Ms tacho issues
Posted: Sat Oct 14, 2017 12:44 pm
Hi all, I have a P6 with Megasquirt 1 V3, running fuel and ignition on a 4L Rover V8. Most things working now except the tacho. To try and get it working, I contacted a company who sells a device called a 'tachfix.' After conducting a few tests, like attaching the IDM to the tacho, where it made the tacho jump a little when engine turned on, and again when it turned off, nothing when running. I then disconnected the orange wire on the EDIS and brushed it against a ground with the ignition on, and the tacho jumped to 500 - 1,000rpm every time I did it. I then connected the SAW to the tacho and that worked but was reading 100rpm low.
He gave me two options, the one I chose was to send him the ECU and he fitted a tacho output, which connected up to the Tachfix. It arrived back and I connected it up, red to ignition live, black to earth, orange to new tacho output wire and yellow to tacho. Fired the car up, the tacho burst into life but the needle just bounced up and down.
As I have a wire fitted to the ECU as a tacho output, a tachfix, and a Tacho which 1/. Worked with the coil set up, and 2/. a spare Tacho I have does the same and jumps, I can only assume that something is wrong with either the output wire or the tachfix. I was hoping that there is something in Tunerstudio was pointing in the wrong direction and that I could just hit a few keys and get it to work - now there's optimism for you
Is there any way, with the help of a multi meter that I can check the output wire and the tachfix?
I have made up a small electronic board from the manual which takes the feed from the –ve side of the coils. This contained 4 x 1N4004 diodes and an 18V zener diode. This works up to 1,300RPM but above that, the needle just drops to nothing. On advice from a google search I changed the zener to a 1000 ohm resistor - then it didn't work at all. I have been given another type of circuit from a non MS source and will be making one of these up as well.
I would however prefer to use the output from the ECU because it would just be neater, so I tried another type which worked from the installed output wire and consisted of a 1000 ohm resistor, a transistor and an old relay. Nothing, not a sausage
This, along with the fact that the tachfix doesn't work from this wire either, and that the tacho works with coils, does make me suspect the installed wire. I took the top off the ECU and found that the person who added the wire, also added this circuit :-
Seems I can't add pictures
Any ideas anyone?
He gave me two options, the one I chose was to send him the ECU and he fitted a tacho output, which connected up to the Tachfix. It arrived back and I connected it up, red to ignition live, black to earth, orange to new tacho output wire and yellow to tacho. Fired the car up, the tacho burst into life but the needle just bounced up and down.
As I have a wire fitted to the ECU as a tacho output, a tachfix, and a Tacho which 1/. Worked with the coil set up, and 2/. a spare Tacho I have does the same and jumps, I can only assume that something is wrong with either the output wire or the tachfix. I was hoping that there is something in Tunerstudio was pointing in the wrong direction and that I could just hit a few keys and get it to work - now there's optimism for you
Is there any way, with the help of a multi meter that I can check the output wire and the tachfix?
I have made up a small electronic board from the manual which takes the feed from the –ve side of the coils. This contained 4 x 1N4004 diodes and an 18V zener diode. This works up to 1,300RPM but above that, the needle just drops to nothing. On advice from a google search I changed the zener to a 1000 ohm resistor - then it didn't work at all. I have been given another type of circuit from a non MS source and will be making one of these up as well.
I would however prefer to use the output from the ECU because it would just be neater, so I tried another type which worked from the installed output wire and consisted of a 1000 ohm resistor, a transistor and an old relay. Nothing, not a sausage
This, along with the fact that the tachfix doesn't work from this wire either, and that the tacho works with coils, does make me suspect the installed wire. I took the top off the ECU and found that the person who added the wire, also added this circuit :-
Seems I can't add pictures
Any ideas anyone?