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

 

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

 

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.

 

Ill be glad to help you with the electrical. Do you have a digital multimeter?


George

 

Thanks George. I have 61psi while cranking.. Yes I have a multimeter. No clue how to use it..lol

 

Check the ECM1 fuse - 15A and power to that fuse socket in the run position.

George

 

11.53

 

What happens to fuel pressure if you charge it up with key on, pull the fuel pump relay and crank the engine?


George

 

55 psi when hooked up. Charged 61psi. when charged I pull fuse it jumps back to 61 then down to 55 and stays there when cranking.

 

What fuse did you pull?