Katoh,

Jag messed with cold starts throughout the early years of the HE. Late '85 saw the end of them.

 

The ECU thst is firing the injector when ign ON is NO GOOD.

The other would be OK I reckon. Leave it in there.

The NO pulse when cranking is purely that wire to pin 18.

Back to early testing again. Put the good ECU in place, ign ON, snap the throttle open, do the injectors fire. IF not, the TPS is NOT talking to the ECU, or that ECU is toast also. IF they do fire, then the pin 18 wire is failing to supply its pulse signal to the ECU.

I have to go to V12 in the storage shed this week, and I will unplug the ECU, and see what voltage reading I get in that wire on that car. It is a test I have needed to do. Continuity repair of that wire to the amp has always fired the engines up.

 

Ok, firstly I beleive Iwas leading you a astray with that last post. definitely WRONG!
As far as colours go the orange wires Orange/White is active side injectors 246A, Orange/Green is active injectors 246B, Orange/blue is active injectors 135A, Orange/Grey is active 135B now the other side are all the same they earth/common and they are Pink/Black. Those 4 Pink Black wires are connected to the main relay which contacts them directly to the Neutral on the Battery when Activated. So you need your Ign on to a reading from those wires to earth/common/body.
Now for active side the orange wires they all go to the power resistors where they change colour too (just to confuse things a little more) the Orange becomes Pink and from there they plug into the ECU in this order P/W (30) P/G (12) P/B (29) P/G (11).
So the activation of the injectors is from the Positive side not the Earth/common, I must have read that wrong. You will only get a closed circuit from the common side with ignition on and pulses should go to the injectors only when the motor is cranking. Hope that clears a few things up.
One other experiment is test your shielded pulse cable to the ECU incase (amplifier to pin18) its being bitten through, it only takes one little mouse to cause a hell of a headache. One last thing with sheild cables the shielding on the cable should only be grounded/earthed on one side only, not both.
Hope this helps

 

Ok,first thing.I have tested the thin coax wire to pin#18 on ecu it has 12v from ign amp all the way back to ecu plug connector.The mesh shielding is not connected on the eng side.Only on the ecu side.
as far as the injectors go I tested multi plug where inj harness plugs to as follows:with (multi plug unpluged) ign on checking at plug chassis side.all pink and black wires have 12v,comming from main relay..all orange wires have 4.6v.(Acording to my meter)Im assuming this 4.6 voltage comes from ecu,via power resister. Now leaving ign on,and pluging multi plug into inj harness, all orang and pink/black wires have 12v.
does that sound correct?
So what I'll do is,with everything connected,while cranking eng,I'll ground one of the pink and black wires,not orang wires,and see if that group of three injectors fire.I see on schematic,that the pink/blk wires,goe from main realay,and ties into all injectors on one side.Four groups of three.Then goes as a single wire directly to pin #22 in ecu.That must be where it switches from ground.. (pulses).So at ign on, not cranking,this pin # 22 at ecu is grounded already??,since I have 12v on all pink/blk wires with ign on not cranking.? So it must switch grounding when eng cranks in sequence.
Hope thats what you mean?

 

Ok,here is someting to add to the mix.
When I disconnect mutiplug from injector harness,ign off.
Ohming the chassis side of plug,If I ohm between O/S and O/G I get ohms.
If I ohm between O/U and O/W I get ohms.with either one of the ecu's hooked up.
You guys might want to check that out on your cars for comparison.
All the pink and blk ohm out ofcourse.

 

Ill try this afternoon to get some readings of mine, to be sure. But the way I read things those pink/black wires are earth/common wires they should be 0v, look at your schmatic, they go to the main relay where and when it is engaged it completes the curcuit and that curcuit leads directly to the negative side of the battery (earth). So when the ignition is on it complets the curcuit on the earth/common side again 0v.

stupid question is, have you connected your battery the right way round?

Again I'm no expert but that's the way I read it, Ill post back with my readings from mine.

 

At this point,nothing is a stupid question.
But yes battery is hooked up correctly.
when I look at schematic in my book.Looks like the main relay energizes,when ign turned on.and the pink and black wires go directly to each side of the injectors,and then tie together and go to pin 22 of ecu.
I figured that at the ecu is where it switches to ground.
As soon as ign is on the pink and black wires have 12v and continue during cranking eng.
I did check the pink and black wires with test light.(Should be same as grounding wire),ign on it lights test bulb.and while cranking eng no inj sprays.I also tried the same on the o/u wire.goes to 1a,3a,5a injectors.I have 1a out of manifold to check operation.No spraying on either test..

 

Again, I will stand corrected, I checked mine just then. Unplug your harness from the side that leads to the ECU only if you check all the Pink and black wires they will have 12v all the orange wires will read 0v with ignition on.

 

ok,There is the discrepancy.when i do same test,my pink and black have 12v,and my orange wires all have 4.9v thats on either one of the ecu'pluged in.
yours must be right since im assuming it runs.
somehow voltage is bleeding through somewhere.To orange wires.

 

I stand corrected,The one ecu pluged in,there is 12v,on pink black wires 4.9v on all orange wires.at plug disconnected ecu side ign on.
The other ecu pluged in.I. have 12v on pink and black,and 0v on all orange wires.
So I guess the second one is the good ecu.
Now I check the ign amp wires,tacho and signal wires.they are not grounded...Pluged in and ign on. I have 12v on signal wire to ecu and only 6v on tacho wire.

Did you try pluging in harness to injtors and leaving plug a little loose and check voltage on all wires where they bridge together. with ign on and see if they all have 12v?
mine do..

 

When the harness is plugged together and ign on all wires have 12v or 11.84v in my case. The wire from the amplifier to the ecu also reads 11.5v.

Furthermore Yes my car does run and runs well.

I would scrap that first ECU you have its got a problem somewhere, the second one sounds a little more promising.
I would try this re-plug with the other ECU, if you still don't get a pulse to injectors, get a temporary lead and replace the lead from Amp to pin 18 and give that ago.
I had a drama on my Bobcat were a wire had decayed enough not to let any current through but still gave a voltage reading. Its worth a try

 

Great,Thanks for the readings.Ill try that bypass for ecu signal wire.and let you know.
If you get a chance,on your time.check the tacho wire also while connected,with ign on,and see if you
have 12v or 6v like mine
Thanks again for your help,its much appriciated.

 

The tach cable came in at 6.44v with ignition on, I presume its the tach cable. When you look down at the amp so you can read the writing properly the 4 wires on the top left. Far left wire is the tach wire the two middle ones are the coil wires and the far right is the ECU

 

Ok, then all checks out on mine.
all my voltage and wires check.
So why no pulse to injectors?
I checked ground at radiator top cross panel,there is a ground on top right side and left side.facing eng.Hope thats the one on right,for inj harness? It goes in at right front panel by headlight area.

 

Ok the wire for ecu signal is coax type I tried replacing with 16 guage wire and no difference.

Here's a discrepancy I found,That doesnt seem right. When I disconnect plug from power resistor and disconnect multi plug at harness,and unplug my ecu.With my vohm meter set at 20k ohms.The pink and green wire from power resister shows resistance 7.71,but,checking on 200 ohms or 2k ohms it shows open.Only on the 20k it has resistance, that wire according to my schematic only goes between power resister and ecu.it shoul be open no resistance,as it is disconnected from power resister and ecu.
All the other wires on power resister plug show open.at any setting..

 

Ok,To much info I know,but i'm determined not to give up
Here,we go,,this for anyone with a good working spare ecu.
I took mine,apart evrything looks ok.So put it back together and decided to check each pin on the ecu
Ok,with my v ohm meter setting on 200 ohm's.My black leaad on ecu outer casing,red lead touching each pin from 1to 35 here is what I found..2,3,20 grounded on 200 ohm scale.17,18,31,33,34,35 has resistance on 20k setting only 7.8900 nothing on 200 ohms or 2k ohms.
so my book manual shows: digital P fuel inj system xjs north American: ecu pins..1,2,16,17,23,34and 35 to ground.Shows coax shielding on signal wire to ground also.
Also I took the ecu plug apart,found that the shield mesh on coax wire to ign amp isnt grounded to anything on ecu plug end.Should i ground it to the black wire that runs with it up at eng ?

 

Nope.

MOST, and I repeat MOST are earthed at the amp end.

Whilst you have all that in bits, do a continuity test on the lowest OHM setting you have, of that inner shielded wire, PIN #18, as in the "core wire, from that ECU plug to the amp (unplugged at the amp). If that has 100% continuity, move one test lead to ground, and ensudre there is 100% NO leakage to earth on that inner core thin wire.

The fact you ran a bypass wire and nothing happened has me doubt you will find anything odd.

I have no time at present to go to the stored car, and see what V is on that Pin#18 wire. Maybe someone has a car close by that can do that.

That resistance on those unplugged wires is not good at this stage of the diagnosis, and I think you mentioned those were the wires that had the strange bullet connectors in the RH footwell area????. Maybe there is an issue in that bundle??

 

yes I did check continuity on that inner thin wire.It has 100% continuity.and I checkeck it to ground from 200 ohms to 2 million ohms its good
and the wires I checked for resistance where the wires between power resister and ecu.they go directly from power resister to ecu and all have no resistance but the pink and green it has 7.01 on a setting of 20k ohms only .so I did a bypass on that wire so its now good.
So as of now im a little stumped on what to do next
This is probably stupid question but,does ecu need to be grounded with attaching bolts to car to work properly?
Mine is just laying loose in trunk.Not bolted to anything.

 

IMHO common sense would prevail and assume (I know, I know, ***-u-me) that "if" the ECU had capabilities to provide a ground source for something then it itself would need to be grounded, or in your case mounted. Just a guess.

 

I agree with the common sense/assumption of the ECU being mounted to earth whatever, but it is not a requirement in this case.

Nothing in the schematics shows any item being earthed via the casing. I also know this from my own workings with the ECU sitting on the carpet in the boot, and the engine doing what it does just nicely.

For some odd reason I am tending towards the resistor in that Blob, that drives the ECU pulse. I know not why, it is just all I can think of at the moment.

I went looking throw boxes of stuff in the shed, coz I am getting impatient for this sucker to actually run.

I have typed my handwritten notes into a Word doco, and it is attached. It explains the resistors INSIDE the Blob, and testing of said resistors.

Maybe it helps, I hope so.


HEI V12 Resistors explained.doc