Engine cutting out

ChrisL · 11-09-05, 05:46 PM

I’m experiencing some very strange problems with my engine at the moment and hoping someone could help me figure it out. The engine is basically a standard RF40 setup ie 5.0w engine with a Motec M800 and all electronic setup (with coil packs etc).

The symptoms are…

1) The car will start and run OK while it is cold (or mildly warm)
2) Once the engine temperature rises it just cuts out under throttle
3) The cut out is total and with no warning, although if the engine is cool enough, it will come back to life if I lift off the throttle.
4) As the engine temperature rises, less and less throttle is required to cause it to cut out
5) At its (almost) worst, it will idle smoothly but ANY throttle will cause it to cut out.
6) At its absolute worst it will always give one burst of life during startup and then immediately die (regardless of throttle position).
7) Allowing the engine to cool a little will allow it to start and idle.
8) Allowing it to cool totally will allow it to again run perfectly until the engine warms up again, and the whole cycle begins again.

I have connected the ECU to the Motec diagnostic/tuning software and confirmed that the temp sensors and TPS (Throttle Position Sensor) are OK. The RefLo and SyncLo show an error while the engine is idling, but the Synced status shows OK suggesting the RefLo and SyncLo voltage levels are good enough. All the above symptoms are repeatable having tried the whole cycle three times to date (the last time with the Motec diagnostics attached).

Also, When the engine finally dies, many errors are reported, but that’s probably an effect rather than a cause (maybe). The strangest error though is Revs Too High.

Incidentally, I can hear the fuel pump still running after the engine cuts out.

The only other thing worth mentioning is that the throttle bodies were sprayed with a carburetor cleaner shortly before the problem arose, some of which ended up on the TPS and Ref sensor. Can’t see any real association myself, but there it is.

Any ideas anyone?

Ross Nicol · 11-09-05, 06:07 PM

Chris
I've got a wideband lambda sensor/meter if you want to check fuel air Ratios.Could be after the cold start enrichment comes off with engine temp rise, your going too lean.A fuel pressure check would't be a bad Idea.It sound like a fuel problem.

Ross

ChrisL · 11-09-05, 07:30 PM

Thanks Ross,
Do you know what a correct fuel pressure is? I probably read it in some document somewhere but can't remember. Failing that I might take you up on your lambda sensor.

Chris

Ross Nicol · 11-09-05, 07:53 PM

Mine runs at 50 PSI, I'm not sure what that is in bar.

Ross

Chris_K · 11-09-05, 08:21 PM

50/14.5= ~3

Jonathan S · 11-09-05, 09:06 PM

Sounds a lot like the problems you get with the Ford TFI distributors. What distributor are you running?

ChrisL · 11-09-05, 10:02 PM

Jonathan,
No distributer. All electronic, including the reference sensor (where the dizzy normally goes) and 2 X 4 core coil packs, each spark-plug controlled individualy by the Motec unit.

ChrisL · 11-10-05, 03:09 AM

Thank you all for your help, but I just got a phone call from Robert Logan from the other side of the world offering to put his best Motec man in Melbourne onto it (Ross Holder). I consider this a very generous offer since I built the car and engine myself and did not consider him under any obligation to do so. Seems even I underestimated his dedication to the cars.

Pete. · 11-10-05, 06:29 PM

Good on you Robert.

Paul Thompson 'Hooligan' · 11-11-05, 05:26 PM

[ QUOTE ]
Jonathan,
No distributer. All electronic, including the reference sensor (where the dizzy normally goes) and 2 X 4 core coil packs, each spark-plug controlled individualy by the Motec unit.

[/ QUOTE ]

I have experienced similiar problems on two 40s. A fully sequential Motec system on a GTD that was caused by too small a gap on the crank pick-up. Gave sync/ref errors above 3000rpm...

Also same problem on a CAV (Electromotive TEC-3/batch/wasted spark), caused by a failing mag sensor on crank 64-2 tooth wheel. The sensor would work for 10 mins or so, then once warm, engine would cut out. Spraying freezer spray on pickup was enough for the car to start working again. Speaking to Electromotive technical, it was due a faulty batch of crank-triggers they had from a supplier. (We had two before getting a different batch - which then worked!)

For the record, ignoring the initial cranking, once the engine is running, if you 'clear' the errors on a Motec system, you should NOT get any sync or ref errors AT ALL! if system has been correctly configured.

The article I wrote for our club magazine details the 'home-brew' setup I configured on club member Bjorn Arnils GTD. Once set up, we could start, clear 'starting errors' and then run the car for say 30 minutes on track or road, at low and high rpm (avoid rev limit) and NOT get a single error recorded. Motec is a great system, once setup, it'll run reliably - full stop... [img]/ubbthreads/images/graemlins/grin.gif[/img]