So I have been working thru some issues lately trying to get my 190K Tahoe back in top shape. One of the problems I was experiencing was a random hard start. The "RANDOM" part I resolved with a new CAMSHAFT POSITION SENSOR. However, post shut off fuel pressure bleed down remains as issue. I have no doubt my old injectors are worn, clogged, and stuck open.. But I also suspect a few other things that I am going to deal with first and rule out.
As far as I can tell there are (3) reasons injector fuel rail pressure reads can drop once the car is turned off...:
(A) Stuck open injectors due to clog or malfunction.
(B) A leak in the fuel line system.
(C) A defective back-flow valve associated with the fuel pump in the tank.
To date I read 42psi at the fuel injection rail and watched it bleed off 3lbs in 5 mins and it was still going. So there is an issue. The 42lbs is lower than the stated required 50-52psi at idle as well and I read that slight variance here can affect performance greatly. I did replace the fuel filter since that read which may have increased the pressure, but I am moving past that as I am concerned with the bleed-off for now. We will read that again once a few more tasks are completed.
(1) First I am going to look under and make sure that fuel filter I replaced is not leaking at the connections.
(2) Next, I replaced the fuel pump a few years back on which the dash fuel gauge sender has never worked right. So I am starting there since it is a lifetime warranty unit. This will ALSO rule out fuel pressure bleed-back into the tank due to pump back flow check valve failure. I'm doing this either way you slice it because I paid for a good pump with a proper fuel gauge sender and I want to have what I bought and expected to get.
(3) Then and dreadfully, I will have to address the possibility of stuck open injectors either by crud blockage or straight up injector failure. I plan to first create a rig from which I can blast high pressure solvent thru the injectors from the fuel rail. If that does not work I will just have to pull the fuel rail and examine them one by one.
IN THE MEANWHILE, and as I complete step 2, can anyone tell me what type of code reader I would need to diagnose cylinder misfires.? Will a 2004 tahoe even log this in the computer? @BillD64 I have not forgotten about the bluetooth unit you recommended. I understand that it's performance capability depends on what particular apps you purchase to use it with? Do you think this vehicle logs misfires and that this unit will pick that up with the right app. I am thinking that even the fancier OBD2 reader I used at O'Rileys this morning that also did ABS system is not designed to read things like cylinder misfires..?? And probably short of a shop with a really expensive machine, my best chance may be to purchase that one on the link you sent me. You can probably tell me the answer to whether or not the vehicle actually logs the cylinder events??, but do you know if any of the APP purchase options will address misfires? If not no sweat I will research the ones listed at the reader manu website.....
Lastly, and while I devise my injector cleaner system in my mind, does anyone know how aggressive I can get in terms of running solvents thru fuel injectors in order to clear them of contamination. Either in or out of the vehicle. Are there any limits? Break cleaner? etc??
I honestly DO Suspect that I will wind up all the way thru step 3 and having to do a hard clean of the injectors because back in 2016 I had my first hard start issue ever, and it was simply injector cleaner in the fuel tank that corrected it that time. Its not exactly clearing it up these days to which I suspect simply that the amount of "Insoluble debris" has increased to the point of no easy fix at this time.
And that's a lot of gas to be seeping by these injectors every time I turn off the vehicle with consideration of fuel prices on the rise again.
I also begin my internal and external forum/internet intensive searching now and will add anything productive that I find out there.
Any help and all thoughts appreciated.
As far as I can tell there are (3) reasons injector fuel rail pressure reads can drop once the car is turned off...:
(A) Stuck open injectors due to clog or malfunction.
(B) A leak in the fuel line system.
(C) A defective back-flow valve associated with the fuel pump in the tank.
To date I read 42psi at the fuel injection rail and watched it bleed off 3lbs in 5 mins and it was still going. So there is an issue. The 42lbs is lower than the stated required 50-52psi at idle as well and I read that slight variance here can affect performance greatly. I did replace the fuel filter since that read which may have increased the pressure, but I am moving past that as I am concerned with the bleed-off for now. We will read that again once a few more tasks are completed.
(1) First I am going to look under and make sure that fuel filter I replaced is not leaking at the connections.
(2) Next, I replaced the fuel pump a few years back on which the dash fuel gauge sender has never worked right. So I am starting there since it is a lifetime warranty unit. This will ALSO rule out fuel pressure bleed-back into the tank due to pump back flow check valve failure. I'm doing this either way you slice it because I paid for a good pump with a proper fuel gauge sender and I want to have what I bought and expected to get.
(3) Then and dreadfully, I will have to address the possibility of stuck open injectors either by crud blockage or straight up injector failure. I plan to first create a rig from which I can blast high pressure solvent thru the injectors from the fuel rail. If that does not work I will just have to pull the fuel rail and examine them one by one.
IN THE MEANWHILE, and as I complete step 2, can anyone tell me what type of code reader I would need to diagnose cylinder misfires.? Will a 2004 tahoe even log this in the computer? @BillD64 I have not forgotten about the bluetooth unit you recommended. I understand that it's performance capability depends on what particular apps you purchase to use it with? Do you think this vehicle logs misfires and that this unit will pick that up with the right app. I am thinking that even the fancier OBD2 reader I used at O'Rileys this morning that also did ABS system is not designed to read things like cylinder misfires..?? And probably short of a shop with a really expensive machine, my best chance may be to purchase that one on the link you sent me. You can probably tell me the answer to whether or not the vehicle actually logs the cylinder events??, but do you know if any of the APP purchase options will address misfires? If not no sweat I will research the ones listed at the reader manu website.....
Lastly, and while I devise my injector cleaner system in my mind, does anyone know how aggressive I can get in terms of running solvents thru fuel injectors in order to clear them of contamination. Either in or out of the vehicle. Are there any limits? Break cleaner? etc??
I honestly DO Suspect that I will wind up all the way thru step 3 and having to do a hard clean of the injectors because back in 2016 I had my first hard start issue ever, and it was simply injector cleaner in the fuel tank that corrected it that time. Its not exactly clearing it up these days to which I suspect simply that the amount of "Insoluble debris" has increased to the point of no easy fix at this time.
And that's a lot of gas to be seeping by these injectors every time I turn off the vehicle with consideration of fuel prices on the rise again.
I also begin my internal and external forum/internet intensive searching now and will add anything productive that I find out there.
Any help and all thoughts appreciated.
