Delayed onset of Oil Light

Here's the symptom; it started today. Started car, drove down the road, after 3-5 minutes, the oil light comes on? Thought I might have a loose wire when it happen this morning, but it checked out OK. Then again on the way home, and same when I drove somewhere else tonight. Topped up oil, but it didn't need much, so oil levels were OK. The light isn't coming on immediately, but only after a little bit of time on the road. So what could this mean? I have a couple of thoughts.

a/ Oil pump starting to go bad?
b/ A blockage/restriction has developed in one of the oil channels
c/ Both of the above.
d/ Something I haven't thought of......

What do people think? What would be your first course of action? I'm thinking the first course of action might be an oil and filter change, and maybe using one of those oil flush additives in the oil just before the change.

Teddy

Start with the cheap stuff. Replace the sending unit and see if that fixes it.

Also hook a cheap gauge to the engine and see what it reads.

Teddy, do as Jack said, hook up a mechanical guage. If you loose pressure after driving, look for a clogged up oil pump screen.
To fix that you will have to drop the pan & clean out the sludge in the lower end. Bill

Thanks for the replies. Jack, your suggestion re: the oil gauge is probably a good one, as I currently have no idea what sort of pressure I'm getting. I'll start looking into that. Bill, dropping the pan probably makes a lot of good sense. I suspect the oil pump could do with some attention and TLC to make sure its still going well. The only problem I've got with that is that when I looked up the procedure for taking the sump off, there seemed to be a lot of other things I'd have to do, and I'm not well enough equiped. Apparently (according to the instructions in the manual) I have to get the stabaliser bar off, and I don't think I can easily do that in my own garage. I'll keep reading and thinking for the moment.

Regards,

Teddy

Teddy-
did you ever solve the problem?
I have a similar problem. I have a 1963 Comet with a 1970 Falcon 250 ci, I honed and re-ringed in 5 years (10 k) ago. I drove it 400 miles from SF to LA and it ran fine at 60-70 mph. But on the way back my oil light began to come on after 5 minutes of driving, first a faint flicker then a steady glow. If I shut the car off and waited 15 minutes the light would turn off, and turn on again after a few minutes of driving. My plan for the weekend is to...
1) check the oil pressure with my gauge
2) change the oil, filter, and pressure switch
3) if that fails then pull the pan and check for blocked oil pickup screen

Other suggestions?

Thanks-
Marc in SF
63 Comet Ragtop 250/C4

I like to run both a gauge and the stock light. You might also check the wire connection at the sender they will get dirty or can be a lose fit.

bubba22349":2jvdkdds said:

I like to run both a gauge and the stock light. You might also check the wire connection at the sender they will get dirty or can be a lose fit.

Click to expand...

Yeah, 2 X bubba baby. I'm a rank beginner, but that allows out-of-the-box-thinking ie don't forget the possability of an ele. issue (no stone unturned). I had vehicles of the era do that for yrs :nono:

MercuryMarc":3vbbj0jc said:

Teddy-
did you ever solve the problem?
I have a similar problem. I have a 1963 Comet with a 1970 Falcon 250 ci, I honed and re-ringed in 5 years (10 k) ago. I drove it 400 miles from SF to LA and it ran fine at 60-70 mph. But on the way back my oil light began to come on after 5 minutes of driving, first a faint flicker then a steady glow. If I shut the car off and waited 15 minutes the light would turn off, and turn on again after a few minutes of driving. My plan for the weekend is to...
1) check the oil pressure with my gauge
2) change the oil, filter, and pressure switch
3) if that fails then pull the pan and check for blocked oil pickup screen

Other suggestions?

Thanks-
Marc in SF
63 Comet Ragtop 250/C4

Click to expand...

8) marc, start by replacing the sending unit. i had a similar issue with my 64 falcon a few years ago, and it turned out to be a bad sending unit.

Just a little FYI here.Some of you guys and gals out there might already know this,but here it is again.
IF the sending unit only has ONE wire hooked to it,DON`T use teflon tape or any sealer on the threads,as the sender grounds through the body of the unit to the block.By using thread sealer of any type,you can insulate the threads fron the block,resulting in a lousy ground situation and erratic sender performance.
Good luck.Have fun.
Leo

Leo, RB, Chad, and Bubba,
Thanks for the suggestions. I replaced the sending unit and checked the wire, and still has the light on. I changed the oil, changed the filter, and installed a $20 oil pressure gauge (with $10 of brass fittings...) and the light pressure seems to be fine- 45 lbs at idle, a bit higher at higher RPMs. I will run the car a bit longer later tonite and see what happens. I wonder if the problem was with a sludged filter- the oil was quite dark and I had not changed it in a while.

Marc in SF
63 Comet 250/i6

MercuryMarc":208rk79r said:

Marc in SF
63 Comet 250/i6

Click to expand...

a sludged filter
'Twould B nice. Keep yer eyes (nose, ears, etc) opened tho...

Update-
Took it for a spin.
Here is what happens after operation for 30 minutes...

40-45 psi when driving over 20 mph
(my 1978 Shop Manual says oil pressure 40-60 psi when hot at 2000 rpm so I think that the driving pressure is fine).
17 psi in neutral at idle when warm (210 degrees when my electric fan kicks in)
14 psi in drive at idle with very low RPM

These low RPM numbers seem low but I am not sure.
Comments appreciated!

Thanks-
Marc in SF
63 Comet 250 i6

I changed the oil, changed the filter, and installed a $20 oil pressure gauge (with $10 of brass fittings...) and the light pressure seems to be fine- 45 lbs at idle, a bit higher at higher RPMs.

Click to expand...

thats great oil pressure you know it is safe!

I replaced the sending unit and checked the wire, and still has the light on.

Click to expand...

You might also check the wire or replace it from sender unit. Have seen them ground out from cracked or missing insulation in spots or pinched.

That should be all right your oil light is set to go on at about 4 psi. As RPM goes up you need more psi.

IIRC.Rule of thumb is 10 PSI per 1000 RPM of engine speed.
Leo

Thanks everyone!
I have ordered the rest of the fittings from Summit and when they arrive I'll hook up a dual system with the light and the mechanical gauge. That way I can check the light and gauge simultaneously.
Marc in SF
63 Comet 250 ci