|
strange symptoms !
I'm thinking it might be trying to fire too far before TDC and maybe predetonation is causing the firing to put more strain on the starter? slowing the starter? that or there is some massive short, but if there is a short that big it must be producing heat and nothhing seems to be frying up.
does placing a jumper cable between the battery - and the engine block make any change? or (carefully ) between battery + and starter positive cable?
I was recently fixing an AC brush motor , it ran intermittently and I was looking for the cause. and realized it had issues due to some grease on the brushes. they looked ok but just as an experiment , I took the brushes to a grinder and took a touch off them , and it was solved.. they file easily as they are just graphite. ,,
a problem with cables or ground does not explain why you are getting different results when you have the firing conditions and not when you remove fuel or spark.
I'm mystified. maybe someone else can reason their way through this one..
i wonder what happens when you have fuel and spark and everything connected except unplug the spark plugs, or maybe as a second test, with plugs removed?
removing the plugs should make it crank fast as there will be no compression and if you can find it slowing under that condition then you have eliminated predetonation as a culrit.. so then it would need to be to do with a short or bad connection then..
if the fuel rail lost its charge by a leaky check valve it might make it need to crank a bit more to establish fuel pressure before it catches.
timing belts didnt slip right? I'd make sure.. just dont want to hear of a valve piston collision event.. ,,
could this modified ECU be picking the wrong map or something? can the OEM one be put back as a test? I was wondering it could be confused and outputting a strange pulse for the spark or the ignition timing. the electronics may be able to advance or retard the spark and perhaps doing so extremely incorrectly? I don't know how one could even check that.
|