From the beginning!

[laugeo]

Ok, I wonder what the wealth of knowledge on here might be able to suggest. I'll relay the story from the beginning and see what you reckon.

My son's V4 StI has had a full bottom end rebuild and the heads done but it wasn't running quite right. Stuttering on take off almost like a misfire or fuel cut but was running ok once it got going - and then was boost cutting under heavier acceleration.

Diagnosis was bad plugs and a leaking boost actuator - both changed on Friday last and running much better as a result but not perfect. The ECU was also suspect as it had got wet 6 months ago and we wondered if it was causing minor running problems as a result (although it has been functioning ok since being dried out).

Anyway, the same Friday evening - it refuses to start, not even turning over - I tell my son to check the ECU connections because I know the mechanic only plugged it in (leaving it only finger tight on the bolts, planning to return to it next week)he pushes the plugs home again, bolts it down and hey presto the car starts.

He drives it home fine but once home and stopped, it won't restart - you can just hear the starter solenoid clicking but that's it.

I stupidly suspect the same ECU problem and when we remove it you could smell that electrical 'burnt' smell. Take the top off and there is a visible small component that looks like it has been too hot and the insulating material is cracking off it. This must be the problem?

So, I get hold of Johno's 1s ECU, plug that in - the same, just clicking.

Now the penny drops - maybe just not enough juice in the battery! Jump leads and sure enough it turns over but won't start. Try a remap? Turns over but won't start?

Back to the original 75 ECU? Turns over, won't start? Remap? Turns over, won't start?

Now in that awkward place - pretty sure the battery is not what it should be but would like to get it running first to isolate whether it is the battery or alternator that's causing the low charge. Now have 2 ECU's, the original which definitely has something at fault but we don't know if it is causing the non-running plus the 1s ECU and we don't know if for some reason it simply won't run the car?

Right now I'm stumped so any suggestions or tips would be welcomed! Cheers, Colin.

[Rosssub]

Can you hear the fuel pump priming when you first turn the ignition on? Is there any spark if you earth a plug onto the block and turn it over?

[laugeo]

I'll check both those things again tomorrow - unfortunately working with noisy rain this afternoon so unable to hear anything going on.

Thanks.

[laugeo]

Now it's quiet, I got my son to check (car's at his place) and no, there's no sound from the fuel pump!

What's the cause I wonder?

[Rosssub]

The missing/boost cutting under load could of been the fuel pump dying, now it's given up. Can use a test light or multi meter to check for power getting to the pump. Or just hard wire it straight to battery to see if it works.

[laugeo]

Thanks, we'll try that next. Could this problem come from the ECU?

[Rosssub]

It could but most likely the pump itself, possibly a faulty fuel pump relay. Or sometimes burnt out wiring between the relay and pump.

[Guest]

Try jumping the fuel pump with 12v see if it works.

[boon]

Some of the ECU ground paths are through the chassis/case of the ECU, if it wasn't bolted down correctly it may have caused a nasty ground path and burnt up some sensitive bits.

Does the car have an alarm? Check that it's not on the way out, if there's no power to the pump.

[laugeo]

Thanks for that. The mechanic is due back out in the morning, he has told me that the battery not charging and the fuel pump not running are both likely features of the failed board. We don't know why the replacement 1s board won't run it either, but I guess we'll know more tomorrow? It will be interesting if it turns out that the board not being bolted in correctly had caused the whole issue though! Cheers

[boon]

Well the ECU switches the fuel pump on and off and on some models it controls the alternator as well (I think by switching the exciter wire?)

Hopefully you get to the bottom of it soon.

[laugeo]

Unbelievable! It turned out to be a stray wire / wires under the dash causing the problem. They were left over from previous owner and poorly fitted previous alarm / immobiliser and just suddenly decided to cause problems. It's just ironic coincidence that the timing of this happening coincided with the other work around the car going on. All credit to the mechanic for tracking it down. Bingo! Now either of the ECU's runs the car, starts first time on both of them! Cars! Gotta lovem!

[laugeo]

The great news is that now we can get on with the rest of the work required to get this car back to its best! Thanks to all for the helpful info.

[Rosssub]

Great news. Frustrating getting bitten by a previous owners dodgy wiring.

Edited August 8, 2014 by Rosssub