Oil Pressure - really low? (part 2)

[Erock311]

This is a response to Gregs 67 2000 post about oil sender issues. I had the same problems w/ my 66. I know the post was several months ago, but had to get some info before I posted this. The 240z and the roadster senders are totally different. The 240z unit (as far as I know) works by variable resistance, the roadster unit works by variable current. I tried finding the PS 202 replacement, it is obsolete from what I have been told. I ended up repairing my old sender (yes, it can be done)as long as it is still reads something. The sender has a set of points inside it (think mech. guage regulator), and the points pit and burn over time. This is why the reading drops down. The short version: 1) remove the cover (hardest part of this job, but can be done, 2)In the unit , you will see the points (the arm has fine wire wrapped around it). I used a point file to clean the points, a couple of strokes should be enough, 3) make a test rig to pressurize the sender w/a guage inline,I used compressed air to check the gauge, hookup to the sender wire in the car. If say 40 psi on gauge , should have 40psi on dash gauge. There is a little toothed wheel (calibration?) you may have to move to "dial in" the sender. 4) Reinstall cover (straighten out edge), I cut little tabs in the cover (4) folded these over to secure it, make sure the rubber seal is installed. In conclusion, my guage was reading close to zero, now it reads 40 psi @ idle. I can give more details, if requested.

[Gregs672000]

I'm glad to see that you looked into this. I can confirm that the 240z one does not work (I have one siting in my tool box in case some Z owner is interested). I was able to purchase a new 202 but it too did not read any better. I know I have good oil pressure because I hooked up a mechanical gauge and it was 40-70lbs. I reinstalled my original and it continues to read 40lbs with moderate rpm, and low at idle. At this point, as long as the gauge moves I'm not worried, but it would be nice to have a something that was more accurate, though I don't plan on adding a mechanical one. Thanks for posting about the internals, I was wondering how it worked.

[Gregs672000]

Bring it back to the front! Thanks man!

How did you remove the cover and what did you learn from this process?

[Erock311]

Bad move on my part, but I don't have any photos when I did this, but hopefully I can provide enough info from memory. I'm not sure if you said that the unit was leaking, if it is the diaphragm may be cracked.etc, leaking oil inside the unit, you will need another one. Another possible leak area could be around the outside edge (will explain further). To remove the cover, you will see a crimped edge around the unit, use pliers (may have to try different types) and work slowly around the edge. It's a pain to do, but can be done (hardest part of this procedure). You will slowly lift the edge up. Under the edge is a solder joint? try not to damage w/pliers. You will bend this edge enough to remove the unit from the cover. The solder could possibly be a leak path for the oil as well (crack). might be able to solder it if it is, mine was dry. You will see the points inside (thin wire wrapped around the arm). I got a point file and couple of strokes cleaned the points, just try to keep the file as parallel as possible, clean the points to get rid of any grit( A piece of paper soaked w/alchohol, just pull it thru the points, then dry paper to dry them.(small amount of alcohol, just barely moisten the paper. Then set up a tester w/ a guage and use it to calibrate the unit.I think the little wheel inside is a adjuster, I had to turn mine slightly to get it equal w/ the gauge ( use the car guage w/jumper wires to check if the readings are the same. If they are, the unit is done. Take a socket, and roll the edge of the cover to remove burrs,etc , test fit the cover until it fits properly. There should be a rubber seal inside (around the edge). Instead of fully crimping it again, I made 4 ears in the cover to hold it in place. Take the cover and seal , put it over the unit and fold the ears over. You're done! Its not for the faint of heart, but it can be done ( mainly to see if I could save the unit). Not to take anything away from the vendors, looked at toyota senders for mr2, look the same , but who knows on calibration? (maybe others)?

[Erock311]

One small note: I put the unit upside down in a piece of pipe in a vise to hold it while I was undoing the crimp to avoid damaging the cover (big socket may work as well), just watch the terminal on top to avoid damage>

[Gregs672000]

Thanks very much for the detailed procedure. I am concerned that mine is pretty harshed as it leaks oil. The outside cover spins around the whole unit if I hold the nut, so clearly not soldered anymore. Is there an actual seal or does it just seal by solder?

I have the other unit that looks very similar and I think I bought it a while back as a correct sender for a Roadster, but who knows. It did not respond like the 240z one did with decreasing resistance, so maybe that bodes well for that one. I may try a test as you described with it hooked to the car gauge to see if it responds, as that would suggest it's working on the same principles, and consider opening that one up. I don't think it's very useful to me right now as it is... at least my leaking one registered somewhat more accurately.

Thanks again!

P.s. I just looked at the Toyota senders and the one I have looks exactly the same except that it uses a small screw to secure the wire just like my original instead of the clip head (smaller screw than my original one though).

[Erock311]

There is a rubber seal sandwiched between the cover and the unit, the solder only seals the unit itself.If the cover can be moved, the rubber sealmay be "collapsed", maybe the crimp just loosened up? All the info i provided was done w/a datsun sender, aftermarket may vary in some details

[Gregs672000]

OK, so I thought I'd finish this out...
I carefully and slowly took the unit apart, and the instructions given are dead on, including the need to cut 4 small reliefs to be able to slowly bend the rolled sealing edge back. Inside I found it to be dirty and I observed the functioning of the unit. The little wheel does appear to be a calibration wheel, and it looks like a toothed tool was used to carefully adjust it. So far so good, but here's where I screwed up... I hooked a jumper from the harness wire into the car so I could watch the gauge and used my test light to create a ground to the body of the sensor, then applied compressed air to watch the gauge respond, which it did. However, with 80lbs of pressure it was only reading about 40lbs on the gauge. My error was my poor excuse for a ground but, being a novice, I didn't realize this. So I adjusted the wheel, first counter clockwise (reduced reading) then clockwise (didn't seem to change, but I think it did). After deciding on a "spot" (a tooth of increase) I spent all kinds of time soldering it back up and sealing the leak (not internal, but where the securing nut contacted the unit itself where the diaphragm is) then reinstalled it... and it pegs with a good ground (body screwed into the block). I don't know if the heat from soldering it hosed it, or that I adjusted it way off. I probably would have left it alone adjustment wise IF I had been using a good ground. But it's not worth trying to open it up again, so I'll just have to get a new one. I did note that I tried the other sender I have, and it would not light the test light (being used to create a ground) unless I put some air pressure to it and then it was a very dim light. That suggests that it works the same but is not calibrated for the gauge, but I probably won't be opening it up. It was worth a try!

[23yrRebuild]

I'm not sure about this, so I would ask Jon Frampton, ...but I "THINK" the oil pressure GAUGE, at least on my '67 stroker, is adjustable, like I KNOW the fuel and water temp gauges are. I know I had to, and was able to, re-calibrate my fuel gauge when Jon had restored all of my gauges.

My restored oil pressure gauge always reads 90, or "pegged",...my old original gauge read through a range from idle to full throttle, I don't remember what those numbers were, but I'm still using the same oil pressure sender that came with the car, when I bought it in 1980.

Again, I would ask for Jon's input, if he is still "out there".....Jon, are you still "out there" ?
Mike

[Habitat.pat]

I know this is an old(er) thread, but it dovetails with what I am experiencing. As I noted in another thread, my oil pressure is reading high. I installed a new PS 202 sender, had Jon go through my gauges & built the 8V instrument regulator. I also am running a U20 oil pump & I have high oil pressure (40 @ idle, 70 @ 4K), but the gauge reads higher than that.

My main question concerns the PS 202 sender. Have others used it reliably? Does it produce close to correct readings or do I need to go in & adjust the gauge to match the sender?

peace, Pat

[david premo]

The pump you are using is a much higher volume than the R16 stock pump. The relief valve is set to that pressure unless it is sticking, you can lower the pressure by removing spring shims or putting in a softer spring for the relief valve. 70 psi is not excessive but it is not necessary for your engine. Just give the thread a little time and you’ll get a bunch more opinions from various people that have their own theories about how to set an oiling system up. What you have is fine, oil pressure gauges go as high as 150 psi, not that anyone would need that kind of pressure for a street engine. When I used to build drag racing engines back in the day, we would use high volume, high pressure oil pumps and clearance the crankshaft to the point it was completely floating in oil so it would grab RPM’s fast in the quarter mile. These were short run and short life engines and very quick in the quarter mile.
Dave

[Habitat.pat]

Thanks, Dave, I'm not concerned about the pressure. Next time I drop the pan I'll remove the 2 shims in the pressure relief to see what that does. My main thing is that I'd like to have a gauge that reads closer to correct & am trying to decide to adjust the gauge with the PS 202 sender, or find another sender that more closely matches Jon's gauge calibration. Short term I'll just use it as an analog on/off indicator!

Peace, Pat

[Gregs672000]

I ended up replacing my sender with a new aftermarket unit from Dean. As I recall it was reading 40lbs while running, but the engine is apart at the moment so I will try to remember to post when it's back together.