TPI 350 oil problem

[Romans, Mark]

Last time I checked GM made over 90 oil pressure senders for different apps.
They do fail occasionally  :-^
Don't over analyze it, just put a sender in in.  99% sure it's a good fix.
Mark
----- Original Message -----
From: "Shannen Durphey" <shannen at grolen.com>
To: <diy_efi at diy-efi.org>
Sent: Wednesday, May 31, 2000 7:39 PM
Subject: Re: TPI 350 oil problem


> dzorde at erggroup.com wrote:
> >
> > Fellow efi'ers.
> >
> > I'm really hoping someone can help me with this one.  Although not
exactly an
> > efi problem it does relate to my TPI 350Chev.  In the last few days it
has
> > started on this weird problem which only happens when the car is HOT.
Whenever
> > you are idling the oil pressure will steadily climb to 100psi (limit of
gauge,
> > so it could be more) then slowly come down to 70ish psi and climb again.
It
> > will do this till the revs are increased to 1300rpm or more, at which
point the
> > pressure will come down to 54ish psi where it has always been since the
engine
> > was built years ago.
> >
> > It uses a hi-volume oil pump and has the oil changed regularly.  I'm
still using
> > the same brand oil and filter I have always used.  Normal driving and
idle is in
> > the viscinity of 54ish psi depending on temperature and the revs used.
Hence
> > this sudden phenomen has me puzzled.  If it was an oil pump problem I
would
> > expect low oil pressure, not a cyclic pressure and since it doesn't
happen when
> > the car is cold it has me at a complete loss.  I can't really see how it
can be
> > a faulty pressure sender unit,
>
> What?!!  Who needs test instruments, when we can make guesses like
> this one so much easier!  You're definitely not speaking like someone
> that has turned wrenches for a Chebbie dealership, or you'd know that
> GM sending units fail.  Just busting chops... : )  Get a mechanical
> gauge and confirm the pressure readings.  The senders really do fail,
> and they give some strange readings.  Like climbing to full pressure
> then quickly dropping where it's not expected.  You could also use the
> throttle and try to see exactly what oil pressure causes the trouble.
> Slowly increase/decrease rpm until the gauge goes nuts, then continue
> to change rpm and see if readings return to normal.
> Shannen
>
> BTW, when you get done with yours, you can come over and fix mine.  It
> rises from 20 psi to 80 and drops down to 45, all in about 1500 rpm.
>
>
>
> so my guess is that it is an actual oil system
> > problem.  My initial question is can it be a sticky valve in the oil
pump as it
> > seems like pressure builds up in the system and is then released so it
can build
> > up again ?  but then I wouldn't think the pressure relief valves would
be
> > operating at idle rpm.
> >
> > rgds
> >
> > Dan  dzorde at erggroup.com
> >
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