Need wire schmatic for oil pressure sending unit.

91 Lincoln Conti Ex · #1 April 20th, 2007, 01:11 AM

Does anyone out there have the wire schmatics for the oil pressure sending unit to the oil pressure gage in the dash on a 1991 Lincoln Continetal EX with 3.8 liter engine? I just replaced the sending unit and I'm still getting an intermittant drop of oil pressure on my dash gage. I know its not actual oil pressure drop of engine or engine would be locked up by now and it does not have any lifter noise when this happens. I've driven car for 25 miles or more at 70 MPH with the gage showing almost zero pressure. It shows just one bar on the gage when it happens then few minutes later it pops back up and shows normal again, four bars.

I also would like to know what is the sensor that screws into the side of the oil pan called and what does it do? It's not a knock sensor is it?

Any help and answers would be greatly appreciated!

ekooke · #2 April 20th, 2007, 08:14 AM

The sensor on the side of the oil pan is for checking oil LEVEL. As far as your oil pressure (OP) goes, check the OP port with a MECHANICAL gauge. If it has the same readings as the one in the car, it's probably a plugged sump screen for the oil pump. If OP shows OK on the mechanical gauge, it could be an intermittent ground connection on the electrical gauge.

MichiganTeddyBear · #3 April 20th, 2007, 10:41 AM

Bad solders on the back of the cluster (where the harness plugs into the circuit board, black connectors) will also cause the oil press gauge to drop to 0 intermittantly.

I know this from experience (my 91 was same way, as well as check DCL, and other intermittant sensor problems).

91 Lincoln Conti Ex · #4 April 21st, 2007, 02:14 AM

Thanks ekooke and MichiganTeddyBear for the replies. As for having plugged oil sump screen I would think it would cause lose of oil pressure which in turn would cause lifters to rattle. IF I can borrow a mechanical gage some where I will double check it any ways. I will also pull out the dash to see if there is any corrosion any wheres and any bad solders joints. Still would like the schmatics tho if someone has them. Again Thanks!

MichiganTeddyBear · #5 April 21st, 2007, 08:08 AM

I will try to get them posted this weekend, but if I dont, I am sure someone else will.

MichiganTeddyBear · #6 April 21st, 2007, 08:24 AM

ok.. well, I just looked at the circuit to see how complex it is and how much work it would be to post it..

lemme just say, no need to post it.

This info is from a 92 manual, but found to be accurate on my 91.

oil press sender feeds the cluster via 1 wire, W/R, all the way to the cluster, pin #1, connector C256. one other connector in the circuit, C107 which is located "lower LH front of engine". in pic, it looks like its just above the bellhousing. but that pic is so cluttered, its hard to read.

single wire, only 2 connectors, one at the cluster, one mid-harness. The manual shows it as a 'switch', with normal oil pressure closing the switch (grounds thru the block).

ekooke · #7 April 21st, 2007, 09:41 AM

Quote:

Originally Posted by MichiganTeddyBear

single wire, only 2 connectors, one at the cluster, one mid-harness. The manual shows it as a 'switch', with normal oil pressure closing the switch (grounds thru the block).

That's another thing to consider. Ford did something devious starting in the late '80s with their pickup trucks and then did the same thing to the car models starting in the early ‘90s that still had oil pressure gauges; they made idiot light functions into something that LOOKED like oil pressure gauges, but they were just really on/off indicators, just like an idiot light. The way to tell is to look at the oil pressure sender down by the oil filter. If the sender is just the 'button' type of sender (snap switch), the car has a dummy gauge. Only if the sender is the 'can' type (much larger), is the sender and gauge "real". To compare the two types of senders, look at this TECH article that shows both types: http://www.lincolnsonline.com/tech/00041.html

91 Lincoln Conti Ex · #8 April 22nd, 2007, 10:19 PM

Thanks again ekooke and MichiganTeddyBear for the replies! I will try to check the wiring using your description MichiganTeddyBear.
ekooke I will also see if when I installed the new oil pressure sending unit if the one I got was for a gage or "idiot light".

nowers · #9 April 24th, 2007, 05:49 PM

You do not have low oil pressure! There is no doubt that you are experiencing an intermittant connection in your instrument cluster. My 91 exec has done the same thing for many years and still does. I disabled the annoying bell tone and forget about it.

If you remove the instrument cluster, you will see the most mickey mouse connector you've ever seen in an auto.....let alone a luxury car. I suspect that's where the intermittant connection occurs. I also experience problems with my fuel gage and all other information systems.

Worst of all, the alternator depends upon one of those connections to excite its field. (and to warn of no charge) When that fails you think you have a bad alternator.

BAD FORD! BAD FORD! BAD FORD!! GO TO YOUR ROOM