Dead RV8 Hotwire ECU???

[chassis 33]

Yes another question about the racer...

Friday in testing I got a flat spot mid session from 3500 to 4000, pulling fine from low revs then flat...not misfiring but no power, then after 4000 it pulled fine again. Pulled the plugs (the 6's I mentioned) and all the drivers side bank were near ice white, the passenger side was better but still a little lighter than expected. I put in a set of B7ECS but still the same flatspot.

Saturday come the race the flat spot was still there although not at such a distinct rev range and very intermittant, sometimes it would be fine others I had no power and was playing about with the gears to get some acelleration.

Sunday I tried to fire the car up to get it off the trailer and nothing, zip not a jot. Cranked it over for a long while then gave it a break because I thought the cylinders would be flooded, but i pulled a plug and it was bone dry. Tracing the wiring showed no brakes in continuity, and 12v was getting to the injectors, however putting a bulb across one of the injector plugs (with the others on that bank disconnected) showed there was no earth being switched.

Is this a typical failure mode for a hotwire ECU, or is there something else thats stopping the injectors from firing? There is still a spark.

Regards
Iain

[Deltafox]

Sounds very much like a fault i had to diagnose on a fiesta race car fitted with the zetec and eecIV injection.
Had sparks, fuel pressure etc but no injector pulse.
Turned out the ecu wasnt switching the earths for the injectors....just happens that way sometimes.

[GreenV8S]

Sounds like it has been running lean. Since you've subsequently identified a problem on the injector control side, that would be the most likely cause of it running lean. The ECU uses the ignition signal from the distributor to trigger the injection, so if this signal was intermittant/failed that would wipe out the whole thing. The trigger wire is a single wire that comes from the distributor LT wiring loom, along the top of the nearside rocker cover and into the ECU loom. You should see a good strong 12v square wave on this while you're cranking. There's an inline resister in the circuit (just before the wires goes the bulkhead on mine) which gives an obvious point of failure.

[chassis 33]

Never let me doubt you Peter!!! Thats exactly the problem (i think), its running now, but I've only just clocked your post, not a knackered ECU (thankfully), just some muppetry in the wiring...
Thanks

Regards
Iain

[rev-erend]

Iain,

Sure that was not Race driver excuse No. 192

[chassis 33]

Rev, Not when you're out dragged by a car that should have 50hp less than you! Having said that I have no where to hide, I built the car so I should of checked the wiring was up to scratch, and should of checked every connection including pin 39 before panicking over a dead ECU, sadly the disco wasn't about at the time to check it against.

Regards
Iain