Injectors do not get a steady voltage, they are pulsed. I suspect you're barking up the wrong tree.

 

Nope. I know they pulse. I'm not getting any pulse. But I am getting a steady 3V. The car runs good with starting fluid and the fuel pressure is good. The starting fluid rules out the Cam and crankshaft position sensors, timing belt, etc.

The problem is that I'm not getting fire to my injectors and I need to know what feeds them.

 

With the key at On, one side of each injector is connected to 12 V through the Main Relay. The other side of each injector goes to the ECM. To trigger the injector, the ECM grounds the "other side", allowing current to go through the injector coil and activating the valve. So with the key at On, but engine not running, there should be close to battery voltage at the injector connectors.

If there's only 3 Volts at the injector connectors with the key at ON (engine Off), there would seem to be a connection problem to the 12V that should be coming through the Main Relay. The source of power going through the Main Relay to the injectors is fuse SBF-2.

The 3 V being measured at all times could be coming from the ECM, which is always powered. Perhaps compare to another car to verify if the 3 V is normal with the key at OFF.

 

Thank You plain OM. That's the kind of info I needed. After sitting a while, I went back out and got no reading until I again turned the key on and then I got the 3v back. Should I be getting 12V at the SBF-2 relay connectors. I will check and trace the continuity and connections from SBF-2.
Thank you, thank you, thank you.

 

Should I be getting 12V at the SBF-2 relay connectors.

SBF-2, which is a "slow blow fuse", should have 12 V going through it at all times. SBFs can look like relays -- they're often a rectangular box with two push-in connectors on the bottom.

The Main Relay is (should be) energized, that is, turned on, only when the key is at ON or Start. When it is energized, the internal contacts should connect a 12 V line coming to the relay from SBF-2, to a wire harness that includes the connection to one side of each of the four injectors.

 

I know where SBF 1 thru 5 or 6 are. Which one is considered the "Main Relay"?

 

I believe the Main Relay is located on the left side of the dashboard. In the attached diagram, the relay is at connector B47, a 6-wire, brown connector. (The relay itself will have 6 pins.) It could be up under the dashboard, or lower down, behind the driver side "kick" panel.

 

Thank you very much for the diagram and the help. I haven't been able to spend much time on it, but I will tomorrow. I'm thinking I have a short somewhere. When I pull SBF-2 out and check the prongs or tabs that feed it, I get 12v on one side and 4v on the other. I'm assuming one of those prongs should be dead unless the relay or fuse is in there to feed it. I'm thinking I have something shorted out somewhere. This could turn into a nightmare. LOL

 

There should indeed be 12 V from the battery on one side of SBF-2.

The other side of the fuse connection goes to the main relay and from there to the injectors.

Can you disconnect all of the injectors? That will isolate the injector harness connectors from the continuity through the injector coils. Then, with the key at ON, and SBF-2 out, check for voltage at the SBF-2 terminal that had 4 V. I suspect it will be gone. If so then the 4 (or 3) Volts is from the ECM, and is probably normal.

With the injector connector off, the SBF out, and the key at ON, you could check for continuity between the pins that had 4 V at the fuse and 3 V at the injector connector. There should be low resistance. The resistance between that line can also be checked for a short, or unusually low resistance to ground.

Keep in mind that the 12 V from SBF-2 has to go through the Main Relay to get to the injectors. If the main relay isn't being activated, that won't happen. The main relay is activated by the ECM. There's a number of fuses that power the ECM and if one is blown, it's possible the relay won't work. Have you checked the fuses by checking their continuity with a meter? In particular, fuse #15 in the cabin fuse panel might be related to the main relay energizing circuit. But there might be others.

 

Awesome! I'll check it out tomorrow!

 

Watch this:

https://www.youtube.com/watch?v=c6q4PaqCJHY

 

There should be 12V on both sides of the slow blow fuse. If not then the fuse is blown.

 

SBF-2 also powers the fuel pump. If the fuel pump runs (it should go for two seconds when the key is turned just to ON, as well as run during START), then SBF-2 is probably okay. But of course, there's no harm in checking it.

Many large Amperage SBFs are encased in a plastic cover that doesn't provide access for a Voltmeter on both sides, as do the smaller fuses. In some cases the top is clear and the fuse element is somewhat visible, but a small break would not always be seen. Best way to check is to pull the SBF and check it for continuity with a meter.

 

Thanx plain OM, that's exactly what I did. I checked the fuse for continuity which was good then checked the prongs while it was out. One side had the 12v and the other side had 4v, which I can't believe is correct. The injector harnesses read the same way, so I think I'm getting feedback somewhere.
From what I've been able to find, the injectors should have a constant 12v on one wire and the other side is a ground that takes ground pulses from the ECM. But I'm getting +4v even on that side.
If I leave the key off awhile and return I get 0v at the injectors, but when I turn the key on I get the screwy readings and they stay that way for a little while.

I've just taken the intake manifold off so I can really inspect the wiring and go from there. Thanx for all the help!

 

... the injectors should have a constant 12v on one wire and the
other side is a ground that takes ground pulses from the ECM.
But I'm getting +4v even on that side.

When the "ground side" isn't active, it's probably in some high impedance
non-conducting state -- where the voltage reading is determined by local
radio stations and/or leakage current thru a multi-megohm "open circuit."
This is especially true if you're measuring it with a high-Z digital meter.

A cheap, old fashioned, 20 kohm per volt analog meter wouldn't tell you
that kinda lie.

When you replace the SBF, I'll bet the ECM-side voltage pops up to +12V.

Looby

One measurement is worth a thousand expert opinions.

 

Check the engine harness. Did you watch the vid as an example?

 

I think it probably was, and that's what led to the intake manifold being taken off.

Thanx plain OM, that's exactly what I did. I checked the fuse for continuity which was good then checked the prongs while it was out. One side had the 12v and the other side had 4v, which I can't believe is correct. The injector harnesses read the same way, so I think I'm getting feedback somewhere.
From what I've been able to find, the injectors should have a constant 12v on one wire and the other side is a ground that takes ground pulses from the ECM. But I'm getting +4v even on that side.
If I leave the key off awhile and return I get 0v at the injectors, but when I turn the key on I get the screwy readings and they stay that way for a little while . . . .

The fact that there's zero voltage at the ECM side of the injector connector initially, and it goes to 4 V only after the key is turned to On, doesn't suggest to me that there's a short or problem in the wiring. Turning the key to ON wouldn't change the status of a short. (In the video wires were frayed and contacting the block, so the fuse would blow as soon as power was applied.)

With the wiring harness at all four injectors disconnected, one of the two pins of each connector should have 12 V when the key is at ON. If they don't, then that has to be dealt with first. The fuse is one place it can be lost, but if the pump works, the fuse is good. Another possibility is the main relay itself could be bad, or, the ECM might not be energizing the relay; in either case, the 12 V from SBF-2 isn't getting past the relay to the injectors.

Another possibility is that a wire (or wires) from SBF-2 to the Main Relay or from the relay to the injectors is broken/cut through. Not grounded, however, as that would blow the fuse.

I've attached a pdf with selected parts of the engine wiring diagram for a '99 2.5. On the first page, we follow from MB-3 at the top (which is SBF-2) down to connection 5 of the Main Relay. When the relay is closed, the power continues to connection 3 of the relay, and from there to the circled "C" on the right side.

The circled "C" is found on the next page; it connects to the small square at the right with the "2" inside.

Finally, on the third page, the square with the "2" connects to pin #2 of each of the four injector connectors.

Also, note that Pin 1 of each of the injector connectors goes to separate terminals at the ECM. With the connectors removed from their respective injectors, with the key at ON, pin 1 of each should have little or no voltage, but you might find that this takes the form of 3 -4 V at each. If this is the case it's not a problem. It's characteristic of the electronic switching circuits in the ECM that allow the 4 lines to charge up in the absence of the 12 V from the main relay.

This could confirmed if another similar Subaru were available, SBF-2 is removed, and the voltage at the injector connectors measured. If 3-4 Volts is found there as well, it means it's coming from the ECM and is normal.

I had a look at the 2002 wiring diagram and the basic routing of the 12 V (from the SBF -- in this case SBF-5 -- through the main relay to pin 2 of each injector connector) is the same. So comparison with a later model is also a possibility.

EDIT:

I have the 12v to the supply side of the injectors.

So there is 12 V at pin 2 of each injector connector?

 

Yup, thanx Cardoc, I did watch the video. I even took the intake off to inspect all of it. I couldn't see any problems.

I have the 12v to the supply side of the injectors. But I'm getting a 4v reading on the other side which I believe is supposed to be ground thru the ECM. I'm in the process of putting the intake back on, but had to take a break from the heat.

Is it possible, that I am barking up the wrong tree? I'm reading that the crank sensor is fire, and the cam sensor is fuel. Could it be as simple as the cam sensor not sending a signal or the wrong signal to the ECM? How do I check it on a 99 OBW with just a multi-meter?

I appreciate your patience guys!

 

I do have 12V at the injectors, the fuel pump runs, etc. It does not "pulse" when I turn the engine over and the 4V at the other pin threw me.

I'm beginning to wonder if it's just the cam sensor not throwing the signal to the ECM. I've just recently read that the crank sensor is for spark and the cam sensor is for fuel. I thought they were both for spark so I assumed they were all right since it runs with starting fluid.

 

Have to defer to cardoc, or another more knowledgeable person to confirm the distinction between the crank and cam sensor in regard to the injector pulses.

I guess I was misreading the earlier symptoms, believing all along that there was no 12 V getting to the injectors. My apology if that misdirected the troubleshooting.

 

Well boys, we fixed it! But don't ask me how. LOL

I took the intake off, inspected all the wires, put it back together and it runs like a new one. I'm suspecting I had a bad connection at one of the pins, but I had checked them all.

Thanks everyone for your help.

 

You have a chaff somewhere and you when you moved the intake you separated the wires causing the short. Or, the Cam sensor could have been loose. Did you go over the whole harness and check for signs of rubbing and cuts?

The Cam sensor relays valve position to the ECM for fuel injector pulse start up. The crank sensor is for TDC position for Coil energizing and firing.

 

. . .
The Cam sensor relays valve position to the ECM for fuel injector pulse start up. The crank sensor is for TDC position for Coil energizing and firing.

Thanks for that clarification. I was hoping you'd have it down pat, which you did.

And, after all, as there wasn't a problem with the 12 V getting to the injectors, then the fact that the injectors didn't pulse does bring it back to the cam signal/ECM. A short, or open, in the connections to/from the sensor is a good possibility.

 

Cardoc, I checked all the harnesses carefully and even pjlled a lot of wrapping off. I couldn't see anything causing concern. I even checked all the plugs prior to that. I'm thinking maybe assembly anx disassembly fixed a weak connection.
Thanx again for the help.

 

Subaru Outback

I have a 2002 Subaru Outback also that is not pulsing a the injector it has power on one side of the injector but will not pulse on the other. I have had the cam sharft sensor checked it is 2.3 and the crank sharft sensor 2.7it has got good spark at the spark plugs . Can any one help

 

Scroll up and read through this thread. You should see +12v one one pin at injectors all the time when ignition is on. The ECU will drop the other pin to ground when triggered by the cam sensor.

 

Scroll up and read through this thread. You should see +12v one one pin at injectors all the time when ignition is on. The ECU will drop the other pin to ground when triggered by the cam sensor.[/QUOT


Thanks for the reply Ihave read them and I have even replaced the ECU so after trying all that and still no pulsing would that mean that the cam sharft sensor although it has a resistance of around 2.3 could be faulty