406 ST 1997 Sudden engine failure

[RodHagen]

Australian release 406 ST 2 litre D8 1997 model with Bosch 5.2 engine management. 205,000kms on the clock. No immobiliser key pad in this one. Engine stopped suddenly while rounding a bend. (probably not relevant, but I had filled up with fuel 10 kms earlier). No earlier sign of engine problems.

Engine turns over fine, but won't start. Looking for an answer for weeks now. Just about to give up and hand it over to a mechanic, but I've been fixing Peugeots and Citroens myself for more than 40 years and I don't like giving up!

First suspected the fuel pump. No sounds of operation even after letting it sit for a couple of days, battery disconnection etc. Checked voltages at "cut out" switch in engine bay and fuse 10 in engine fuse compartment. 0 volts. By-passing cutout switch makes no difference.

Checked voltage at pin 2 of tachymetric relay : 13 + volts.
Checked voltage at pin 9 (fuel pump feed) of tachymetric relay: 0 volts

With ecu removed for safety I directly earthed pin 10 on the tachymetric relay (which activates its other "side"). Fuel pump began running (audible).

Checked power feed to ECU at pin 18 (main power feed to ecu) . Regular power available. Pin 10 on the tachymetric is not continuous with earth with the ignition on.

Despite power at the ecu there is clearly no creation of the necessary earth at pin 10 of the tachymetric relay to provide power to the fuel pump (which I gather there should be to provide the voltage at pin 9 to the fuel pump) .

So power to the ecu, power to most circuits on the tachymetric relay, but no earth on pin 10 of the tachy to activate voltage on pins 9 & 1 of the tachy to power the fuel pump.

The obvious culprits here would seem to be either the ecu or, just maybe, the tachymetric relay, but are there other possibilities?

Could a bad ignition switch or a dead key chip produce these symptoms? Is there any way that a simple wiring problem could be implicated (he said hopefully, being in a currently parlous financial state)? Are there other things (like a failed ignition module) that might "feed back" in a situation like this to produce the lack of power to the fuel pump?

What about the TDC sensor? Even though the car was driving normally right up to the engine failure is this likely to produce these sorts of symptoms if it has died or is dirty? Or would I be experiencing erratic, rather than complete, failure if this was the issue? Any other places to look?

THis doesn't seem to be a common problem in Australia from what I can see, but there are one heck of a lot more 406's in the northern hemisphere!

Any thoughts would be greatly appreciated. And hey, many moons ago I was born in England and still support the MCC in the cricket! ;-)

[mjb]

Interesting.

The immobiliser (if fitted, and without keypad) works off a passive RFID chip in the key being activated by an aerial which fits around the ignition barrel. However, I've always been under the impression that this mechanism is merely triggered by the ECU asking for authorisation to run at wake-up time, and a failure after engine start would have no effect until the engine's stopped. I may be wrong, but I can't recall any immobiliser related cut-outs being triggered while driving

Almost certain the TDC sensor just affects spark and injection, not fuel pump activation

With ecu removed for safety I directly earthed pin 10 on the tachymetric relay (which activates its other "side"). Fuel pump began running (audible).

Try earthing it at the ECU end of the wiring. If it fires up from there, I'd suggest finding some way of getting diagnostic information from the ECU (find someone with a PP2000, or acquire one yourself)

[RodHagen]

Many thanks mjb. Just been chatting with a local Peugeot mechanic who suggests that a problem with the TDC sensor can result in a "no power to the fuel pump" situation, so I'll check that first (should have done anyway when I think about it). If still no go I'll pursue the erath at the ecu end.

[Rame]

Hi,

Currently having the same issue. Got no ground to "switch on" relay at pin 10 from engine ecu pin 3.
I know its an old post, but did you solve it in the end?

Peugeot 406 1997 ST in Australia. =)