PDC

Maybe some of you scanned my "Mystery Power" post from last month. I swapped my Johnson CM30 for the 'new(er)' Bosch 010 intercooler pump and I thought (hoped? prayed?) that I had returned all of my lost ponies to the corral. Well, car drove like a C350 yesterday in 82* weather. No CELs, no 'limp home', no backfires or misfires. Just no power. Floor it in drive and no downshift, no traction control light happily blinking away, and no tire spin. Just smooth, lazy, 'what's you hurry, hotshot?' type of acceleration.

I know that the vast majority of the time, a loss of power with no CEL, backfire, or misfire is correctly diagnosed as a faulty IC pump or air in the IC circuit. I checked my schraders at idle after getting home and I have a STRONG stream of coolant shooting out of each one.

Clearly, I could have a bad ignition module or coil pack, but those things tend to induce misfires and set off CELs. BTW - I did all new plugs and had to replace 1 coil pack last year.

From hours of reading the forum, it sounds to me like the following gremlins can cause sneaky power loss loss with noticable ignition symptoms and no CEL: loss of air pressure on the boosted side of the turbos from something as simple as a loose band clamp; a faulty MAF / MAP / or airbox sensor; or a dying fuel pump that is providing less than adequate psi to the injectors.

Here is my list:

1) MAP / MAF / Airbox sensors

2) Intake plumbing - especially on the bosted side of the turbos

3) Fuel pressure / fuel pump

Can anyone think of anything else I should be sure to check?

My hope is to make a checklist based on everybody's experiences to try to identify and weed out the sneaky gremlins before diving right into the really expensive stuff (ignition module, coils, cats, etc) that might be just fine, and are alot more likely to set of a CEL in the first place. ANY thoughts and ideas welcome and appreciated.

PDC

Forgot to add to the list: Boost Pressure Sensor.

P.S. - I did check the turbo plumbing clamps and found that the clamp at the bottom of the Y feeding the intake was actually snapped at the fitting. I got a heavier-duty clamp and installed it no problem. Of course, I had to let the motor get cool to the touch to avoid giving myself 3rd degree burns while cranking around in there. So that post-install test drive was thrilling. Car felt strong as sh*t. Broke the tires loose with ease, etc. I just want to have all the potentially loose ends checked and tightened up.

WHTEVO

A way to check the said sensors would be great info as well. Although you would think that if one of them went bad, it would throw a malfunction warning of some sort. Hell, even a burnt out bulb throws a malfunction warning.

Regarding the intercooler lines, i am trying to come up with a easy way to pressure test the system for boost leaks how i do on some of my other cars. It is just a bit more difficult on the 65 IMO. Will update with what i come up with.

Aaron

alx

Have das and log boost. Wot = about 21 psi stock tapering off at around 19 at higher rpms.

Anything less than that indicates leaking intake.

carlsturm

Food for thought. My SL would occasionally misfire without throwing a CEL but would run noticeably sluggish afterwards until I shut it off / on. In my case the misfires grew more frequent over time and ultimately threw a code I had my coils replaced. I'm not saying its your coils necessarily but rather the car can get sluggish without putting a CEL to the dash.

Could your issue be fuel filter?

Good luck

alx

it makes sense- misfires retard timing (until ignition is cycled or fuel tank is refilled from below 1/3 to over 3/4) which reduces power. if severe enough and you throw a code this becomes permanent until code and engine adaptations are reset.

replacing the fuel filter is a good idea.

my bet is you are leaking boost from somewhere or the boost sensor is bad. have the car read and look at code freeze frames as well as do some boost logging while driving.

PDC

I spoke with my SA this morning - wife's ML was in for oil service. He is betting he will find loss of boost pressure or loss of fuel pressure. I will say that after discovering and replacing the broken hose clamp on the intake "Y" the car felt noticably livelier. Could it only be that simple. I will take a faulty sensor (or a snapped hose clamp) over a faulty turbo any day of the week!!!!

I do like the idea of having the tech log the car whie driving.

If I do end up replacing the fuel pump, how much damage ($$$) should I brace myself for?

THANK YOU

Welwynnick

If its a fuel supply problem, it might not simply be the pump and filter. The V12TT uses a regulated pump, and there's a pressure sensor and pump control unit that might also be to blame. Not saying its likely, but the pump isn't cheap (I was quoted 290 GBP just for the part) so I'd try to eliminate some of the other possibilities first.

With my car, I was slightly surprised to find that the lower pressure sensor appeared to be defective. I replaced that and lots of faults went away.

Nick

PDC

I will DEFINITELY have my SA check fuel pressure sensors and regulators as well as the pump and filter.

I have learned not to be overly optimistic in this world, but DAMN the car feels strong since discovering and replacing the snapped hose clamp on the intake "Y". It was the larger one that actually clamps the bottom of the "Y" to the intake itself. Maybe it was letting just enough boost pressure leak out that the sensor told the ECU to throttle everything back?

If all the sensors, intake and fuel delivery system components check out, it will be well worth 1-4 hrs of tech time to get a confirmed clean bill of health. If they run into something totally unrelated to the clamp that I replaced, then it makes me all the more glad that I had them check. I will post what we find, but right now I think we moght not find much. She seems to have come back to life!?!?

WHTEVO

I figured i would add an obvious one to your list only because i had a question about it.

Intercooler pump

I have seen some say the pump should come on when first starting the car cold, and some say it only comes on in the SL65 when the charge temps reach a certain temperature and the engine is at a certain rpm. I would like to know if for a fact, when starting the car cold, if you depress the two schrader valves on top of the intercoolers, if liquid should be spraying out of there? I installed a brand new CM30 pump not too long ago just as preventative maintenance, and on a cold start, i do not get any strong stream of fluid coming out. Only small drips. I do not know if it did it with the OEM pump either since i never tried it before replacing it. I just want to know it is working as it should.

Does anyone know which relay it is that can be jumped to keep the pump running all the time while the car is on?

Aaron

PDC

O.K. - my problem was the band clamp that attached the bottom of the "Y" fitting into the intake manifold. Although I doubt that this fitting allowed enough boost pressure to escape to 'physically' cause such a dramatic loss of power, it obviously let just enough pressure escape to cause the ECU pull everything back. It also seemed to fit just tight enough that it did not throw a code - especially during predominantly mild and reserved traffic driving: not as much boost to deal with. I am pretty sure that if I drove it like that for a greater number of miles, and drove more aggressively, it eventually would have registered a boost pressure fault eventually.

I will tell you, after finding and replacing the clamp myself, the car was literally a different animal. It has been hotter than hell here this summer, so having some loss of boost and any downward ECU compensation along with very toasty ambient temp and IATs made for one DEAD SL65. Yesterday, the high was 70* and the car is just simply dangerous. I had forgotten just how violent the acceleration really is.

WHTEVO - when I had the Johnson CM30 pump put in this car - which I now have swapped for an '010' Bosch unit - I asked about wiring for full time operation. Basically giving the intercooler pump keyed voltage in the ignition run position. Unfortunately, my SA was unable to figure out how to bypass the ECU without giving a steady code. Maybe this is something that Cory at KLEEMANN can override with ECU programming? Anyway, I was told that after the car gets to operating temp, if you accelerate above 2K rpms for 3 seconds - basically any steady pull through 1st or 2nd gear - the intercooler pump will run continuously untill the car is turned off. That seems to be a pretty easy way to flip the switch without pissing off the ECU.

aeroman

My 2007 SL65 had all those symptoms until I ran a bottle of Techron Special Formula in half a tank of gas. Then all that went away.