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Somewhat low oil pressure: Gauge or... ?


Guest Anonymous

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Guest Anonymous

I installed a VDO 150 psi electric oil pressure gauge on my stock early '71 (now 125k miles) last summer before O'Fest, using a dual-terminal sender and an adapter. Since then, running 20W50 oil, I have never seen much higher than 60 psi on the gauge, even on cold startups last winter (when I should have expected, based on others' experience, to have seen over 100 psi).

I usually see between 30-45 psi while driving at any speed with the engine warm. At warm idle, it will dip to around 15 psi, but the idiot light remains dark. It will occasionally flicker at idle after an extended highway run on a hot day (like parking at a rest stop). At times, even at highway speeds, the gauge will drop to around 15 psi without lighting the idiot light. Sometimes rapping hard on the gauge will cause the needle to jump up briefly, but it then falls again, often surging up on its own later to the 30-45 psi range.

I'm a bit confused and slightly concerned about the long run to Texas in October (can't afford O'Fest but will caravan down and spend the week with family in Longview). At any rate, is this likely a gauge, sender or more serious problem (i.e., oil pump)? Should I take it somewhere and have 'em put a mechanical gauge on there? I need to start moving if it will need attention before the trip.

Thanks!

-Dave

Colorado '71

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Guest Anonymous

1. Gauge wiring, especially grounds and the terminals on the sender unit.

2. VDO dual sender has idiot light set to go on around 15 psi; stock sender is about 7 psi (1/2 atm)

3. If you can find one, hook up a mechanical guage temporarily to check the engine's oil pressure.

4. Remove oil pressure check valve, clean spring, ball and orfice then replace.

My 69's original engine with 211k will flicker the oil light at hot idle with 20w-50 oil and after a long highway run show about 45-50 psi at highway speeds (3-4k rpm) on a warm day. The 73 with 196k runs about 60 psi hot on the highway and 25-30 at hot idle.

Bet it's the gauge, or a sticking check valve...

Mike

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Guest Anonymous

Something isn't right. The reading is too low, particularly on cold starts - my gauge regularly pins at 150psi when cold if ambient temps are below about 60F. Hot operating pressures should be somewhere around 12-15psi/1000rpm.

First off, make sure the wiring is correct and that you've got the wires on the sender correct (WK to the idiot light, G to the gauge) and that the sender is cleanly grounded through the threads (this is a common problem if you used teflon tape to seal them - use one drop of blue Loctite only). Check the voltage to the gauge - it should be very, very close to the operating voltage of the system or you will get slightly lowered readings.

If all of these things check out, get a mechanical gauge and check the actual pressure. If the readings are the same as with the electrical gauge, you have some sort of internal engine problems.

Good luck.

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Guest Anonymous

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i probably have the same gauge you have( vdo off the dual sender) and i see similar numbers . I am running thin oil for break-in, and that will have a small effect on oil pressure, but i am seeing around 45 psi on cold start-up at 1700 rpm idle. But, my oil light goes out immediately after ignition: that is important! When oil temp is up to normal range ( around 160-180 degrees indicated) i am seeing about 10 psi for every 1000 rpm. That is a normal equation. At hot idle, i am at 15 psi and i get a light flicker once in a while too when I engage clutch to go uphill if i have not goosed the engine up to 1500 or so. I was hoping to see higher oil pressures on a brand new pump/engine, and i may see some improvement once i get some good oil in the car. Also, i cannot get into 4k plus range sustained yet, so i dont get to see what the pump really does in the 4-6 k range. But your numbers sound about right. I remember when my oil pump went bad in my Sahara : on start-up, the oil light stayed on for a long time. That is one very good indicator that the pump is on its way out. Some people say that you may see really high pressures, before it dies too- kind of counter-intuitive to me. If you can get a better/more accurate pressure read-out from a shop, it might indicate pump is o.k., or that pump needs replacement. I think that is a good idea before you tear into a swap job.If you have to throw a new pump in, it is a PITA with sway bar and subframe on, but it is do-able. It will help to raise engine a bit if you can. lots of posts on how to manage that at home with home materials. dont forget to take dizzy cap off before you move the engine up . Hope you get it sorted -out before the road trip: that is definately a car-"life-threatening" situation that is best rectified at home . Those pumps are expensive as it is! get a new pan gasket too if you do the swap. good luck///

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Guest Anonymous

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too. I have the 3 gauge pod and the volt meter does wacky stuff occasinally. i dont like hitting the pod( too often) to get different results. Time to tear into the whole damn thing and redo all connections. Now that i have read your posts, and reflect on gauge read-out history with old engine and new engine, i definately need to get in there and check I bet that will give me more accurate readings once i clean and secure all connections and check voltage . Thanks guys.

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