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EDIS question


94range
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I have a 1994 Rover NAS.  I purchased a MJ kit and have installed the EDIS components but can't get the vehicle to fire up.

I started poking around with a multimeter and discovered that with the plug connected to the EDIS module and battery power going to the number 6 pin, I am reading battery voltage coming out of all of the other leads, even the ground.  The only slight difference is the leads for the vr sensor read about a half volt less. 

With the plug disconnected and power still hooked to number 6, when I probe the back of the connector, I am getting battery voltage on 8,9,11,12 (the ones that go to the coils)

Is all of this normal or do I have a bad EDIS or plug?

Thanks

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After some more poking around, it turns out the voltage on the coil wires, at the edis plug, is coming from the coil itself.

With voltage going to the center pin on coil plug there is voltage present from the other two coil plug wires but only when it's plugged into the coil.

When I unplug the coil, I no longer have voltage at 8,9,11,12 on the edis plug so at least that is solved.  

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While checking wires, I discovered a bad ground so now it at least tries to start on starting fluid.  During a conversation with trigger wheels, the person helping me mentioned that the tach driver needs to be hooked up in order for the ecu to send the fuel.  Can any of you confirm that for me and whether I would use the output from the edis or from the mj for that, and where is the wire I need to hook into on the Rover? Is it connected to the old coil or the alternator maybe?

I look forward to a reply.

Edited by 94range
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I am not sure how the old system worked - but from a quick look around it looks like the ECU took a feed from the coil negative to tell it that the engine was firing. 

If this is the case you can generate the same signal one of two ways, using a relay to generate a high voltage pulse like this (ignore the fact it is for MS, it will work the same on MJ connected to the appropriate pin):

Tach out (MS manual, but principles the same)

Or you can do the zener diodes thing from the EDIS coilpacks themselves which is shown at the bottom of the page linked above.

 

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I guess rather than being all multimeter about it, you could just test for spark by pulling a plug?

Then, as above, you probably need to make the engine ECU think it is spinning, before supplying fuel. 

 

 

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If you bought it from Trigger Wheels I would very much hope it should have the relevant modifications to drive the TACH input to the ECU directly from a spare pin - and that they'd have supplied the info to say which pin to wire up. The EDIS IDM output likely wouldn't be suitable.

If you've got power, ground, and the VR sensor the right way round then EDIS will make sparks - getting the coil wiring/firing order wrong is a very popular failure ;)

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Thank you all for the replies.

Thank you for the link Quagmire.  I had kind of ignored the whole tacho issue until now, thinking it wasn't a big deal if my tachometer worked or not but I guess it has to in order for fuel to flow?

Bowie, I had considered pulling a plug and checking for spark while cranking but I didn't have anyone else here to crank while I grounded the plug.  I  can definitely tell whether there is spark though by spraying a little starting fluid in the intake before cranking, the difference is obvious but after looking up edis diagnostics, I think you're right that using the multimeter is basically useless in this scenario.

Fridge.  The kit I got from trigger wheels seemed complete.  The mj, edis, coils, and a whole bunch of new plugs and pins and wire that I had to put together myself along with some decent instructions but it wasn't clear to me whether I use the tachometer out from mj or some output from edis and there definitely was no modifications already done as I had to wire everything myself. Those molex pins were a bit tricky without the right crimper. I destroyed several.

After a discussion with trigger wheels, they confirmed that I need to install the tachometer driver in the lines between the edis and coil packs and send the output of that to the tacho feed of the rover.

You're right about the wiring the coil/plugs wrong as I did that the first go round but I'm sure I have that part sorted now.  Firing order 1,8,4,3,6,5,7,2 so the left coil pack is A toward front, B toward back with pin8 to A and 1,6 and pin9 to B and 8,5.  The right coil pack is facing the other way so the back row is C from pin11 and going to 4,7 and the front one is D from pin12 and firing 3,2

I hope I wrote all that down right.

Know I just need to figure out which wire on the rover I use to hook the tacho driver to. Any ideas of where the tachometer was driven from on the original system? Is it one of the wires on the original coil?

Edited by 94range
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I *think* black with white stripe?

Did/does it have a single coil? (Sorry, I know NAS spec stuff can be a bit odd), in which case the wire that goes from the coil negative needs to go to the tacho driver output.

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I'm not home right now but from memory, there is one coil and 4 wires attached to it.  2 on one side and two on the other.  They are definitely white and black or some mix thereof.  There is also a white wire and a brown wire that come off the back of the alternator and I thought that when I changed the alternator, the tach didn't work until I hooked up one of those wires but that might've been on my Discovery and not this RRC.  I also bring up the alternator because I haven't put any of the belts back on so the alternator isn't turning and I want to make sure that's not my issue.

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Yes, the fact the tacho isn't working isn't why the engine isn't running, it is run from the back of the alternator as you suggest.

The engine ECU needs a signal to say it is spinning over, and that comes from the coil, and doesn't go anywhere near the dash.

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Careful!

The Flapper/Hotwire V8 ECU's take their feed from coil -ve on a WHITE wire with BLACK trace although if there's a relay in the way (Flapper over-run cutoff) it switches to WHITE with BLUE trace if memory serves.

DO NOT take it from the alternator W terminal, that's for diesels and maybe some aftermarket tachos and is only vaguely related to engine RPM by the belt drive of the alternator, unlike the coil or EDIS which is coming direct from the dizzy or crank sensor.

I thought white/brown was oil pressure switch but I've slept since I last wired one of those in.

Here's the correct coil wiring - you can switch PAIRS around (EG move 4+7 and 2+3) if you want to get funky but it's very easy to end up cross-eyed;

coil_wiring.jpg

 

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This is what is confusing the **** out of me.  I get that I need to send a signal to the ecu from the coil to replace the signal from the original coil but then trigger wheels is telling me wire in a tacho driver between the edis and coils and send that to the ecu.  I was under the impression that the tach signal and ecu signal were two different things.

I will try to add pictures of the original coil wires and the alternator wires.

The alternator has a brown with yellow trace and a white wire in addition to the power wire.20200302_163210.thumb.jpg.6e1bd39be1b8035250c23cf82133d190.jpg20200302_163627.thumb.jpg.30b76d9b61c0e3710a26817cacb7a635.jpg

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Here's the message from trigger wheels, hence my confusion over the term tacho driver and sending signals to the ecu. It sounds like it's the same thing.

 

Hi Shannon,
 
Do you get any spark at all? A great way to test is by squirting some easy-start into the inlet - if it splutters and tries to start then you know that you have ignition.
 
I guess that you're running a fuel injected vehicle so the injection ECU takes the feed from the coil to sense the engine speed and know that it needs to squirt in fuel. When you fit the Megajolt/EDIS setup then you need to use the tacho driver to connect up to the tacho feed so the injection ECU still gets that signal.
 
Chris
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After rereading all of your posts several times, it looks like what you are all saying is that I use the tach out or tach driver instructions to actually supply a signal to the ecu and continue to actually drive the tachometer from the alternator.  Yes?

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Yes, and yes, and yes;

The ECU needs a signal that pings up & down at the same rate as the original one from the coil - I.E perfectly in sync with the crank turning, the tacho signal box thing is a bit of a bodge IMHO, often just a few diodes on a PCB that channels the 4 coils into one signal line for the ECU - Nige at MegasquirtV8 has them (top of linked page) if you're peed off with TriggerWheels :lol: especially as they seem to have sold you less than a full kit!

The Tachometer / rev counter is a separate thing and is just a nice gauge for you to admire, don't know & don't care how that's fed :SVAgoaway:

 

TBH I'd question why not just megasquirt it, the MS ECU can do the EDIS AND the fuelling in one unit.

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Quick bodge for the purposes of testing (absolutely not for driving around for weeks because you haven't got round to sorting it properly...* :ph34r:) is to put a single plug lead and spark plug on the old coil. Cable tie the spark plug to a decent earth. Obviously, don't use anything flammable near it!

* - anyone using a radio in the vicinity will not thank you.

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