Need to tap into your collectively vast knowledge

[Simran]

Hi guys, i need a few questions answering, some of them will probably make me look very stupid but better safe than sorry hey
what i need to know is:

1) How do i work out what each of the three pins on the crank sensor are? -, + and shield but which is which

2) same question, different part, throttle pot wiring but not the standard bx one, its a universal jobby that has ground, signal and 5v ref ( im gonna give this one a go with a multimeter and see if i can figure it out) WORKED THIS ONE OUT

3) Do injectors have a polarity, and if so which pin is which (im using standard yellow injectors if that helps?)

4) Which is firing cylinder no1? This is probably the most important question as this determines how i wire the coil pack and the injector batches.

Cheers

Simran

[Vanny]

1) the SMOT sensor as the Europeans call it requires an oscilloscope, basically connect a scope to the + and - and spin the engine over, when it pulses it will either speak high then low or low then high. I THINK if it goes high then low then you have the wires connected to the scope the right way around, and visa versa.

3) they dont have a polarity as far as i am aware (its just a coil at the end of the day).

4) i think the firing order is in the Haynes (i think 1,3,4,2,) and the cylinders are numbered one to four FROM THE FLY WHEEL end of the engine.

send me an email and i'll reply with a detailed manual on how to setup up Walbro ECUC1A Ecu, its an ecu for a motorbike or car, but it has an excellent setup manual on how to figure out many of these 'strange' things.

[Simran]

5) Which is the fuel pump relay? one of the ones near the lhm tank or one of the ones behind the bulkhead?

Think ive figured out the crank sensor wiring, good old haynes says the shield and earth are joined near the ecu so should be able to distinguish the three wires apart, good job as the only place i can think of to get an oscilliscope to play with is my old college and i doubt they will have lent me one

I was originally confused about the injectors as a coil wired one way will pull one way, wired the other will push but your idea vanny seems to match up with my first thoughts as well as a few other people ive asked so im sticking with that.

[Vanny]

to be honest, i've always been a bit confused about it, but i take what i'm told on this mythical journey. By the way, the coils CAN be non polarised dependant on configuration. Doe the Haynes wiring loom not give clues?


5) 'the black one sir' technically its the 5 pin one, but there nearly always black. If you have relays by the LHM tank than its one of them, other wise its under the drivers seat by the ECU

[prm]

Hi, Simran


The CAS, possibly - Bosch Pt. No. 0. 261. 210. 043. on a 3 wire control.

With the CAS plug, central casing locating pin uppermost and left and right lugs underneath, pin allocation left to right should be, black, yellowish/cream colour and, screen but your plug type body might vary.
Screen is joined to Pin 23 @ ECU.
Reading between t1 and t2, (yellow and black) should be around 500-550 ohms static.
Test the AC voltage cranking between t1 and t2, but don’t forget to remove the distributor cap first!! when checking, should be AC at about 3-4 volts, interchange the test leads to confirm + cable, as cable colours could differ.
Take the plugs out and retest, there should be an increase in AC voltage generated.

Point to take into account with any mods, the CAS is polarity conscious and being AC voltage generated.
Might be worth taking out the CAS to check the body for and dents, as adjacent to the housing you may find a casting hole, where you can just view the flywheel and ring gear, plug this with a modified plastic battery shipping cap with small vents. Have been known to be quite handy for dropping small nuts and cable tie off cuts down!!!!

I believe the ECU needs to see an AC voltage generated from the CAS before the fuel pump and main injector driver relays operate.

Vanny was quite right with injectors, they have no polarity, all connected in series and all fire at the same time.

Fuel pump relay should be adjacent to LHM tank, main pump wires should be yellow,- with normal type relay,
The adjacent main relay, should have blue main wires connected. This relay unit should indicate a 5 terminal connection on the outer body, indicating with a + marker - diode application inside, but you can use a standard BX type for testing if you have no dash engine management light.

Regards

[Simran]

Cheers guys, i found the right relay and have wired everything apart from the injectors, started raining this afternoon, wires are all laid, just not connected The new ECU fires the injectors in pairs, 1+2, 3+4. After this i will be ready to fire her up and see what happens, nothing should, hopefully as there is no map on the ecu yet but all the right lights should come on if ive done everything right. Im getting very excited now as this si where the real fun starts with the mapping

[Toddman]

Good to hear you are making progress Simran.

One thing you might need to consider is that the std TPS is not a potentiometer but merely a switch pack which tells the std ecu that the throttle is either in closed (idle) or wide open (full throttle) mode - I suspect if you are using megasquirt you will need to ditch the std TPS for a pot that gives an output all the way through the throttle opening range as this will tell your ecu what is happening in place of the AFM unless you are using a MAP or pressure sensor.

Cheers
Luke

[Simran]

Already thought of that The suzuki throttle bodies had a throttle pot already mounted to them (the actual throttle bodies are made by mikuni i believe), a potentiometer type so saved me the hassle of finding one that would fit. The meagsquirt ecu also runs a MAP sensor and the maps can be created using either device or both to work out load. Alot of people recommend starting with just the throttle pot for getting a base map quickly as it is more direct, then using both sensors to fine tune later on. Another matter that might give me some trouble is the wiring for the rev counter. Ive been shown a simple circuit that will allow me to use the wasted spark coil to drive the tacho, it suggests tapping into each input of the coil and running it through a diode to prevent the two sides joining and then running the joined signal through a zener diode with a block out voltage of 15-18v. I cant get hold of one of these from maplins so ive bought two others, one is 13volt jobbie the other is a 30volt. Im going to use the 13volt one, this should be ok shouldnt it? i cant see why the rev counter would need upto 15v, 13v will still be enough to drive it wont it? I should know what im trying to do as i was taught all this at the beginning of uni but a years break has done me no good The ecu doesnt have a seperate tacho driver, well one that runs at 12ish volts so i need to replicate the signal that would have come from the old coil.

[prm]

Don’t worry about trying to remember what you were taught at Uni, as it seems to get worse as you get older!!!!!

With your tacho, there are several alternatives. Optical, where reflective tape is attached to the crank pulley for a positive detection, or any engine speed pulley – alternator.
Spray the reflective tape once positioned, with an acrylic clear lacquer, holds it in position and is easy to clean. Displays are usually quite small and digital. Very easy to install and around £25-45.

AC impulse generator attached to the CAS circuits. Can be expensive, with fitting diodes in-line, generators etc. Never fitted, one, because I’ve always been apprehensive about connecting into ECU circuits.

Alternator driven. Tapping into alternator coil outputs, prior to the diode circuits.
Just a single wire required, but any possible belt slip needs to be taken into account.
Some tacho can be expensive, marine type can go over £100.
A trip to the breakers to find a suitable unit might be worthwhile. Look for any diesel, under say 1.6L,and below, these can indicate, 7-9000rpm. Unless your expecting to go higher than this!!!!!!

Heard of one unit where you just plug into the cigar lighter. Relies on the fluctuating impulses from the alternator, but this is a hand held test unit.

Not sure what ECU unit you are using, as some Bosch units had a tapings adjacent to the main multi- pin plug, enabling diagnostic test equipment to be connected.

Regards