TPI 350 oil problem

[Shannen Durphey]

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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