Date: Tue, 13 Apr 2004 11:41:18 -0700
Reply-To: Mike Pedersen <mikeped@SHAW.CA>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mike Pedersen <mikeped@SHAW.CA>
Subject: Re: testing a fuel pump (long)
Content-Type: text/plain; charset=iso-8859-1
From my days when I owned beater English cars, I took a few fuel pumps apart to fix. They were $100 cars... and heck it is just a positive displacement pump... right? Of course these pumps had screws and nuts on 'em so you could take them apart. I'm not going to crawl under the van to see, but I doubt they are. Probably disposable like everything else these days...
On an old style fuel pump, the current flows through a solenoid and to ground via a pair of double contact points that are normally in the closed position. Regardless of the polarity, the solenoid coil produces a magnetic field that causes the armature rod to plunge out and that in turn pushes on a cam mechanism that opens the contacts. The forward motion of the rod also causes a diaphragm to move and create suction (or discharge). The pumping, that is... Once the contacts have opened, the spring loaded rod returns to its original position and in doing so pumps fuel out (or in). When the rod pumps fuel out (or in), the contacts close and it begins again. The cam spring mechanism that operates the contact points ensures that they are either open or closed and can't be in between. But like in old ignition parts, the contact points erode from rapid current across the "points", so a capacitor is used.
On the newer pumps, (late 70's) the capacitor is replaced be a diode across the coil. Of course the diode could short the coil out (and burn up the diode) if connected the wrong way, so these pumps are sensitive to polarity. I would replace the diode from Radio Shack and as long as I didn't burn up the coil from having it reversed to long it would still work.
I'd bet that vanagon (and Roadmaster, and Landcruisers and Testarossas...) pumps would be similar...
Regards,
Mike
----- Original Message -----
From: "Stan Wilder" <wilden1-1@SBCGLOBAL.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Tuesday, April 13, 2004 10:02 AM
Subject: Re: testing a fuel pump
> Mark.
> How long did you work on the Space Shuttle project before they caught up
> with you?
>
> Stan Wilder
>
> ----- Original Message -----
> From: "Mark Seifert" <theburnvictims@HOTMAIL.COM>
> To: <vanagon@GERRY.VANAGON.COM>
> Sent: Tuesday, April 13, 2004 9:43 AM
> Subject: Re: testing a fuel pump
>
>
> > bentley says a lot of things that really dont have much validity. like not
> > using a click-type torque wrench on the heads. why not? there's no solid
> > explanation. i dont see any reason why reversing a pump could damage it.
> > i've tried it and it works. hitting it with a hammer also works.
> >
> >
> >
> > >From: Stan Wilder <wilden1-1@SBCGLOBAL.NET>
> > >Reply-To: Stan Wilder <wilden1-1@SBCGLOBAL.NET>
> > >To: vanagon@GERRY.VANAGON.COM
> > >Subject: Re: testing a fuel pump
> > >Date: Tue, 13 Apr 2004 08:59:27 -0500
> > >
> > >I think that if you read Bentleys instructions it states that reversing
> > >polarity can ruin your pump.
> > >You can go ahead and try it and let us know.
> > >
> > >Stan Wilder
> > >
> > >----- Original Message -----
> > >From: "Mark Seifert" <theburnvictims@HOTMAIL.COM>
> > >To: <vanagon@GERRY.VANAGON.COM>
> > >Sent: Tuesday, April 13, 2004 12:15 AM
> > >Subject: Re: testing a fuel pump
> > >
> > >
> > > > you can try reversing the positive and negative wires to the pump (+
> > >to -, -
> > > > to +) and crank the engine for a few seconds. this will make it pump
> in
> > > > reverse. sometimes when the fuel pump is clogged, running it in
> reverse
> > >for
> > > > a few seconds will clear it out. if not, you can try hitting it with a
> > > > hammer. seriously, this works too.
> > > >
> > > >
> > > > >From: Matt Faust <mobytype2@YAHOO.COM>
> > > > >Reply-To: Matt Faust <mobytype2@YAHOO.COM>
> > > > >To: vanagon@GERRY.VANAGON.COM
> > > > >Subject: testing a fuel pump
> > > > >Date: Mon, 12 Apr 2004 09:50:36 -0700
> > > > >
> > > > >Hi all,
> > > > >
> > > > > What is a solid way to test a fuel pump?
> > > > >
> > > > > Here is my problem... My '84 van quit running the
> > > > >other day. I removed the line that exist the fuel
> > > > >pump, no fuel. I performed the relay test according
> > > > >to the Bentley and it passed. I measured the current
> > > > >draw on the fuel pump, it read 7 A. I removed the
> > > > >line from the tank exit, a nice steady stream of fuel
> > > > >poured out. I removed the line from the exit of the
> > > > >filter, also a nice steady stream poured out.
> > > > >
> > > > > Can the fuel pump be plugged or bound somehow? If
> > > > >it is jammed, will it still draw only 7 amps?
> > > > >
> > > > >Thanks in advance,
> > > > >Matt
> > > > >
> > > > >=====
> > > > >Matt Faust
> > > > >'84 Wolfsburg Weekender "Moby"
> > > > >'63 Westy SO-33 Sub-hatch "Rusty"
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >__________________________________
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