The Forum

Garage => Mechanicals => Topic started by: rumb on 15 August 2016, 03:22 PM

Title: fuel pump jump relay
Post by: rumb on 15 August 2016, 03:22 PM
I received back my fuel distributor and it said to run the fuel pump for an hour with supply and return lines connected.  I have gathered that I need to jump pins 30 and 87a to do so.  There are 3 relays in my fuse box, I suppose I just try them all until I find the right one? Do I need the key on pos 1 or @ and will this hurt anything else leaving the ignition on this long?
Title: Re: fuel pump jump relay
Post by: rumb on 17 August 2016, 11:01 AM
I'll answer my own question.

Put 5 gallons gas in and then found my fuel pump was DOA anyway.

I plan on hooking up my 12V power supply directly to the terminals on the pump with the key off.  Then I dont have to mess with anything else.

Title: Re: fuel pump jump relay
Post by: w116john on 17 August 2016, 03:36 PM
hi

i think if you leave the key in position 1? you could damage one of the ballast resistors, as its not supposed to be on all the time just when starting.

i am sure people here have swopped a fuel distributor, i would be surprised if you had to run it for an hour. i am going to change mine in the near future so i am interested to see how you get on.  i have a spare and its the only part of the fuel system i have not changed, in search of a cure for my warm start issues.

all the best
Title: Re: fuel pump jump relay
Post by: polymathman on 17 August 2016, 05:14 PM
Sorry to take so long with this reply...

In the photos I have marked the location of the fuel pump relay and shown a simple jumper I made from parts on an old harness. There is white paint I put on the socket of the relay to show me where to connect the jumper.

If running pump for a while, I disconnect one wire to the coil and the one wire each to the ballast resistors. Key is in ON position.
Title: Re: fuel pump jump relay
Post by: rumb on 17 August 2016, 05:36 PM
Thanks for the info, those are great pictures!
Title: fuel pump jump relay
Post by: ortolani on 11 March 2020, 08:08 PM
Hi,
Of which Mercedes is this relay / fuse box?
Thanks in advance.