No start. ECU not switching relay on.

[Rame]

Hi,

I have a Peugeot 406 1997 ST Auto 2.0
ECU = Bosch MP5.2, OE Ref Num = 0 261 204 696

I've been browsing this forum and came across some similar issues.
Putting into simpler terms, I would just call it,

A no start due to the 2nd ignition relay (Voltage input = pin 2, Output/ground = pin 10) supplying fuel does not close on ignition switch on.
Pin 2 has +/- 12 V on ignition on
Pin 10 has NO GROUND.

1. From the circuit diagram (http://peugeot.mainspot.net/wiring406/index.shtml), pin 10 comes from the ecu pin 3.
2. Tried grounding ecu pin 3 and relay DOES close. So its not the ecu-relay wiring issue.

Help anyone? Looking at the ECU i see no burnt marks. Or can i be wrong? TDC? I don't even know what that is.

Thanks in advance

[steve_earwig]

Hi there, welcome

Umm, TDC - top dead centre, this will be referring to a sensor on the converter housing seeing magnets or a missing tooth on the starter ring gear to tell the ecu when the crankshaft is at tdc. I guess if it's got no output then the ecu can't tell if the engine is turning or not.

See item #6 on this diagram - http://peugeot406coupe.nl/catalogus/D8F/1/19G25A.HTM (not sure if this is the same motor as you have there but the principle is the same)

[Doggy]

Hi & welcome aboard.

Does it have a fuel shut-off switch / have you checked it?

[Bailes1992]

Somewhere in the engine bay, usually bolted to the struts is an inertia switch. It's usually red and rubbery!

[Rame]

Sorry, should of stated that also.

Checked the inertia switch and its closed.
Once i ground the pin 10 on the relay, the fuel pump is heard running on ignition.
So its surely something from ecu.

Gonna have a look today. Wish me luck boys.

[Doggy]

I had a similar problem with a Citroen Xsara HDi 90. The fuel pump would not run, or only run sometimes. I changed the double relay, it made no difference. I got it working temporarily by bypassing the ecu to make the pump run, as you have.

Discovered 1 of the 3 +12V supplies to the ecu was missing - this was the power for the egr valve and fuel pump relay.

It turned out to be a fault in the wiring loom that I never found. I overcame the problem by linking two points that should have been connected but no longer were.