Intermittent starting issue from cold

I recently acquired a 2002 Jimny auto with an odd starting issue. From cold/warm it will either start immediately or crank and not even try (mostly the latter). Once started it runs smooth and quiet. No misfires or any other miss behaving. The check engine light remains off. When it's hot it seems to start every time. I don't currently have an OBD2 adapter so I can't read out any fault codes. I have one on order.

Here's where it gets a bit odd. When it won't start I still have a spark, fuel pressure is just under 50PSI and I can see the injectors are getting pulses as it cranks. It just doesn't fire. If I then give it a sniff of easy start spray it will start straight up. It feels like a fuelling issue to me but the injectors are getting triggered and there is fuel pressure. I don't think the fault is in either the crank or cam sensors. If I disconnect either one it won't spark or fire the injectors. I have to admit I'm a bit stumped on this one. Any ideas would be gratefully received!
 

Huh, I just found something interesting. I hooked one of the injectors to an oscilloscope. When it won't start the cranking injector pulse width is about 1.4ms, which seems very short. Idle is ~4.2ms and I'd expect more fuel than that when cranking. I managed to catch one good start and cranking pulse width looked like 10ms or more. I only caught a glimpse before it started.

It sounds like either a ECU fault or more likely a sensor fault, that is not providing a long enough pulse for the injectors when cold.

I take it battery voltage off s good? After that it could be the crank position sensor, giving a wrong position and reduced pulse to the injectors.

It might also be a faulty temperature sensor, the ECU thinks the engine is really warm.

A code reader might help give further insight.

Robin

Thanks for the reply. The battery's pretty new and I tried jumping it off a big battery. It cranked a little faster but didn't start.

Hopefully my code reader will turn up in a few days. If that doesn't shed any light on the issue I guess I'll have to load up the parts shotgun and throw some new sensors at it.

wrote:

Thanks for the reply. The battery's pretty new and I tried jumping it off a big battery. It cranked a little faster but didn't start.

Hopefully my code reader will turn up in a few days. If that doesn't shed any light on the issue I guess I'll have to load up the parts shotgun and throw some new sensors at it.

Les read this  www.rhinopower.org/diag/cel.html