Fuel pump diagnosis and full test routine.

[TxGR8White]

one's codition is really unknown - there isn't a good way to test these under load (and that is where they fail-causing the bank to shut down).

To eliminate the DME itself, swap over the plugs in the E-box and see if the problem swaps sides swaps sides, if yes, then possible DME damage (can come from faulty coil)...

...and the beat goes on.

[rocket.science]

what is the engine temp when the car runs? can you check it via the diagnostic tool?
if one of the engine temps sensors is faulty it will do things
to the fuel mixture via the o2 sensor being out of the loop.
check that, it's worth it

[nathan8]

dme swap does not change the bank

coils I have 4 of these now error does not swap sides when swapping them - and the error is most manifest at idle

[nathan8]

OK o2 sensors are within normal range (on the mans tester)
Temperature sensors both came up at -79.9 degrees, on both DME's and the man thinks that this is simply the tool not reading it correctly. He's seen fault sensors and does not think its this same kind of die, recover idle problem.

[nathan8]

OK CPS sensors are still on the list
Regarding the pulse senders and CPS, did your car throw any error codes?

[nathan8]

Well we did not find the exact problem!

He also thinks it could be the throttle bodies, so I've grabbed a pair off ebay at £170 (good deal thank heavens). I'm going to swap those in when they arrive and see. TB can not be swapped side to side as they are handed.

Occasionally DME for cyl 1-6 would throw a knock sensor error. Once he got something about a valve and assumed perhaps throttle body, but there is apparently no real check that the car can perform on the TBs.

Temp was wildly out, he thought it was his machine misreporting.
Fuel pump wiring re-checked and seems ok. FYI ground on the pumps is direct to ground and from BMW original diagram the order is relay, fuse, pump (I'd wondered about this)

One of the DME's occasionally would not appear. The system booted him out a few times. We swapped the dme harnesses over and the situation / idle did not change.

The idle timing angle was all over the place changing 320 - 40 - minus 47 280 etc all the time. The injector timings were also changing 1.2 to 4.5 up down. His thoughts is that this is getting feedback

At the end he said its a weird one, offered to drive around a bit with a more advnaced computer thing and monitor the engine as its going, however I think that the problem is worst at idle. Mentioned doing the coast down reset. Will do it again once I've got the new throttle bodies in as I've already both done it and been driving around 40 miles and to my mind it should have fixed itself.

Does anyone have knowledge of knock sensors causing a die/surge idle problem?

How about the temp sensors, can this cause a regular almost die then surge at 2 second intervals?


Thanks for all your help guys. This board in its entirety is easily 20x more knowledgeable than the best individual mechanic!

[TxGR8White]

[chromeowner]

[TxGR8White]

side to side - you only need to move the plug and the breather hose to the "correct" locations on the DK.
What Diagnostic system did your "Electrical" guy use?

The timing can be idicative of an intermittant CPS and?or impulse sender.
What year is your car? The "knock sensors" are on the M73 (1994-on), the M70 (1990-1993) won't have them.

...Your turn!

[nathan8]

[nathan8]

I dont think I can do a stomp test - this is an euro 1991 850 - which according to the below does not have the CEL

------

On the E31 Euro cars....the CEL light bulb was removed at the factory.

With this light bulb removed....you cannot do a stomp test as this bulb completes the circuit for CELs and stored codes.

http://forums.bimmerforums.com/forum/showthread.php?t=1397106

[nathan8]

Must add - its a UK right hand drive model!

[TxGR8White]

[TxGR8White]

as there is NO knock sensor on your car.

[nathan8]

You are right.
Back on my own again! Throttle bodies and CPS next. How hard is it to swap over CPS?

Putting a bulb in my dash is going to be hard and I'm not sure justifiable to do a stomp test. Might not be all that is missing after all?

N

[TxGR8White]

5 minutes to do a light bulb install. CPS sensors are more involved - you need to "move: the power steering pump out of the way to access them. Try reading the resistance across the contacts first - should be around 540 ohms. Both need to be close to one another in values. If not, best to replace them both - remember, your car is almost 20 years old! and they are most likely the originals...

[chromeowner]

Also sounds like that one fuel pump is leaking gas, if you say it's squirting out of the motor housing.

[nathan8]

Hi Yes we swaped the DME over and it does not swap which bank runs badly.

Could be the EML that is not controling the two DME's correctly?

[nathan8]

Hi TX

I have a pair of throttle bodies on order (ebay £170). Plan from here is

1/ Check resistance on impulse senders and CPS sensors is in range
2/ Compare side to side on Impulse and CP sensors
3/ Check if pulling one side or the other makes a difference to running.

4/ Install new throttle bodies (when I rebuilt mine the paths that I presume report how open the body is were very worn).

5/ Consider either new CPS outright or installing the lamp in the cluster so I can do a stomp test.

6/ Impulse senders are new as I replaced the cables approx 2 years ago. I will see if there is a way to test these while running.



I'm a man with a plan. Running out of things that can be wrong here!

Nathan

(PS Have checked for vacum leaks thoroughly with break cleaner)

[Harold]

without using the diagnostics built into the system, you are just throwing darts into the air hoping you hit the target.

Replacing the CEL bulb is really easy and that stomp test will tell you what you need to figure out your issue.