L Series 3 plug ecu gurus - disabling tips ?

steptoe · Post by **steptoe** » Thu Mar 13, 2008 11:31 pm

alrighty, as some of you may know I am in the process of converting my 87 GLTA (close enuff described as an auto L series RX) to dedicated LPG. Due to the more modern mixer ring systems not compatable with intake manifold pressure of the turbo EA82 I am going old school. If things go well and I can work out a vapour injection sytem to work without an ecu of the car that may be the go later.
This current installation will not need the ECU I AM THINKING. For those of you with experience of ECU duties especially the three plug L series can you see anything the ECU does that will not work if it is all unplugged ? I am staring at some electrical diagrams

I can see the idle up for AC on will not work if it is disconnected, and the overboost? and some other controls clutch switch

I am hoping the ECU does not intervene in the general functions of the car other than fuel requirements. If necessary I can just disconnect the injector plug and maybe smash the ECU alert bulb

to stop it coming on. Some duel fuel conversions need injector emulator to trick the ecu, others use a relay to simply prevent the ECU dash light from coming on when in LPG mode

The whole method is to run the baby in a Brumby without an ECU but retain the separate knock control box and throw much of two L series out

ta

Gannon · Post by **Gannon** » Fri Mar 14, 2008 5:20 am

It should run without the ecu fine.

Im not sure how the 3 plug system idles up for AC (is it a solenoid on the throttlebody, or the articulator that pulls the throttle like carby cars)
But i cant see why it wont work.

I wouldnt worry about overboost fuel-cut, its just a safety thing

Thats a good idea to use the seperate knock control unit, and you should be able to wire it without the ecu also.

Good luck

discopotato03 · Post by **discopotato03** » Fri Mar 14, 2008 7:58 am

Hi steptoe , if you look at your 3P Fuel Injection System manual it shows power to the 3P computer at pin 40 . This is in the connector with 3 rows of pins and looking into it with the latch side up its the top left hand end one . You can't miss it because its the largest sized wire going to the computer - white with a black trace on it .
It appears to be the only power input to the ECU so if its disabled I doubt it could do anything .
Just for the record I think its ignition switched powered via fuse 11 .

The fast idle solenoid is just to add more air when the A/C is running at idle , simple on/off solenoid valve and an adjustment screw to set the fast idle speed when energised . Permanently earthed and positive switched .

If this engine is going in a non factory EFI Brumby then its probably easiest initially to fit it with a carburettor in place of the throttle body on the inlet manifold . That gets you running so you can use the car whilst developing the gas side of things .

Cheers A .

steptoe · Post by **steptoe** » Fri Mar 14, 2008 12:50 pm

Gannon, don't quote me on this but I thought the idle up was an air bleed of some sort. Ah, Adrian has found it. Yeah , Adrian I spooted that 40 pin. It almost looks fine if you note the wiring split in two on the long fold out page, but noting the little arrows C, D, J etc that zip off to meet up on the lower diagram at the bottom of the ECU dia is an ignition relay. I may just have to give it power instead of from the ecu ? suck it and see....

discopotato03 · Post by **discopotato03** » Fri Mar 14, 2008 2:05 pm

Something going on with pin 42 Red wire as well , FICCD .

Cheers A .

steptoe · Post by **steptoe** » Sat Mar 15, 2008 11:12 am

Have spent some time pondering the fold out electrical diagrams of the factory shop manuals for the 86, early 87 Lseries. The longer I look the clearer thngs become. FL ? FL? what the #@*^ ? Aha, Fusible Link and its number and rating !!

Then there is the obvious, alongside the 'rails' above and below each set showing the power source as in FL1, FL2, IG, ACC , ST and E for earth, but I am stumped as to what M stands for. In some sketches an M is an electric Motor, and there is also the alphabetically ordered diagram 'links', linking the two long diagrams on each page together, but this M is a power 'rail' on these diagrams and appears to be connected to many things on the other side to Earth on all the warning lights (so it is not an Earth 'rail'.) M for Mains battery? I have trouble seeing its power come from the battery Pos terminal on the drawings

Any clues, although it looks too common to be any specific component wiring, more the whole car !

Then I see a Car Speed Sensor in the diagram for the height adjustable suspension. It is a switch ON or OFF and not a variable MORE or LESS switch that you might imagine may be the speedo inbuilt VSS. It seems to be enclosed type switch as opposed to a boot light switch that is physically exposed to outside elements. Anyone discovered this Car Speed Sensor to be anywhere different than the speedo head? I recall someone asking similar question and being told it was in the dizzy?

steptoe · Post by **steptoe** » Sat Mar 15, 2008 11:17 am

pin 42 looks to be connected to A/C FICD dia on the next page so idle up circuit as such ?

FICD? FIICD ??

steptoe · Post by **steptoe** » Sat Mar 15, 2008 11:20 am

looks like boost light will need rerouting if i completely disconnect ecu

steptoe · Post by **steptoe** » Sat Mar 15, 2008 11:22 am

and the ignition relay provides power to the ecu and fuel pump maybe so that will be OK.

Just being cautious as I would rather disconnect completely so as not to burn out a good ecu

steptoe · Post by **steptoe** » Sat Mar 15, 2008 11:25 am

the egr solenoid also , but egrv has been sealed up anyway

discopotato03 · Post by **discopotato03** » Sat Mar 15, 2008 8:15 pm

If you have a factory manual go the the start of the electrical sections and look for legends .

The fusible link info in the 87 manuals is in the section 6-2 Body Electrical Section . Its there for the Aus RHD version on P 19 and 20 .

For a 4 plug car permanent power is supplied to the computer via Fusible Link (FL) 1 .
FL 4 supplies permanent power to the ignition switch , amongst other things . The ignition switch powers up the fuse panel - fuses 10/11/12 in the IG position (on position) and fuses 13/14/15/16 in the ACC (accessories) position .

That fuse 11 , that the Ignition Switch powers up in the IG on position , supplies the Ignition Coil and MPFI Control unit .

So there you have it - for a 4 plug .

In the Factory FSM Fuel Injection System section 2-7 , P48 shows a diagram of the Ground System of Control Unit Power Supply .

The ignition switch powers up the Ignition Relays coil which closes the contacts and allows fusible link power to flow to the MPFI Control Unit at pin 38 .

The way that L series cars control the EFI pump is not straightforward .
The computer not only earths the pump motor at pin 50 (3P ECU) but it also completes the earth side of the circuit at pin 39 (3P ECU) to close the fuel pump relays contacts . Two tier control if you like .

What you have to understand is that there is permanent power to the Ignition and Fuel Pump Relays (and Ignition Switch) and the Computer selectively earths things like relays to power up the necessary circuits .
Its the ignition switch that supplies positive current to power certain things .

If you want to remove the ECU from the equation you need to isolate its power supply , and the EFI pumps , but not the ignition coil or it won't run .
All the ECU really does is control the injectors and a few solenoids (purge/EGR/ EFI pump) for the 3P system and same plus ignition timing on the 4P system .

Brain fried , cheers A .

Suby Wan Kenobi · Post by **Suby Wan Kenobi** » Mon Mar 17, 2008 8:39 pm

If its going in to a brumby then use original Brumby wiring and add the LH circuit for the knock control all you will need is the wires to connect it to the dizzy and coil. As for AC just use one from an MY setup or add a power wire into the clutch for the compressor, that way the idle up is only when the compressor is running which is how it should work anyway. Choke on the EFI L is controlled by the top of the thermostat so you will only have to run an ignition power to it so it has hot start function.

steptoe · Post by **steptoe** » Mon Mar 17, 2008 10:59 pm

The L Series (Project Cheap Grief) is really the test bench for the LPG system on EA82T. When that is sorted PROJECT EA82T Brumby starts most likely with my other engineless Brumby and the EA82T sitting on my shed floor. I am in two minds about retaining AC in either Brumby as one has been decommisioned with bad condensor and the other has just leaked out RDrier. But I guess an idle up won't be too tricky to wire up. As for fast idle for choke - have never needed a choke in the past with straight gas, just a few cranks with frottle open a bit

Then it has to be a clean up. Got two 81's to cracked open for inspection, keep good bits chuck the rest

steptoe · Post by **steptoe** » Tue Mar 18, 2008 9:50 pm

I can now say that with the 3 plug ecu all I needed to do to disable the injectors from opening (oops ! fuel pump ???) was pull the plug that sits apart from the other two. I have connected up the gas mixer components and the jammed open flapper AFM - and she runs. But has a little problem on boost. The boost pressure balance line between mixer and converter loses pressure somewhere and causes a lean out on boost. Not good coz the backfire blew me silicone ducting off, spitting hose clamps across the road. I can hear a hiss loss of air pressure just before it backfires. Impco specs state 5psi of boost as a max but they are known to do a conservative 8psi without work. I know of a mod to the converter to withstand 35psi. Investigations continue...