Diode Replacement-No power to ECU

[John Croucher]

Working out the bugs on the 2000 (not a hyper motard) Quota, I would get a no start problem.  First I addressed the ignition switch.  It was extremely corroded.  Still had no start issue.  Moving wires below the gage's gave me a false sense the problem was there.  Then onto replacing all the relays and fuses.  Then moving wires around at the relays,  I narrowed it down to the ECU relay area.  Then the wire that has the diode shown in the wiring diagram N4007. 

Chasing down a no start, no spark, no fuel pump running problem, I found that the diode N4007 between the ecu and the relay for the coil, fuel pump is broke.  I can push the solid copper wire into the diode and the engine will run.  I can pull the copper wire and the engine will stop.

In doing some research, I found this from This Old Tractor.

I am not clear if this is adding an additional diode or the diode that I am having problems with is an original factory fix.  The diode currently installed is referenced in the OEM wiring diagram. 

ECU protection and transil diode installation
Moto Guzzi Quota 1000 and Quota 1100 ES models

 https://www.thisoldtractor.com/moto_guzzi_quota_ecu_protection_and_transil_diode_installation.html
 

[guzzisteve]

I'm on a Quota lately for work. Haven't put a batt in yet, so .  All the earlier FI have that diode. Now you found it an issue, replace it if you can't fix it. Electronics store may carry it, if you could unplug it would be nice to take it in. Otherwise, snip snip.

I haven't had to deal with one yet.

[pauldaytona]

The transil diode if mounted is only to protect the ecu from over voltage or voltage peaks.
The 1N4007 if between one of the injection relays, and should measure nothing in one direction and 30 ohms or so in the other also depending on the measurement device.

If you don't trust it, buy another one. One side should have a ground connection, other to the injection relay.
Newer types like v7 have the diode in the relay build in.

[Wayne Orwig]

As mentioned, the transil diode is a surge protector. It goes across the power lines and shorts surges to ground.

A 1N4007 is a simple 1 amp series diode. Current one way, none the other way. I don't know where it is, or why it is there. Sometimes they are also used to prevent surges but it a 100% different way. They can let power into say a relay coil, but when power is turned off, the diode blocks any surge from coming out of the coil.