Secondary air pump code troubleshooting - valve, pump or both failing?

[bond007]

Trying to troubleshoot a persistent P1423 code...

Things checked:
* SAP operates upon startup and "reasonable" airflow is felt at the feed tube for the exhaust valve
* Exhaust valve seems to flow air only in one direction (can blow but not suck through the air pump side)

Observations/potential causes for the code:
1) Not all rivets are in place in the SAP. Does the SAP have reduced airflow if not all rivets are in place? If so, I guess I will be removing it, drilling the remaining rivets, inspect it while I am at it and replacing with hardware.

2) I put a vacuum gauge inline to vacuum line that is fed by the solenoid and found that some engine vacuum is present when the system operates but it is reduced (5" Hg) from the normal engine vacuum found at the manifold (20" Hg).

Can anyone tell me if this is normal or if you should see full engine vacuum at that port with the valve hooked up? I don't see why you would not from my previous encounters with electric-pneumatic systems (reference, "rat's nest" of 3rd generation RX-7). My next test will be to look at the vacuum without the valve connected.

My guess from this diagnostic info is that there is a leak in the vacuum line somewhere from the fitting on the intake manifold up to the air valve. #3 seems to point to the valve itself.

3) I connected a mityVac to the valve and it seemed to have trouble maintaining vacuum to keep it open. I had to continue to pump the mityVac to open the valve to flow air through the air port and was blowing air through the port with my mouth to verify airflow. Prior experience with these systems would point to a diaphragm failure in the valve preventing vacuum from being maintained.

Any thoughts/comments would be appreciated.

[cooljess76]

It's common for the rivets to break and fall out. This allows the pump body to separate and air to leak. When I first got my car, I noticed that the SAP was significantly louder than to one on my previous ti. Upon further inspection, I felt a high volume of air escaping when the SAP was running. I also had a SAP code stored in the ECU. I removed the pump, and found that 3 of the 6 rivets were no longer in place. I drilled out the remaining 3 rivets, took the pump apart, cleaned it and reassembled it using bolts/nuts instead of rivets. I then reinstalled the pump, cleared the code and it functioned perfectly, no more leaks, no more codes.

[CirrusSR22]

Interesting. I have the P1423 code on my new 97' 318ti. I removed the valve today and I think mine is stuck open. It blows back a little exhaust air with the secondary pipe and vacuum hose removed. Is it correct that the valve should close with no vacuum?

[CirrusSR22]

I did just find an offical BMW "fault analysis guide" on secondary air systems.

VS-24/Seyfried Baugruppe/Group: 11
11 05 02 (888)
weltweit Datum/Date:
07/2002
Update: 08/2002
Failure of secondary air system (fault analysis guide)
E34, E36, E38, E39, E46, E52, E53, E31 / M60/1, M62 LEV, M73, M73LEV, S50, S52,
S54, S62, M54, M52TU, M52, M44, M43TU
Complaint: - Failure of secondary air system
- Entry in DME fault code memory "Throughput of secondary air system too low"
- "Check engine" lamp illuminated on US vehicles
Cause: Past experience has shown that the failure of the secondary air system is not attributed to a
component fault in the secondary air pump but rather to the secondary air check valve not
closing/opening or the actuating relay sticking.
- Secondary air check valve does not close:
The secondary air valve is located between the secondary air injection channel (either
integrated in the cylinder head or on the exhaust manifolds) and the secondary air
pump.
The electric valve switches through the vacuum from the intake system for the purpose
of opening the secondary air check valve.
Due to soiling, the electric valve can no longer close mechanically. Consequently, the
secondary air check valve is also no longer closed. Hot exhaust gas constantly flows
through the secondary air check valve thus damaging it and possibly also the
secondary air pump.
- Secondary air check valve does not open:
The secondary air check valve will not open in the event of the diaphragm leaking or
sticking. Consequently secondary air injection does not take place although pressure is
applied by the secondary air pump.
- Actuating relay stuck (sticking of relay make contacts):
After starting the engine, the actuation time of the secondary air pump is from 2.5 to
105 seconds depending on the engine temperature and engine speed.
The relay make contacts sticking or sporadically sticking result in continuous power
supply or impermissibly long power supply to the secondary air pump.
The secondary air pump is not designed for permanent power supply and is operated
up to its destruction.
Affected
vehicles:
E31 / M73
E34 / M60 B30
E36 (incl. Z3) / M43TU, M44, M52, M52TU, M54, S50, S52, S54
E38 / M52TU, M60 B30, M62LEV, M73, M73LEV
E39 / M52, M52TU, M54, M62LEV, S62
E46 / M43TU, M52TU, M54, S54
E52 / S62
E53 / M54, M62LEV
Production period: from introduction of the secondary air system
Procedure: Proceed as follows in the case of customer complaint:
- Actuation of secondary air pump via the DIS tester:
SI Failure of secondary air system (fault analysis guide) E34 E36 E38 E39 E46 E52 E BMW AG - TIS 03.11.2005 13:49
Issue status (02/2004) Valid only until next CD is issued Copyright Page - 1 -
- Secondary air pump is not operative:
Check whether voltage is applied at the secondary air pump.
If not:
Check electrical lines and plug connections of the secondary air system and replace the
actuating relay if necessary.
If so:
Replace secondary air pump and actuating relay.
Check whether the secondary air check valve is closed on conclusion of secondary air
injection.
For this purpose:
Visually check the secondary air check valve for dirt/soiling at the pressure hose
connection to the secondary air pump:
No soiling:
No further action necessary.
Soiling (black particles/combustion residue) found:
Replace secondary air check valve and electric valve (= solenoid valve that switches
the vacuum from the intake system through to the secondary air check valve).
- Secondary air pump operative:
Check the vacuum hoses from the intake system to the secondary air check valve as
well as the pressure hoses and pressure lines from the secondary air pump to the
engine for leaks and correct installation:
If necessary, replace or correctly install leaking lines, leaking or bent hoses.
No fault found in lines or hoses:
In this case, the secondary air valve is stuck or its diaphragm leaking and therefore
does not open.
Replace secondary air check valve.
SI Failure of secondary air system (fault analysis guide) E34 E36 E38 E39 E46 E52 E BMW AG - TIS 03.11.2005 13:49
Issue status (02/2004) Valid only until next CD is issued Copyright Page - 2 -

[CirrusSR22]

Ok, I did some investigating on my system. I checked the electric valve (direct connection with 12v battery) and it seems to work well. I think my secondary valve is shot which is leaking air back to the pump. This is also confirmed as the supply hose to the SAP (from the air filter box) is just mush, indicating exhaust back flow. Also, the air filter I took out of the car when I got it has a big black spot right where the SAP tap is, again indicating exhaust back flow all the way to the filter.

[bond007]

Update after this evening's quick wrench session:
* Two rivets were visibly missing from the SAP
* The remaining four had come loose but were not visible from above once removed

I drilled out the holes and replaced with #10-32 x 1.5" (with lock washers). The car did not cycle the SAP when I started it up to check that I put everything back together correctly with respect to the intake plumbing.

In the process of removing the SAP for repair, I noticed the hose that goes from the fitting on the oval TB elbow is cracking. Yet another item to order/repair. At least BMWs are maintenance friendly.

I am pretty sure I pulled this out before to check them and did not find the rivets loose. Then again that was probably several months ago and sometime during two years of master's degree work, which is enough to turn anyone's brain into mush (I find I have forgotten a ton of car "stuff").

I am going to clear codes and see if that cures it or if there is still a valve / electro-pneumatic control system issue.

[cooljess76]

Originally Posted by bond007

Update after this evening's quick wrench session:
* Two rivets were visibly missing from the SAP
* The remaining four had come loose but were not visible from above once removed

I drilled out the holes and replaced with #10-32 x 1.5" (with lock washers). The car did not cycle the SAP when I started it up to check that I put everything back together correctly with respect to the intake plumbing.

In the process of removing the SAP for repair, I noticed the hose that goes from the fitting on the oval TB elbow is cracking. Yet another item to order/repair. At least BMWs are maintenance friendly.

I am pretty sure I pulled this out before to check them and did not find the rivets loose. Then again that was probably several months ago and sometime during two years of master's degree work, which is enough to turn anyone's brain into mush (I find I have forgotten a ton of car "stuff").

I am going to clear codes and see if that cures it or if there is still a valve / electro-pneumatic control system issue.

The SAP doesn't come on every time you start the car. It's only supposed to run for about 30 seconds when you first start the car on a cold engine. The engine pretty much needs to sit overnight without running for the SAP to kick on.

[fugi318]

does any of you can provide any pics fronm the secondary air valve integrated in the cylinder head? thanks