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ECU problems

T

t11ner

New member
Apologies for the blatant blag as I'm only an occasional visitor on here but as an ex-911 owner myself I thought it was worth a go [8|].

My day job is diagnostics on all kinds of cars but right now I'm a bit stuck on a 3.2 Carrera. It's a car the chap uses for about six months per year and this springtime he came to start it up and it wouldn't go. I got called to it a few weeks ago and found that it has no spark or pulse to the injectors but just occasionally it will start and then run fine; turn it off and try again and it refuses to go again.

When it is playing up I've got good power and earth feeds to the ecu and power to the coil and injectors etc, the engine speed and position sensors are perfect on a scope.

The obvious conclusion is an ecu fault so my customer found a place to fix it and they seemingly found and repaired a fault at the cost of £300 but it's still the same on the car! The unit has now been re-tested and passed a rig test.

Despite this, I'm pretty convinced that the ecu is at fault so here's where the blag comes in! Does anyone in the Stafford / Stoke area know of a spare ecu that could be borrowed to confirm this fault? If it does work I'nm sure the guy would be happy to pay a reasonable price for it.

Any other suggestions welcome also!

Thanks

Steve H
 
Hi Mark, thanks for the reply [:)]

The fuel pump part of the dme had already been bypassed before I saw the car (something that ought to be remedied at some stage for safety reasons) but the main feeds to the ecu etc are spot on.
 
flywheel sensors
there are two that acquire a signal which confirms to the ECU that the engine is running. I had a similar problem 2 years ago. The sensors are prone to corrosion so apparently it is becoming a common problem with cars of this age.
Mine would start and run OK but refuse to restart once warm
 
They both have resistance readings as per the spec and both give perfect patterns on the scope, identical whilst cranking on the times that it does start and the times that it doesn't.

Warm or hot starting problems are common with these inductive sensors as the windings can break when hot but sadly not in this case!

Keep em coming [8|]
 
Steve has it got an immobiliser or alarm fitted I think from memory one of the feeds from them stops the ECU from working , one may have a intermittent fault as other cars have had
 
It has got a Cat I alarm/imob but all feeds to the ecu and injectors/coil etc are solid at all times.

When I first went to the car it had about 3v on the earths to the ecu which turned out to be a snapped earth strap to the engine (the ecu picks it's earths up off the block, not the chassis) - I thought I'd cracked it then but I hadn't!
 
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