How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Euro Specialist Your Own Question
Euro Specialist
Euro Specialist, Mercedes Technician
Category: Mercedes
Satisfied Customers: 664
Experience:  Master Certified Mercedes Benz Technician - ASE Certified
49268239
Type Your Mercedes Question Here...
Euro Specialist is online now
A new question is answered every 9 seconds

I need to locate the fuel pump relay for a 1997 Mercedes E320.

Resolved Question:

I need to locate the fuel pump relay for a 1997 Mercedes E320. I tried looking next to the battery under the rear seat...not there. I tried looking in the fusebox in the engine compartment next to the right hood hinge...not there. Did I miss it, or is it elsewhere? Thanks
Submitted: 6 years ago.
Category: Mercedes
Expert:  Euro Specialist replied 6 years ago.
Chat Conversation Started
HighwayRepair :

Hello, the fuel pump on your vehicle is mounted to the frame underneath the vehicle between the two rear tires. I am attaching the workshop instructions for replacing it right after this post

HighwayRepair :

There is a picture in the workshop instructions that shows where the pump is mounted. Let me know if there is any further information you need

HighwayRepair :

Below is the component location for the relay itself

HighwayRepair :

Fuel Pump Relay location

HighwayRepair :

This is the wiring diagram for the fuel system in case you need to inspect the system beyond the fuel pump and the fuel pump relay

HighwayRepair :

hello, did you see where the fuel pump relay is located in that diagram?

JACUSTOMER-msu1h3ul- :

No still looking....

JACUSTOMER-msu1h3ul- :

The second document you sent "Fuel Pump Relay Location" appears to be the same as the first document...could you recheck? The wiring diagram is helpful, but doesn't tell me where in the car to look for the fuel pump relay.....Thanks

HighwayRepair :

im sorry, you are correct, i linked the wrong document, one second......

HighwayRepair :

Here you go - fuel pump relay location

HighwayRepair :

its underneath the rear seat, inside the car, by the battery

JACUSTOMER-msu1h3ul- :

That is what I thought also, from reading web articles. But I checked, and it isn't there. There is no relay in that location for my vehicle. I will get the manufacture date....

HighwayRepair :

you are sure you have a 1997, and a v6?

HighwayRepair :

can you check the date on the driver door jamb, you might have one of the early builds

JACUSTOMER-msu1h3ul- :

Yes, manufacture date is 09/96. VIN WDBJF55F7VJ036068

HighwayRepair :

ahh, then you have a k40 relay, one second.......

HighwayRepair :

when you go to buy a replacement relay it will be called a "k40 relay". and will look more like a computer/fuse box than a relay itself. the fuel pump relay is built into this module

HighwayRepair :

actually, i take that back

HighwayRepair :

you will be able to buy just the relay and replace it. It will be called a "k40/4"

HighwayRepair :

after further research only some of the k40 modules will let you replace just the relay, some of the the fuel pump relay is integrated inside of the module like i thought it was

HighwayRepair :

you will have to inspect the k40 module and see if there are external relays plugged into it or not, if you do not see external relays on it, the entire k40 will need to be replaced

JACUSTOMER-msu1h3ul- :

Ok, that is helpful. Do you know the location of this module in the main engine compartment? Is is located near the fuse box (near right hinge of hood?)

HighwayRepair :

It is located right next to the left or right hood hinge ( i forget which on this model) inside of a black plastic box with a removable lid

HighwayRepair :

you will see the black box with the black plastic lid, you will have to remove the lid in order to see the module itself

JACUSTOMER-msu1h3ul- :

OK. THank you, XXXXX XXXXX very helpful. THis is related to the car stalling out, not starting, then having to wait a few hours for it to restart. From the research I've done, it's it the fuel pump/relay, or the crankshaft position indicator module.

HighwayRepair :

MUCH more likely the crankshaft position sensor. they fail constantly and cause exactly what you describe

HighwayRepair :

if the relay can be replaced by itself, go ahead and replace it, but if it is integrated into the K40 module, replace the crankshaft position sensor, not the K40. it is almost always the crankshaft position sensor

JACUSTOMER-msu1h3ul- :

Good. I ordered that part. Is this something a non-mechanic can replace? If yes, could I get instructions for that?

HighwayRepair :

CKP sensor

HighwayRepair :

its on the back of the motor, by where the motor connects to the transmission, "simple" to replace, but kind of hard to reach, do it with the motor cold to prevent burning yourself and be prepared to "struggle" getting a tool on the bolt that holds it down, but all in all a simple job, just fristrating

HighwayRepair :

Glad i could be of help, good luck and take care

HighwayRepair :

If anything else comes up post it here and I will check first thing in the morning and post a reply

JACUSTOMER-msu1h3ul- :

thank you very much. First time I used, "just answer", and very worthwhile. I also signed up for the ongoing Mercedes question support, so thanks again.

HighwayRepair :

You are very welcome. If you are satisfied with you answer please hit the green "accept" button to confirm this question as answered, Thank you.

Euro Specialist and other Mercedes Specialists are ready to help you