wrote:
> In article
> <1174490056.637817.60...@y80g2000hsf.googlegroups.com>,
>
>
>
>
>
> "N8N" wrote:
> > On Mar 21, 9:13 am, aarcuda69062 wrote:
> > > In article ,
> > > "Scott Kelley" wrote:
>
> > > > I am putting an electric fuel pump into an older car & want to use a fuel
> > > > pump relay that will sense when the engine quits and shut off the pump.
> > > > I
> > > > know that many vehicles had this type of relay.
>
> > > > I'll probably get something out of a wrecking yard - I would prefer to
> > > > get a
> > > > relay AND socket. Any suggestions as to what vehicles to steal this
> > > > from?
> > > > Reliability & availability are the two obvious issues that come to mind.
>
> > > Late 80s early 90s GM or Ford truck
>
> > > > Again, I'm not looking for a normal relay, but a "fuel pump relay" that
> > > > remains active only as long as it is receiving pulses from the ignition
> > > > tachometer line.
>
> > > Are you building a relay control circuit that responds to the
> > > tach pulses or do you think that a relay can literally be run
> > > from the coil negative?
> > > The latter isn't going to work.
> > > Running thru an oil pressure switch would work much better.
>
> > I don't like the oil pressure switch idea simply because there may be
> > situations where you make the educated decision to fry your engine to
> > get out of harm's way. but that's just me.
>
> Not sure I understand...
>
Let's say you spin a bearing in the hammer lane of the freeway, or you
run over some unavoidable debris that holes your oil pan. Oil
pressure suddenly drops to zero. However, to get over to the
shoulder, you still need power to merge through three other lanes of
traffic... Also, with the oil pressure switch, you won't have
immediate fuel pressure for lightning-fast starts unless you also
incorporate some kind of timer running off the rising state of the
ignition switch; the engine will have to crank over and build oil
pressure before the pump will start feeding the engine.
> > The VW relay works like this; when power is applied to it (i.e. you
> > turn the key on) it will run for 5 seconds and then shut itself off -
> > this pressurizes the fuel rail for initial startup. Then when it
> > starts receiving pulses from the coil, it will latch in until it no
> > longer receives a signal from the coil.
>
> Didn't know that was how VW did their fuel pump relays.
> Gotta store that one in the data banks.
> Thanks.
If you or another poster wants scans of the factory diagrams showing
how to wire it up, I can try to accomodate... I am actually
contemplating just this kind of thing for my '55 Stude if I ever go
with an electric fuel pump. (the stock mechanical pump is LOUD and I
don't know why; I've tried several different pumps including one NOS.
Works fine, but it sounds like a rod knocking at idle, which is bad.)
So I've already taken a stab at puzzling out the factory diagrams (I
have several Bentley manuals for various VW's I've owned) but haven't
gotten as far as sketching a simple "retrofit" diagram. I think you
probably just need switched power, ground, battery power, coil, and
output to fuel pump, but I can't swear to it. i'd probably throw an
"ice cube" at it to take the load off for a heavy-draw racing pump.
i'd be willing to bet that other mfgrs. use a similar fuel pump
control scheme; I just happen to be *familiar* with VW's so that is
what I suggested.
nate