case had a shielded wire so I connected the outer sheath to one terminal and the inner to the other. The pickup produces an AC signal which rises as the tooth approaches the sensor and then reverses as it moves away. I tested the polarity of the pickup first to try to get the connections the right way round to match the edge detection logic in the ECU, but if I'd got them wrong it would just have meant changing a flag in the software to read it the other way round. I'd be astonished if you didn't have something similar in the MS software.

ETA:

Although I wired it straight in wothout any problems, if it had given me any trouble I'd have connected the ignition amp back with a resister in place of the coil and used that as a pulse generator. Going direct to the pickup just gave me a simpler setup with fewer things to go wrong in future.

Edited by GreenV8S on Saturday 21st July 00:49

[adam_rbts]

Hi Adam.. apologies if you've already seen these but there are comprehensive diagrams on this site:

http://www.extraefi.co.uk/drawings.htm

The second diagram shows how to link to the coil -ve.

I'm in the middle of building MS for the Griff so will be interesting to see how you get on..!

cheers