300E Fuel Relay Location
 

Where is the fuel relay located in a 300E and does anyone know the part number...Would it be in the same location in a 87 and in a 90...thanks Jim

behind the battery...should be the same for both models. there are two relays in the same area...black , rectangular.... one is the a/c relay...may say "klima" on it...

Don't know if it's unique to the 400E, or just later-year W124s in general, or what, but on my car, the fuel pump relay is under the rear seat cushion on the right side.

Part number for 1987 model is 002 545 27 05 up to engine number A396764 and 003 545 24 05 for engines after that, is what I was told.

However, important to make sure you get the 6 cylinder relay, not the 4 cylinder version. I was using a pattern relay numbered 003 545 24 05 in my 300E and it wouldn't rev over 4,000 rpm. Turned out it was for a 4 cylinder engine.

The correct item should have 6zyl/6350 stamped on the side.

About the location, you'll find it behind the battery in the front on the 4 and 6 cylinder 124s. I'm guessing that the 400E and 500E relays are located in the boot next to the battery because there isn't room under the bonnet

The fuel pump relay contains the rev limiter function, so if you use a four cylinder relay in a six cylinder engine, you will only get two-thirds of design engine revolutions.

Conversely, if you use a six-cylinder relay in a four, the rev limiter will be about nine grand, but I definitely would not recommend this "mod".

Duke

Hmmm....Isn't the fuel pump relay a part of the MAS computer on the 1990 300E? And not a separate relay like on the earlier models?

Or am I experiencing confusement?

95% sure that it part of MAS Relay. Think I remember that because when I first got my '90 300E one of the lists recommended carrying a spare relay.
Couldn't find one, because it's part of the MAS relay.

Steve

fuel relay part
 

http://www.***************/catalog/lookup_parts.cfm?SubcategoryID=3380&VehicleID=1193846&Qualifier=%20&CFID=514133&CFToken=80575963

See if this link will work... it's the listing from one of the suppliers.

I carry a spare in my 1989 300e trunk. Also have an OVP spare

You are correct... the 1990 is different.

http://www.***************/catalog/lookup_parts.cfm?SubcategoryID=3380&VehicleID=1193857&Qualifier=With%204%20Pin%20Connector%20and%203 0%20Amp%20Fuse&CFID=514133&CFToken=80575963

Jim,
You evasive rascal. You are not going to tell us what year we are dealing with so I'm not going to tell you where it is, because I don't know.

Peter

1987&1990
 

Peter, I am parting out 2-300E's... a 1987 and a 1990...I have had 4 different answers so far...I have found the fuel relay in the 87.....The 90 is being evasive...Jim

not there? maybe that's why the car isn't running :)

N16/1 is the item you're looking for.

If it's a 103 engine, it's behind the battery, next to the OVP relay and adjacent to the AC relay (which is marked klima)

Yup, on my 1990 m103 (300SE) it's part of the MAS.

Confused
 

Yes, I was confused and it is next to the battery with the klima on the 87...The engine was running when I started stripping the car....thank every one for their help and ideas...I am going to close this thread....Jim

Danwatt is correct. In the 1990 model the fuel pump relay is included in the MAS unit along with the Klima relay. That is the unit by the battery that has the knob on it. Sometime in 1991 the MAS unit was eliminated and the fuel and A/C relay are incorporated into the main computer.

Peter

So they went from a free-standing relay near the battery(maybe $50), to one incorporated into the MAS($450 @ dealer), to one incorporated in a computer(sell your house-sleep in the car).

Things get old, they break and you PAYYYYYY.

Love ya MB.

Nope, MAS unit not eliminated. My '92 124 certainly has one, as I had it replaced.

Steve

Actually it was eliminated, but the 124 is the first chassis that I have seen from MB that had continous design changes over the course of the model run. If you have an early 89, you will have two decorative strips on the door. If you have a late 89, you will have a solid decorative panel. You can't swap wiper blades from an early and late 124, because the blades are offset by about 30mm. If you have an early 89, you will have light off cats below the headers, late ones don't. This is true of Calif. versions at least. I'm not sure about 49 state cars. Up to about 90, you have to pull the ash tray out. After that it operates like a viscous clutch. Modes up to 90 have the standard door locking system. 90 and newer allows you to close the sunroof and windows while locking the car by holding the key in the lock position while everything closes up. 90 and up had decorative wood strips along all the doors. I have an 86, an 87, an 89, and a 90. I'm amazed at the design changes in the car. I have never seen this many changes in any model in the 30 years I've been an MB mechanic. The only other model to make changes was the 123, but that was a one time thing. In 83 the 123 was upgraded with electric right side mirror, lighted sunvisor mirrors, velour carpeting, and roof strips and stiffening in the wagon version.

Peter

Can anyone verify that theirs does this? I have a 1991 300E. I'll check again when I go out for lunch, but I'm pretty sure this is not the case...

I hereby verify that my '90 and '91 300Es both do this.

I just went out and tried it - it works!!! I never knew... This is cool. Any other "hidden" features I might not know about?

Hello I have a 1987 300E


I am also having trouble physical seating the fuel pump relay and the climate control relay down in their sockets. They are located side by side next to each other. On the sides of the relays towards the bottoms of them there are slight tangs that stick out from the longer sides of the relay case. It seems like the tangs of both the fuel pump relay and the climate control relay are fighting each other and keeping them from fully being seated.

I am thinking of taking a utility knife to one of the tangs on one of the relays and shaving it off.

Ideas?

Carefully check the relays for bent pins and the receptacles for any debris or damage.

I just removed my FPR a couple of weeks ago following a no-start condition. I did a careful inspection, but found no obvious issues, so I cleaned the pins with electrical contact cleaner... reinstalled the relay and it started right up.

I documented the above in the following thread:

http://www.peachparts.com/shopforum/tech-help/399783-sometimes-i-call-mercurial-benz.html

Duke

thanks for the post.

I removed both relays and the pins are straight and they are not discolored. I took a small wire brush to the pins and then sprayed the pins with deoxit.

The issue I am having is the physical contact of the tangs on the sides of the relays, in particular the two tangs on the sides where the climate relay and fuel pump relay are side by side. If both relays are removed, the fist one in seats fully but then when the second relay is installed the tang from relay being installed next hits the tang of the relay that is already installed, this keeps the second relay from being fully seated.

ideas?

The only thing I can think of is that you might have an incorrect relay... physically larger than original, but maybe functionally correct???

If all else fails I don't think filing or cutting off the interfering retention tangs will cause any problems. The pins themselves should hold the relays in place, and they make removing the relays a PiA.

A couple of years ago I tried to remove the FP relay to inspect when I was having starting problems. I used a couple of small putty knives to carefully pry the tang slots back, so the tangs would clear, but it wouldn't budge. I recall even starting a thread here asking if anyone knew how to get the damned thing out and got no response.

It turned out the problem was the due to an internal leak in the fuel accumulator that was shorting fuel back to the inlet hose from the tank, which prevented proper fuel pressure from building up at the regulator, so no big deal.

For whatever reason, it came out came out last month without much effort.

Duke