M800 hot starting issues and fuel shutoff

[Esprit]

Hi all,

I'm running a M800 on a 4 cyl N/A (cammy, ITB, EFI) engine and it's run for a few years just fine. However, lately it's been getting troublesome to warm-start. Car is only used infrequently so battery usually sits on trickle charge when I remember to hook it up.

Cold start is always fine (provided the battery has enough juice), but often warm-starting can be problematic. Sometimes it just about catches first crank but if it doesn't catch it then often refuses to catch. Sometimes it doesn't even fire at all.

Does the M800 cut fuel if you hold the throttle wide open during cranking? If not, can this be set up? Occasionally I can get it to fire up using this method if it's being difficult. However, it's got a small battery so it's easy to drain the battery to a hopeless point with repeated attempts to start.

In times when the car has refused to start (provided I haven't cranked the battery to death), walking away and leaving it for an hour and then trying again almost always results in it firing straight up again, no issues.

Cranking speed is all good, but I'm seeing the battery voltage drop to the low-8V range when cranking so it may just be the battery is on the way out. Strange though that cold starting is just fine if this is the case?

Backing up the low cranking voltage theory is that the car will push-start just fine if it's refused to start. It's not difficult to push start at all, always fires up first pop in an instant.

All sensors seem to be reading normally, haven't yet plugged in the laptop to see whether it's syncing up while cranking, but it seems to sync up just fine most of the time so doubt this is an issue.

Other than my question regarding the fuel shutoff, and maybe replacing the battery, is there anything else to look out for that could help?

Thanks in advance.

George.

[stevieturbo]

8v is pretty low, I'd definitely look at a new battery

[Esprit]

Yeah, that's becoming my increasing focus, the problem has been getting worse I think, and definitely if the battery hasn't got a good amount of charge it seems worse.

Does anyone know whether the M800 cuts fuel during crank at WOT or is this something you'd need to set up in a table?

[stevieturbo]

Yeah, that's becoming my increasing focus, the problem has been getting worse I think, and definitely if the battery hasn't got a good amount of charge it seems worse.

Does anyone know whether the M800 cuts fuel during crank at WOT or is this something you'd need to set up in a table?

Nothing is done automatically, someone would need to configure it. whether that's already done you'd need to look yourself.

[Scott@FP]

I believe there is a 'clear flood mode' where injection is 0mS during cranking if TPS or TPD is above 90%. Be easy enough to test. TPS and run RPM point must be set properly.

Important to have proper injector battery comps at low voltages and proper pre and post start comps for good startups under all conditions. In many cases hot start injection comps need to be higher than warm settings. Fuel first inj with ET as an axis can help.

However dipping below 9v when cranking is more than likely the root cause, low cranking voltage can cause ECU resets and other issues.

[zzj]

02:34:42
【GTR】33 2015-12-29 02:34:42
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