Hello, new member looking for verification on my 2003 blazer 4wd with 4.3l.
It all started when it died in a parking lot and wouldn’t start.
i changed the fuel pump and it ran good for a while, but then started running rough and blowing the ecm1 fuse. Sometimes a new fuse would last a day other times 5minutes and then immediately as I turned the ignition switch.
i replace the ignition switch and the ignition coil, still not fixed.
Today I pulled the connector off the spider injectors and tested the harness to ground and it was fine. Then I tested the actual pins on the injector spider and I got continuity to ground on pin E
So my question is, do you agree that injector 3 coil is shorted and causing ecm1 fuse to blow?

im getting tired of working on this $1000 truck and don’t want to waste any more money than I have to...
thanks to anyone who replies!

 

My reading of the schematic is that when a logic high pulse is applied to the transistor gate/base for an injector in the VCM (labeled as the "Fuel Injection Driver"), that acts as a switch and allows current to flow from 12V at the fuse through the injector coil then through the transistor to ground. This current opens the fuel-injector (like a relay) allowing fuel to be delivered. When there is no voltage to the input of the transistor, then no current can flow, the fuel injector coil is closed and no fuel is allowed out.

So when you say you measured continuity to ground through Pin E, did you do this measurement with all of the connections to the injector spider disconnected?
What did you use as ground?
Did you measure continuity through each coil? E.g. E-F, C-D, H-G, etc?
Did you also measure continuity between Pins A, B, C, D, F, G, H, J, K, L, and M and your ground?

 

The wire connector to the spider was disconnected. There is a ground stud on the firewall that i tested pin E with. I also tested pinE and F and it had continuity (a coil should have continuity though, so I tested to actual ground on the firewall) I did test the other pins on the other injectors and they tested open. I can’t remember the code I got on my scanner, but it was a misfire on cylinder 1. I feel like the spider is bad or at least E and F, which is the injector for cylinder 1. Can you change just the 1 injector or do you have to change the complete spider? Or are you thinking the vcm is the problem?
thank you

 

Pin E on injector harness is for injector#1. If the injector is shorted, just replace it. A 2003 should be the second type down in the remanufactured listing here. GB REMANUFACTURING 83322105
https://www.rockauto.com/en/catalog/...+injector,6224

First you might want to take the plastic cover off the intake for inspection and check to make sure the wires to that injector aren't worn through and grounded on the injection spider bracket. Keep in mind that a shorted injector could damage the VCM, but they are typically internally protected against that happening. Does a noid light flash for #1 on the injector harness. If so, the PCM should be fine.

 

OK, So you have a scanner error that you have a misfire on cylinder 1, with the fuel injector electrical connector disconnected there is a ground path from both pins E and F to ground, and with the electrical connector to the injector disconnected no other pins for the injector coils were connected to ground?

I would say your diagnosis is likely correct. The one puzzling thing to me is how there could be a ground path from the injector body to ground. I thought it had an all plastic body. But I must be wrong.

I guess there is a possibility that the transistor that controls the current flow through injector 1 could be shorted. But I think that possibility could be excluded by the evidence that the injector coil for injector 1, through either pin E or F, is connected to ground at all times. The only way the injector could be grounded through the VCM is if the electrical connector to the injector was connected. But to do your tests, the plug was removed. So at the minimum the injector is bad.

A check of the injector 1 control transistor could be done but be sure first to touch your multi-meter leads to a grounded surface along touching your hands to a metal surface. Doing this will discharge any accumulated static electricity on you that could damage the solid-state electronics (the transistors). And set the Ohm-meter setting to the highest setting which will limit the current that could go through.

As for replacing the single injector, the answer is yes. I took a look at Rock Auto to get a picture of an injector body and saw that they sell the individual injectors.

But if you are interested in keeping the truck, you might consider doing the CSFI to MPFI upgrade if your truck did not already come with the MPFI system. Being a 99, mine had the older style.

This explains the difference. https://www.motormanfuelinjection.co...onversion.html

 

hello, I have a 2003 s10 4.6l and am struggling to pin point my exact repair needed. My problem has started 3 weeks ago with my truck not wanting to start or show that I have any fuel in my tank. There is one wire on my #4 & #6 injector that goes to my fuse block which get extremely hot and smoke if I use a wire instead of the required 15 amp fuse to try and start my truck. I'm having a very hard time figuring out electrical issues since I know very little and have no prior experience. If I unplug my spider injector harness and replace the ecm1 fuse then turn my key my truck cracks with no start (obviously due to my injector harness being unplugged), but my ecm1 fuse doesn't blow. There is the other side on both injectors 4 & 6 that lead to my ecm. I desperately need some help. I've tried everything I can think of. I have a new fuel pump and filter, spider injector set, crank position sensor, coolant temp sensor. I feel real confident that it has to do with my 4 & 6 injectors or the electrical connection that my harness plugs into.