Fried ECU ?

[Bruce Reader]

So i had the motor out replacing the cam chain tensioner amongst other things

and while putting the battery back in for the 100th time in 8 years i think i

have fried the ecu with a nice spark from the battery.

 

I now have power to starter and dash lights but no cycling sounds of fuel pump.

 

I have Roys drawings but would like some step by step to testing the circuits to

see if i need a new ecu.

 

Cheers

 

Bruce

[Kiwi_Roy]

So i had the motor out replacing the cam chain tensioner amongst other things

and while putting the battery back in for the 100th time in 8 years i think i

have fried the ecu with a nice spark from the battery.

 

I now have power to starter and dash lights but no cycling sounds of fuel pump.

 

I have Roys drawings but would like some step by step to testing the circuits to

see if i need a new ecu.

 

Cheers

 

Bruce

 

******* Modified *********

Bruce,

I doubt you have fried the ECU, more likely a fuse gone, it might be just a tiny break

 

With your multimeter or a lamp check you have power on both sides of every fuse to chassis with the key ON

 

If you have the electric petcock you should see voltage either side of Fuse 8 to the chassis even if the ECU is not working. At this point you should also have voltage at test point f. If not start on the left hand side and work your way across, with relay 3 removed and the sidestand up there should be voltage at TP b & c

 

12V also at the top contact (30) of Relay 4 & 5

 

Check that Relay 4 is energized, you should hear it click as you poke it into the socket. The fact that you have cranking tells me your safety circuit is probably made.

 

Make sure the ECU is grounded, the wire is quite small you may have burnt it off, perhaps where you can't see it. The ECU is rubber mounted so it needs that ground.

 

Try substituting the relays in 4 & 5 for a couple of others. Actually the start relay spot is good for checking a relay, both NO & NC are used.

 

Good Luck

 

Roy

[Bruce Reader]

Thanks for your time Roy.

 

Just to check that i'm using the correct testing technique.

 

I checked for voltage on each side of the fuses by using positive

to fuse terminal and negative to battery/earth.

 

I got these results

 

Fuse

 

1 12v left

 

2 12v right

 

3 10.9v left, 12.3v right

 

4 12.3v left

 

5 12.4v left

 

6 12.3v right

 

7 10.2v left, 12.3v right

 

8 12.3v left

 

Fuse 8 runs a line to an extra headlight relay (no electric petcock)

 

Test point

 

f 12.13v

b 12.17v

c 12.17v

 

Relay 4 clicks when inserted but no voltage at terminal 30

Relay 5 has 12v at terminal 30

 

Relay 4 felt warm when removing

 

Ecu earth appears in good condition and was attached when this mishap occurred.

 

The bike cranks.

 

I had the engine out and the crank sensor checked and wire re routed against frame. You mention

that relay 5 can be affected by this. Or should the fuel pump prime at least once regardless of this ?

 

Cheers

 

Bruce

[Kiwi_Roy]

Thanks for your time Roy.

 

Just to check that i'm using the correct testing technique.

 

I checked for voltage on each side of the fuses by using positive

to fuse terminal and negative to battery/earth.

 

I got these results

 

Fuse

 

1 12v left

 

3 10.9v left, 12.3v right

 

Relay 4 clicks when inserted but no voltage at terminal 30

Relay 5 has 12v at terminal 30

 

Relay 4 felt warm when removing

 

Ecu earth appears in good condition and was attached when this mishap occurred.

 

Bruce

 

Yes your testing is correct.

Relay 4 is the relay that feeds the ECU terminal 26, at least it is on mine. It's possible that Luigi put the 12 Volts to terminal 87 instead of 30, either way will work.

It is possible that the relay socket is loose not making proper contact with the relay pin, a bad contact there will cause the relay to get hot.

It's very easy to tighten the contacts, just make a little tool to release the clip and they pop right out (see attached)

If you shorted out the battery through the relay it's possible something fused inside, swap it around with another relay to be sure it's not that.

 

Test the relay in the Start Relay position, that gives them a good workout.

 

Double check the voltage on fuse 3 & 7. All fuses should have the same Voltage on both sides, if it's different points to a loose contact or bad fuse. F1 feeds Relay 4, what's on the right side? Measure by touching the socket part, not the fuse itself. Warm fuses are a sign of a bad connection.

 

Just to be sure check the ECU ground with your meter, it should be 0 Ohms back to battery negative.

 

What actually happened when you flashed the battery, did you see any smoke or other bad signs?

 

To reiterate, I think your problem it the lack of 12 Volts on relay 4, the ECU needs that.

 

Pins 23 and 24 of the UCU plug should also be connected to ground, in fact I'm not even certain the case needs it.

I have attached the ECU drawing, you can check the plug for the various voltages. Look for 12 Volts on 17 & 26.

26 is switched by the ECU relay R-4

 

 

Tell me more about the cam shaft tensioner, why did you change that?

I'm thinking perhaps mine needs replacing because the bike won't idle properly. It's not broken but the spring seems a bit weak.

Relay Base Repair.pdf

ECU Test Points.pdf

[Bruce Reader]

Thanks Roy for steering this electrical journey for me.

 

Your diagrams are indispensable !

 

So to the quest.

 

Every relay works in the starter relay position. (cranks bike)

 

Relay 4 has no voltage on pin 87 or 30 (86mv)

 

All fuses have 12.4 v insitu- my previous checks were with fuses removed therefore some voltages l and r

 

Ecu case to neg battery terminal .8 ohm (key off) and 3.2 ohm with key on

 

Ecu connector pin 17 and 26 to earth (300mv)

 

Pin 87 of relay 5 to ecu connector 6 and 13 (17 ohms each)

 

pin 87 of relay 5 to ecu connector 14 and 20 (.7 ohms)

 

ecu connector pin 7 to 12 (680 ohms)

 

When i was putting the battery in all i saw was a good white/blue arc.

No obvious burning smell/smoke or obvious insulation melting on wires.

 

I changed the tensioner as the spring had broken and the grooves from the

chain were obvious. I had left this for a few months before doing it. I had a

mild intermittent stumble on deceleration. The type i have in it has the spring

stretched over an internal metal part of the timing case which may be the spring/designs

weak point.

 

I also have a high idle problem in hot weather that i hope will be fixed with valves done and

throttle body rubbers refitted.

 

Cheers

 

Bruce

[gstallons]

This ? is after the fact. Why did you do such extensive work to this bike and leave the battery terminals connected?

[Bruce Reader]

i didnt.

 

cheers

 

Bruce

[Kiwi_Roy]

Bruce,

12 Volts goes directly from Fuse 1 to Relay 4 contact 30, it also goes to pin 17 of the ECU plug.

Since you are missing voltage at both points I suspect you may have burnt the wire off between the fuse and relay base.

 

I assume when you connected the battery the key was off so there shouldn't have been a spark. If you pinched the wire somewhere that might account for the spark you observed. It might also be a couple of wires rubbed together inside the loom, the wire probably goes fairly direct from the fuse block to the relay, from relay to ECU but don't take that for granted, sometimes Luigi made soldered joints inside the loom, you may have to remove the covering but check each end first. Whatever happened you need to get that Voltage back.

 

Pull the fuse base and relays off, I'm sure you will find something there. The wire is marked BI-VE on my drawing (I don't speak Italian).

 

The fuse base is plugged into a couple of rubber grommets, just pull and wiggle it. Check the wire for continuity, I think you will find it open between F1 and the relay but intact between the relay and ECU pin 17.

 

If you can't find the fault you might have to run a new wire.

 

To be safe leave the ECU unplugged until you have re-established the Voltage.

 

Since you have the relay bases off take the time to tighten the contacts, I like to use petroleum jelly (Vaseline) to stop corrosion.

 

BTW, I think the 300 mV and different Ohms readings you observed Key On/Key Off are voltage drop in the wiring.

I didn't mean for you to take all those readings, just included the drawing for reference.

 

Good Luck

Roy

3067_001.pdf

[Bruce Reader]

All sorted thanks to Roy.

 

Fuse 1 plug was snug inside the fuse holder underneath but 'beside the terminal !!!

 

Cheers

 

Bruce

[Kiwi_Roy]

Glad you are back on the road.

 

Moto Guzzi - making electricians out of riders for 90 years

[gstallons]

Oh yeah !!!