Cranks with no start
#1
Cranks with no start
Hello everyone.I been coming here for a while now fixing up my 99 LT. Lots of helpful info!! However I can't figure this issue out. I have changed to MFI and installed a new cat. She drove fine for 3 weeks. Daughter takes the car and 3 days later cranks but no fire. Fuel pressure checks out and spark is good. Ideas? I have checked Ing switch,passcode. New fuel filter new coil and tune-up. AC Delco parts.also new distributer
Last edited by whislinwings; 10-10-2020 at 12:06 PM. Reason: update
#2
It's fuel, spark or air.
Since you did injector work first check all the wiring and connectors.
Any codes?
Can you read fuel trims and look at sensor values in live data?
Do you maintain fuel pressure while cranking or alternatively 12V at the fuel pump relay while cranking?
Assuming that you have no clues from codes, sensor data or fuel trims, proper fuel pressure, a good fuel pressure regulator and strong spark with good timing then its either air or fuel delivery. With no engine turnover at all during cranking, the likely issue is fuel delivery.
First thing to check is the fuse for power to the injectors - ECM1, 15A.
If good then 12V to the injectors.
If good then low side control pulses from the VCM with a noid light.
If good then injection balance with a balance pulse tester (IM intact) or spray pattern if you have the IM apart. A crude version of this for basic injector pulses and some fuel delivery is fuel pressure while cranking and fuel pump fuse disconnected.
Let me know if you need any help with these tests.
George
Since you did injector work first check all the wiring and connectors.
Any codes?
Can you read fuel trims and look at sensor values in live data?
Do you maintain fuel pressure while cranking or alternatively 12V at the fuel pump relay while cranking?
Assuming that you have no clues from codes, sensor data or fuel trims, proper fuel pressure, a good fuel pressure regulator and strong spark with good timing then its either air or fuel delivery. With no engine turnover at all during cranking, the likely issue is fuel delivery.
First thing to check is the fuse for power to the injectors - ECM1, 15A.
If good then 12V to the injectors.
If good then low side control pulses from the VCM with a noid light.
If good then injection balance with a balance pulse tester (IM intact) or spray pattern if you have the IM apart. A crude version of this for basic injector pulses and some fuel delivery is fuel pressure while cranking and fuel pump fuse disconnected.
Let me know if you need any help with these tests.
George
Last edited by GeorgeLG; 10-10-2020 at 12:17 PM.
#3
Thanks George. No it's not setting codes.(1st time i wished it would..lol). I get 61 at key turn and holds @ 55. I've been trying to find how to check the power for Injectors. I'm not very good with electrical. I did swap relays around. I have no way of seeing live data. I will check pressure while cranking in a few mins.