Hi guy I'm new to diesel and the duramax.i have a 06 gmc sierra 3500 lbz got this truck not running and in need of headgaskets I did those. Everything bad together and now I only have .34 volts to my injectors from ecm have done ohms test on all injector wires all are good. I have checked what I can of the ecm power. I even put in another ecm which only gave me .18 volts any help would be greatly appreciated.
Injector voltage issue
- Thread starter Notadieselmechanic
- Start date
So I was testing without cranking last night I checked while cranking most it jumped to was 5 volts then seemed to stay around 1to2volts I am only testing the number 2 as I'm bye myself. I'm having a no start issue. Fuel pressure is around 58 as desired is around 56. I thought the injectors were to have a steady voltage to them.
The voltage is a pulsed signal and will be hard to read with a normal volt meter. An oscilloscope would be needed to see the waveform. It's supposed to be a higher voltage spike of around 24 volts then drops down lower for a holding open current. This of course is only a fraction of a second so a normal meter may not register fast enough or be able to deal with the varying voltage pulses.
Do you have a proper code reader? What if any codes?
When you say fuel pressure is 56 is that in psi? Is that 5600 psi?, or mpa? Just 56 is either the wrong units or way too low unless it's mpa
Do you have a proper code reader? What if any codes?
When you say fuel pressure is 56 is that in psi? Is that 5600 psi?, or mpa? Just 56 is either the wrong units or way too low unless it's mpa
Ya sorry about that I'm lost with diesel so I borrow my friends scan tool snap on. So it is a good scanner I believe those readings are mpa. Or it would be 5600 psi I don't have any codes which add more confusion for me no direction to. So are you saying these pulse the power voltage not the ground on these?
I'm not 100% on which side controls the voltage but the on / off is controlled on the ground side of the injector
I haven't heard of many having good luck probing the voltage of the injectors with a regular DOM. I would use your scanner if it has the capability and watch the mm3, commanded fuel rate, etc and see if the ECM is even trying. Something else might be holding it up. More often then not the ECM is fine and there is something telling it it's not ready. Wether it be the fuel pressure, cam or crank sensors or maybe even low voltage or cranking rpm. These don't always present with a code but sometimes they do. Sometimes you have to look at the missed counts on the sensors and watch fuel pressure, etc to figure out what is holding it up
I haven't heard of many having good luck probing the voltage of the injectors with a regular DOM. I would use your scanner if it has the capability and watch the mm3, commanded fuel rate, etc and see if the ECM is even trying. Something else might be holding it up. More often then not the ECM is fine and there is something telling it it's not ready. Wether it be the fuel pressure, cam or crank sensors or maybe even low voltage or cranking rpm. These don't always present with a code but sometimes they do. Sometimes you have to look at the missed counts on the sensors and watch fuel pressure, etc to figure out what is holding it up
I appreciate all the info and input I will recheck all those things and on the mm3s when I can and let you know thank you again
Hey 2004lb7 sorry for the late update. So went throught fuel system because I was losing prime did all of the rubber lines brand new and got that issue fixed. Now I'm at a point were she cranks and spits and sputter but won't catch blowing smoke out the exhaustso getting fuel to some point
It's hard to tell what may be happening to your truck. Having a scan tool surely makes the job much easier. . The links below may provide you with some information that makes sense in your situation, but maybe not. Check to see if any injectors are shorted. Shorts can happen in cold weather but not when warm. Perhaps the truck will start by adding some propane to the intake - be careful if you decide to do this.
https://www.underhoodservice.com/duramax-dilemma-injector-circuit-diagnostics/ This is on a FICM-equipped truck
https://oregonfuelinjection.com/ser...gnostics-repair/chevy-gmc-diesel-diagnostics/
https://www.dieselogic.com/blog/how-to-test-your-fuel-injectors-in-just-30-minutes/
https://www.underhoodservice.com/duramax-dilemma-injector-circuit-diagnostics/ This is on a FICM-equipped truck
https://oregonfuelinjection.com/ser...gnostics-repair/chevy-gmc-diesel-diagnostics/
https://www.dieselogic.com/blog/how-to-test-your-fuel-injectors-in-just-30-minutes/
As Ron said, it can be hard without scan data for fuel pressure, cam and crank signal, rpm and others.
It is possible that since the heads where removed for head gaskets that the valves could have been setup wrong and it's preventing it from building compression. There can be numerous reasons. But we need more information
It is possible that since the heads where removed for head gaskets that the valves could have been setup wrong and it's preventing it from building compression. There can be numerous reasons. But we need more information
Are you sure you reconnected the crank sensor and didn't damage the wiring? It's right in front of the engine and common for people to damage wires if they're not careful.
Did you bleed/prime the fuel system? It can take along time to get all the air out. Classic sign is what you are seeing.
Does the scanner say cam/crank sync is good? Does it show cranking rpm?
You said you bought it not running, did you try and get it running before you tore the heads off? Why wasn't it running?
Does the scanner say cam/crank sync is good? Does it show cranking rpm?
You said you bought it not running, did you try and get it running before you tore the heads off? Why wasn't it running?