i have read 20 pages of search w/o finding my issue. so here goes . looking at buying a 83 sd 270,000 miles not started for 6 months . i put in my battery & it started on the 1st turn over. so great oil pegged at 3 quickly. then dropped to 2 1 0 I reved the motor a little still no pressure . so i shut it off check the oil on dip stick ok. no odd noises. looked in the oil cap appeared to be oil there. so i restarted it . same stuff full oil pressue immediately then drop to zero . quit at that point to seek advice.
soooo is it the oil sending unit? bad pump ? something to do with sitting for so long ?

help

thanks in advance
JOHN M

There are a few things could cause the oil pressure to read zero on this car, and most are not real good.
First to check would be the oil sending unit. Having sat for some time, the sending unit could be plugged, or the wire to it could be corroded off. The sending unit is mouinted below the oil filter cannister. You would need to get under the car to get to it.
Next possible is the oil pump. It is accessable through the small crankcase pan under the engine. It could also be plugged up, or the crankcase could be all gunked up. That oil pump is chain driven. Has a small chain that goes around the end of the crankshaft and spins the oil pump itself. Not unheard of for that chain to break, but not common either.
Of course the oil pump could be worn out. To check that remove the valve cover and hand crank the engine over, use a 1 1/16 socket (or the 27mm) to turn the crankshaft bolt and see if oil circulates through the oil gallies up there. It should be very apparent with even a little turning of the crank. If that don't happen then either the oil pump is out, the chain is broke, or all of the oil passages are plugged. Not a good outlook.
You sure you want to take on this one ? There are a few other things could have happened. The sending unit wire could be off broken anywhere.
Well, good luck.

thanks for the quick reply . i will check the sending unit wire tonight.
why does it register full pressure and then drop to zero?
that is what does not make any sense?

JOHN M

Don't know why, but anything can happen with oil lines and wires. Be carefull running the engine. That engine has solid lifters and by the time you hear anything it would be too late, you would have done big time damages to the engine.

need more help .
see 1st post
THANKS
JOHN M

Find a mechanical gauge and install it at the oil filter housing and check to see what's going on -- sending unit could be bad.

Otherwise, sounds like the relief valve is opening and staying open. Fresh oil MAY fix that, but I'd presonally replace it (must replace the housing, I think).

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

THIS CAR HAS AN ELECTRIC oil sending unit. so dont know how i would put a mechanical guage on it.
ideas?
thanks for your help.
JOHN M

Madsen,

Remove the electrical sensing unit and plumb the mechanical gage into the hole where the electrical unit came out.

I'm also suspicious of the oil relief valve. The spring could have broken while the car was sitting.

P E H

i went back & started it up again. took off the oil cap & looked to see if there was oil. there was oil running out of a hole on the top rail above the cam.
so does this mean that there is oil preassure & it is just not registering or does it mean nothing?
the guage did the same thing went to 3 & then slowly dropped to zero
help
thanks in advance
JOHN M

Madsen,

Seeing the oil run out of the cam lubricator means oil is getting to the engine initially when the oil pressure (OP) is up. The problem is why the OP drops.

I still think the first thing to check is the OP relief valve if you are sure the gage is correct.

P E H

starting it; and the pressure is dropping to 0 psi, you will destroy the engine.

After oil guage went to zero i went out & saw that there was oil pumping out of the top rail above the cam. So does this mean i have pressure just not reading it or still no pressure?
thanks for your help.
JOHN M

Madsen,

That oil is getting pumped thru the engine when the engine first starts is shown by the OP showing on the gage and the oil coming out of the cam oiler.

That's why I think the problem might be the OP relief valve. The valve closes when engine is not running but opens too soon.

P E H

Disconnect the oil pressure sender at the oil filter housing and temporarily install a shop mechanical gauge to test and you'll have your answer. Thread size is 12 X1.5, I think. Might be 1.25. The mechanical gauge just connects a small tube with a compression fitting to the housing; like on any older 123.

__________________
The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

THANKS I WILL GO GET THE PARTS TO DO THE TEST

john m