M42 Full Rebuild now won't start

[theTBLACK]

Updates from today.

1. Got a friends running m42 - pulled the CPS, CKS, and DME and put them on my car. Still nothing.

2. Replaced spark plugs with even newer ones, verified spark on all four and in the right firing order. Still nothing.

3. Timing is 100% correct as we established previously.

4. With the 3 relays mounted on the firewall, I replaced them with the 3 from the running car, as well as jumping the fuel pump. Still nothing.

5. Replaced AFM with working AFM. Still nothing.

AT THIS POINT - I'm assuming it has to be a crushed or broken wire somewhere, as even with starting fluid it won't even attempt to fire.

6. We have fuel pressure. All new vacuum lines. Plugs are wet. New filter. New pump.

If anyone has any other ideas, let me know.

[bmwman91]

WTF. Fuel and spark. Did you verify that the coils are connected to the right connectors on the ECU harness? That seems like the ONLY way that you could have fuel and spark without combustion. That, or somehow a ton of water got into the gas tank.

[theTBLACK]

WTF. Fuel and spark. Did you verify that the coils are connected to the right connectors on the ECU harness? That seems like the ONLY way that you could have fuel and spark without combustion. That, or somehow a ton of water got into the gas tank.

I just pinned all 4 and they are correct. Haha.

[theTBLACK]

Also - I just pinned 56 to 1 on the 80 pin connector and when I turn the key the fuel pump comes on. With the DME plugged in, it doesn't.

[theTBLACK]

88 pin*=

[theTBLACK]

Newer update - took intake manifold back off - injectors are not firing.

[bmwman91]

Not quite following. So the fuel pump does NOT run when the ECU is connected, but it does run when you jump something with the ECU removed?

Here's one more thing to check. Sort of obscure, but it has happened to people (including me about 10 years ago). See the attached image. You should see battery voltage (11-14V) on the circled terminal. It is a dedicated power line for the ECU and all injection electronics. There is an inline 50A fuse on the smaller of the 2 wires that comes off of the battery's positive terminal, and sometimes it gets corroded and will start breaking continuity. Probe between the circled nut and ground to see what voltage you get. If you have a friend nearby, have them go in the trunk and shake the big black wires coming off of the battery while you measure.

If that doesn't yield anything, it's time to probe other stuff. Check to make sure that you see battery voltage on relay terminal 87 of the main relay. Since you need the ECU and main relay plugged in to do this, you can unplug the ICV and probe terminal 2 in the harness plug since that is connected to the main relay's pin 87. See diagram 1360-1 in the wiring diagram PDF that I linked you to previously. When probing, turn the key to Run position and it should turn the relay on.

If that checks out and the ECU is enabling the main relay, next you can check the fuel pump relay. It's output goes to fuse 11, so see if you get a 12V blip on there when you turn the key to Run mode since I think the ECU primes the pump when you do that.

Other than this stuff, I can only think that maybe a wire got damaged somewhere. You said you have had wet plugs during earlier checks. Try replacing fuse 11 (or grab a different one to test quick if you don't have a spare). Sometimes they get a hairline failure and intermittently make contact.

[theTBLACK]

Okay. So we took the fuel rail off and put plastic bags on the injectors.

With a new relay in and ECU connected, nothing happens. Even when you crank - the injectors aren't filling the plastic bags with anything. They aren't firing.

With the ECU connected, and the fuel pump jumped and on, they still aren't firing.

I just saw your reply - I'll try that next!

[bmwman91]

Well, if the fuel pump is running and you are getting sparks, then I think that the fusible link is likely OK. Sorry I mentioned that, it seems super unlikely.

Maybe your fuel pressure regulator is plugged? How about the fuel filter...did you replace that? It is also known to clog. If you did replace it, did you put it in backwards?

http://www.realoem.com/bmw/enUS/showparts?id=AF93-USA-10-1990-E30-BMW-318is&diagId=13_0308

This diagram at least says which hse is the supply and which is the return. I forget which is which under the hood. Maybe you can CAREFULLY disconnect the hoses and stick the ends into a jar or something to verify that you are in fact getting fuel flow, and the proper line is connected to the proper place on the rail?

You can also check to see if the electrical signal to the injectors is good. Take the plastic wiring block off of the injectors. Make sure that you see 12V on one of each of the terminals when the key is in Run position. If you get a small incandescent light bulb from an electronics store, one that has 14 or more Ohm resistnace, you should be able to stick it into one of the 4 connectors and see if it lights up at all. Basically you are stuffing a light bulb into the harness in place of an injector to see if the ECU is actually driving them.

[theTBLACK]

Well, if the fuel pump is running and you are getting sparks, then I think that the fusible link is likely OK. Sorry I mentioned that, it seems super unlikely.

Maybe your fuel pressure regulator is plugged? How about the fuel filter...did you replace that? It is also known to clog. If you did replace it, did you put it in backwards?

http://www.realoem.com/bmw/enUS/showparts?id=AF93-USA-10-1990-E30-BMW-318is&diagId=13_0308

This diagram at least says which hse is the supply and which is the return. I forget which is which under the hood. Maybe you can CAREFULLY disconnect the hoses and stick the ends into a jar or something to verify that you are in fact getting fuel flow, and the proper line is connected to the proper place on the rail?

You can also check to see if the electrical signal to the injectors is good. Take the plastic wiring block off of the injectors. Make sure that you see 12V on one of each of the terminals when the key is in Run position. If you get a small incandescent light bulb from an electronics store, one that has 14 or more Ohm resistnace, you should be able to stick it into one of the 4 connectors and see if it lights up at all. Basically you are stuffing a light bulb into the harness in place of an injector to see if the ECU is actually driving them.

How would I check if the regulator is plugged? I'm sending my injectors off to be cleaned for good measure I think.

I did pull the hoses and use a jar. The silver line is the feed and black is return. I made absolutely sure that the feed was getting fed haha.

I did replace the filter - I'll double check to make sure it isn't backwards.

I also pulled the entire rail and pinned it out to make sure it's good. I'll connect it. I'll check the electrical signal to the sensors right away.

[bmwman91]

OK, so you definitely saw fuel coming up to the rail. In that case, yeah it must be something electrical related to the injectors. It seems unlikely that they would all jam at the same time. Were the rebuilds or something?

Even if the regulator was stuck open I think you would at least get enough fuel for misfires. it is seeming more and more like the injectors are not getting fired somehow. It's weird though, because you said you had wet plugs that smelled like raw gas at one point right?

[theTBLACK]

Yup. It was coming out of the feed line right at the rail. And they weren't rebuilds - which makes me think they aren't firing at all,

At some point, the plugs were wet. But I'm not sure what's happening now.

[bmwman91]

Just to check the obvious...the injector wiring harness is plugged into the big black wiring box under the manifold?

[theTBLACK]

Just to check the obvious...the injector wiring harness is plugged into the big black wiring box under the manifold?

Yes. The only thing we haven't checked is from the DME to the injector ports all the way through, and the fuseable link.

[varg]

See:

Have you cranked with the fuel rail out (injectors attached) and verified that they are firing?

The injectors get +12V from the main relay via the red/white wire coming from Pin 87, leading to the harness box under the intake manifold. Verify +12V is present here when cranking. The ECU grounds the injectors in pairs (1&3, 2&4) to fire them. If you haven't, check continuity of the wires between the injectors and the ECU (pins 3 and 32)

I'm trying to help you out. Please check that your injectors are getting 12V while cranking before going any further or spending money getting your injectors cleaned.