Author Topic: Both CPS? at the same time? (Read 16147 times)

keflaman · « **Reply #30 on:** June 25, 2012, 02:50:58 PM »

Time for another DME? You said the car seemed to run worse when you swapped a replacement in; did you happen to swap the original back in to see if it ran better? Maybe try a DME from a running car? I believe I have one that I could send your way.

If everything seems to be working correctly during bench tests, but not when installed together on the car that would seem to indicate wiring problems. Check for chaffing on the wiring bundle going to the DME?

sfinsf · « **Reply #31 on:** June 25, 2012, 04:36:12 PM »

Quote from: keflaman;113371

Time for another DME? You said the car seemed to run worse when you swapped a replacement in; did you happen to swap the original back in to see if it ran better? Maybe try a DME from a running car? I believe I have one that I could send your way.

If everything seems to be working correctly during bench tests, but not when installed together on the car that would seem to indicate wiring problems. Check for chaffing on the wiring bundle going to the DME?

I have another members DME on the way, but Thanks though!

So with the original DME, it just cranks away and doesnt really seem to be catching or doing anything. The replacement DME is much different, engine gets really close to starting but never makes it all the way, we shall see what the next DME does, should be here in a day or two.

My mechanic was completely baffled by the fact that all the individual components, sensors and elements tested good and worked independently but when they all try to come together, something is missing or not occurring.

I am reluctant to do anything significant with the harness because I'm afraid I will be adding one more thing to check.... do you have some specific things/places to check that have proven successful for you?

sfinsf · « **Reply #32 on:** June 26, 2012, 08:31:18 PM »

third DME arrived today and made no difference in the no-start condition.

bmwman91 · « **Reply #33 on:** June 28, 2012, 07:50:50 PM »

I tried to check the previous posts, but couldn't see if you mentioned this...

When you crank away, do you smell raw gas at the tail pipe, or see wet spark plugs or anything? If you have a working fuel pump in there and get the proper fuel pressure, but there is no sign of fuel getting to the cylinders, then at least that narrows it to the injection system. That could be due to a broken wire in the injector harness. It isn't too hard to check.

With the key removed form the ignition, unplug the injector harness from the black wiring box and test the resistance between pins 1-2 and 1-3. In both cases you should see something like 6-9 Ohms. If you see 14-16 Ohms, a really high value or near-zero then there is a broken wire or short in the injector harness. Also check for 14-16 Ohms between pins 2-3. If that checks out, then put the key in accessory position (the second click where the gauge cluster lights up) and look for 12V on pin 1 on the main black box.

sfinsf · « **Reply #34 on:** June 29, 2012, 06:21:51 PM »

Quote from: bmwman91;113448

I tried to check the previous posts, but couldn't see if you mentioned this...

When you crank away, do you smell raw gas at the tail pipe, or see wet spark plugs or anything? If you have a working fuel pump in there and get the proper fuel pressure, but there is no sign of fuel getting to the cylinders, then at least that narrows it to the injection system. That could be due to a broken wire in the injector harness. It isn't too hard to check.

raw gas and damp plugs with black soot after much cranking. replaced fuel rail, FPR, injectors and elec bar just yesterday with no change in status.

With the key removed form the ignition, unplug the injector harness from the black wiring box and test the resistance between pins 1-2 and 1-3. In both cases you should see something like 6-9 Ohms. If you see 14-16 Ohms, a really high value or near-zero then there is a broken wire or short in the injector harness. Also check for 14-16 Ohms between pins 2-3. If that checks out, then put the key in accessory position (the second click where the gauge cluster lights up) and look for 12V on pin 1 on the main black box.

pin test revealed 10 ohms at 1-2 and 1-3

18 between 2-3

12+ volts in pin 1 male at main box

oh how I wish that would have been it.... anything else?

bmwman91 · « **Reply #35 on:** June 30, 2012, 12:56:28 AM »

Those values sound just fine. Bummer.

1) You said you measured fuel pressure and got acceptable readings. Where and HOW did you measure this? It sounds like you popped the input hose to the fuel filter and measured on that, with it disconnected from the rest of the system?

2) You said that you see no signs of fuel being injected into the motor (no gas smell at the tailpipe)?

If 1 & 2 are true, it is possible that you have a completely dead fuel pressure regulator. I would assume that it is designed to fail open to prevent the system from blowing up. It is exceedingly rare that they fail, but that may be why nobody could diagnose it since that is probably the last thing they would check.

The other thing coming to mind right now, and this is a really really long shot, is that the CPS wires are damaged somewhere between the wiring box & ECU. You could try checking continuity between the receptacle terminals on the wiring box and the main ECU plug. The pins numbers are all listed in the scans I posted here:
http://m42club.com/forums/showthread.php?t=5098

zacrl1230 · « **Reply #36 on:** June 30, 2012, 11:05:44 AM »

Nothing constructive to say; just....I think the FPR is the only piece he hasn't replace in the fuel loop... but I'm betting it's an electrical gremlin(rubbed wire behind the dash)

sfinsf · « **Reply #37 on:** June 30, 2012, 02:19:40 PM »

Quote from: zacrl1230;113473

Nothing constructive to say; just....I think the FPR is the only piece he hasn't replace in the fuel loop... but I'm betting it's an electrical gremlin(rubbed wire behind the dash)

the FPR has been swapped out with a salvage bought one along with fuel rail and elec bar and injectors

sfinsf · « **Reply #38 on:** June 30, 2012, 02:28:32 PM »

Quote from: bmwman91;113468

Those values sound just fine. Bummer.

1) You said you measured fuel pressure and got acceptable readings. Where and HOW did you measure this? It sounds like you popped the input hose to the fuel filter and measured on that, with it disconnected from the rest of the system?

2) You said that you see no signs of fuel being injected into the motor (no gas smell at the tailpipe)?

If 1 & 2 are true, it is possible that you have a completely dead fuel pressure regulator. I would assume that it is designed to fail open to prevent the system from blowing up. It is exceedingly rare that they fail, but that may be why nobody could diagnose it since that is probably the last thing they would check.

The other thing coming to mind right now, and this is a really really long shot, is that the CPS wires are damaged somewhere between the wiring box & ECU. You could try checking continuity between the receptacle terminals on the wiring box and the main ECU plug. The pins numbers are all listed in the scans I posted here:
http://m42club.com/forums/showthread.php?t=5098

1) I actually have not measured the fuel pressure, the BMW tech said that he found acceptable pressure. I have not been able to find one easily that will measure in line.

2) There are signs of fuel. Pulled line going into fuel rail and cranked engine to confirm fuel was getting to the rail. pulled each plug after cranking and plugs were wet. smell of fuel at tailpipe which smells like gas thru CC not fresh 91 octane

3) FPR on second rail that I tried from Dbl 02 salvage. Can't imagine that both are dead but it is possible.

I will check your long shot cuz it's all I got. only I'm not sure of what I'm testing, diagram only lists speed sensor, is that the crank or cam? either way, it's pin 74, correct?

bmwman91 · « **Reply #39 on:** June 30, 2012, 06:38:31 PM »

Pins 67 & 68 are the ones connected to the CPS, in the last diagram in the post.

If you swapped fuel rails and have fuel in the cylinders, then it isn't that.

sfinsf · « **Reply #40 on:** June 30, 2012, 06:45:42 PM »

Quote from: bmwman91;113481

Pins 67 & 68 are the ones connected to the CPS, in the last diagram in the post.

If you swapped fuel rails and have fuel in the cylinders, then it isn't that.

damn, well thanks anyway, if you think of anything else let me know.

bmwman91 · « **Reply #41 on:** June 30, 2012, 08:44:21 PM »

It's no consolation, but I think that you get the award for the most mysterious no-start problem. Is there nay way that you mixed up the ignition coils / wires & the wrong ones are firing? Check to make sure that you have a good connection between the wiring box and pins 67 & 68 at the ECU too.

wazzu70 · « **Reply #42 on:** July 02, 2012, 05:26:52 PM »

Like I mentioned in PM, have you grounded the plugs to the valve cover while cranking to make sure they are sparking?

Also on mine when I had similar issues on engine reinstall I had to trace the ECU pin for each coil to the coil itself to veryify which was which. You can also do this by applying a voltage to the ECU connector pin and measuring which one has the juice on the other side to identify without ripping into the harness.

If any of the cylinders are swapped the car will not run. The ignition is sequential, not wasted spark.

sfinsf · « **Reply #43 on:** July 02, 2012, 06:28:37 PM »

Quote from: wazzu70;113537

Like I mentioned in PM, have you grounded the plugs to the valve cover while cranking to make sure they are sparking?

Also on mine when I had similar issues on engine reinstall I had to trace the ECU pin for each coil to the coil itself to veryify which was which. You can also do this by applying a voltage to the ECU connector pin and measuring which one has the juice on the other side to identify without ripping into the harness.

If any of the cylinders are swapped the car will not run. The ignition is sequential, not wasted spark.

Yup, grounded plugs to chassis, confirmed spark to each plug from each wire

will test out the individual wires, really no reason why they would have been swapped, again this is not an engine swap issue, no one has moved any significant wiring since is was running perfectly, but I will still check it to cross it off the ever growing list

sfinsf · « **Reply #44 on:** July 06, 2012, 10:10:29 PM »

so I traced and confirmed the wiring and sequence involved with the step by step start up procedure as outlined in the thread. http://m42club.com/forums/showpost.php?p=47710&postcount=4
all was good

then tested my fuel pressure, pretty much confirmed that my mechanical fuel delivery system has no faults that I can find. The only aspect that could be at fault is the actual firing of the injectors, which essentially is electrical

got another afm from another member installed, no change in no-start