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'additional' fuel pump - kinda long 700 1991

posted by  interstition on  Thu Dec 29 06:53 CST 2005
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last visit: Mon Apr 28 10:13 CST 2014
[RELATED]

I know there are many times more Volvo experience on this board at any given moment than I have on my best day. Multiply that by the years this board has been around and I have to think about everything has been suggested, and many of them tried. But my recent experience with a windshield washer and recent posts about in-tank fuel pumps has me wondering ......

When the front washer pump went in my Town and Country, I replaced it with a spare Volvo one I had. The old one was right in the resevoir, so I just cut the "new" one into the fluid line above the old and spliced in the wires. Voila, fluid is sucked through old pump and out onto windshield.

Recently, there was a thread about how the heck to get the sender out of your 740 sedan's gas tank (and then get it back in straight) when you need to replace the one and only fuel pump that Rex-Regina cars have. My one experience with that was taking one out at the pick-n-pull where I could hack and even then it was a struggle.

So, why couldn't one add a working fuel pump outside the tank (like the Bosch cars have) as an alternative? Yes, the Bosch's also have the "helper" pump in the tank for low fuel situations, but one could avoid those situations. The exact same kind of pump wouldn't work, but I'm sure one of similar output could be found.

I haven't seen this mentioned on this very wise board, so I assume there must be a big hole in my plan and you guys will pour through it. I also assume that because I talked about it so much, one of my Regina cars will punish me by teaching me how to R and R the fuel sender soon.

happy New Year
--
1991 745 213K miles, 1991 745 210K, 1990 744 GL 183K, all Rex-Regina - past 240s








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    'additional' fuel pump - kinda long 700 1991

    posted by  someone claiming to be chandrakumar on  Thu Dec 29 07:23 CST 2005 [RELATED]

    I can't offer more than speculation: achieving rail pressure is usually the task of a positive displacement pump, similar to a cam offset roller or gear pump contrasted with the centrifugal pumps used as fuel transfers or window washers. I'd guess you might easily bypass a stationary centrifugal pump, but perhaps not one with positive displacement design. If you pull the check valve from an inline main pump, you can blow through it, but it is very restrictive compared to a transfer pump. A Regina pump may allow enough past it to keep an in-line fed, I don't know. Worthy of experiment if safely hacking an external pump is really less work than replacing the one inside.








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      'additional' fuel pump - kinda long 700 1991

      posted by  c_j_mooney on  Thu Dec 29 07:58 CST 2005
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      last visit: Wed Sep 14 17:39 CST 2011
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      Good point, I had an Audi single-in-tank-pump out once and the check valve affixed to the outflow port was very restrictive - granted it's not restrictive to an output of 45psi, but the stout spring in it would impede the suction feed to that external main pump - a pump that is designed to be fed with positive pressure rather than drawing vacuum to overcome that high-pressure check valve. If the Regina pump has a similar valve then we've got a roadblock - it's got to come out.
      --
      Chris, Dartmouth NS Canada 70 M-B 280SE, 83 245DL, 84 244 turbo, 90 780 turbo, 92 VW Golf, 90 740 Rex/Regina








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    'additional' fuel pump - kinda long 700 1991

    posted by  c_j_mooney on  Thu Dec 29 07:11 CST 2005
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    last visit: Wed Sep 14 17:39 CST 2011
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    Seems like it should work... except for the hassle of wiring, which shouldn't be a big problem either. Though with the regular main pumps being somewhat starved when the prepump dies, I wonder if the additional restriction of drawing up through the original pump might be too much even with a full tank & cause pump overheating. Perhaps it's possible to just install the pair, both the in-tank prepump and an external main pump, much more readily available at the local junkyards than good Regina pumps.
    --
    Chris, Dartmouth NS Canada 70 M-B 280SE, 83 245DL, 84 244 turbo, 90 780 turbo, 92 VW Golf, 90 740 Rex/Regina







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