Ok, so the car has had problems with the Mass air flow sensor before which caused it to run rough, stall out or diebut it always set a code when it did. My last maf was 6 mths ago, original bosch unit. Well, the 97' E320 inline 6 with 90k, this time drove fine, no indication that anything was wrong. Suddenly, this am, it sputtered and died ( in traffic no less).
Symptoms:
The car will crank up and run for 15-20 secs just fine,
stores no codes
the gas pedal has no effect on engine idle once it starts to die.
It seems like its starving to me.

Could it be a fuel filter/pump situation? Thats what I'm thinking? Can anyone suggest something else?

Clogged cat? Maybe but it wouldn't start up and run like a top for 20 secs at a time would it?

Could still be the MAF, but why would it immeadiately restart like nothing had happened and run fine again for 20 secs?

THanks for the help.
Robert

 

ALSO, the ETS traction control comes on the dash board information area.. no codes though.
MAF or fuel pump or filter? Something else?
Help please,
Robert

 

Some electrical circuits or components don't open (fail) until they warm a little bit so it is quite possible that a part will function for 20 seconds and then fail.

Did you buy your sensor from an Authorized Mercedes-Benz Dealer, is it OEM? If so it is guarenteed, over the counter purchase, for 12 months parts and labor with proof of purchase receipt, or if installed at the Dealer 12 months or 12,000 miles which ever occurs first.

If not take what you saved in the aftermarket and your vehicle to your local Authorized Mercedes-Benz Dealer and request an itemized written estimate of repairs.

I know I sound like a broken record (boy there's a cliche that nobody will recognize much longer) and I'm prejudice after so many years of Dealership employment but it is often more expensive to try to fix hit and miss than taking it to the experts. Let them beat their heads against the wall for a while. They will find the problem.

 

I bought the sensor from Az Autohaus. I bought from them on everyones reccomendation that they have the best parts/prices and who can't install a Maf sensor? WHy pay the dealer 500 plus to do what I can do for 200 is the mentality. Anyway, why would the car drive perfectly fine, then suddenly have this problem? I understand your reasoning with the circuits, but do they simply reset themselves?

I'll have to have it towed there and then diag'd at the dealer.. ouch. Thats why I'm trying to save the money (here at Christmas time) and figure it out by myself and with the boards help.
Thanks for the suggestions,
Robert

 

Hopefully you'll get fortunate and hit it right, but again I've stood shoulder to shoulder with factory trained technicians plugged into the factory supplied computerized test equipment running diagnostic after diagnostic searching for the failing part and often they will barrow new parts from the parts department to start replaceing one by one suspect components.

Once found the test parts are returned to the parts department and the customer ends up paying only for the replaced part with some preauthorized diagnostic labor time.

You can't barrow and return electrical parts from the dealer and neither can an independant repair shop which means you end up paying for everything they use. I feel your pain.

I say frequently, ask anyone, "bring back breaker point ignition and the carburator" we could figure those out by ourselves.

 

Hi,
Les4parts is in one sense correct!

The people best placed to respond to auto problems are the manufacturers representatives = dealer trained staff.
They are (allegedly) trained for this role and have the very best equipment to support them.
However, the level of training given is very specific to a make, model and year and basic principles aren't taught. Just which "black box" to change etc. as instructed by their VERY expensive SDS diagnostics, Excellent tool but its only a tool. It doesn't replace basic understanding,.

Borrowing parts from the stores IS NOT AN UNDERWRITTEN PROCEDURE. When I get my spares from MB (for which I pay a premium because they are Quality Assured by the manufacturer) I don't want them to have been used for diagnostic purposes. In using them for this purpose thety can be damaged. (particularly relevant to electronic black boxes)
I ensure the hologram seal remains in place.
Of course customers who have their cars repaired by the dealer can't ensure that the component packaging was still hologram sealed
....or for that matter whether MB Genuine spares were used (if charged for them!)

HOWEVER, you only have to read some posters experience to see that not all dealerships appear to offer the expertise that you would expect recognising the charges levied.
In the UK this is running at up to 300USD an hour + parts + VAT 17.5% in the London area!

Yes modern auto are difficult to diagnose without the backup and equipment afforded by the dealers BUT this does not mean that shared knowledge, general experience, affordable equipment + of course some LIMITED dealer input (MB SDS Diagnostics) can't resolve the problem.

I don't profess to have any specific MB experience other than that gained on my own cars BUT I am a professional engineer (retired) and understand in depth how most machines, electrics and electronics work whatever they they be.
This is as a result of experience gained as a PRACTICAL engineer for 45 years during my career in automotive design, test and quality engineer in the European car industry

The biggest issue with a diagnosis is the case history. i.e. ALL the relevant details leading up to the failure.
Hot/Cold, Wet/Dry, repeatability, frequency etc etc they all signal something.

Determining the cause is NOT LUCK! Its the result of a process of elimination.

OK back to this case.

COULD be the cat blocked since this COULD "recover" after a few seconds as back pressure dissipates.
However a total blockage of this sort is very unlikely.
FWIW Disregard for the time being until other possibilities have been eliminated

MAF is unlikely to prevent the engine from continuing to run at idle for extended period.
Unplug the MAF and you likely shouldn't notice any difference other than a code will be set.

CPS Cranks Position Sensor. Doesn't set codes.
Usually gives hot restart problem.
Can give cold start problems. Engine doesn't know when to fire.
Possible but certainly not at the top of the list.

Quote: the gas pedal has no effect on engine idle once it starts to die.
Does this mean that the accelerator pedal works OK up to the piont of dying?
Note: Accelerator on this vehicle is electronic. Fly by wire
Yep, fuel high on the list of possibilities.

How would I proceed. On the info provided?
I would measure the fuel rail pressure. Valve provided for this purpose on the fuel rail. (Like you blow the tyres up with)
What pressure do you get at ignition on?
What pressure exists when the engine dies?
Suspect that you MAY find that the pressure drops.

FYI The fuel pump is initially powered by a connection made to the cranking circuit or alternatively a timed source.
Once the engine is running power is maintained by engine oil pressure.
No oil pressure or a faulty sensor/switch WOULD give your symptoms.

Lots of other possibilities but that is where I would start.
Once you know that you have good fuel rail pressure you can eliminate a whole tranch of possible causes without having to spend a penny.

Now I'm not familiar with your specific engine installation so you may need to ask how you gain access to the fuel rail valve assuming one is fitted to your model). On most recent models 2000+_ you have to jerk up the plastic air filter / cosmetic cover to get to see the injectors etc.

Have you checked the oil level?

Since the oil pressure switch is a low cost item many people go straight to changing the component. I do not recommend this hit / miss (expensive) approach.
Establish an explanation BEFORE spending your money.

It could of course be
No fuel in the tank,
Fuel pickup dropped off in tank
Blocked tank strainer
Damaged supply line (rock / stone damage)
Intermittent supply to pump. Wiring, relays,
Faulty pump,
Faulty pressure relief valve.
etc.

In fact maybe it has nothing to do with the fuel system!!

Good luck,

Stuart

 

Stuart,

Thank you for the information. I appreciate it. I'm stuck between a rock and hard place. Leaving town in 2 days and won't be back to even look at the car till then.

I took it to a local shop and they could find nothing wrong with it? It ran fine at their shop for a long time (they said) and then I picked it up and drove it home 10 miles. I even got on it a couple times to test it out. It never missed a step. Then my wife gets in it this morning and it began acting like it was going to die again. She pulled over to a safe place and had me take her to work. What a drag. So, now, I've got to likely take it to a Merc. shop and have it fixed, hopefully while we are out of town. I don't know what else to do with my limited time frame and need for the car.

I don't have a FP gauge, are they cheap at a local autoparts store?

THanks again,
Rob

 

A pressure gauge (not fuel specific) should be available from a local auto shop but it may not be worth buying just to confirm that the pressure IS OK. On the other hand..!

Intermittent faults are always the most difficult to resolve.

Due to the intermittent nature of this fault I favour a bad electrical sensor connection somewhere in the fuel electrical supply system (gut reaction. No definitive process to support this) but no silver bullet solution exists to your problem I'm afraid.
Process of elimination and as somebody else stated...may be a bit of luck.

First step...Is the fuel pressure OK when the car starts to exhibit fault? If NOT this will then take you down a clear diagnosis route.

If the fuel pressure is OK then you will be looking at something totally different.

One small step....etc.

Sorry can't offer much more assistance at this point

Stuart

 

Ok, sorry for the long time since the last post... Just remembered it.

So, I had the car at the house. I turned it on and drove it around 2 miles to see what it would/wouldn't do. It wouldn't make it past 1500rpm without falling on its face. It made no sense to me logically that it was electrical. Something wasn't getting fuel. So, I get down and listen to the fuel pump and its grinding a bit. EPIPHANY!! Thats it..
So, I ordered one for 235.00 plus 1 hour of my time. Its now installed and the car runs like it should.

THanks for all of the information guys. I appreciate it.
I'm glad it's fixed and so is the wife. Especially that it didn't cost a grand to figure out chasing parts, or crazy dealership labor rates etc...

Rob

 

I don't see how a 97 could be much different than a 90....short of a couple of things...engines are engines.....90% of what keeps a 2005 and 1990 mb engine from starting is common....the principle is the same....