1997 s320 cranks, won't start. Fuel pump relay?
 

m104 engine.

it appears you can buy a fuel pump relay for this car... but I don't know where it is located. does the car actually have a fuel pump relay?

fuel pump fuse is fine.

That's one of many things it could be. Are you able to check codes? Do you hear the pump hum for a moment when you turn the key to on? Listen by the right rear wheel (I think). Have you checked for spark?

Sixto
98 E320s sedan and wagon

no codes... not sure if i can hear the pumps or not...

i haven't checked for spark.... but i can't imagine that all of a sudden i have that problem.

i am not sure if this car has a fuel pump relay.... that's what I am trying to find

IIRC in my '95 S420 is was in the trunk fuse panel above the battery.

With no familiarity with that engine my first suspect is the crank position sensor. It's not fun to get to in an M104 requiring removal of the starter or oil pressure sender. So I'd listen in the area ahead of the right rear wheel while someone turns the key to on (not start). There's probably a fuel line in the engine bay you can crack to check for pressure.

Sixto
98 E320s sedan and wagon

thanks... CPS would be an easy fix... actually I have fuel pumps too.... but it's Sunday... and I just don't have the time like I used to..

There is a trunk fuse panel above the battery...but it's just that... a fuse panel.

oops sixto you were right...it's buried in the fuse panel

The fuel pump relay should be green if I recall correctly. If you look at the diagram that is usually printed on the relay, you can jumper to terminals to make the pump run manually for testing.

Fuel pump relay is silver. Went to the boneyard and got two. No luck.

Let's see if I can clarify. Battery was low when I first started. As I Started it , it was dying. Ac panel went from off to on, on its own. Battery would then not take a jump. Got a new battery. Now it cranks, but won't catch

Try another key.

This car uses a DAS X security system with a RFID chip that is read and written to ( rolling code ). If the write portion of the process is interrupted ( low battery ) , the security system will no longer recognize the key.

Typically, the car will start and run for a few seconds though. The system allows the engine to run while it interrogates the key rather than delaying the start up process.

I will try another key....didn't know that... Key is standard with no chip. I will try another. It did briefly cross my mind that the security system may have been compromised.

All keys for this car will have a chip, even the clipped head wallet key as well as the round head valet key.

The single button remote flip key has a chip in it as well, a good remote battery is not required for the car to run.

i have at least two other keys... my wife's and another spare. I will try tonight.

If this works..it is valuable info. I have tried to search this as an issue..and no one else seems to have had it...

To sl320
 

Blown away. I have owned a 108. And a 140. With 4 or 5 124's in between. I tried my wife's key in her car and it started right up. No one anywhere in the Internet offered your suggestion. Thank you sir.

Lee, glad to hear you resolved the starting problem with your 1997 S320. The Owner's Manual provides instructions to replace the round battery in the key. I replaced the battery in both keys for our 1998 E320 for the first time in the past 6 months.

You are welcome. The real test will be that the car continues to keep starting. I've been involved in diagnosing various intermittent problems where I think it is fixed but it acts up at some future random time.

If it makes it a week, I'd say you are 90% there, a month and it is 100%.

You can get a clipped head " wallet key " for about $ 45 from the dealer by providing proof of ownership. A flip key is about $ 250 last I checked. The new key will start the car without any programming. In any event, the old key is still good to gain access to the car.

The key will be programmed at a MB USA parts depot. They know what keys have been issued to the car and will select another slot / version in the cars computer. Basically there are 8 key slots I'll call 1 through 8 , each slot has 3 or 4 versions below that I'll call A through C. This will give 24 possible keys per car but you can only use 8 at a time.

There are readers from China where you remove the DAS box, unsolder the chip, read it out then program your own key.