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.
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.
nate
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