Should I worry about low oil pressure reading until revs above 1500 on Yanmar?

tudorsailor

tudorsailor

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Recently I have noticed that on first starting the engine and idling that the oil pressure gauge reads zero! Once I increase the revs to greater than 1500rpm, the needle pops to the usual position in the middle directly up (I am not on board, so do not know what the number is when the needle is straight up). The engine is Yanmar, Model 4JH3-HTE. Now 11 years old. The gauge is on the remote panel in the cockpit.

How does the pressure gauge get its reading? Is there a pressure sensor and then a electronic relay to the gauge?

Could the pressure sensor be sticking until the pressure gets high enough to register?

Should I worry about this phenomenon?

Do I need a new oil pressure sensor? Is this a DIY fix?

Thanks

TudorSailor
 
tudorsailor said:
Recently I have noticed that on first starting the engine and idling that the oil pressure gauge reads zero! Once I increase the revs to greater than 1500rpm, the needle pops to the usual position in the middle directly up (I am not on board, so do not know what the number is when the needle is straight up). The engine is Yanmar, Model 4JH3-HTE. Now 11 years old. The gauge is on the remote panel in the cockpit.

How does the pressure gauge get its reading? Is there a pressure sensor and then a electronic relay to the gauge?

Could the pressure sensor be sticking until the pressure gets high enough to register?

Should I worry about this phenomenon?

Do I need a new oil pressure sensor? Is this a DIY fix?

Thanks

TudorSailor
Click to expand...

Sounds like something sticking. What happens to the reading when you go back to idling after running at 1500rpm? If it drops back to zero, it's serious.
 
I have a 7 year old Yanmar 4JH3 TBE 650 hours logged. Cold start and idle 4 bar, above 1000rpm 5 bar.

If you really have zero at idle I would have thought that your engine would have started to have a serious bigend death rattle. More likely to be a sticking gauge, or faulty pressure switch.

The pressure switch on the 4JH3 engines is mounted starboard side below the intake manifold just ahead of the rear bell housing.

Good luck with tracking the fault.

Moonshine
 
Daft I know, but try tapping the gauge. It may just be the needle sticking on the face if it's slipped on it's pivot or the face has moved.
Then, as suggested, replace the sender, you could check the electrical contact on the end first and see if a bit of corrosion is preventing the gauge from moving initially.
 
Lakesailor said:
Daft I know, but try tapping the gauge. It may just be the needle sticking on the face if it's slipped on it's pivot or the face has moved.
Then, as suggested, replace the sender, you could check the electrical contact on the end first and see if a bit of corrosion is preventing the gauge from moving initially.
Click to expand...

AGGGHHH !! gauge tapping is my pet hate

If you feel the need - tap the surround not the glass , the glass is very thin easily broken or pushed against the needle .
I have lost count of the gauges i've had to replace because of over enthusiastic tapping.
 
Just clarified with my co-owner who is on board at present.

He says that initially on first starting that the pressure is ok. Soon afterwards the pressure is zero when idling even when the engine is warm. Once the revs go There is no increase in noise and no increase in smoke in the exhaust

How easy is it to change the pressure sensor?

TudorSailor
 
padge said:
AGGGHHH !! gauge tapping is my pet hate

If you feel the need - tap the surround not the glass , the glass is very thin easily broken or pushed against the needle .
I have lost count of the gauges i've had to replace because of over enthusiastic tapping.
Click to expand...
Sorry. I was assuming the OP was mechanically sympathetic.
 
tudorsailor said:
initially on first starting that the pressure is ok. Soon afterwards the pressure is zero when idling even when the engine is warm.

TudorSailor
Click to expand...
Ooo. That doesn't sound so good. I'd still check the wiring connection. Maybe a bit of resistance heats up the connection and further increases the resistance.
Certainly try another sender unit. Be very careful starting the new unit in the threads. They are very fine and if it's a taper thread unit it's really easy to cross them.
Is there a pressure relief valve in the oil system, possibly in the filter head? Swarf could make it stick slightly open.
Treat it as important to solve the problem.
 
Lakesailor said:
Ooo. That doesn't sound so good. I'd still check the wiring connection. Maybe a bit of resistance heats up the connection and further increases the resistance.
Certainly try another sender unit. Be very careful starting the new unit in the threads. They are very fine and if it's a taper thread unit it's really easy to cross them.
Is there a pressure relief valve in the oil system, possibly in the filter head? Swarf could make it stick slightly open.
Treat it as important to solve the problem.
Click to expand...
What he said, especially the bit I've put in bold.
 
According to the w/shop manual* there is a pressure gauge with a pressure sensor and a low pressure warning light with a separate pressure switch.

Does the warning light work and does it come on when the pressure indicated by the gauge falls. If the light does not come on then it indicates that there is a problem with the pressure gauge its sensor or the wiring and no great cause for alarm...... not all versions have a gauge.

If the warning light comes on urgent attention called for.


You should be able to distinguish between the prssure gauage sensor and the warning light switch by the colour of the wiring. Yellow/black for the pressure gauge sensor and yellow/white for the warning light switch.

* http://www.motoren.ath.cx/Download.php?filename=/yanmar/4JH3.pdf
 
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Dont know the age of your engine but the good news is that Yanmar did have problems with oil pressure sensors in general a few years back. IF the low oil pressure warning light goes out then it seems that all is well BUT there it is vital that you check it out before the engine wears out.

A few jury rig suggestions to ascertain if there is any oil pressure:

Take a good sensor from another engine - find a willing donor on the pontoon who will lend you one for a beer.

Buy a cheap foot pump with a gauge on it (£5.00 ish) and see if you can fit the gauge to the engine with the pipes and bits from the pump for a one off pressure reading - take it off again when your done in case it all goes pear shaped and sprays oil everywhere. (dont expect the reading to be very accurate but it should indicate if there is and pressure.)

Take the pressure sensor off the engine and put your thumb over the hole while someone starts and stops the motor - you should feel pressure.

Beg borrow or steal a gauge from a garage mechanic.
 
I had a similar problem with a different engine and bought and temporarily fitted a mechanical gauge , which thankfully showed good oil pressure so then changed the electrical sender/sensor.
 
Rather than buy a new sender at £12, buy one of these and know your pressure is right. http://www.ebay.co.uk/itm/TIM-Oil-P...pe-52mm-Race-Rally-Kitcar-Track-/400526050297

The thread on your engine is 1/8 BSPT (Yanmar pipe threads are to Japanese Industrial Standard JIS B 0203, which is identical to British Standard and DIN which have a thread angle of 55° and 28 threads per inch in the 1/8-inch pipe size). This is similar, but not compatible with the American 1/8 NPT thread.

If fitting a gauge you need to use the correct connector. They usually come with a few different ones.
I had this problem on my engine swap and got some BSPT (male) to NPT (female adapters). I have 3 spare if anyone needs one. Postage costs only.

DR684.JPG
 
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Zero oil pressure is pretty much impossible, assuming there is some oil in the sump. I have known engines with seriously failed big-end bearings and I have personally experienced a broken crankshaft on a BMC A-series engine. In both cases there was lots of noise but some oil pressure, in the case of the broken crankshaft the noise of the two ends banging together was horrendous but the oil pressure was only down about 5 psi from normal.
 
Thanks for all the input. Seems that replacing the pressure sensor is the first step. Having discovered that "original" Yanmar parts are somewhat expensive and also re-badge Bosch components, where should I go to get a new sensor?

TudorSailor
 
Lakesailor said:
One for £11.81 about halfway down this page http://www.keypart.com/yanmar/diesel-engine/4jh3hte
Click to expand...

tudorsailor said:
Wonderful. I have emailed them

What a great thing this forum is!

TudorSailor
Click to expand...

vyv_cox said:
Does that do the two jobs of pressure sensor and switch? Ones I am familiar with have two terminals, one for each job. I think the keypart one may be switch only.
Click to expand...

Yes that is I am sure the switch for the warning light.

The sensor for the pressure gauge is a separate component ITYWF

See my post #11 and the link to the workshop manual ........ look at the wiring diagrams.
 
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