injectors not firing.. again

**91dime** · 02-23-2016

I actually have not tested if it will run with fuel or not.

As far as the noid light, correct me if im wrong, but if the noid light flashes properly when turning over, that means the PCM is grounding properly correct? Now if its grounding properly to flash the light, why would it not pulse the injector? Im not trying to question your intelligence or be rude in any way, Im just a bit confused.

**EDZIP** · 02-23-2016

Originally Posted by 91dime

I actually have not tested if it will run with fuel or not.

As far as the noid light, correct me if im wrong, but if the noid light flashes properly when turning over, that means the PCM is grounding properly correct? Now if its grounding properly to flash the light, why would it not pulse the injector? Im not trying to question your intelligence or be rude in any way, Im just a bit confused.

The noid will flash as you attempt to start the car, which means you have both power (12v we hope) and the signal ground from the ECM. If you are working on a TBI engine you should be able to see the injectors pumping fuel, if it's a TPI engine obviously you can't.

I'd get some gas or starting fluid and have someone turn it over while you supply fuel...if it starts you know you have a fuel problem and not electrical.

One problem I recently ran into was a plugged return fuel line...pressure was so high the injectors wouldn't open. Squirted some fuel in the throttle body and it fired..so I knew it was a fuel problem

**91dime** · 02-23-2016

I failed to mention this is a TBI, Its a 7427 computer controlling it all. I recently redid the fuel system to include metal lines and fittings on most all of the fuel system and an adjustable FPR set at 20 PSI to get it to support more power. I have everything set up in the BIN to accommodate the new upgrade. It ran great previously. I also have a gauge rite before the tbi to monitor pressure and it never goes over 20 so i wouldnt think the fuel system has a blockage. I also confirmed that both injectors do spray properly when connected to power and they do receive the proper 12V of power.

I hate to think but how likely is it that the 7427s injector driver has failed me?

Tomorrow i will manually pulse the injectors to see if it actually fire. All of the ignition stuff is new except for the coil.

**EDZIP** · 02-23-2016

Originally Posted by 91dime

I failed to mention this is a TBI, Its a 7427 computer controlling it all. I recently redid the fuel system to include metal lines and fittings on most all of the fuel system and an adjustable FPR set at 20 PSI to get it to support more power. I have everything set up in the BIN to accommodate the new upgrade. It ran great previously. I also have a gauge rite before the tbi to monitor pressure and it never goes over 20 so i wouldnt think the fuel system has a blockage. I also confirmed that both injectors do spray properly when connected to power and they do receive the proper 12V of power.

I hate to think but how likely is it that the 7427s injector driver has failed me?

Tomorrow i will manually pulse the injectors to see if it actually fire. All of the ignition stuff is new except for the coil.

You have done everything except give it fuel manually, if it fires with fuel manually sprayed into the throttle body I would also do a fuel sample...in case you have bad (water) fuel. Just the basics first.

**91dime** · 02-23-2016

So if it does fire up with fuel added manually, where do I look next?

**EDZIP** · 02-23-2016

Originally Posted by 91dime

So if it does fire up with fuel added manually, where do I look next?

Then you know it's a fuel related problem since you have spark, compression, ignition etc.

That's why I keep extra ecms and throttle bodies on the shelf..it's a lot faster to just swap with a known good component.

Make sure you have "spark at the plugs" ..I know you replaced the ICM...but those GM trucks are known for burning up ignition control modules...I keep a few of them on hand for that reason. If you don't have spark and wind up replacing the ICM...remember the engine might be full of raw gasoline from trying to start it...with spark your muffler could go boom.

Autozone can test the ICM for free...but they need to run the test at least 3 times and make sure you use thermo lube under the ICM to transfer the heat or it will burn up.

**91dime** · 02-23-2016

I have another ICM that Hopefully works along with thermal compound I use to build computers. Is it the heat that kills them or other factors along with heat?