Help!! Complicated Problem - Fed up

kalsingh1

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Hi all.

My underline problem is intermittent stalling. I have a SL55 AMG KOMPRESSOR 2004.
I have been on this a long time to try and find why the car inetrmittently stalls in the first 10 mins of driving then ok for the rest of the day.

Already cleaned the throttlebody, new fuel filter, new fuel pump.

I have access to STAR, and showed a fault with the secondary air pump, I replaced the relay, and this problem was solved, but immediately STAR reported fault on Heating Circulation pump -M13 or check wiring (N10/11) 3.20 to M13 for short circuit to positive. WOULD THIS HAVE NOT BLOWN A FUSE? IMG_7933.JPG

I checked the M13 pump and it was shot, but fuse f23(10 amps) was ok. So I replaced the bosch pump, but it is still showing the same fault, I know the pump is new, so it has to be the wiring right ?

Heres the strange thing, when I had the fuse f23 on the Heating Circulation pump -M13 pulled out, the stalling on the car improved by 95%, i did this several times to make sure.

1. Can someone please guide me on how to check the short circuit STAR is reporting, where to start ? (Could this be more likely a fault in the front SAM N10/11).
2. Have a plausable explanation how the stalling at very low speeds/idling is connected to the wiring to front SAM N10/11 ?
3. Do I need to perform a Exorcism on the car by a preist ?
4. Is there a relay that controls the Heating circulation pump - M13 that could have gone bad, if so I cannot find such a relay, I tried pulling them to kill F23, but nothing killed the power to it.

I hope someone on here has some experience of a problem like this.
 

LostKiwi

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1169409d1414013805-wiring-diagram-color-code-help-pump.jpg


Above is the wiring diagram (you should have this on STAR?)
Does the pump run? Its should run with the 'rest' button on the aircon control unit pressed). Failing that basic continuity/resistance checks.
 
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kalsingh1

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Hi LostKiwi

Would you be able to tell me if the negative side of the Heat Circulation pump is permanently grounded ? and its the positive that switches on and off, and is there a relay or direct switch.
 

LostKiwi

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I believe (but cannot confirm) that the 12v is permanent and the -ve side of the pump is switched by the control electronics.

Simple test - disconnect the pump connector and see if the fault code changes. If the pump is shot that could be your short circuit reported by STAR.
 

ajlsl600

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I believe (but cannot confirm) that the 12v is permanent and the -ve side of the pump is switched by the control electronics.

Simple test - disconnect the pump connector and see if the fault code changes. If the pump is shot that could be your short circuit reported by STAR.

stand to be corrected but think op, says he replaced circulation pump.
 

Westheath

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As a side note to this problem, have you checked the ECU temp sensor is reading correctly.
 
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kalsingh1

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Thanks guys for your prompt replies.
The heat pump is new, and I tested it before replacing.

I have pulled the plug off, I was getting voltage only when car warmed up, and the heaters were switched on.
Tommorrow I will check if physically works under these conditions. It’s just when I do connect it, the intermittent stalling becomes amplified. The pump probably has nothing to do with the stalling, but there must be a clue here or a link?

I remember I tried some time a go to tap the cigarette lighter fuse to power some led lights, and again the stalling was Amplifed. There seems a link to drawing a small amount of power to make the car behave badly.

Any way small steps at a time, I will connect plug into pump Tommorrow and check and run STAR again, may be we can then look at what the link could be.

West Heath can you guide me on how to check Ecu temp sensor reading, I can do that tomorrow as well - what’s the thinking behind that?
 

LostKiwi

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Check the power connections to the SAM and the earth connections from the SAM.
If either are bad the high resistance will drop the SAM voltage and may cause unrelated circuits to fail.
I'd be looking at the earth points first.
 
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kalsingh1

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I know in the UK cars, on the pass side footwell there are some earthing points, I will check there and try and follow any other earthing points from the N10/11 SAM. Looks like I got my hands ful tomorrow if the damn weather here ever stops raining.
 
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kalsingh1

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UPDATE:shock:
Guess what I have been looking at the wrong pump!

There are two pumps side by side, a larger one (inter cooler) and smaller one - Aux Heat Pump - M13 (which I mistaken for a high pressure headlamp washer pump, because it was so small). See picture circled in red.
I had replaced the bigger pump which happens to be the inter cooler pump (What the hell it was broken anyway), that's where the confusion came from, as I was expecting a permanent live, but it was testing dead. Incidentally on my Sl55 amg, the inter cooler pump has two hoses connected, and the Auxiliary Heat pump has three hoses connected.

Anyway when the coin dropped, I checked the connector on the back of the smaller pump, and the positive side wire to connector was corroded badly, it just fell off when i touched it. I had to strip the little connector to solder a new wire.
Anyway I did not have to follow all the wiring to find a short, this saved time. All pumps now working, no more codes on STAR about short circuits on M13 pump wiring.

Although the car is stalling less now with electrical connection, there is definitely a connection between a electrical wiring fault and a amplified fault of a existing/new stalling problem, I think the electrical system on theses cars is very delicate and very easy to upset, anyway it is on my car and have proven it by pulling fuse f23 out to test.

Next step, is to find the stalling issue (much better now after wiring repaired to heat pump), while I had the car jacked up, I notice some oil on the UK drivers side manifold (Headers), I changed the rocker cover gasket 6 months ago, but will strip on weekend to investigate, could this be the issue with stalling, could it be air leaking in, where the oil is leaking out ?

Any other ideas, or possible tests I could carry out ?
 

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LostKiwi

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As I said earlier check power and earth connections to the SAM. A high resistance connection to the SAM will cause the SAM voltage to drop under load and it may be this causing your issues.
An oil leak from the rocker cover gasket won't cause stalling unless its really major (and causing a manifold vacuum leak on the breather system).
 
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kalsingh1

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Been busy over the weekend with fitting in household tasks.
I pulled out the n10/11 sam and fuse box, it was a task squeezing it out without stripping the bonnet hinges. All the connects looked clean. I cleaned what I believe to be a earth connection in the UK passenaser footwell. It was a nut holding several brown wires to the point. Just had the car washed an hour before and noticed a small amount of water gathered there. The week before I cleaned out all the drain points, so I don’t know how that has happened ?

I have not checked the other front main fuse board and Sam yet.

Noticed a small oil leak from the UK drivers side PCV cover ( I originally thought the cam cover gasket was leaking). What issues would this cause, stalling, hesitation?

I cleared all the faults using STAR, test drove and put SAM on again. The car did give the odd hesitation a couple of times when driving. STAR reported a fault in the Secodary Air Pump. On checking this, the secondary air pump was dead.

If I could not do some of the work myself, I would have bankrupt my self, this car is a money pit.

Should I replace this pump, how important is it ? Can I get it repaired ?

Where do I go from here
 
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kalsingh1

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Update
Now replaced secondary air pump. The third bolt was hell getting of, as there is limited space. Ended of taking the front fog lamp unit of to get access.

Car is now running much more smoother than before. Stalling has now become a minimalist problem. Actually not even stalling but a little miss/hesitation on the rare ocassion. But would still like to sort that out.

My conclusion is that my car does not like when components that are not working even if they are not essential. This upsets the electrcal load, and it amplified this minor problem I have of stalling.
The other thing is I found diagnostics may not point you in the right direction unless you repair what it is pointing to currently.

Incidentally the faulty secondary air pump, faulty heat pump and the intercooler pump were all fixed in the same location under the front bumper and the weather shield for that quarter was destroyed and missing. So a warning to make sure your underbody weather shields are intact.
 

alexanderfoti

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Unless I am missing something here, why are we looking at Secondary air and aux heater pumps while trying to identify a stalling problem?
 

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