Author Topic: Fuel Pump Stuck?  (Read 1734 times)

TJMart

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Fuel Pump Stuck?
« on: July 12, 2022, 17:55:04 »
I just finished replacing my fuel tank, fuel tank drain screen, all fuel hoses and fuel filter. Got it all back together and put in 6 gallons of gas. Tried to start the car and it just kept cranking but would not start. Checked fuel filter housing and no fuel in it. Checked fuel tank to fuel pump hoses (return and supply) and fuel is coming into the pump. Loosened screw/nut at top of fuel filter canister and turned ignition on to start pump to bleed air out of lines and still no fuel to canister. Reversed positive and negative wires to fuel pump and turned ignition on to "unstick" fuel pump". Still no fuel delivery to filter housing.

I can hear fuel pump when ignition on and fuel pump was rebuilt about 18 months ago. Can fuel pump be stuck and what I'm hearing is not the impeller running??

Thanks in advance
Tony
Tony
1970 280SL, 4 Speed

Kevkeller

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Re: Fuel Pump Stuck?
« Reply #1 on: July 12, 2022, 18:12:27 »
I had to use a slight vacuum from the engine bay end to get my pump primed.
1970 280 SL

TJMart

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Re: Fuel Pump Stuck?
« Reply #2 on: July 12, 2022, 18:17:47 »
How did you create the slight vacuum?

Tony
Tony
1970 280SL, 4 Speed

Kevkeller

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Re: Fuel Pump Stuck?
« Reply #3 on: July 12, 2022, 18:31:49 »
With my mouth.  I disconnected the line.  Just have someone ready to shut the pump off because it comes fast. 
1970 280 SL

Jordan

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Re: Fuel Pump Stuck?
« Reply #4 on: July 12, 2022, 20:34:27 »
Did you clean the fuel filter in the pump itself?  Can't think of any other reason it wouldn't pump.
Marcus
66 230SL  Euro 4 speed

dirkbalter

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Re: Fuel Pump Stuck?
« Reply #5 on: July 12, 2022, 22:31:27 »
You could also disconnect the rubber exit line at the pump and try to pump into a bucket or bottle to insure your pump works. May be your (metal) line has a blockage?
Dirk
66 230 SL
70 280 SEL
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TJMart

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Re: Fuel Pump Stuck?
« Reply #6 on: July 15, 2022, 16:21:29 »
Thanks every one for your posts.

As an FYI for others who may run into the same problem, it turned out that the entire fuel system had to be bled. I disconnected the return line to the pump and crimped the hose as fuel will come out of the tank. Tightened the bleed screw/nut at the fuel filter canister and turned on the ignition to start the pump running. I could hear the difference in sound of the pump right away as the air could escape from the fuel pump fitting for the return hose and a small amount of fuel began to run out once the air was removed. Reconnected the return hose and it is back to normal.



Tony
1970 280SL, 4 Speed

ja17

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Re: Fuel Pump Stuck?
« Reply #7 on: July 15, 2022, 19:25:42 »
Just add more fuel. Since the system "gravity feeds" to the electric fuel pump, you may need a little more fuel to get primed up!
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
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TJMart

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Re: Fuel Pump Stuck?
« Reply #8 on: July 16, 2022, 14:51:17 »
Thanks Joe,

I originally put in 4 gallons and I thought that was enough. No fuel to the engine, so I added 5 more. When it still would not pump fuel to the engine I was stumped. When I reinstalled my rebuilt fuel pump about 2 years ago it primed itself just like you said so I thought it would do it again this time. I think air was in the fuel lines as they were bone dry from evaporation so the air had no way of escaping until I disconnected the return line from the pump. It primed in like 15 seconds once I did that.

All is fine and it started right away!!
Tony
1970 280SL, 4 Speed