1998 chevy blazer 4dr. Fuel pump issue!!!???
#62
I don't know that your ECM is definitely bricked, I am trying to help you stay away from expensive damage. If you checked your ECM fuse and it was good then blown after all this work then you shorted something and I am cautioning you to be careful. Ready, aim, fire. Our electrical systems are pretty resilient except for a few places like computer lines and modules. I applaud you for learning and doing your own work, I am trying to help you get to the finish line. This is why I am the diagnostic guy, so we can do a targeted fix and keep snowballing problems and cost down. Also. unnecessary replacement parts can be of inferior quality and increase problems not solve them.
George
George
#63
1998 chevy blazer
Well that's good to know, also when I was changing my crank senor, I seen that the plug was brittle and damaged, so I replaced it, it's three wires, well as I was stripping back the wire two of them touched and started sparking, I should have disconnected the battery beforehand, so I'm not sure if I really did short the ecm?
#64
Replacing your fuel pump was a separate exercise and so are all relay and wiring/power/ground discussions from the relay to the tank. Replacing the ECM fuse corrects the previous diagnostic short, we still need to finish post #55 and find out why your ECM is not controlling the fuel pump relay properly. Report back and we will go from there. I am trying not to condemn your ECM which is a common mistake here, they rarely fail actually. That said, this one has seen some abuse but hopefully its still good.
Regarding the crank sensor and spark, it depends oh where you grounded the pink power wire. I it was to the engine block then worst case is a blown ECM 1 fuse. If you shorted it to one of the ECM sensor wires then yes ECM damage was possible. Minimum damage would be to ignition spark and timing. After a crank sensor replacement you need to perform a CASE relearn on the new crank waveform.
George
Regarding the crank sensor and spark, it depends oh where you grounded the pink power wire. I it was to the engine block then worst case is a blown ECM 1 fuse. If you shorted it to one of the ECM sensor wires then yes ECM damage was possible. Minimum damage would be to ignition spark and timing. After a crank sensor replacement you need to perform a CASE relearn on the new crank waveform.
George
#65
1998 chevy blazer fuel pump
I have something interesting that I just noticed, when I turn the key to the on position, I can hear a clicking on a relay, so I felt each relay until I found the one that was clicking every time I turned key on, and it's the relay labeled GRND HDLP, it's the relay directly above the fog lamp relay, its also a 5 prong relay, it's never done this clicking before? Perhaps there's a bad ground somewhere???
#69
OK so Les' chart agrees with one of my two charts so we will go with that one. I have simplified here:
So there are three possibilities here. First, a bad ground(s) to the VCM. The second is a bad power input. The third is a bad or improper VCM:
George
So there are three possibilities here. First, a bad ground(s) to the VCM. The second is a bad power input. The third is a bad or improper VCM:
- First check the ECM B fuse then measure the always on voltage from that fuse to pin 21/C3 orange wire at the VCM (connector in place, back probed)
- Second check the 4wd fuse and then turn the ignition to run and check the voltage from that fuse on pin 13/C4 brown wire
- Third check the clstr fuse then turn the ignition to run and check the voltage on pin 17/C4 pink wire
- Fourth check the ECM1 fuse and then Turn the ignition to run and look on pins 18/C4 pink wire and measure the voltage
- Check the grounds at the back of the engine block/heads
- If all of this checks then we will have to check the quality of the grounds at the ECM connector(s) but I don't you unplugging those deteriorating connectors unless we have to. In addition, these grounds are also listed in two places at the ECM: pin 17/C3 and pin 18/C3, both blk/wht wires.
George
#70
So after watching a video of scanner Danner, showing the reason a fuel pump relay won't prime pump, is becuase of a bad connection, corroded or burnt wire from a junction box, so I honesbelieve this is the issue.
Last edited by Jrt71282; 09-20-2023 at 03:23 PM.