Injectors won't pulse; weird voltage problems please help

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1993SS
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Injectors won't pulse; weird voltage problems please help

Post by 1993SS »

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
'93 Legacy SS, 5sp, TD05, FXT TMIC, lotsa mods at 11psi
'76 Ford F-150, 4x4, built 390, 4sp
1993SS
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Posts: 7
Joined: Sun Dec 25, 2016 3:09 am
Location: Ogden, Utah

Re: Injectors won't pulse; weird voltage problems please hel

Post by 1993SS »

Tried a JY ignition relay and no change, had her towed to the ol’ family mechanic today. Will report back what I hear.
'93 Legacy SS, 5sp, TD05, FXT TMIC, lotsa mods at 11psi
'76 Ford F-150, 4x4, built 390, 4sp
Legacy777
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Re: Injectors won't pulse; weird voltage problems please hel

Post by Legacy777 »

Welcome!

Regarding your problem, I had an issue before where the car stalled intermittently and one time in particular wouldn't start right away. It eventually started and left a code. The problem was the MAF sensor. I can't say for sure whether your problem is the same, but something you could do to test this theory would be to unplug the electrical connector to the MAF sensor and see if the car starts or if anything changes from how it's currently behaving.

Regarding the wiring and injectors, there should be 12v power going to the injectors all the time. The other lead on the injector goes to the ECU. From what you described it sounds like you have the proper power going to the injectors. The ECU will only pulse the injectors when cranking. So you need a noid light or something to confirm the injectors are pulsing electronically. If they are and the plugs are still dry then I'd install a fuel pressure tester to confirm you have good fuel pressure.
Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

If you need to get a hold of me please email me rather then pm
1993SS
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Posts: 7
Joined: Sun Dec 25, 2016 3:09 am
Location: Ogden, Utah

Re: Injectors won't pulse; weird voltage problems please hel

Post by 1993SS »

Thanks for the reply, Josh! I forgot to mention that the MAF was one of the first things I tried. I unplugged it and nothing changed, then took it off and sprayed it with some MAF cleaner (didn't dare take it apart) and it didn't seem to help. I checked my local JY inventories and couldn't find any '90 legacies that might have one. It now occurs to me that I have a JECS MAF that I've been saving for the Robtune. I know it's not advisable to get anywhere near boost with the JECS and the 22t ECU, but I probably should have put that in and tried to start it.. But it's in the shop now, so we'll see if they can figure it out. If it ends up being the ECU or the MAF, I might as well just get some 550's and finally take the Robtune plunge.

That is relieving to know that they are supposed to get constant power, that simplifies the problem significantly. Haha I also wouldn't be surprised if there was a fuel pressure issue, I did not check that. While I do have the Walbro, it's got the original FPR, rails and injectors. I get pretty bad gas mileage (15mpg) but my right foot is pretty husky so it could just be that..
'93 Legacy SS, 5sp, TD05, FXT TMIC, lotsa mods at 11psi
'76 Ford F-150, 4x4, built 390, 4sp
Legacy777
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Re: Injectors won't pulse; weird voltage problems please hel

Post by Legacy777 »

You're welcome!

Keep us posted on what the shop finds out.
Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

If you need to get a hold of me please email me rather then pm
1993SS
In Neutral
Posts: 7
Joined: Sun Dec 25, 2016 3:09 am
Location: Ogden, Utah

Re: Injectors won't pulse; weird voltage problems please hel

Post by 1993SS »

Alright guys I'm gearing up to get back into this wiring problem. The car has been at the shop this whole time. My mechanic basically just confirmed what I had already found out, which is a wiring problem causing low voltage at the injectors. He says he doesn't want to mess with it since he doesn't have proper manuals and I don't blame him. Also, a couple weeks ago I got another 22t ecu from a lovely member here and that didn't change the issue, so at least I can rule that out. Since I've already taken the engine harness apart, I know which wire supplies the injectors. It's a heavy gauge wire that splits off into smaller ones and since all 4 injectors have the same problem, I'm assuming that there must be a partial break/corroded section in the thicker wire. So my plan is to strip the insulation off of that wire and see what it looks like. But what I'd like to confirm is that I can use an N/A engine harness on this car in case I somehow screw mine up. I've read that the only real difference is the location of the CTS (easy enough) and the boost control connectors. The turbo I'm running is at 10psi wastegate and before that I had a TD04 with a MBC so I think it's safe to say I don't need the factory boost control. The real question is, do I need to get an N/A harness from a '93-'94 car so the connectors are all the same near the fuse box? There's two '91's at my local junkyard but I read some vague info about the connectors being a different shape for '91-'92'.
'93 Legacy SS, 5sp, TD05, FXT TMIC, lotsa mods at 11psi
'76 Ford F-150, 4x4, built 390, 4sp
Legacy777
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Re: Injectors won't pulse; weird voltage problems please hel

Post by Legacy777 »

Unfortunately the turbo engine harness plugs are different for the 92-94 MY's.

The 90-91 NA engine harness has three rectangular plugs. The 91 turbo engine harness has the same three rectangular plugs. The 92-94 NA engine harness just has two rectangular plugs, and the 92-94 turbo engine harness has two rectangular plugs and one round plug.

Since you have a 93 SS, you would need a 92-94 turbo engine harness.
Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

If you need to get a hold of me please email me rather then pm
1993SS
In Neutral
Posts: 7
Joined: Sun Dec 25, 2016 3:09 am
Location: Ogden, Utah

Re: Injectors won't pulse; weird voltage problems please hel

Post by 1993SS »

Ahhh that makes sense, thanks for clarifying and saving me the time/trouble! I'll try to fix what I've got when I get the car back home and report back when I make some progress.
'93 Legacy SS, 5sp, TD05, FXT TMIC, lotsa mods at 11psi
'76 Ford F-150, 4x4, built 390, 4sp
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