Oil Pressure Low
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Junior User
Joined: Sep 2003
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Oil Pressure Low
My van has been driving fine, 91 E150, and the other day i get in it to drive and the Oil pressure gauge is at L or sometimes less. Sometimes it will raise into the normal level and stay for the rest of the drive, othertimes it will not move from L or sometimes slowly go from normal to Low. The car sounds and drives great, but I don't want to end up replacing an engine, at least not yet 
. Has anyone had this particular problem, or if it is the gauge could you point me in the right direction as to where the wires are located on the engin?
Thanks!!
. Has anyone had this particular problem, or if it is the gauge could you point me in the right direction as to where the wires are located on the engin?Thanks!!
Mountain Pass
Joined: Jan 2003
Posts: 136
Likes: 1
I believe that the 91 gauge is a fake one. That is, it is a calibrated idiot light. The sending unit is for an idiot light. I have the same problem with my 95. Gauge is all over. I don't worry about it due to the gauge being fake. There's an article on this site about making the gauge real. In the meantime, if you want to replace your sending unit, it is behind the power steering pump on the 5.0-5.8 and on the driver's side of the block on the 4.9.
Hope this helps,
Tim in Detroit
Hope this helps,
Tim in Detroit
Post Fiend
Joined: Jun 2001
Posts: 5,228
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From: Running Springs CA
This problem is often caused by a loose/corroded connection at the sending unit, a simple fix. Test the guage itself by grounding the sender lead on the engine. The needle should read right in the middle. If you have a 302-351 the sending unit is located just forward of the oil filter.
Jim
Jim
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Joined: Jan 2003
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From: Still under the hood in O
For peace of mind, the safest bet would be to obtain(beg/borrow/steel) a mechanical gauge and test it. You don't need to perm mount it, just hook it up temporarily under the hood to test it. But check the guage first since that's an easy and free test.
Laughing Gas
Joined: Mar 2003
Posts: 877
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From: Colorado, U.S.A!
On my 89, the oil pressure gauge wanders in unison with the water temp. and fuel level gauges. I was advised that this was a ground wire problem, but i haven't addressed it yet. I have a mechanical oil pressure gauge teed in with the factory sending unit. The mechanical gauge reads consistently while the factory gauge wanders.
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Update--
I changed the oil today Motorcraft 5W-30 and a Motorcraft filter. When i drained the oil out it seemed a bit "thin" like water?? a little bit of a gas smell. Since I changed it, I have driven about 20 miles and the Oil Pressure gauge has stayed in the normal position. Hmm. Could the Low pressure be due to cheap Firestone Brand X oil and filter.. or is something leaking into the oil to make it thin... The oil level has stayed at the correct reading since it was last changed. Thanks, 91van
I changed the oil today Motorcraft 5W-30 and a Motorcraft filter. When i drained the oil out it seemed a bit "thin" like water?? a little bit of a gas smell. Since I changed it, I have driven about 20 miles and the Oil Pressure gauge has stayed in the normal position. Hmm. Could the Low pressure be due to cheap Firestone Brand X oil and filter.. or is something leaking into the oil to make it thin... The oil level has stayed at the correct reading since it was last changed. Thanks, 91van
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Joe Kucinski
Lead Driver
Joined: Feb 2003
Posts: 8,140
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From: Oak Harbor, OH
If it's a 302 I wouldn't run anything thinner than 10w30 in it. The higher the mileage gets the more the bearings and everything get work out, so the clearances open up needing a thicker oil to fill the gaps, this can cause low oil pressure. Howerver if it wasn;t making any noise then it's just the gauge.
Mountain Pass
Joined: Jan 2003
Posts: 136
Likes: 1
Hey 91 van,
Tim in Detroit (actually New Baltimore) again.
Ya, mine does the EXACT same thing as yours. When cold, no reading. Then it comes up. Worse on cold mornings. Motor is fine. Been doing this for a year now, and I just haven't gotten around to fixing it. Sometimes, it even wanders when warm. Did this all the way to S.W. Kansas last winter, and all the way back. On the way back, I had a car trailer with a '50 Mercury on it. All is well. I'm sure the problem is just the gauge, just like mine.
Tim in Detroit (actually New Baltimore) again.
Ya, mine does the EXACT same thing as yours. When cold, no reading. Then it comes up. Worse on cold mornings. Motor is fine. Been doing this for a year now, and I just haven't gotten around to fixing it. Sometimes, it even wanders when warm. Did this all the way to S.W. Kansas last winter, and all the way back. On the way back, I had a car trailer with a '50 Mercury on it. All is well. I'm sure the problem is just the gauge, just like mine.
Post Fiend
Joined: Jun 2001
Posts: 5,228
Likes: 5
From: Running Springs CA
The connector on the sending unit is a very poor push on type. If it is loose, temperature and voltage variations will cause changes in readings. Make sure the connecton is clean and tight.
Jim
Jim
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Joined: Mar 2003
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From: NE TX
On higher mileage engines and heavy service engines or some that lack maintenance, the oil pickup screen in pan going up to oil pump can carbon over restricting oil flow to the pump. When ever I have the pan off I remove the metal cover over the screen with tin snips, pliers and screwdriver. It is pressed on. This lets all the screen show and effectively doubles the amount of oil that can get in to pump. Without high volume oil pump it will cause no problems. I don't have experience with high volume pumps because they can suck pan dry and ruin bearings under some circumstances. I do hope it is a gauge or sending unit problem but please don't assume so. The test described above is easy/cheap enough. It'd be even better if you fixed it. It beats ruining the engine and walking.