Serious fuel injection problem.

[estrada42]

I've been trying to fix a fuel problem on my 89 525i 5-speed for a few weeks now, and searching just isn't fixing my problem.

I went to show the car for sale and the car started and idled fine. After the car warmed up, there sounded like there was a misfire. After giving it some gas three cylinder stopped firing all-together.

I limped the car (about .3 miles of flat surfaces) and pulled the engine code via the pedal stomp. Got code "1251 Fuel Injector 1 (or group 1)". I took my results to a mechanic friend of mine and he suggested resistance checking all the injectors and making sure there in spec. Also to try dis-connecting an injector at a time and see if the other five fired up.

All the injectors measured at either 15.8 or 15.9 ohm. If I disonnect any of the injectors, the car won't start at all. Right now the car starts but only runs on three cylinders.

My next thought is to test what ever it is that triggers the injector grounp to fire. Also to check and see if the injectors are getting a signal in the first place.

So my question is, whats the next step? Whats the next test I can try to get this car back on the road? Any thought? TIA.

[Bill R.]

starter and in front of it. The 2 groups of 3 injectors each fasten at this connector. If there's a problem with this connection you can lose one group of 3 like you did. Also on your car the sensor for the injectors is on one plug wire but even if it was bad the injectors would still trigger they just wouldn't trigger semi sequentially. So its not a sensor problem. Its most likely at that connector by the starter, if not check the harness from that connector up to the bad injectors for continuity, If there is no problem in the harness then its most likely the DME itself. I personally would suspect the connector though.




I've been trying to fix a fuel problem on my 89 525i 5-speed for a few weeks now, and searching just isn't fixing my problem.

I went to show the car for sale and the car started and idled fine. After the car warmed up, there sounded like there was a misfire. After giving it some gas three cylinder stopped firing all-together.

I limped the car (about .3 miles of flat surfaces) and pulled the engine code via the pedal stomp. Got code "1251 Fuel Injector 1 (or group 1)". I took my results to a mechanic friend of mine and he suggested resistance checking all the injectors and making sure there in spec. Also to try dis-connecting an injector at a time and see if the other five fired up.

All the injectors measured at either 15.8 or 15.9 ohm. If I disonnect any of the injectors, the car won't start at all. Right now the car starts but only runs on three cylinders.

My next thought is to test what ever it is that triggers the injector grounp to fire. Also to check and see if the injectors are getting a signal in the first place.

So my question is, whats the next step? Whats the next test I can try to get this car back on the road? Any thought? TIA.

[estrada42]

starter and in front of it. The 2 groups of 3 injectors each fasten at this connector. If there's a problem with this connection you can lose one group of 3 like you did. Also on your car the sensor for the injectors is on one plug wire but even if it was bad the injectors would still trigger they just wouldn't trigger semi sequentially. So its not a sensor problem. Its most likely at that connector by the starter, if not check the harness from that connector up to the bad injectors for continuity, If there is no problem in the harness then its most likely the DME itself. I personally would suspect the connector though.

I can't really find a 7-pin connector. There's a black block-off plate right infront of the starter, is it behind that?

[estrada42]

Is this it?
http://img.photobucket.com/albums/v72/estrada42/Car%20for%20sale/DSCF0645.jpg

[Bill R.]

.
I can't really find a 7-pin connector. There's a black block-off plate right infront of the starter, is it behind that?

[estrada42]

The connector doesn't come loose. It seems to have a screw ring around the connector that doesn't come loose or come off. Or am I being too much of a sissy?

[Blitzkrieg Bob]

The canon plug side is facing down, so it is easier to unscrew by reaching it from underneath.

It's a little tight, but it comes off once the plug is unscrewed.

[estrada42]

Okay, did some testing this afternoon. Here's what I've found.

I decided to check for continuity between the DME connector and all 6 injectors. No problem there.

I also checked to make sure I had the correct voltage at the DME connector with the key on, engine off. Everything check good here as well.

At this point I'm fairly confident it's the DME itself. Untill I decide to manually fire the injectors.

I ran a jumper whire from pin 17 to battery ground. I can hear half the fuel injectors spray. Pin 17 is group 1 (injectors 2, 4, and 6).

I do the same with pin 16 ( injectors 1, 3, and 5) and find that nothing happens. Just a light single click, then nothing.

Now I'm really confused. Any thoughts?

[Ross]

Are you sure the injectors are not working in the odd/even groups? Maybe some aren't getting the power to open, maybe a break in the 12V side of the circuit.

[estrada42]

With the key on/engine off, I've got battery voltage at pins 16 and 17 of the DME connector. If there was a break in the circuit, I wouldn't have power there right? Since it's the last stop on the circuit before ground, if there was a break in an injector harness, then there shouldn't be power, right?

[estrada42]

I went back and checked, I have correct volatge at the actual injectors.

I think the big question I have is why can't I manaully trigger the injectors by grounding them out.

[stu1]

If I'm reading you right you say you have 12v across the injectors and they don't fire? I find it hard to believe that all three injectors have gone unserviceable.

Are you sure you have 12v across the injector? Possibly disconnect the ECU then run a wire from the battery plus terminal and another from a known good ground. If the injector still doesn't operate check the resistance of the injector coil - if it's in spec then the injector is physically jammed.

Stu

[stu1]

Just been looking at the wiring diagram. The ECU pulls pins 16 and 17 down to ground to fire the injectors - on your ECU they are wired in two groups of 1,3,5 and 2,4,6.

So a simple check now is to get a voltmeter first on injector 1, and crank the engine on the starter, then on injector 2. They should be pulsing as the engine cranks.

I suspect one of them wont be so then you should do the same test at the ECU end on pins 16 and 17. If both of these are pulsing when cranked on the starter then you have a wiring break. If one isn't then you have a broken ECU.

Hope this helps,
Stu.

[estrada42]

Whats the injector coil spec? I'm not at work today, so I don't have access to all my usual information sources.

[Bellicose Right Winger]

Why?....insufficient current. You need to find/inspect/clean the connector Bill R. took the time and effort to post a pic of. It supplies the power as well as the ground for the injectors. Corrosion on pin 6 explains all your symptoms. It creates high resistance in the ground circuit for injectors 1,3 & 5. High resistance prevents the injectors from drawing enough current to open. Your voltage measurements are normal because the DMM, by design, draws very little current (like microamps) from the circuit. A properly working injector draws several amps. Follow the injector harness and you'll find the plug.

Paul Shovestul


I went back and checked, I have correct volatge at the actual injectors.

I think the big question I have is why can't I manaully trigger the injectors by grounding them out.

[estrada42]

I can find the plug, but I've torn my hands up so much trying to get the thing off, I can barely type. If it is that plug I'm screwed, because it just won't come off. The collar won't turn past a certain point in either direction.

[estrada42]

Is there a special tool needed for this plug? I've broken my right index finger in an un-related incedent and am taking some time to heal so I figured I could get a better idea of how to tackle this.

Any thoughts?