1971 280sel fuel pump issues any help appreciated - Mercedes-Benz Forum

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post #1 of 8 (permalink) Old 12-01-2009, 12:52 PM Thread Starter
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1971 280sel fuel pump issues any help appreciated

I have a cherry 1971 280 sel. It is in amazing condition inside and out. No rust rips or tears. However the thing doesn't run due to the fuel pump. I bought it this way from a guy who had been messing with it and was unable to make it run. It is fuel injected and has the expensive pump. I really would like to see this thing run but at this point the price of the pump is breaking the bank. So my question is does anyone have a used one? Are there alternative pumps that can be used? Can the pump be rebuilt? Any help would be greatly appreciated................
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post #2 of 8 (permalink) Old 12-02-2009, 12:47 AM
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Which pump do you mean? the leectric pump in the rear by the tank or the MFI (mechanical fuel injection ) pump in the front?
Before messing with the Fuel make sure the engine is OK by checking the compression,then make the ignition 100%perfect.
The previous 'mechanic' obviously knew too much and proceeded straight into the fuel system so you have to do better than him and start with the basics first.
so it's Valves,compression,ignition then Fuel.

You need 1 liter in 15 seconds fuel volume at 14 PSI minimum pressure . You measure the pressure at the cold start valve on the intake manifold.
Until you have those things sorted out you will not get the engine to run. Good luck.
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post #3 of 8 (permalink) Old 12-02-2009, 10:24 PM
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If you mean the electric fuel pump, there is a screen in the inlet that may need to be replaced or cleaned. The whole electric pump can be overhauled and parts are available.

There is also a fuel filter attached to the engine mount. It may be clogged.

We need to know.

Near Manassas Va. '65 220S, 2006 Ford Crown Victoria Police Interceptor, '99 Volvo V70, '72 350SL 4 speed

Not part of the in-crowd since 1952. It's BRAKES not breaks. You break a bone, use brakes to stop your car. /rant

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post #4 of 8 (permalink) Old 12-03-2009, 10:10 PM
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The pumps are indeed expensive! Are you sure you have a bad pump, and not electrical issues? Or as noted, clogged screens or filters?

When you turn the key on, do you hear the pump run for a second or two?
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post #5 of 8 (permalink) Old 12-07-2009, 06:01 PM
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I agree with previous posts about getting ignition and compression right first. Also, consider the fuel is old it is gummy and may have clogged filters and lines. Try to supply fresh fuel from a remote tank and outside mounted fuel pump. This could be from an air pressure charged tank for a short starting test. BE CAREFULL! Any air pressured tank must be suitable for the pressure - not a normal gas container. IF you have any doubts - don't try this.
If 14 PSI is all that is needed, (I do not know the specs) any fuel injection pump of any brand should be able to make this pressure. Newer Bosch pumps do not appear to be repairable. I think these all have aluminum cans. Older Bosch pumps for Volvos (Mid 1970's) could be disassembled and cleaned. They could get stuck if old gas was left to sit in them. These have steel bodies and screws on the inlet end. Maybe you could get a used Volvo pump and clean it up. Do not run any Bosch fuel pump for more than a second without fuel. They are cooled and lubricated by the gasoline.

1973 280 W114 (Driver - 140,000 miles)
1974 280C W114 (Now running - driven off and on this summer)
1968 200D (Engine rebuild planned)
1964 200 (gasser parts car) & 1966 200D (complete car - Got to run. Now to see if clutch can be repaired.)
1980 300D W123 (Parts car - engine runs, but trashed)
1981 240D W123 4 speed ( In sad shape when bought - many parts from '80 300D has back on the road. Needs work, but shows promise.)
1988 300TE W124 (Does not run. 180,000)
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post #6 of 8 (permalink) Old 12-08-2009, 10:37 AM
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Fleet, you touch on a subject that I've seen asked over and over. A fuel pump is a fuel pump is a fuel pump. If it's not Bosch, it would require specialized mounts and a (possibly) unique electrical or plumbing setup. However, with wire crimpers and pipe clamps, one can hook up the fuel lines to anything.

Additionally, the Benz's have fuel and pressure regulators to maintain correct parameters. In theory, if one jurry rigs in a pump with high delivery pressure and volume, the regulators should manage them to what the Benz engine needs.

I just wonder if anyone has ever tested this. I saw a new (Bosch) Benz pump on eBay for a little more than $700 recently. I paid something like $560 for my own fuel pump a few years ago. A Ford fuel pump costs a tiny fraction of this ...

What the hell!
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post #7 of 8 (permalink) Old 12-08-2009, 10:59 AM
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IIRC, the specs call for minimum of 14psi of pressure and a volume of 1L every 15 secs… which a properly working Bosch electric fuel pump can consistently produce.

If you go 3rd party, then be sure to meet these conditions. Many recomment do it right the 1st time around by sticking with OEM, however to each of his own when it comes to rigging-it in one way or another.

Regarding fuel delivery... be sure to ascertain the condition of the tank, its internal 'flower-pot', strainer, and all the hoses and connections, etc...
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post #8 of 8 (permalink) Old 12-11-2009, 01:58 PM
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Yep do the basics first.

If the car has sat for a few years there may be goo in the bottom of the tank that is interfering with the operation of the "flower pot". Here is a link to help you better understand the fuel tank.

Pagoda SL Group Technical Manual :: Fuel / Tank

I couldn't get my barn find to run well until the tank was cleaned and I had sufficent fuel flow & pressure. If you determine that you need a new pump there are several ways to go but I found through the school of hard knocks that the Bosch pump made for the engine works best.

Though the electric pump can be rebuilt I couldn't get mine to perform. I ended up getting this one.


If it's not broke it dosen't have enough features.
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