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MJ on '89 RRC with flapper HEEEEELP!!!


karlos01

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Hi all, this is my first post and im begging too.

i have an 89 range rover v8 3.5 flapper type efi. im trying to add mj to it and it has the over run relay on it. do i connect the over run relay white and blue wire to the tach out on the MJ or the Tach out on the edis 8?

im confused to the point of it all going in the bin!

many thanks in advance

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From memory the over run relay is the one bolted next to the resistor pack, it shuts off the injectors when you take your foot off the gas and are coasting,I can't remember what triggers it but I can look in a manual I have tomorrow night if you haven't got an answer by then.

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It's triggered by the vacuum switch on the back of the plenum, up to you if you keep it in-circuit (tach to white/blue wire) or just take the tach wire to the white/black on the ECU side of it and ditch the relay. You will want to connect the tach signal from the MJ unit as I think the EDIS unit puts out a special tach signal when the engine's stopped. It may work, you can try it and report back if you want :D

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might be a stupid question but why megajolt an efi instead of megasquirt?

I don't know Karlos' reasons, but (at the risk of triggering a flood of posts in defence of MS), the two things that occur to me are that MJ is less expensive and is easier to set up correctly...

In my case I run on LPG 99% of the time so it's a no-brainer, but even if I was sticking with petrol, to me it seems a logical first step and - having tried to comprehend some of the posts and replies in this forum about setting up the fuel side of MS, I would feel more than a little daunted by the prospect.

Back to the original post:

I am confused by this 'relay' - it appears to take a pulsed signal along the white and blue wire, and is triggered by a vacuum switch... So what does the tach signal do? Is there some electronics in the relay?

If the blue/white wire originally picked up the flyback voltage from the coil, then you would need to simulate that signal and the tach-out from either MJ or EDIS is not suitable, but the circuit you would need is shown on the MegaJolt website.

Karlos - if you decide to go this route then I can post chapter and verse on the simplest way of doing it for a V8 14CUX setup - in fact I think I will do that on the MJ forum anyway since I know that the vagueness of the circuit at the link is a bit worrying (well it was for me anyway)

Hope this helps :)

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Just wondering as the failures i had had were the ignition module & ecu itself, with the megajolt you still have the ecu, although i appreciate the cost, complexity & LPG factor.

According to the manual I have the over run relay is connected;

pin 87 to ecu pin 1

pin 30 to coil -ve

pin 86 to earth

pin 85 to vacuum switch

its a regular relay that allows the coil signal to pass to the ecu operating the injectors correctly, so i guess the signal is pretty important but the coil signal isn't what triggers the relay, so that side of the wiring should be ok. It seems that pin 1 on the ecu (&therefore -ve at coil) should fluctuate between 6 & 9v (but you could check on a running engine) when running but i dont know at what frequency, i think there are 8 pickups in the dizzy so i'm guessing once per injector fire?

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It's a normal relay, all it's doing is connecting the signal from the coil -ve side (so the points or ignition amplifier, or now the coil pack) to the ECU so that the ECU gets one 12v (ish) pulse every time the coil fires, which it then uses to fire the injectors. The reason it's there is only a Lucas bodge to switch off the signal (and inject no fuel) on over-run, you can jumper it out by connecting the white/blue to the white/black (so jumpering pin 30 to pin 87) so the signal is always there.

GroupImage1.gif

If you do this you should have continuity all the way from the tach output to the ECU connector (pin 1).

It's worth going over what you've done already and how your setup is built/wired.

Stepping back to basics you can leave your distributor & coil in place & working and install the MJ&EDIS alongside, that allows you to check the MJ is working before making the switch (which just means swinging the TACH wire from the coil -ve to the MJ/EDIS tach). So, first step - if you haven't already thrown it in the bin, try running it up on dizzy&coil and see if the MJ is getting a good RPM reading from the EDIS - if you have a problem with the EDIS or MJ then it's not even going to be giving you a tach signal in the first place.

Your MJ unit may not have a tach output circuit built into it (it's a build-time optional extra with MS) so unless you know it has one, and that it puts out a train of 12v pulses, you may be using a disconnected output.

This is what I believe is the common way of doing it, from the coil pack wires:

EDIS8_Tach.gif

And this is the rest of the wiring:

Mjlj_v4_minimal_pinout.png

EDIS_system_diagram.gif

Once you are sure your EDIS & MJ are happy you can then switch the HT leads across to the coil packs and maybe swing the TACH lead, although you could happily leave just the TACH wire running from the coil & dizy to take it one step at a time.

It's not a complex system, but you need to be methodical about it. Most of the frustrated users I've seen with non-working installs it's been something silly that they've been in too much of a rush to notice and then been too agitated to spot when it doesn't spring into life first time.

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right, ive basically gone and put the 4 diodes on but grouped 2 coils to one zener twice and then grouped them to one wire to feed the blue and white wire. i have a lovely spark from the edis so no issue there.

the fuel pump works now. i tested it by fingering the flapper (ooh err), and using the multimeter i have found that there is a constant 11.8v off the wire i used on the coils with the ignition on which i think is correct. that then went to the white / blue wire. i may need to try to finger the flapper and crank it over at the same time.

the issue here is that i havent had all the bits with this engine and ive thrown it together as best as i can.

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right, ive basically gone and put the 4 diodes on but grouped 2 coils to one zener twice and then grouped them to one wire to feed the blue and white wire. i have a lovely spark from the edis so no issue there.

the fuel pump works now. i tested it by fingering the flapper (ooh err), and using the multimeter i have found that there is a constant 11.8v off the wire i used on the coils with the ignition on which i think is correct. that then went to the white / blue wire. i may need to try to finger the flapper and crank it over at the same time.

the issue here is that i havent had all the bits with this engine and ive thrown it together as best as i can.

So you've done it? Excellent!

You should find I think, that the flapper will open up enough as soon as you start cranking... (I think that warrants an "oooh Matron" this time ;) )

Roger

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i think i need to test whether the injectors work. i was cranking it over with my mate the other day. edis connected, diodes all connected, he had the multimeter across an injector plug to see if there was a voltage but alas not. im thinking if i bodge the flapper open and crank it too then it should surely fire the injectors?

friggen thing

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Very unlikely that the injectors don't work - you may get one or two dead/stuck ones but should be able to fire it up. Remember the ECU won't fire the injectors until the flap is open AND it sees the pulses on the TACH wire. You should have 12v to ground at the injectors with the ignition on I think - there's a massive flapper fault finding manual in the tech archive, could be of use to you.

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i think i need to test whether the injectors work. i was cranking it over with my mate the other day. edis connected, diodes all connected, he had the multimeter across an injector plug to see if there was a voltage but alas not. im thinking if i bodge the flapper open and crank it too then it should surely fire the injectors?

friggen thing

Very unlikely if you have a digital multimeter that you will be able to see that the injector is opening or not, they open only for milliseconds at a time to squirt fuel in, especially at cranking. If you want to check for power here, the injectors are earth switched, so one of the pins should be live when ignition is on, so measure between engine block and pin and it should give you 12V+

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Very nice and thanks, but..

that must assume an MS2...? (4 wire idle valve)

SAW to Pin 30? :huh: All other docos have it on 36... do you have a special mod?

To really nitpick (and off topic too) your relays are wired backwards. :) Doesn't matter until you start using 5 pin relays.

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From memory the fuel pump is powered under cranking without holding the flap open :unsure:

Aye, there's the special red "relay" which is an arrangement of diodes to keep things working during cranking, it may be a good idea to check the MJ & EDIS / coils aren't powered from something that goes dead when you turn the key.

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