Fuel Pump Relay Help Needed - Mercedes-Benz Forum

LinkBack Thread Tools Display Modes
post #1 of 1 (permalink) Old 02-02-2010, 03:31 PM Thread Starter
BenzWorld Senior Member
waybomb's Avatar
Date registered: Apr 2005
Vehicle: 2005 S55; 2003 ML350; 2002 C240; 1997 C280 Sport; 1991 300SL; 1986 190e 2.3 16V (2); 1968 W30 442
Location: South of the North Pole
Posts: 547
Mentioned: 0 Post(s)
Quoted: 11 Post(s)
(Thread Starter)
Fuel Pump Relay Help Needed

I have posted the entire problem on the 126 forum here, and have had some responses. 1987 420SEL. I am thinking the operation of the FPR is the same on this car as other models that vintage. Mybe a non-126 tech could help. I hope.

Problem - car starts fine, idles fine, hits about 50c, seems to go into closed loop, the idle jumps up to the 2200rpm range, and after 20-30 seconds it dies. If restarted immediatly, it will almost immediately jump up into the high idle and die almost instantly. If we wait a while, and restart, the time to race/die is longer.

Jumped FPR. Car runs fine.

Tried a known good FPR in place of existing one, issue is the same.

I have the schematics for this car; FPR is shown on page 106, 108, 108/1, and 110. Many things are feeding or are fed by, or just passin' through the FPR.

Does anybody know, or can send a document, on how to troubleshoot the various items connecting to the FPR socket that could cause the above problem? I am thinking both FPRs are ok, but something connecting to it is somehow disconnecting it.

Or am I completely off and need to buy a new FPR? I still don't understand why, if the FPR is bad, it races like it does when in closed loop.

What if I left the FPR in, let it get to 50c, and when it races, pull the plug on the "thermoswitch" to trick the car into running cold? If it settled down in cold mode, would that indicate anything?

Thanks in advance for your time. This is a tough one for me. Besides, it's my son's car and he's driving the 202 now. Need to get him back into his car.

2005 S55
2003 ML350
2002 C240
1997 C280 Sport
1991 300SL
1986 190e 2.3 16V (2)
1968 W30 442
1988 46' Cougar US1 with Triple blown 572s
Warming the Globe, 24 Cylinders at a Time
Point me to a 126 wagon in the States PLEASE!
waybomb is offline  
Sponsored Links

  Mercedes-Benz Forum > General Mercedes-Benz Forums > General Mercedes-Benz

Quick Reply

Register Now

In order to be able to post messages on the Mercedes-Benz Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode

Similar Threads
Topic Author Forum Replies Last Post
1988 260e w124 no fuel...changed fuel pump and relay!! salthepal W124 E,CE,D,TD Class 11 01-07-2012 08:32 AM
Fuel pump relay problem ? big Help needed Serintek W126 S,SE,SEC,SEL,SD,SDL Class 12 03-25-2011 12:02 PM
300E-W124 Fuel Pump Relay- Overvoltage relay Homebrewer For Sale/Wanted/Trade/Giveaway 0 08-09-2009 06:17 AM
Fuel Pumps or Fuel Pump Relay MKUltra R/C107 SL/SLC Class 21 05-31-2009 08:32 AM
Fuel Pump Relay andreifs W124 E,CE,D,TD Class 10 02-28-2006 01:43 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Title goes here

video goes here
description goes here. Read Full Story
For the best viewing experience please update your browser to Google Chrome