I'm having some oil pressure problems with my SPI (93, 1275). It's not injection related so I'm posting this in the general forum - hope that's OK.
So, here are the symptoms:
The oil light comes on every now and then. Only at idle and it seems that it is only when the engine has warmed up a bit (doesn't have to be hot, but the light doesn't seem to come on after a cold start). I have the original (7-10psi) oil switch and the pressure release valve is the non-adjustable spring and cap type. I hooked up an oil pressure gauge and the pressure seems to creep up very slowly on start-up. it will then sit at about 20-25psi if the engine isn't revved. A decent bit of gas (~3000rpm) and the pressure shots up and hovers around 50-70psi. It isn't all over the place, but it does go up and down a bit - there don't seem to be any sharp jumps in pressure, but that may be the gauge. After revving it sit's at 50-70psi for a while, even at idle. After about a minute of idling the pressure slowly drops until the light goes on (0-5psi!!), a quick rev and it shoots back up and stays high until it's been idling for while. The cycle continues...
I thought the release valve may be sticking open. I pulled it out and it has some serious gouges in it (I recently rebuilt the gearbox and the amount of loose metal in there was unreal - there was even a munched up needle bearing cage attached to the sump plug). I am a bit concerned about this but confident that I won't see this again if I replace it. I cleaned it up a bit but couldn't get a good look into the recess to see if the guide in the block has been chewed as well. Cleaning off the burrs didn't make a difference, my next step would be to replace it with a ball and spring type valve and to make sure the guide is smooth.
I am also wondering if the oil pump is on the way out. I don't think so as the pressure is good most of the time. I can't imagine how the pump could cause this sort of problem - but I'm open to an education :)
If it is the pump I think I'll have a breakdown - I just got the gearbox rebuilt and the motor back in! I didn't bother to look at anything attached to the block as it 'was running really well'! Live and learn I guess.
This problem is new since the gearbox rebuild. The only change that I think could affect the pressure would be the central oil pickup I installed.
Any thoughts/ideas or even better solutions?