Hello all, could someone explain the wiring to the compressor. I see + and - to the compressor ,then there are two smaller gauge wires going to what looks like the output side of the pump, what purpose are they for? thanks

 

Hi,

Pump has several connections.

Heavy duty cable is fused and relayed power supply. Connect direct +/-ve to this and the pump should run.
Small dia cable is pump pressure information to ECU.

Simply put, the power is turned On/Off in the heavy duty cables by demand generated from the wheel height sensors subject to under / over pressure as measured at the valve block and compressor output as evaluated by the ECU.

Hope that helps.

I guess the real question is what problem are you experiencing.,

Stuart

 

Thank you for the reply Stuart. Whats the "real problem I am experiencing" now that"s a heck of a question. Fortunately it"s working out ok so far. I am working on a family members 2000/s500/v8. I am tackling a myriad of problems. #1 Po410/large Evap leak(the fuel cap was defective,replaced,repaired) #2 po455 secondary air pump code( smog motor burn"t,replaced,repaired) #3 Brake linings worn (replaced all rotors+pads,repaired) #4 Airmatic warning lamp on, car is LOW. (compressor is toast,replaced,repaired) cleared check engine lamp with my scanner. Cleared the dash warnings by disconnnecting the Batt. twice. #5 slightly rough Idle I will change the spark plugs tommorro morning. The airmatic problem had me going nuts. After r&r the pump I could not get 12v to the pump nor at the 40 amp fuse I thought a fusible link was melted or something I looked everywhere even dis- assebling the r/s fuse panel to look inside, but nothing, finally after I disconnected the battery. The 40 amp f32 powered up. What a relief. I drove the car for 20 miles street and Hyw. No warning lamps on. The car powers up the air pump twice after coming off the HYW. I suppose this is normal adujsting its ride height from hi speed to city driving correct? Are the spark plugs easy to change on this engine? I know I am very lucky to be able to tap this forum and knowledgeable people like Stuart for help I very much appreciate it. Chris

 

Hi,
Looks like you are doing OK without our help!!

An OBDII compliant scanner will only access CAN A = Engine Trans highspeed bus.
i.e. not CAN B & C Body / Chassis bus = ABS, SRS, Airmatic etc.

Airmatic pump is controlled by a module on a lower speed bus than the engine but is still digitally controlled.

As a consequence the system monitors pump current etc and if the pump started to seize or whatever the ECU may have shut the system down.

I would have expected a "battery off" to have reset the module but the specific operation/.code in these systems is a matter of guesswork.

The system was presumably trying to prevent overheating for safety / component protection in parallel with the 40amp circuit link.

The car lowers itself at speed so will need to replenish the air pressure reservoir as it returns to street speed. This may or may not require the pump to run.

Best indicator of system integrity is whether the system can stay up over night without the vehicle being right down on the bump stops in the morning.
Ideally it should should manage a few days.

Some leakage is acceptable (even from new) and this is why a pump is fitted.
However as losses get greater the pump has to work overtime until it eventually expires.

My own pump has lasted 140k miles although a strip (in order to understand the system!) revealed that the carbon rings and valves were wearing so I purchased a spare (new OE excess stock £25!) from eBay just incase it finally expires.
Incidentally an E Class pump is almost identical to the S Class pump with the exception of some interchangeable (from displaced unit) plastic piping.

Are you picking up a misfire code? If so you will know which cylinder is likely the problem.
If not I suspect that it is not the plugs at fault. Mileage?

Have you inspected the coil packs and leads carefully for dirt, cracking etc. I would clean off with a silicon based cleaner and see if this effects a difference before lashing out on new (expensive) and possibly inferior (in some way i.e. suppression if not genuine OE) parts.

Next I would determine cranking compression to ensure you don't have a valve seating problemwhich may influence idle yet be unnoticed at higher speed.

I just don't like spending money until I am 100% confident that there is no alternative BUT this does burn time. Anyway beats watching TV.

Stuart

 

"Best indicator of system integrity is whether the system can stay up over night" I looked out on the driveway this morning and the car is still sitting up high. What a relief !! the old airmatic compressor was melted internally so was expecting a leak. About the miss, its a very slight occasional tremble at Idle. I have no engine miss-fire codes and I dont" think its enough to be pickup by the OdbII. I have 75,000 miles on it. It could a spark plug wire or a coil as you mention. What is a "silicon based cleaner" you mean solvent? degreaser(brake clean),choke cleaner or something like WD-40? Are the OEM sparkplugs "not" suppression plugs. I thought most were. To me a good name brand regular-double platinum spark plug is good . I respect your opinion , I am just not a loyalist when it come to parts and fluilds. IE must use MB engine oil,MB brake fluid etc. thanks

 

Ok so after pulling the front left spark plug boot off. I can see this will be a hell of a job. The leads are stuck on there pretty tight (OEM 10 years later). Even the spark plug is on incredibly tight. The risk of damage to the leads is great so its not something to go after lightly. Besides at this stage the leads and the plugs should be changed anyway.I will stop here and call it a day. The engine runs pretty well anyway. I don"t have the experience of working on MB. I was thinking along the lines of a typical car. Ford,Gm,Honda. Chris

 

Nothing "special" about MB. Its just like any other modern hi spec car.

Use an open ended spanner to lever the boots off ...with care. Don't pull on them.

Leads should be OK at 75k. Plugs need change at circa 70k dependent upon model and market.

Cleaner. Solvent. Special preparation. Yep WD40 would be OK but there are better preparations specifically for the purpose. i.e. Cl;ean grime and ensure water integrity without damaging the "rubber" lead.

WRT to OE vs Aftermarkert. I'm not going to get into this endless debate.

MB, as do all other manufacturers, test their cars extensively using parts that a spec laid down by MB.

Use OE and you can be sure that you will not experience any issues that the manufacturer are unaware of. Use aftermarket parts and although they may work, at least for a time, they MAY introduce unknown issues which can be extremly serious / catastrophic.

Couple of examples.
There are many types of oil including different grades, different additives. etc etc. Use regular mineral oil ilo 100% Mobil1 Synthethic and change the oil at the RECOMMENDED change points (ie as per ASSYST on the dash) = possible wrecked engine.

Use "special" 3 point whizz bang, gas mileage extending plugs and the end can drop off. = wrecked engine.
Use spurious MAF sensor and you may well end up with more problems than you started with.

IMHO the small premium (OK considerable!) but I negotiate a discount...is well worth it in terms of peace of mind and knowledge that the "new" parts will last as long as the original.

I am more outspoken on the issue of changing things MORE often than required. i.e. oil change at 5000miles Why do it? = WASTE / Bad for the planet. Bad for your pocket.
MB have spent millions determining change points etc. Take advantage of their extensive knowledge.

The car manufacturers objective is for a vehicle that doesn't require any regular maintenance during its planned lifetime. When you dismiss this as fanciful remember the days when you had to have a 1000 mile post build inspection / oil change. 5000 mile service intervals are long gone. 15k miles is now the norm which matches average yearly mileage (at least in the UK)
.
Stuart

 

Thanks for sound advice. I agree with you. Even though I am a certified ASE master mechanic for 30 years, that shade tree mechanic in me just keeps coming out. [sm=happybounce.gif]

 

Ok! So the Airmatic system to working great. Now I get the complaint that its too loud or that there is too much vibration coming from the compressor. Is there a mounting kit with new bushings or springs to quiet down vibration transfer to the body? The compressor is new genuine MB. thanks

 

Hi,
The pump is mounted on extremely light springs.
In normal use it should be almost inaudible.
I certainly don't notice it when the engine is on and what noise is present is airborne rather than structure transmitted.
Could the installation have been reassembled incorrectly?
Are you sure that the pneumatic pipes aren't pulling the compressor in a particular direction and basically "shorting out" the isolation rubber bushes and springs?
likewise the electrical connections.
Stuart