low oil pressure

[kcmd]

Hi my Nissan 2.7 turbo diasal I have had 3 yrs in a project boat all new seals fillter has been running perfectly its not had a propper run as its going in the water this easter, now its decided to show me on tick over a flickering needle,as i rev it,oil pressure seem to drop on the gage the oil light go out as soon as it start.
This engine is sweet as a nut, no oil burn very clean exust.

As im here another Q I have an out board petrol tank for my diesal it has a rubber hand pump the cap has a air screw do i need it open or closed, and if I loose pressure in the hand pump line will this affec my diesal supply to the engine as a couple of times my engine will splutter and die with smoke from the exust when i pump the hand pump so it is hared with pressure its semm to work fine a mind bender for me as im trying to irone out any problems befor i get it in the water.

[Adler]

Dear kcmd,

Before any discussion regarding the referred issue, please inform us if your engine is supported by any kind of Oil/Soft Water Heat Exchanger ; adding to that I would like to know what kind of Soft water Heat Exchanger is installed:
1. Air / Soft Water or
2. Raw Water / Soft Water one?

[Dean Smith]

try tapping into the oil gallery with a pressure gauge for a real reading
As far as the gas outboard tank goes, it is ok but sounds like your fuel pump maybe dikky, try raising the tank above the primary pump level
Do you speak English, because you do seem to have some trouble writing it cheers

[kcmd]

Thank you for your help . I have fresh water cooled with a sea water jabsco pump feeding the heat exchanger.

Mabe some people have had a better education then others no need to be arrigant and rude over a question its a pity, for years i been admirering this site and the kind people that put there self out to help other's .

[anthony goodson]

Quite right too kcmd I can understand perfectly well what you mean ,and that is all that matters. You don't say if your oil pressure gauge is electrical or mechanical ?

[Frosty]

His oil pressure guage is electrical, mechanical guages do not act in this manner but electrical often do. A new sender should fix this common problem.

Oil pressure can be low and it can be high but it does'nt jump from high to low.

Your diesel tank needs the screw open , this is the vent that can be closed as it is a portable tank and needs to be sealed for transport.

When running it needs to be open or fuel can not be pulled out.

[kcmd]

Thank you Anthony and Frosty for your helpfal answer's to my Question's.
Frosty is right its electrical guage.

[anthony goodson]

In that case check the wiring connections on the back of the gauge ,particularly the wire to the sender . cheapest option first.

[Boston]

Originally Posted by Frosty

His oil pressure guage is electrical, mechanical guages do not act in this manner but electrical often do. A new sender should fix this common problem.

Oil pressure can be low and it can be high but it does'nt jump from high to low.

Your diesel tank needs the screw open , this is the vent that can be closed as it is a portable tank and needs to be sealed for transport.

When running it needs to be open or fuel can not be pulled out.

Actually Frosty it can. Most oil filters have a pop valve designed to mitigate pressure issues over the filter element. Its supposed to activate on start up when the oil is cool and might rupture the filter element because of its viscosity and presure. Once the oil warms sufficiently to lower the viscosity and allow effective filtering then the valve is supposed to close and the filter begin filtering.

Its a five dollar part so you can imagine how often they go wonky. A lot of the time engines that are noisy on start up simply have a bad filter. It happens more with a clogged filter but with something like a cheap Fram ( known for going bad regularly or being bad from the factory ) filter it happens all the time. If the valve gets stuck one way or the other you will see some really weird readings in the oil pressure .

might be it
might not
but for a few bucks I'd say change the oil filter and see what happens

[Dean Smith]

Originally Posted by kcmd

Thank you for your help . I have fresh water cooled with a sea water jabsco pump feeding the heat exchanger.

Mabe some people have had a better education then others no need to be arrigant and rude over a question its a pity, for years i been admirering this site and the kind people that put there self out to help other's .

i,m not being rude pulling your leg,trying to help , but if it offends i am apologising

[Boston]

oh and ya the electric ones can have false low oil readings and phony pressure readings, might be going bad and might be a contaminated connection that is shorting out

[anthony goodson]

kcmd just to clarify, has this combination of gauge and sender unit been ok so far? .If it is aftermarket what make is it. ?As regards the tank .you do not mention a return to tank ,does it have one if so how have you run it, ?Lastly you mentioned a raw water pump ,what have you done about the high pressure feed from the jet ?

[Frosty]

Originally Posted by Boston

Actually Frosty it can. Most oil filters have a pop valve designed to mitigate pressure issues over the filter element. Its supposed to activate on start up when the oil is cool and might rupture the filter element because of its viscosity and presure. Once the oil warms sufficiently to lower the viscosity and allow effective filtering then the valve is supposed to close and the filter begin filtering.

Its a five dollar part so you can imagine how often they go wonky. A lot of the time engines that are noisy on start up simply have a bad filter. It happens more with a clogged filter but with something like a cheap Fram ( known for going bad regularly or being bad from the factory ) filter it happens all the time. If the valve gets stuck one way or the other you will see some really weird readings in the oil pressure .

might be it
might not
but for a few bucks I'd say change the oil filter and see what happens

Actually Boss thats wrong, the oil pressure relief valve controls all line pressure to the filter and galleries.

The valve in the bi pass type oil filter is to allow oil to pass the filter if it becomes totally clogged---yes it will be unfiltered but better that no oil at all.

It can not be replaced --it is part of the filter.

The fluctuation of his electronic needle is very erratic --oil pressure does not act like that.

A very common electric guage problem

[Boston]

your right the pop valve is within the oil filter and cant be replaced, you gotta replace the entire filter ( $5 bucks ) but it can be defective and it can pop open at any time when it is. Means that at the pressure guage your going to be looking at a sudden drop in pressure or rise in pressure I cant remember which, I think its a drop first followed by a rise and so on. It looks a lot like a bad sensor but it cycles slower or at least it can. Oh well in either case its cheap to change and it "might" be the problem. Besides ya cant go wrong with a new oil filter. The electric senders are cheap as well, maybe $15 bucks around here. It can be the sender or it can be the contacts. One of my vehicles has a soaked sender from a punctured oil filter so I'm pretty familiar with what that looks like on the gauge as well, your right in that its all over the place.

anyway I hope that helps in some way

cheers
B

ps
Frosty hows the burn
and hows the tank coming along
got it all fixed yet

[Frosty]

[quote=Boston;450657]your right the pop valve is within the oil filter and cant be replaced, you gotta replace the entire filter ( $5 bucks ) but it can be defective and it can pop open at any time when it is. Means that at the pressure guage your going to be looking at a sudden drop in pressure or rise in pressure I cant remember which, I think its a drop first followed by a rise and so on. It looks a lot like a bad sensor but it cycles slower or at least it can. Oh well in either case its cheap to change and it "might" be the problem. Besides ya cant go wrong with a new oil filter. The electric senders are cheap as well, maybe $15 bucks around here. It can be the sender or it can be the contacts. One of my vehicles has a soaked sender from a punctured oil filter so I'm pretty familiar with what that looks like on the gauge as well, your right in that its all over the place.

anyway I hope that helps in some way

cheers

Sorry boss -- seeing as though this is the purpose of the thread,-- if I can just clarify that most filters are in line, there is no provision for a drop in pressure as does the releif valve that can "blow off" excess pressure.

The bi pass valve is internal and allows flow through past the filter. The bi pass is only about 10 psi meaning that if the difference of oil pressure from in and out ports were to exceed this it would bi pass the filter internally. This would not cause a drop in pressure as the pressure is already reduced by the blockage but re direct "some" of the flow. If the pressure were to drop the valve would close again

In other words a dirty clogged filter can not reduce oil pressure more than the values of the bi pass valve which is approx 10 psi or less.



The burn dropped off last night leaving a pink scar and the tank is drop dead gorgeous.