oil pressure gauge low- 1990 4.3 merch v6

[al0311]

hi all new here to forum and boating in general. I have a 1990 4.3 v6 mercruiser. the other day when starting it I noticed that the oil gauge was reading zero.
Checked the oil, oil is full no sure where to go from here.
been reading on a few forums and they said to ground the oil sending unit wire? I did look at the engine and i couldn't find it I'am assuming its near the oil filter but I couldn't see anything. any ideas of where to look? and to what it looks like?
then I read I should do a mechanical gauge test. I'm at a lose of where to I would hook in the gauge into the motor? and then just turn it over and see where the gague pings?
If the pressure reading on the gauge is zero then I should assume my oil pump is shot?
I hope its just the gague on the console not reading right....
thanks for any information and help

 

[alldodge]

Howdy

Did this low pressure just start showing up or has it been getting worst over time?

Look for the sender (item 10) below and behind the distributor. To install a mechanical gauge you will need to either remove the sender, or put a Tee fitting in so you can have both connected.

http://www.mercruiserparts.com/bam/subassembly/31478/951/70

To test the gauge, turn key ON then remove the sender wire and ground it on the block. If the gauge pegs high then gauge is good. If it does peg install mechanical gauge to see what your getting

If it does not peg, then go to the gauge and see if there is 12V on the purple wire with the key ON. Gauge should also have a good ground. With key on ground the sender post wire which should be light Blue. If gauge pegs its good and the sender is the issue.

 

[al0311]

Howdy

Did this low pressure just start showing up or has it been getting worst over time?

Look for the sender (item 10) below and behind the distributor. To install a mechanical gauge you will need to either remove the sender, or put a Tee fitting in so you can have both connected.



To test the gauge, turn key ON then remove the sender wire and ground it on the block. If the gauge pegs high then gauge is good. If it does peg install mechanical gauge to see what your getting

If it does not peg, then go to the gauge and see if there is 12V on the purple wire with the key ON. Gauge should also have a good ground. With key on ground the sender post wire which should be light Blue. If gauge pegs its good and the sender is the issue.

Thank you so much for your help I was able to locate the sending unit and I grounded it and The Gague pinged. I will go tomorrow and get a mechanical gague and test that.
It only pinged when I pressed it pretty firm to the motor does that mean anything ?
When I do the mechanical gague and it doesn't show no pressure should I assume the oil pump is bad ?
Thanks so much

 

[alldodge]

Thank you so much for your help I was able to locate the sending unit and I grounded it and The Gague pinged. I will go tomorrow and get a mechanical gague and test that.
It only pinged when I pressed it pretty firm to the motor does that mean anything ?

Maybe a bad connector on the wire connector, may need replaced

When the mechanical gauge doesn't show no pressure should I assume the oil pump is bad ?

No, it could be the pump but it could also be the bearing surfaces are to large. If it is real low pressure, its rebuild time

 

[al0311]

Maybe a bad connector on the wire connector, may need replaced



No, it could be the pump but it could also be the bearing surfaces are to large. If it is real low pressure, its rebuild time

Okay thank you for helping me I'll get back to you tomorrow with an update thanks again

 

[al0311]

Maybe a bad connector on the wire connector, may need replaced



No, it could be the pump but it could also be the bearing surfaces are to large. If it is real low pressure, its rebuild time

Sorry for the late reply I was in the process of rebuilding my carb due to a no idle situation. But that's done now. Now that it's running the reading I get on the gague says around 30,000 is that low ? It seems to drop a little after it's been idling for a while.

 

[al0311]

I'm sorry 3,000 psi

 

[Baylinerchuck]

Do you mean 30 psi? My 1990 4.3 runs about 45 to 50 psi.

 

[al0311]

Do you mean 30 psi? My 1990 4.3 runs about 45 to 50 psi.

Yes sorry 30 psi
Would you say that is low ?

 

[alldodge]

Yes sorry 30 psi
Would you say that is low ?

Depends on what rpm you had the reading, was it at idle or WOT?

 

[al0311]

Depends on what rpm you had the reading, was it at idle or WOT?

That was at idle.

 

[alldodge]

That was at idle.

Your in good shape :thumb: