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Little Trucks, Big World

Hello all!  I noticed the other day that my oil pressure drops off to approx. 10-15 (factory gauge)psi while I'm driving it.  When I first start it up the oil pressure is normal.  It normally runs at 45 psi on the gauge.  I checked the oil level, which was good but I added 1/2 qt to see if it made a difference.  It did not make a difference, I still have the same problem.  The oil pressure light never comes on just a drop in pressure.  If I cut the engine off for a while and start it back up the pressure comes back up, but then eventually drops back down.

I have a haynes manual and found the section on the oil pump and I was wondering if it could be the pressure regulator in the oil pump.



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Sounds like a faulty oil sender unit. They are prone to fail in just that way. They are $40-$60 available at most auto parts store. The inlet in the sender unit is incredibly small one little piec of carbon and they will partially clog. 

Thanks for the reply Mike.  I will give this a try.  I am trying to think of where this part is on the engine.  I am drawing a blank on this one and I can't find it in the haynes manual.

Thanks again.

right next to the oil filter. pass side of block.  tip   remove oil filter for clearance. channel locks will work best, its nearly impossible to get a wrench on the nutted flange of the sender. grab the body of sender and twist. they tend to be damn near welded in there.  Careful with the threads they are m10x0.9

yep... what he said

I would say try  to use the proper wrench either 9/16 or 17mm?? I've twisted them in wrecking yards to get them off and buggered them. The single wire ones might be ok but the two wire gauge ones are fragile.

i agree that is the proper way to do it. but good luck trying to get that wrench on and create any useable torque to get it broken loose. the nutted flange is 14mm. either way good luck. there a pain in the butt

proper size ia 14mm but a 9/16" standard will work in a pinch with little risk of rounding it out. There is a trick to get better response from the electric sending units by opening up the hole from that pin hole size to 3/32"but you will need to use a drill stop so it only goes thru the hole and doesn't damage the inside of the sending unit. It's a popular mod in the Z32 300zx forums and it makes the electric oil pressure gauge respond like  a mechanical unit.

Try it on an old sender or make sure you got a spare if you're not sure what you're doing.

That is so interesting. My try it on mine. Mike and Dave... do you know why Nissan does not use National Standard Pipe Threads on the oil pressure sender?

Steve you need not apply.

The reason that nissan uses the bpst instead of npt is the old partnership with austin motors years ago. (to the best of my knowledge)     interesting tidbit there dave. good option for people who want the electrical gauge

i am a old school guy. i like a mechanical. i will be using a "t" fitting. i will run the factory sender to keep the idiot light function (as the idiot light is run from this as well as the gauge)  and the mechanical gauge for a "true" instantaneous reading.

Hey guys!  I was able to replace that part.  It was a PITA for sure but I got it.  I drove it around for 10 miles or so without any problems, but I will for sure keep an eye on it.  

Just to let you know, the old sender unit took a 17mm and the new one was a 9/16.

Thanks for all the help!

glad to hear it. those things don't take much to clog up and read like that 


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