So I completed my swap going from a L03 TBI to a L98, but now I have a no start. It will fire up for a half second then stall then just crank/no start until it sits a while then same thing again.

I have spark and fuel. The injectors pulse once when it start for a split second then no injector pulse.

Coolant temp sensor, MAT, and TPS all check good. Injectors ohm out fine, fuses are good.

ECM has good powers and grounds.

What is next to check? Is there any type of flow chart out there for diagnosing this type of problem?

 

 

Have you had VATS disabled in the tune?
VATS stops the injector pulse if the fuel enable signal from VATS module is not seen by the ECM

Read
https://www.thirdgen.org/vats_passkey_system

 

The memcal is from utilityguy a v6 jumpered cylinder select aujp no vats. If the tps voltage is too high on the feedback the ecm will go into clear flood mode.

 

But do you still get the short inj pulse with Hi TPS V like you do with VATS fault?

 

problem solved, im an idiot, left the connector with the tach sig off the distributor.. started up, runs rough, dialed in fuel pressure at 48 at idle with vacuum line off.

Still runs rough, wide band reads rich at idle leans out at about 3k. suspecting vacuum leak.

fans wont come on, and running rough seem to be the only 2 problems as of now,

 

you mean it was a bad ignition coil module

 

exactly what i meant

 

Is ECM going into closed loop?

 

not sure i gotta hook up the scanner and check that out tomorrow, i was just happy enough for today that i got it started...


also very hard start gotta give it gas while cranking to fire it up

 

You can't give a EFI engine " gas" ; there is nothing to add extra fuel like the pump shot on a carb engine

Refer post # 4 above

Holding throttle open pass a certain point ( X % TPS volts ) while cranking over actually causes the ECM to cut the fuel
by shutting off the injectors ( because it thinks you are trying to clear a flooded engine )
so you must be way rich if engine will only fire up that way
Injectors too big , leaking ??????

 

yeah true, i guess i meant give it a little throttle, the injectors are stock, what do you think is the best way to go about diagnosing that problem