S52 OBD1 no start...been working for 10k miles until now?!

[gkurey]

Hey guys...much appreciation for those who are taking the time to read and possibly help.

I have an s52 converted OBD1 in my 89 325is. I has been working awesome for the last year with no motor-related issues until yesterday.

I went to go hop in my car to head to work and it just wouldn't start. Battery voltage is great, starter engages and all, but nothing happens. I have done a lot of troubleshooting since yesterday and am still dead in the water. Below, I will detail my setup and the steps I have taken:

S52/ODB1
TRM chip in 413 Red Label DME
e36 manual harness converted by a r3v member
(that's all I care to list, I can add more, not sure if anything else is relevant).

I originally suspected a fuel pump issue because about a week ago, my car died right after start up and I successfully restarted it about 5 minutes later...no hiccups since then til now. Now it won't start at all...

I suspected the fuel pump but I was able to jumper the fuel relay and got the pump to run. To be sure, I disconnected the fuel supply line and when trying to crank, filled a quarter of an empty water bottle. I also removed and inspected the pump...looks OK. Also, I can smell gas every time I start so I believe fuel is making it to the combustion chamber.

I suspected spark, so I replaced my plugs. Nothing happened yet again. I checked for spark by grabbing an old plug, removing coil #1, placing it on the plug and grounding the plug to the shock tower bolts and attempted starting. No spark there.

I then read on here about possible difficulties with the DME and/or crank position sensor. I overnighted a crank position sensor and still nothing...it had the same resistance as the one I removed, ~570. As for the DME, I believe it is good, as I have a CEL with the key in the on position. If I remove the DME, the CEL isn't present, so I know in some fashion, the DME is responsive. ICV is also humming.

I also checked the main relay and the fuel relay for functionality. Both click and have good functionality when tested.

I feel like I'm running out of options here. I don't want to purchase another DME as I am not suspicious of mine yet....but maybe. I doubt it is the fuel pump...I may try to check for spark again with a fresh plug to see if I can see a spark, but as of now, no spark from what I have checked. Relays are good...wiring was good, not sure why that would have changed....

Speaking of wiring, I also have looked over my grounds. I have a motor/chassis ground (looks good), a harness to chassis (near the diagnostic port, looks good), and another from the harness to the distro block (also looks good). I took them all off and reseated them to be sure.

I am at a loss...if anyone has anything I can check, I'd be very grateful!

Thanks guys,
Gavin

[Adrian_Visser]

Ok so you have no spark but you think you have fuel, the DME is getting power as indicated by the CEL coming on with the key in the on pos. so the main relay is working (icv hum also confirms)

You should really verify at this time that you are in fact getting power and a pulsating ground at the injectors, back probing the connector with a dmm will accomplish this.

Getting fuel?

No? Verify the crank signal at the DME connector (x6000)

Yes?

The ignition coils get power from the big green wire on your ignition switch which runs through the c101 (pin 1 IIRC)

With the key in the on/run pos. the ignition coils should have 12v.

The coils are grounded by the DME as you have said you verified ground there. For posterity's sake check again. I cant remember the x6000 pin number on the DME but the ETM will tell you that much.

Check back with your findings.

[gkurey]

Adrian, thanks for the response...I will research what you posted.

In the mean time, I disconnected the battery to check the fusable link, just in case. It was fine which I expected to see. When I hooked the battery back up, and tried to start again just for the hell of it. Still no start, but the the CEL flashes now while cranking...slowly at first then at a faster rate. Stays on steady when keyed to on. I can't get the DME into the stomp test for the life of me. I've gotten it to do it before...can't seem to get it now and I'm pretty sure I'm doing it right.

On to check ^^^^.

Thanks for the help!

[Adrian_Visser]

I should clarify that you must test the injectors and coils while cranking obviously

[gkurey]

OK, just got back in from doing half your tests...I'll finish up the others shortly.

I also verified once more in a dark garage that I have no spark with a coil and spark plug while cranking...no sparks there.

As for what you had me check...I back-probed injector #2 while attempting to start and got a pulsating voltage while cranking, so I assume this is good to go.

Checked pin 21 on the x20 while cranking, started with 11.5v on key-up and while cranking was around 9-10v. I'd say I've got good ignition power too.

I need to check the DME ground on the pin you reference above still...will report back.

[gkurey]

Checked pin 55 for good continuity, which according to the ETM is the ground in the coil/ignition circuit. I also checked the continuity on other labeled grounds (pins 28, 34, and 6) and they all came up good too. I am perplexed!

I don't have any EWS items in my setup and my chip doesn't support it, but is there any way something EWS related could be interrupting my start all of a sudden?

[gkurey]

OK, so I did a little more checking. I have power (~11.2v) on pins 50, 51, 52, and 23, 24, 25 while key is on and also while cranking...this should be power to the coils...also pin 56 which should get power from the key, has power (as long as I am reading the diagram right).

I checked power at each coil, the left most pole of each connector gets power as well...this tells me I should be getting a spark and all the systems are working properly, right? I don't get it though...how could all of my coils fail to produce a spark at once...I can see one of them going bad but all 6 simultaneously....that's a tough sell. Any ideas gents?

[gkurey]

I thought I had this nailed down when I found a resistor in pretty bad shape on the common ground for all the coil grounds...it looked smoldered and I couldn't get continuity across it...so I replaced it with a few resistors from radioshack that were equivalent. Still no start...and once I cut the old one out, it ended up reading the appropriate resistance as well...so I guess it was good. Back to the drawing board.

[gkurey]

Now I decided to look into the harness for a random short or something as it seems like the rest is working like it should. At first inspection some of my harness seems a little hacked, but I know it did work before...so I'm hopeful I'll find a poor connection somewhere. As I began looking, I ended up losing my CEL @ key up, and no main relay clicking. Jumpered the relay again, and got the CEL back. The CEL flashes while cranking at various speeds...not sure what to make of that. I guess my main relay is also now failed....the struggle continues.

[Adrian_Visser]

Might have fried some wires in the harness somewhere. Maybe try a new harness or dissect the shit out this one to see.

[gkurey]

Yeah I think I am arriving at the same conclusion. I bought the harness and an adapter from a guy on here about 2 years ago and I'm now hearing maybe they aren't the best quality...that might be the best explanation of what I'm experiencing. I pulled apart the adapter just to check and found several wire ends just hanging with no tape or anything. I pulled back some covers on the main harness and found more or the same. Ugh. I may just get a new harness and do the wiring myself...like I should have from the beginning. I can always go through what I have myself but it can be hard to find the potential small flaw causing big headaches. Not good...

FWIW, does anyone know how the ignition coils work? I get 12v to one pole with the key on and it falls to 9-10 while cranking, the other two poles I think are grounds? How does this translate to operating the coil? Purely dme signal?

[gkurey]

So I have somehow lost my CEL, I have checked power at key on position to pin 26 and 56, I get 12.1v. I have verified my relay working, and just to be sure, got a new one from the stealership. The CEL is out and no relay clicks or ICV hum at key-on. When I pull the relay and jump 30 and both 87's, I get ICV hum....when I go and set the key on, I get a CEL. Any ideas on that? A CEL and icv hum has got to mean my DME is communicating on some level right? Why won't it do this with a good relay in place?

[gkurey]

After looking at the ETM for awhile, and troubleshooting a little further...I believe I have a bad DME...new one will be here in a few days, and we will see if my situation improves.

[Slovik]

I would suspect the cam position sensor more than a crank position sensor. I have had lot of BMWs over the years and probably close to a million miles combined and have never had a crank position sensor fail, but have had at least 6 cam position sensors fail. I even keep a spare in each car just in case. You are going to need one sooner or later worth changing it out even one off of a junk car for a couple of bucks will give you an answer. Hope you get it going it's hard to live without driving a swapped e30 once you have a taste for it.

[Adrian_Visser]

Pretty sure the cam sensor won't cause a no start. And crank sensors do fail; I had one go in a very strange way last year it is a fairly common problem.

That is a moot point here though because the OP is getting fuel but no spark which means his crank sensor is functioning not to mention he measured the resistance and found it in spec. The cam sensor is used by the DME to time the sequential fuel injection and nothing else.