Adarah

I was driving from Texas to Louisiana - I often do this for work - and had a terrible die out on I10 Sunday night. Everything was fine for about 120 miles, but all of a sudden right as I was getting out of Houston the cruise control cut out, and the car started to lose speed.

I pressed on the gas, and the car lurched forward slightly, but pressing the gas pedal didn't provide the car much power. I had to limp at about 25 miles an hour to the nearest exit - which thankfully wasn't far.

I pulled off the road and put to car in neutral, got out to check there wasn't anything I could visibly see - and it did ok idling for about a minute, then as I got back in the car stalled out. I got it to start up again but it just wouldn't do much when I pressed the gas.

I had it towed to the dealership in Houston and today they looked at it briefly (they were supposedly backed up) and the service agent told me the technician said it was "some kind of fuel problem."

I did a bit of research here last night, and if I am understanding correctly, it might be something to do with a fuse that regulates the fuel that maybe causing this? I was originally thinking alternator or transmission?

I have noticed a couple times in the last few months that when I put gas, the gas pump would cut off like the tank was full, but I had just begun fueling. Also, my husband told me that I shouldn't ever let the tank go below a quarter, so I always fill up before then.

Has anyone else had this issue? If it is this fuse - how much should a repair on that run? Any ideas on what else it might be?

I have to be in Louisiana for most of this week, is it ridiculous that I feel separation anxiety with the car being so many zip codes away? Just look at this sad sight…

Glyn M Ruck

It sounds like a blocked fuel filter or a fuel pump failure.

They need to check fuel pressure at the Schrader valve on the front fuel rail. s/b > 3.8 bar or 55 psi while cranking.

Adarah

Thanks Glyn - I'll make sure that's done.

I was thinking also that maybe it's the throttle sensor?

Still no word from the dealership - Houston Greenway is starting to seriously disturb me.

Glyn M Ruck

Unlikely the TPS if the car lost power with cruise control as well.

Could be TB actuator but then it could be many things. Without codes etc fuel starvation is a good starting point.

Adarah

Finally heard back from the dealership - it is the fuel pump supposedly. They want like $2600 to replace the whole thing, they say there is a new upgraded fuel pump and they want to install it. They are charging $1400 just for the part. Seems very high to me… ?

Glyn M Ruck

They are absolute robbers. There is not a new "upgraded" fuel pump. There is just a new fuel pump. The older ones are no longer available.

The Genuine OEM fuel pump & sender unit for your car is $237.67 at RMeuropean.

Glyn M Ruck

The lower back seat has to be removed & one round cover plate removed to replace. It's easy. Take the car to an Indy & buy the part online.

Adarah

Thank you so much Glyn! You are amazing.

I'm having the car taken to an Indy tomorrow so I'll let you know how it goes.

I guess people call them stealerships for good reason.

Glyn M Ruck

A pleasure. Dealers make me sick.

Here is method in Wiki.

https://mbworld.org/wiki/index.php/F..._fuel_pump.pdf

Adarah

Ok so - I took the car from the dealership to a recommended indy in Houston and the guy says he doesn't know for sure if its the fuel pump - he thinks maybe the catalytic converter. I did a bit of research and I suppose some of my symptoms do fit that - loss of engine power and occasional stalling out - but my engine wasn't running hot, and I didn't notice any changes in fuel consumption. Could that cause this issue? If so, how much should something like that run? Thank you so much for all your help Glyn!

Glyn M Ruck

It's extremely unlikely that it's a blocked Cat. Tell them to check the fuel pressure as I specified early in the thread. I can't understand why all these people have such trouble with simple diagnosis. Ask them what the fuel pressure reading is. 99.9% of the time what you experience is CPS (crankshaft position sensor) or low or non existent fuel pressure due to pump failure or blocked filter.

Cats can get quite expensive & you need to make a decision whether you want genuine Benz or aftermarket.



https://mbworld.org/forums/5971117-post2.html

Rudeney

Like Glyn pointed out, it is very simple to check the fuel pump pressure at the rail. When the catalytic converters go bad, they disintegrate and spew hot molten metal down the exhaust pipe where it clogs the resonator and muffler. This can cause very poor performance and can be difficult to diagnose. About the best way to determine it its the cats is ruling out everything else and mileage over 100K.

Adarah

The dealership said that the fuel pressure was about reading about 20, which from what I understand is low. The car has just under 79,000 miles on it. I just had the fuel filter changed in January - I was wondering if something might have gone wrong when I had it changed? My indy said it had never been changed before. I had no noticeable performances issues up to the point the car just basically stopped going on the highway. I lost about 80% of the engine's power in what seemed like less than a minute or two.

I looked up catalytic converters on the website you posted above Glyn, and saw two that ranged from $250 - $450ish, although I don't think they were OEM.

Thank you guys so much! You have no idea how much I appreciate all of your help and information.

On a side note, I was actually wondering if you all learned all of this yourselves from trial and error, and research? Or did you ever get anyone to help show you how to do this stuff? Also, I was looking at the wiki you posted as well - I am so scared that I would screw something up, but I can't stand not being able to work on my own car, I really want to do it myself. This breakdown it's not going to be possible, as it happened 200 miles away from where I live, but I can't deal with not knowing and understanding how to really take care of my own car anymore. Where do I begin? Obviously I don't own hydraulic lifts - what are the best jacks to buy? Any advice you guys have I would love to hear.

& Thank you again

Rudeney

If the fuel pressure is only 20psi, then I'd say you've got a problem with the pump. I guess it could be the filter, though. Did you use a genuine MBZ filter? Some cheap no-name aftermarket filters might be suspicious.

As for learning this, I have been working on cars and other electronic and mechanical things as a hobby since I was old enough to pickup a screwdriver - over 40 years now. My great grandfather owned one of the first motor vehicles in the state. As a matter of necessity, he taught himself how to keep his cars running. He passed this onto his son (my grandfather) who in turned passed these skills and love of repairing cars onto his son and then on to me.

I have learned by doing. I read what I can and for MBZ, I also worked fro about 9 months as a QA consultant for "a premier German auto manufacturer" and even had the opportunity to spend a few months working in one of their dealer's service departments. I bought my own "Chinese clone" copy of SDS that has WIS and EPC and I get a lot of knowledge from that. Being a "techie", understanding the electroncis also comes a bit naturally.

Glyn M Ruck

You definitely have a fuel pressure problem. Make sure that you used an OEM genuine filter. The external filter contains the fuel pressure regulator. So it's either pump or filter or both. Pirate aftermarket filters frequently have faulty pressure regulators.

My knowledge comes from having an enquiring mind & a 39 year career in the oil industry where I had direct contact with all the major OEM's. Both Industrial & Automotive. Started life tearing my Alfa's apart at a very young age similar to Rudeney. Owned 7 Alfa's in a row.

I looked after 227 global markets, & mainly in Asia & to prove that senior management could role up their sleeves, my Benz business associates & I would swap roles & do some training of bright Asian minds. The Benz guys would present my Lubrication courses & I would present their technical modules on whatever. M272 engine, 722.9 transmission etc. It was fun & the questions asked required you to understand the subject. A win ~ win situation.

I like to understand my possessions from Audio equipment to Automobiles intimately.

Adarah

Thank you so much guys for all your info and help.

The car still isn't done, but I have confirmation that it is the fuel pump and its going to be about $480 total to replace. The guy also wants to do the crank shaft sensor I believe, which I am getting quoted about $150 to do. I am fairly certain that my usual indy used OEM for the fuel filter replacement as well. I can't believe that this whole thing has taken two weeks to sort out, although being forced to take care of it from 200 miles away played a big part in that.

I very much enjoy hearing about your experiences, and I definitely agree about understanding your possessions. It sounds crazy but I want to find someone near me that can "tutor" me on the mechanics of my car. I don't know anyone who knows much about cars, so I was thinking of just going to some of the indy places around here and straight up asking the mechanics? LOL I was also thinking of getting an older model Benz to be my guinea pig, so that I don't screw up my CLK during my initial learning curve.

Glyn M Ruck

Sounds as though you are now getting a fair deal. Where do these dealers come from with their pricing? The CPS runs very hot on these cars due to it's location & replacement is not a bad idea. They always fail sooner or later.

Having a less important car to learn on is a good idea. We all make mistakes & hopefully learn from them.

Rudeney

Yes, if you are going to "learn by doing" you don;t want to be tinkering with your daily driver. If you want some real fun find yourself a workable W123 (old 300D). They are so much fin to work on. Challenging, but fun. And I highly recommend you invest in your own copy of SDS. You can get the Chinese clone version for under $500. It includes the diagnostics as well as WIS (shop manuals) and many other great utilities like parts catalog and diagrams.