Atown206

My 97 C36 AMG with 158k on it is having an intermittent starting issue, the place I bought it from is now kinda scratching their heads about it.
Intermittently when starting it you hear the starter, you feel it roll over once and then nothing. It acts like you just didn't turn and hold the key long enough. There's a new battery in it so it's not that. Has 1/2 tank of premium gas.
Sometimes it'll start up the first time, sometimes will take up to ten tries start. But the kicker is When it starts it runs just fine!
Happens more often once it's warmed up and has been driven a few miles.

Any ideas what the hecks going on?!

I heard it could be the cps? It doesn't stall or anything while driving though.

cm60k

Many things could cause starting problems..!,

prefer if you can diagnose the car, codes will helps to narrow the issue..!

ZAYED,,

Atown206

No codes in system

cm60k

Do you using STAR/SDS or aftermarket OBDII scanner..?

ZAYED,,

Atown206

I'm not sure what the shop used. Probably an aftermarket OBDII

cm60k

Never Mind..,

Fuel pump/fuel pump relay/fuel filter/bad or dirty injectors/bad CPS/MAF hot film went bad/dirty throttle body/bad battery/bad starter solenoid/alternator regulator went bad, all these could cause bad starting..!

do you replace any of these recently..?

Atown206

I haven't! I just bought the car maybe a month ago. I checked the cps, the things full of oil and so is the wiring connectors. I have a feeling it's the cps now.

But It probably wouldn't hurt to replace the fuel filter as well! Lol

How do you suggest I safely clean the fuel injectors on these?

cm60k

The car cranking but not starting isn't..?, is your battery good..??,

when you switch the key in position 2, do you hear fuel pump sending fuel ...???,,

are all interior/exterior lights working with the car OFF..????

ZAYED,,

Atown206

Yes cranking but acts like I didn't hold the key long enough to start. Only Sometimes will roll over on its own once maaaaaybe twice. Will start up maybe once out of every ten tries sometimes just two tries sometimes twenty tries (and then runs just fine).

All lights work with car off and just but a new battery in it a week ago.

The shop I bought it front just spend three hours of diag time testing the wiring harness and said everything tests okay. But they just don't know where to go with it now. (Not a Mercedes shop). I'd bring it to a specialty shop or MB dealer but it's
On the dealer I bought it from's dime. (so of course they rather their own shop figure it out.)

Sulaco

fuel, air, and spark. highly unlikely it's not getting air, so that leaves fuel and spark.

the fact that it runs normally sometimes indicates fuel supply is most likely fine.

that leaves spark. for some reason it's not getting spark at random. likely cause is some failing sensor, also sense it gets worse when it's warm. on pre-update cars they had an OVP relay that caused exactly this situation most of the time. afterward, it's CPS and a few other things cm60k said.

cm60k

^Agreed with Sulaco^,

is C36 got that OVP relay..?, i thought it comes in 96 only, but i'm not sure about that..!,

did you test if there are fueling delivered in fuel rail, did you listen to fuel when turn the key to position 2...??

ZAYED,,

Sulaco

97 does not have it, some 96's do not have it. all 94 and 95's have it, with some in 96. 96 was transition year.

Atown206

It's hard to hear when I put the key in and turn it I just hear the car beeping and the climate control flap open.

I was able to et it started today but noticed at idle the RPM tach seems to me constantly moving between 700-800rpm will occasionally drop to 600 then right back up. also noticed there is a bit of an extra vibration to the car. Only happens at idle or park. Not sure if this is normal.

Atown206

I do occasionally smell a fuel smell near the fuel door after the cars been driven a bit. Not sure if it related? May just need a new fuel cap.

cm60k

If RPM constantly playing, MOSTLY; MAF is suffering..!

ZAYED,,

cm60k

When the Engine running, try to unplug the MAF connector, and see if there is any difference with plug & unplug MAF connector...!

ZAYED,,

Atown206

I will. How easy is the MAF to completely replace?

Sulaco

Easy if you have two hands and 45 seconds. It's that thing on the intake hose just past the air filter box, has one black cable running to it.

Atown206

So I unplugged the MAF it ran steady RPM seemed a little more steady, still had a little play but not as much, then after a good 45seconds swiftly die. But with it unplugged car seems to start everytime. (Not sure if it's a fluke because of how intermittent the starting issue is or if it's in fact the unplugged unit).

cm60k

Seems MAF already dead, do you have a spare one to try..??

ZAYED,,

Atown206

Unfortunately I do not. I saw some in Amazon for about $50 same part number and everything. Is that a fair price or should I look else where?

eFifty5AMG

Stick with a genuine Bosch MAF. Have you tried cleaning your current one to see if it helps? I still recommend replacing even if it does help.

cm60k

^^+1^^,,

Don't go with these crap sensors, just go with OEM or Bosch only,, clean it may help but will not cure it, plus less performance...!!

ZAYED,,

Atown206

I don't have any. Just made an order so now waiting for it to arrive. (Be about a week) in the mean time how do you suggest I clean out the MAF? Any special do and donts?

cm60k

Some video's here:-

https://www.youtube.com/results?sear...edes+maf+clean

ZAYED,,