kia optima 2001 2.4 wont start

they changed the ecm, maf, cam sensor the injectors. Diagnostic procedure: volt drop test both sides good, battery 12.4v, cranking rpm 430, cylinder compression test 165psi, fuel pressure 55psi, injectors pulse 3ms, injectors flow 4oz 1min, crank and cam relation correct, timming mark correct, cat no bad pressure, new ignition coil, good ignition timming by pressure transducer, all Mitchell test pass, ecm good power, ground, voltage and reference voltage. All the sensor have a good signal. only start when u block the fuel line, fuel pressure goes up to 100psi.

why the car start only when I block the fuel return line????

carlos.gonzalez wrote: ...fuel pressure 55psi, injectors pulse 3ms, injectors flow 4oz 1min...

Hey carlos! Just to be clear, 3mS is the injector pulse width you saw on the scanner during the cranking? That number sounds low to me. Which might explain why the car starts with the fuel return blocked. Jacking the rail pressure up to 100 PSI forces enough fuel through the injectors at that smaller pulse width to get things started. You could verify this theory by adding carb clean to the intake instead of blocking the return. Once running, does it run well?

If that 3mS number is correct, then I'd suggest looking closely at the ECT and IAT. These help determine cranking injection pulse width, and could potentially cause the ECM to underfuel the engine during cranking. An easy test of the ECT and IAT is to let the vehicle sit overnight, and see if they agree with each other (within a few degrees) in the morning.

Tyler wrote:

carlos.gonzalez wrote: ...fuel pressure 55psi, injectors pulse 3ms, injectors flow 4oz 1min...

Hey carlos! Just to be clear, 3mS is the injector pulse width you saw on the scanner during the cranking? That number sounds low to me. Which might explain why the car starts with the fuel return blocked. Jacking the rail pressure up to 100 PSI forces enough fuel through the injectors at that smaller pulse width to get things started. You could verify this theory by adding carb clean to the intake instead of blocking the return. Once running, does it run well?

If that 3mS number is correct, then I'd suggest looking closely at the ECT and IAT. These help determine cranking injection pulse width, and could potentially cause the ECM to underfuel the engine during cranking. An easy test of the ECT and IAT is to let the vehicle sit overnight, and see if they agree with each other (within a few degrees) in the morning.

Good eye!
The question of cranking injector on time came up in THIS THREAD also.

Noah wrote: Good eye!
The question of cranking injector on time came up in THIS THREAD also.

Yeah, that's the one I was thinking of!

I don't have any known good data off an Optima with a 2.4L, otherwise I'd have a better idea if 3ms is good or not. :lol:

I've got an '01-ish Optima in the shop right now. If it's a 4 cylinder, I'll see what the cranking on time is and post back tomorrow.

Wow, the data rate on this is absolutely junk!
I finally managed to capture the cranking injector on time at 5.1ms.
Cold idle no load is 3ms.

Up here in Canada, they are called Magentis(Besides the point). I have seen intake gasket leak from manifold to cylinder head, but so far I have only seen this in cases where its flagging a lean code.