oil pressure questions

50 Proof · Jan 28, 2012

An interesting problem is starting to develop on my '01 Bullitt with 110k miles. Immediately after I start the engine in the morning the oil pressure gauge goes up to its normal position then the needle drops all the way down, appearing as if I've lost all oil pressure. The needle will stay down for a couple of seconds then pop back up to the normal position. It'll repeat this once or twice more before staying in the normal position. So far I've only seen this occur in the morning when I start the car up for the first time for the day.

Does this sound like a bad oil pressure sending unit, bad gauge, oil pump starting to go bad? Anyone else experience this before?

wmburns · Jan 28, 2012

Just wondering if you know that the oil pressure sending unit is a simple on/off switch. If the oil pressure is above 6 PSI, it's grounded. Otherwise it's open.

The analog dash needle is really an idiot light. The needle position is meaningless. The sweep of the needle does not indicate the amount of oil pressure.

For further proof of this consider has there ever been a motor that has the exact same oil pressure cold as hot? How about the same at idle vs. WOT?

The oil pressure sending units do go bad. The electrical connection can get dirty/loose causing an intermittent reading. However, one would expect this to occurs at other times not just when cold.

If this were my car I would be tempted to change the oil pressure sending unit just because it’s easy and cheap. Then if the problem continued, likely the low oil pressure is real.

If the oil pressure is really right at 6 PSI cold, that’s very low oil pressure. IMO it should be investigated further.

1987stangman · Jan 28, 2012

I acually just ran into this same exact issue only sometimes it would do it and then be fine for 3 or 4 days. Changed the sending unit on the oil filter adaptor and never had an issue since. Removing the sended and reinstalling a new one could not be any easier to DIY right in your driveway.

musclemustangcb · Jan 28, 2012

I'm having the same exact issue, I troubleshot it and found that the wire broke inside the insulation right before the sending unit. I cut the wire back,changed the pin in the connector and bam! Proper readings all over the place!!!!!!!

50 Proof · Jan 29, 2012

Thanks for the input guys. I'll inspect the wiring and replace the sending unit if the wiring checks out fine. If it still acts up after that then I'll know I have problems.

musclemustangcb · Jan 29, 2012

I'm willing to bet that this is an electrical fault. Keep us posted. Good luck dude!!!!!!!

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