dumb question: Where is the leak detection pump on a 2000 Z3M Coupe

[sevenracer]

Per the title. I can't seem to find the Leak Detection Pump on my car. Not seeing it listed on any realoem diagrams either. I thought this was mandatory for cars of this vintage.

Chasing a "evap large leak" trouble code. New cap didn't fix it. both valves seem to work and can't see any loose or damaged hoses. Trying to check the LDP now.

Thanks,
Neil

[bluptgm3]

Not #1?
http://www.realoem.com/bmw/enUS/show...diagId=13_0372




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[LannVouivre]

https://www.google.com/url?sa=t&sour...bmuK9lSrEl4aXr

Sorry for ugly URL, about to lose temper with terrible phone interface design. Search "leak" and it should take you to the connector for the pump and show a picture.

[rf900rkw]

It's that big thing in the front with six cylinders. S52 uses the old M52 emissions; purge valve, shut off valve, and engine vacuum. There is no separate leak pump.

[LannVouivre]

Oh, EVAP system leak. I zeroed in on the leak diagnosis pump and read absolutely no further, apparently. I had to look in that MS42 MS43 pdf at when and how that test is run. I'm more familiar with the Toyota version of the newer system, which runs like 5 hours after the ignition is switched off and uses. Usually it does this in the middle of the night when you're alone in the garage with the car and badly startles you.

Why is the solenoid for the 3/2 valve called a leak diagnosing pump, if all it does is send fuel from the rail back to the tank until 20 sec after startup?

[sevenracer]

Thanks for all the replies and links to the electrical guide. My car is a 2000 built in 11/99. And if I look at the correct pdf in the right section, it does look like the S52 in my car does not use an LDP.

Is there any link to a document that explains how the test is run? I am guessing that the computer closes the shut off valve and opens the purge valve for a bit to create a vacuum on the tank and then it closes the purge valve and monitors the fuel tank pressure sensor for a vacuum leak down? Do I have that right? Does anyone know under what conditions it performs this test?

And are there any other common issues I should check for that cause the large leak code to be set? I replaced the gas cap, verified that the purge and shut off valves function, and I verified that the charcoal canister isn't plugged (I can blow air through it - not sure if that is a valid test but YouTube suggested it). I have not opened up the fuel pump area on the tank yet to see if all is in order there, but I have not noticed any gas smell. Beyond that, I am thinking I need to get a smoke test to find the leak.

Thanks again

[bluptgm3]

I have seen suggestions to purge the line that runs from the front of the car to the back of the car from the breather valve.


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[rasmuw]

I kept getting an Evap leak code. The first thing done was a smoke test. My mechanic said there is no sensor he knew of that could read such a little loss. The next thing we did was to take the system apart, checking to make sure the charcoal canister was not plugged. After blowing air through everything and re-assembling, the code has not come back. All he could think is that there was a small leak somewhere that the sensor could pick up, and that tightening all the clamps got rid of the leak. I never did have to replace the gas cap, where these leaks so often occur.

[BimmerBreaker]

Sometimes, I feel it is I that is the leak detection pump for my car

[LannVouivre]

It detects EVAP leaks by activating a solenoid with a diaphragm over and over. If the speed deviates beyond allowed parameters, then it determines a leak is present. Pretty sure it's the vacuum switching valve but I'm tired and lazy and I don't love *any* of you enough right now to go check.

"The MS42 Evaporative Leakage Detection uses a Leak Diagnosis Pump (LDP) to pres-
surize the fuel tank and the evaporative emission system (approx. 25mb.). The LDP
equipped system is capable of detecting a leak as small as 0.5 mm. The LDP is replaceable
as a complete component. The vacuum supply line (required for pump operation) is in the
wiring harness from the engine compartment to the rear of the vehicle.
The LDP is a unitized component that contains the following:
• Vacuum Chamber
• Pneumatic Pressure Chamber
• DME Activated Vacuum Solenoid
• Reed Switch - providing a switched voltage feedback signal to the ECM
In the inactive state, the LDP diaphragm is at the
bottom end (of down stroke). The diaphragm
pushes a rod downward against spring pressure
to open the canister vent valve.
This open valve serves as the filtered air inlet
path for normal evaporative “breathing”.
During Leak Testing of the evaporative system,
the vent valve is sprung closed to block atmos-
pheric venting. The Evaporative Emission Valve
is also sprung closed to seal the system.

During every engine cold start the LDP solenoid
is energized by the ECM. Engine manifold vac-
uum enters the upper chamber of the LDP to lift
up the spring loaded diaphragm.
As the diaphragm is lifted it draws in ambient air
through the filter and into the lower chamber of
the LDP through the one way valve.
The solenoid is then de-energized, spring pres-
sure closes the vacuum port blocking the
engine vacuum and simultaneously opens the
vent port to the balance tube which releases the
captive vacuum in the upper chamber.
This allows the compressed spring to push the
diaphragm down, starting the “limited down
stroke”. The air that was drawn into the lower
chamber of the LDP during the upstroke is
forced out of the lower chamber and into the
fueltank/evaporative system.
This electrically controlled repetitive up/down stroke is cycled repeatedly building up a total
pressure of approximately +25mb in the evaporative system. After sufficient pressure has
built up (LDP and its cycling is calibrated to the vehicle), the leak diagnosis begins and lasts
about 100 seconds.

The upper chamber contains an integrated reed switch that produces a switched high/
low voltage signal that is monitored by the ECM. The switch is opened by the magnetic
interruption of the metal rod connected to the diaphragm when in the diaphragm is in the
top dead center position.
The repetitive up/down stroke is confirmation to the ECM that the valve is functioning. The
ECM also monitors the length of time it takes for the reed switch to open, which is
opposed by pressure under the diaphragm in the lower chamber. The LDP is still cycled,
but at a frequency that depends upon the rate of pressure loss in the lower chamber. If
the pumping frequency is below parameters, there is no leak present. If the pumping fre-
quency is above parameters, this indicates sufficient pressure can not build up in the lower
chamber and evaporative system, indicating a leak."

Hope that's not copyright infringement or anything.

[sevenracer]

I really appreciate the help, but I think that description is for a different motor. Per the elec troubleshooting guide, my s52 motor has MS41.1 controls and no LDP.

You wouldn't happen to have the evap operation info for the MS41.1 system would you?

Thanks,
Neil

[LannVouivre]

I don't have that, but from what Randy said, it just has the shut off valve and the purge valve (purge valve is the one that the above post calls a leak detection pump). It just uses the purge valve and manifold vacuum as an LDP without having the newer type that runs 5 hours after the car is turned off after a specific type of drive.

[cleanerPA]

I don't know if you searched the forum, but I posted about this a while ago. Now I can't tell you the difference in an S52 car but on my S54 car, the leak detection pump sits right next to the fuel filter underneath all of that aero underbody paneling. Easy to tell, it's a black Bosch plastic thing with an electrical connector, nothing else like that in the vicinity.

What was your issue? I had a repeated "check gas cap" light and evap error codes. Replaced the pump and no issues since. You need to clear codes, fill the tank and drive for at least 30 minutes I think to make sure that everything has cycled through- this is going from memory, but filling the tank and driving is part of the procedure needed to cycle the system.

[LannVouivre]

The S54 uses an actual LDP. S52 doesn't have a real LDP so much as it uses clever observation of how fast the purge valve solenoid can actuate repeatedly against the pressure it puts into the EVAP system. If it pumps too fast, then there's a leak allowing pressure to escape.

This is assuming that the MS41.1 relies on the same method as the MS42 and not something different, and also that the text in the MS42 document is calling the purge solenoid the leak detection pump. I don't know for sure, because I think BMW uses 3 different terms for the dang thing.

[sevenracer]

Not trying to be argumentative at all, and I really do appreciate the discussion, but I don't think MS41.1 can use the same method - the purge valve is just a valve, actuating it will not pump anything or build any pressure.

I got a bentley manual today, but no real detail given (in fact doesn't really go into the different variations of this system on the different motors).

May have to give up on understanding the theory of operation, and just try to find the leak with a smoke machine.

[LannVouivre]

Well, the MS42 version is more complicated than the MS41. Apparently the MS41 uses the purge valve to out a vacuum on the EVAP system when the engine is running under specific conditions, seals it, and watches for vacuum loss via pressure sensor.