aarcuda69062 wrote:
> In article
> <1174508586.907025.68800@b75g2000hsg.googlegroups.com>,
> "N8N" wrote:
>
>
>>>>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.
>
>
> When the OP stated that this installation was in an older car, I
> assumed* it was a carbureted vehicle.
> (* TMOAFU's)
So was I, honestly... my only carbureted car tends to sit for weeks at
a time, so it takes a bit of cranking to fire it. That's a selling
point to me of an electric fuel pump - no worries as to whether the
battery is going to run down before it lights off.
>
>>>>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'll take a look thru Mitchell on Demand and see if I can pull up
> a schematic.
>
>
>>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.
>
>
> Similar in that a tach signal is needed, but they usually rely on
> the engine computer to recognize it and thusly control the FP
> relay. That VW has this ability self contained in the relay is
> intriguing.
Yup, it's all in the little relay. The downside is that the socket is
generally contained in the main fuse block, so the OP's idea of using a
pre-made socket would probably involve a hacksaw, unless a generic Bosch
relay socket has the right holes in it.
nate
> A pre computer era example would be the Chevy Vega (spit) and its
> variants, carbureted engine, electric in tank fuel pump
> controlled by an oil pressure switch.
> A post computer GM car would have the FP relay and the oil
> pressure switch in parallel
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