Nissan/ Tohatsu Oil Pump

[r16409]

I have read several posts about these oil pumps leaking. My motor ,(2006 Nissan NSD90B), and has oil pump leak. After research I believe the oil pumps are the same or similar to those manufactured for some of the oil pumps used in the Mercury Optimax line.... https://edli.com/edl-major-programs/34-mercury-marine-optimax-engine-oil-pump.html In my case its an older motor so I decided to try to replace the o-ring. It was not the o-ring but rather a brass piston type component, (see video), which has a crack. I am curious how often these crack? I have heard a few reports of new units from Tohatsu having cracks/leaking. One thing is if the cap is tight one may not see the oil leaking from a crack in the internal brass piston component. At this point if I order a new pump from Tohatsu would that be a recently built unit or something from inventory given the age of the motor. Thank You.

 

[pvanv]

The electric pumps are pretty reliable. MSRP around $400. I changed one in all my years working on these. There are fewer than 10 units in stock at Tohatsu America.

 

[r16409]

I called Tohatsu and can confirm what you said. I also asked if these are new units or old inventory. Was told they are new and build in Japan. Will be ordering one! Thank You!

 

[r16409]

I was thinking of starting a new thread but this is related. My immediate issue is trying to show compression on the fuel shrader valve without an expensive tool, (see below). I am thinking I need to do further diagnostics before buying a new Oil Pump. The short story is the Air Compressor seized. The motor had sat for about 4 months and I did not purge the oil lines via the procedure in the manual. I was able to get the compressor un-seized and sourced another good used compressor but before I installed it I was trying to figure out what caused this. I had thought it was from lack of lubrication in the compressor because it sat for about 4 months. Then upon further inspection I noticed a small oil leak at the base of the over on the Oil Injector pump and thought perhaps that was related by way of air getting into to oil lines when ever it leaks. I have noticed air bubbles when the pump solenoid is running during the purge/bleed process, (video attached to this post - not sure if that normal or not). I also tested the air side shrader valve which holds about 74lbs via a bicycle pump with gauge. Understood this is not the correct tool. The problem I am facing is I am unable to show any pressure what so ever on the fuel side with either the same tire pump used for the air side or using a cheap analog tire gauge. Should the fuel side shrader valve show some pressure on any of these gauges if its working? Otherwise the motor starts fine, idles good but does have some rough running under-load and does not plane out as well as it did before the air compressor failure. Cold dry compression of motor is 120LB Top, 120 Middle and 150 bottom. Thanks in advance for comments/time!

 

[r16409]

Trying to get the correct air/fuel pressure testing tool. In the mean time Reading thru the manual, (specifically pages on air supply system and fuel supply system), to understand how the air rail distributes air and to which component. Its unclear if the rail takes air from the compressor and delivers to both air injector and fuel injectors? I do not think the fuel pump alone can deliver aprox 90PSI of pressure?

Any info greatly appreciated!

Thank You

 

[r16409]

Well, I was able to show pressure of 74lbs and 84lbs on the air/fuel rail shader valves while idling using a bicycle pump with a gauge. That seems a tad low but now sure what what would calibrate to using the correct gauge. My plan is to replace the plugs, (I have run the oil line prime a few times after removing/installing the compressor), and put her under load to see if the mid to high range rpm stumbles/difficult to get on plane still happens. Thank You.

 

[pvanv]

Pressures sound s bit low.

 

[r16409]

Pressures sound s bit low.

Could both be related to slightly low Air Compressor Compression? I was thinking of honing the cly and replacing the rings/head gasket. After it had previously seized I was able to free it but did did nothing other than lightly sanding the cylinder with very light sand paper to the cylinder which has a decent score on both sides, (photo attached). Otherwise still planing on replacing oil pump and fuel regulator and possibly the air compressor if all else continues to check out.

Thank You.

 

[pvanv]

That cylinder looks pretty bad.

 

[r16409]

That cylinder looks pretty bad.

Agree, Thanks for the input! Do you think it could do other damage to the motor by running it with the lower compression air compressor? I was thinking of replacing the oil pump and fuel regulator first and then the air compressor. Thank You

 

[pvanv]

Definitely need a compressor cylinder. If oil pump is leaking, need that too. Then see whether pressures are OK.

 

[r16409]

Thanks for the Reply!

Replaced the oil pump, fuel regulator and thermostat and ran 40 miles pushing about 2000Lbs. Ran very good but found another problem which existed before but was very intermittent. The problem is when the Engine is hot sometimes when you try to start its totally dead. I had replaced battery cables with marine grade and new AGM Battery. But this time I was not able to start it so I tapped on the side of the starter when someone turned the key and every time that worked. So thinking its the starter but not sure if the solenoid can also cause that symptom.

 

[pvanv]

Sounds like brushes in the starter are getting hung up. It is repairable.