FPR Location ???

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johmarq
Dernburg Wagon
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Model you own: w114
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FPR Location ???

Post by johmarq » Wed 21 Nov, 2018 8:59 pm

Hi all,
I have a 1974 280E sedan W114, Could someone please tell me where the Fuel Pump Relay is located.
Cheers, John

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Lance
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Re: FPR Location ???

Post by Lance » Wed 21 Nov, 2018 9:55 pm

In upper part of passenger footwell, middle relay, lower row.
Regards,
Lance Smart

W114 280E 5 speed manual
W123 280E

johmarq
Dernburg Wagon
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Joined: Wed 31 Oct, 2018 7:56 pm
Model you own: w114
Region: New South Wales
Location: Goulburn

Re: FPR Location ???

Post by johmarq » Thu 22 Nov, 2018 10:20 am

Thanks Lance,Found it.
Turns out the relay is fine.
My problem is the Fuse 5 keeps blowing
after a bit of detective work it seems that the return line in the fuel tank appears to be blocked
If I disconnect the return line the car car starts and runs ( catching the returned fuel in a container), but when I reconnect the return line it stops and won't start.
Lots of back pressure in the return that appears to be stopping the pump and blowing the fuse.
I tried blowing air into the return in the tank and it is definitely blocked.
Any Ideas how to fix the problem?
Cheers, John

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AMG
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Re: FPR Location ???

Post by AMG » Thu 22 Nov, 2018 10:35 am

There is absolutely only one way to permanently fix this issue. Remove the tank and clean it and the lines.

The return lines on these tanks return the fuel to a swirl pot, where the tank screen and main fuel line originate.

The swirl pot over time fills with crud, rust, shellac and other buildup and needs to be properly cleaned.

The fact that your return line is blocked should be sounding a mild alarm.

disconnect it at both ends and blow it in reverse firstly, to ensure the return line itself in isolation is unrestricted.
Then fill it with a cleaning solvent ( acetone is OK but be careful and do not leave any rubber hoses attached if using acetone, it will destroy rubber, paint etc etc. use a cork to keep the fluid in the steel line overnight)

once it has thoroughly soaked, drain and blow it clear again (be careful of residue!)

the tank needs to be cleaned with a pressure washer, and a properly good surfactant. after which examination can take place via the fuel sender hole and a strong torch.

any rust in the tank will need to be treated with a chemical rust converter (phos acid based) and then the tank needs to be thoroughly cleaned out with solvent.
Under no circumstances should you use a tank sealer, as it will block the swirl pot.

heavy rust should be treated by taking the cleaned out tank to a blasting service, and placing it in a vibrating cleaner or having it soda blasted - NOT sandblasted, after which it is advised to have the tank electroplated (zinc or nickel) and the outside powdercoated to protect it for the rest of eternity.

It goes without saying that a new tank strainer and oring are required, You're also more than likely going to want to replace the main fuel hose from the tank to the pump (age) and also while you're at it replace the fuel filter.

Fuel systems are even more sensitive on djet and kjet than on a carb'd engined vehicle. It is one of those jobs that is not fun, costs quite a bit to properly fix, and if not done properly, will soon have you back underneath repeating the process until it is done properly.

There are a couple of threads on here about the fuel tank blockages and rust. I think Greg posted one about the tank on his 500slc needing the same treatment, but he got it before the problem became serious.

good luck.[*]
Current:
1987 560SL 4sp. auto Signalrot "Stella"
1987 190E 2.3-16 5sp. man. Blauschwarz "Hermann"
1992 300CE-24 6sp. man. Perlblau / Iceblau "Gretel"
1992 Range Rover Classic 4sp auto Ardennes Green "Oswald"
2012 E63 AMG Speedshift MCT Diamantweiß "Klaus"
Previous:
1986 560SEL Anthracitgrau "Schultz" - In Mercedes Heaven
1987 190E 2.6 4sp. auto Signalrot "Sabine" - which now resides/owns Andrew M's Garage
1972 350SLC Astralsilber "Lurch" - now in the loving care of Craig B
1989 2.5-16 Blauschwarz 4sp. auto (parted) formerly owned by Derek/Hasan.
2012 Renault Sport Megane RS265 Trophy 8:08 6 sp. man. Liquid Yellow "Jean Rédélé"

johmarq
Dernburg Wagon
Posts: 5
Joined: Wed 31 Oct, 2018 7:56 pm
Model you own: w114
Region: New South Wales
Location: Goulburn

Re: FPR Location ???

Post by johmarq » Thu 22 Nov, 2018 12:05 pm

Thanks so much for your detailed reply,
I guessed that it was a blocked strainer or swirl pot but I wasn't sure the return went into the swirl pot.
This all started because I am getting the old girl going again after 20+ years sitting in the shed.
I replaced the fuel pump and filter and all the fuel lines in the rear, It then started and ran for 30 or so seconds, then it sounded like it was starving then it wound stop.
It them wouldn't restart, and I noticed the pump wasn't turning on, Chased it through the Start solenoid back to a blown fuse #5, replaced the fuse and it started again and stopped again, another blown Fuse.
I pulled the hoses feeding forward and noticed heaps of pressure on the return line.
So I guess there are no short cuts and out comes the tank foe a good clean and new bits.
Thanks again fellas for all your help, I'll keep you posted.
HooRoo, John

johmarq
Dernburg Wagon
Posts: 5
Joined: Wed 31 Oct, 2018 7:56 pm
Model you own: w114
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Location: Goulburn

Re: FPR Location ???

Post by johmarq » Thu 22 Nov, 2018 3:33 pm

Just a quick update
I put a "T" connector into the supply line to the pump and ran the return line into the T connector.
Hey presto! She now starts and runs just like 20 years ago.
So it is definitely a blocked return inside the tank that is stalling the fuel pump and blowing fuse 5.
So tomorrow the tank comes out!
Thanks again , John

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AMG
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Re: FPR Location ???

Post by AMG » Thu 22 Nov, 2018 3:51 pm

What a bummer. the culprit will likely be the swirl pot full of varnish sludge and crud.

You might get lucky and get away with a serious hit with the gerni on the insides........ buy a couple of large bottles of metho to absorb the moisture in the tank after it's been washed and blown out.

Believe it or not some of that ultra-evil CT-14 bilge degreaser is not too shabby against that kind of crud, but if it's not shifting, You're going to need the big guns to get it clean inside - petroleum based heavy duty solvent degreasers.

That is of course, if there is no rust inside.
Current:
1987 560SL 4sp. auto Signalrot "Stella"
1987 190E 2.3-16 5sp. man. Blauschwarz "Hermann"
1992 300CE-24 6sp. man. Perlblau / Iceblau "Gretel"
1992 Range Rover Classic 4sp auto Ardennes Green "Oswald"
2012 E63 AMG Speedshift MCT Diamantweiß "Klaus"
Previous:
1986 560SEL Anthracitgrau "Schultz" - In Mercedes Heaven
1987 190E 2.6 4sp. auto Signalrot "Sabine" - which now resides/owns Andrew M's Garage
1972 350SLC Astralsilber "Lurch" - now in the loving care of Craig B
1989 2.5-16 Blauschwarz 4sp. auto (parted) formerly owned by Derek/Hasan.
2012 Renault Sport Megane RS265 Trophy 8:08 6 sp. man. Liquid Yellow "Jean Rédélé"

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