Jump to content

djwarner

Series I oil pressure sender question

Recommended Posts

My Series I has the original 140psig gauge and the sender was leaking when I bought the car. A trip to the local auto supply store sourced a compatible (?) sender.

Later I found out that the original sender part number was superseded with the same part number as the ones found on Series II and later cars.

Still later, I found out that the shop instructions state to also replace the gauge with a 90psig when replacing with the superseded sender. This makes sense for the then modern model car, but sucks when trying to restore a 43 year old car and desire to keep the original gauge.

From what I can tell, the original sender was a 10 Bar sender (10 atmospheres or 145psig) and the replacement sender is a 6 Bar sender (87 psig).

So what readings do I get when I use a 6 Bar sender and a 10 Bar gauge?

I did find a modern 6 bar sender that had the following specs:

6-8psig open circuit (this explains why our gauges go to zero when idling after a hot run).

15 psig - 50-79 ohms,

70 psig - 10-30 ohms,

90 psig - 8-22 ohms.

I have no idea what the original sender specs were, but the 6 Bar specs seem pretty loose.

Does any one have specs for the 10 Bar sender?

Or better yet, does anyone know of a suitable sender from a different model/make?

Share this post


Link to post
Share on other sites

I replaced my series I oil sending unit PN 25070-89910 in 1979 with the correct 10 KG OEM switch and it stills seems to read OK on the 140 psi gauge. Attached is a parts page showing different PN's for the 10 KG and 6 KG units. Is there a date on shop instructions sheet that you have? Sorry I don't have any specs for the 10 KG sender.

post-8626-14150829837342_thumb.jpg

Mike

  • Like 1

Share this post


Link to post
Share on other sites

Hey Mike,

I double checked with Courtesy Nissan and that part number was discontinued by Nissan as I was told.

Share this post


Link to post
Share on other sites

Sorry about that, good luck on your search on an NOS part, maybe you will get lucky. I did a quick search and saw this on ebay, no idea if this is a good vendor:

Vintage Nissan Oil Pressure Sender Part Number 25070 89910 | eBay

Sorry, just noticed it was an old auction, but at least they do come up, cheers.

Edited by CanTechZ

Share this post


Link to post
Share on other sites

Hello dj,

This may, or may not help, but here is what I have found in trying to understand the inherently low pressure readings on series 1 cars.

Here is what Wick Humble in his book "How to Restore Your Datsun Z-Car" had to say. By the way, this low pressure reading is, indeed,

inherent to our early cars as this low pressure anomaly was present the day I drove it off the lot with zero miles on the clock.

My car has the 140 psi gage and the 25070-89910 10kg sender switch. I asked my mechanic to check my oil pressure with

his mechanical gage and these were the reading:

Idle - 22 psi

3500 RPM - 64 psi

My stock 140 psi gage and 25070 - 89910 sender the reading are:

Idle - 0 psi

3500 RPM - 35 to 40 psi

My car is 100% stock with a pretty tight engine with approximately 5M miles on it. My compression readings are 167, 166, 168,

176, 167, & 175 for cylinders 1 thru 6 respectively.

I have peace of mind knowing that zero psi really means at least 22 psi as everything on my car will always remain factory stock.

I also know that many mechanics, to give owners peace of mind, would install a roadster sender which will always give a

positive reading. I used one for a time, but don't remember what the specific readings were except that it was always positive.

I hope this helps in your quest for a sender.

Dan

post-2148-1415082983859_thumb.jpg

  • Like 1

Share this post


Link to post
Share on other sites

Thanks Dan,

Your attachment confirms what I have found.

I was hoping someone found a 10 Bar sender from a different application that would work.

Many modern senders appear to be voltage based rather than current based, so finding a substitute sensor may be problematic. I will probably rig up a 500 ohm pot to simulate a sender to extract a set of specs for my search.

Share this post


Link to post
Share on other sites

Thanks for the heads up Jim. He states the unit he has is for 70-76 models and is probably the 6 bar unit as the 10 bar unit was only used in the 69-70 production.

I made some tests on the gauge. It appears to be looking for:

0 psi - 83 ohms

25 psi - 60 ohms

50 psi - 40 ohms

90 psi - 24 ohms

A note to anyone trying this, the water temp/oil pressure gauge has an internal voltage regulator that is a bi-metal mechanical type that is to slow for our digital meters.

Share this post


Link to post
Share on other sites
On 8/26/2014 at 4:14 AM, AZ-240z said:

Hello dj,

This may, or may not help, but here is what I have found in trying to understand the inherently low pressure readings on series 1 cars.

Here is what Wick Humble in his book "How to Restore Your Datsun Z-Car" had to say. By the way, this low pressure reading is, indeed,

inherent to our early cars as this low pressure anomaly was present the day I drove it off the lot with zero miles on the clock.

My car has the 140 psi gage and the 25070-89910 10kg sender switch. I asked my mechanic to check my oil pressure with

his mechanical gage and these were the reading:

Idle - 22 psi

3500 RPM - 64 psi

My stock 140 psi gage and 25070 - 89910 sender the reading are:

Idle - 0 psi

3500 RPM - 35 to 40 psi

My car is 100% stock with a pretty tight engine with approximately 5M miles on it. My compression readings are 167, 166, 168,

176, 167, & 175 for cylinders 1 thru 6 respectively.

I have peace of mind knowing that zero psi really means at least 22 psi as everything on my car will always remain factory stock.

I also know that many mechanics, to give owners peace of mind, would install a roadster sender which will always give a

positive reading. I used one for a time, but don't remember what the specific readings were except that it was always positive.

I hope this helps in your quest for a sender.

Dan

post-2148-1415082983859_thumb.jpg

Hi Dan , your  data helps everyone a lot  , I was also wondering too about the low readings of the oil pressure. My first Z is a 1972 240Z when I was living in Bakers Field CA which always showing middle in the gauge. Then I bought a 1970 240Z , it always stayed very low in the gauge.

I remember I was reading Mr. Wick Humble ‘s book and learned  my 1970 car was not wrong .

Here are pictures which were taken recently, my 1970 Z432 ( shared with all the other S30 DOM & EXPORT using the same 10kg switch , 10kg scale ) and 1970 Datsun 240Z , And 1972 Fairlady 240ZG ( 6kg switch with 6kg scale ) .

Just for your reference.

By the way , 25070-89910 ( 10kg ) switch is now approximately 200-400 USD if it is a new , S20 owners are seriously want it . 

Looking at my Z432 , S20 might able to be said it’s oil pressure relatively higher than L -series engine , what do you think of it. 

Kats

695444B9-EEC1-4048-83AA-9CD9315E3B4C.jpeg

281AFA46-C09F-41D2-B97A-103E8503AB57.jpeg

EEEDFF3B-C0B7-4CB8-A09E-1AC0DCED010D.jpeg

9883D5EC-5FED-42AC-9A02-9DFEBEE0E344.jpeg

C32CF867-B5A3-495F-9F83-F99080EE2AEA.jpeg

108B954F-C638-4869-BE5F-E2F93D132B0C.jpeg

  • Like 1

Share this post


Link to post
Share on other sites

I forgot to put this , my 1972( 12/71 made ) Datsun 240Z . I think a 6kg switch cooperated with a 6kg / 90lb scale work pretty good, it makes me feel happy .

Kats

3F10AC91-040B-468F-845D-EE80C5172FFF.jpeg

57E7FCD6-5A6B-46ED-9CB9-FE84B9619B21.jpeg

  • Like 1

Share this post


Link to post
Share on other sites

Hi Blue , thanks ! Is there any chance you would trade your 140 switch for my NOS 90 switch 89901 ? 

Kats

E95B99B2-11B4-40C1-8703-9C0728A25F7C.png

E5E55CD8-EDC6-4F7A-98ED-94CDEE030105.png

6E71BD05-7CA2-42CA-98F5-85610DE6FA04.png

Share this post


Link to post
Share on other sites

🙂 It is not my switch.  Hovered.

But I have some early 1969 240z engines that may have the 140psi senders. I have to check them. Do you need a new one or will a used one that functions do the trick?

Share this post


Link to post
Share on other sites

I would like to have a new 140 one for my S20 . I have some used 90 ones and 140 ones . 

Thanks ! 

Kats

Share this post


Link to post
Share on other sites
5 minutes ago, kats said:

I would like to have a new 140 one for my S20 . I have some used 90 ones and 140 ones . 

Thanks ! 

Kats

OK I'll try to find one. Ebay only has this substitute currently:

https://www.ebay.com/itm/MANUFACT-GEN-Engine-Oil-Pressure-Switch-25070-89972/272853013165?epid=140384145&hash=item3f874e92ad:g:VMkAAOSw4Z5aMHt6

 

Share this post


Link to post
Share on other sites
15 hours ago, kats said:

I forgot to put this , my 1972( 12/71 made ) Datsun 240Z . I think a 6kg switch cooperated with a 6kg / 90lb scale work pretty good, it makes me feel happy .

Kats

3F10AC91-040B-468F-845D-EE80C5172FFF.jpeg

57E7FCD6-5A6B-46ED-9CB9-FE84B9619B21.jpeg

Hi Kats,

I am glad that my experience with a car originally purchased new on 3/25/71 helped confirm the reasons

a redesign of the oil pressure gage/sender combination was needed.  I had used the 90psi/6kg combination

with the good results that you describe, but I needed to use the 140psi/10kg combination to retain the originality

of my series 1 car.  During periodic maintenance, my mechanic, who has worked on these car since the mid

1970s, confirms my oil pressure with a direct reading gage knowing that this was a problem from the start.

It also, as you say, gives me peace of mind.

Sorry, I am no help when talking about S20 engines in Z432 cars, but wish I had this Z432 problem.  👨‍✈️

Dan

 

  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.