Injectors won't pulse; weird voltage problems please help
Posted: Mon Mar 04, 2019 2:40 am
Hey guys, first post here. I've had my '93 SS for a few years and have done a ton of mods in that time, thanks to this wonderful website. But after a week of diagnosing and searching all over the internet, I can't figure out this electrical gremlin that is causing my car to crank forever but not start.
So let's start from about a week ago. The car was running fine (it's been my daily for about 2 years) and on my way home from work, the car randomly died. i pulled over for a few minutes, couldn't see anything wrong, so i tried to start it back up and it eventually ran again. i got a few more miles closer to home, died again. Same thing, just waited and it eventually started. This happened a couple more times, but i was able to get it home thankfully. Then the car would just crank and hasn't started since then. The only other time it showed these symptoms was about a year ago when the fuel pump went out. I replaced it with a Walbro 255 and it has been good since then.
So, that was the first place I checked. I can hear the pump priming when I turn the key, I pulled the fuel hose between the filter and fuel rail and put the hose in a container. The pump flows as it should (double checked with the green connector hooked up, flows every time the relay clicks.) So that's not the problem.
Next I checked for spark, which I had plenty of. Installed new plugs at this time just because it had been a while. So that's not the problem.
At this point I noticed that the plugs were all bone dry after lots of cranking. Ah-ha! The injectors must not be opening!
So I check the injectors (stock pinks) they are all are in spec as far as resistance, but instead of having 12v with the ignition on and 0v with the ignition off, it had 3v in both key positions at all 4 injectors. WTF? I found one other thread where someone was having a similar issue, which turned out to be a bad connection of some kind. They fixed the problem by just disconnecting/connecting harness connectors. I was not so lucky. After messing with every connector I could see, no change. So I thought that maybe there was a some wires with damaged shielding somewhere in the harness that were making contact. From the FSM diagram I saw that there is one wire that feeds power to all 4 injectors, the Ignition coil and CPC. So I figured that must be the culprit. A few of the pins on the connector for that circuit (coming out of the fuse box in the engine bay, F25) were corroded, which seemed to back up that theory. I cleaned these first and the voltage went up to about 9-10 volts (still constant, key on and off) After that I removed that entire chunk of harness and after taking off the crusty old tape and loom, I frustratingly found all of the wires intact, confirmed by testing every wire to every pin with a 12v power supply and a test light. This is also when I found that the wire colors of my 1993 harness are all completely different from the 90-92 FSM diagram I downloaded from Josh's post. So I put some fresh loom and tape back on the harness, put it back in the car and tested again.
After all of this work and testing, I now have about 10v at the beginning and end of this harness, both with the ignition on and off. At this point I don't really know what to do. I looked at the other side of this circuit, and from what I can tell it goes to SBF2 (confirmed by pulling it, no power to injectors) which I have switched out with several other SBF's, all have the same result. From there, the diagram shows the power wire going to both the fuel pump relay and ignition relay. As I said at the beginning of this novel, the fuel pump relay seems to be doing it's job. I can't tell if the ignition relay is clicking with the green connectors hooked up (is it supposed to?) and I can't seem to get it off of the bracket it's connected to. (any tips for this? I can barely get one hand up there.) And would that relay being fried somehow allow current to flow constantly instead of switching on and off with the key?
If that isn't the problem, I am completely out of ideas.
Another problem is that I didn't take any pictures of the injector wiring before I took the harness out, since at that time I assumed the diagram would match up. My wires on the passenger side of the engine are black/red on one, black/brown on the other. Driver's side are yellow/green on one, yellow/blue on the other. I plugged the injectors back in how it seemed like they should go, judging by length of the wires. But without a proper diagram, I'm not positive that they are hooked up right. If I can't figure out the voltage issue soon, I'm going to have to take it to a shop. But I want to make sure that the injectors are at least hooked up right. So if anyone with a '93 can take a picture of their injectors hooked up, that would make me feel a little better. Thanks for any input, I've overcome some frustrating challenges with this car but this one is really breaking my spirit. haha
So let's start from about a week ago. The car was running fine (it's been my daily for about 2 years) and on my way home from work, the car randomly died. i pulled over for a few minutes, couldn't see anything wrong, so i tried to start it back up and it eventually ran again. i got a few more miles closer to home, died again. Same thing, just waited and it eventually started. This happened a couple more times, but i was able to get it home thankfully. Then the car would just crank and hasn't started since then. The only other time it showed these symptoms was about a year ago when the fuel pump went out. I replaced it with a Walbro 255 and it has been good since then.
So, that was the first place I checked. I can hear the pump priming when I turn the key, I pulled the fuel hose between the filter and fuel rail and put the hose in a container. The pump flows as it should (double checked with the green connector hooked up, flows every time the relay clicks.) So that's not the problem.
Next I checked for spark, which I had plenty of. Installed new plugs at this time just because it had been a while. So that's not the problem.
At this point I noticed that the plugs were all bone dry after lots of cranking. Ah-ha! The injectors must not be opening!
So I check the injectors (stock pinks) they are all are in spec as far as resistance, but instead of having 12v with the ignition on and 0v with the ignition off, it had 3v in both key positions at all 4 injectors. WTF? I found one other thread where someone was having a similar issue, which turned out to be a bad connection of some kind. They fixed the problem by just disconnecting/connecting harness connectors. I was not so lucky. After messing with every connector I could see, no change. So I thought that maybe there was a some wires with damaged shielding somewhere in the harness that were making contact. From the FSM diagram I saw that there is one wire that feeds power to all 4 injectors, the Ignition coil and CPC. So I figured that must be the culprit. A few of the pins on the connector for that circuit (coming out of the fuse box in the engine bay, F25) were corroded, which seemed to back up that theory. I cleaned these first and the voltage went up to about 9-10 volts (still constant, key on and off) After that I removed that entire chunk of harness and after taking off the crusty old tape and loom, I frustratingly found all of the wires intact, confirmed by testing every wire to every pin with a 12v power supply and a test light. This is also when I found that the wire colors of my 1993 harness are all completely different from the 90-92 FSM diagram I downloaded from Josh's post. So I put some fresh loom and tape back on the harness, put it back in the car and tested again.
After all of this work and testing, I now have about 10v at the beginning and end of this harness, both with the ignition on and off. At this point I don't really know what to do. I looked at the other side of this circuit, and from what I can tell it goes to SBF2 (confirmed by pulling it, no power to injectors) which I have switched out with several other SBF's, all have the same result. From there, the diagram shows the power wire going to both the fuel pump relay and ignition relay. As I said at the beginning of this novel, the fuel pump relay seems to be doing it's job. I can't tell if the ignition relay is clicking with the green connectors hooked up (is it supposed to?) and I can't seem to get it off of the bracket it's connected to. (any tips for this? I can barely get one hand up there.) And would that relay being fried somehow allow current to flow constantly instead of switching on and off with the key?
If that isn't the problem, I am completely out of ideas.
Another problem is that I didn't take any pictures of the injector wiring before I took the harness out, since at that time I assumed the diagram would match up. My wires on the passenger side of the engine are black/red on one, black/brown on the other. Driver's side are yellow/green on one, yellow/blue on the other. I plugged the injectors back in how it seemed like they should go, judging by length of the wires. But without a proper diagram, I'm not positive that they are hooked up right. If I can't figure out the voltage issue soon, I'm going to have to take it to a shop. But I want to make sure that the injectors are at least hooked up right. So if anyone with a '93 can take a picture of their injectors hooked up, that would make me feel a little better. Thanks for any input, I've overcome some frustrating challenges with this car but this one is really breaking my spirit. haha