Recently I became concerned with a possible oil pressure issue when my stock gauge began showing erratic readings. It would show zero pressure at startup then after about a minute it would rise to 60 psi. Under acceleration it would often drop again to zero. Before panicking I checked the actual pressure with a mechanical gauge and to my relief discovered that once again it was the sending unit that was faulty and my pressure was fine.
The faulty sender is my 4th in 5 years. The first was the original which I replaced with a new $80 Nissan one which failed after two years. I replaced it with an aftermarket which seemed to work much better. When I swapped in the JDM engine I tried the OEM it came with and ended up swapping in the aftermarket unit which has now failed. This has led me to come up with a new solution. I want to retain the original gauge mostly because I don't want a dead gauge in my display and I don't want redundant gauges. I began looking for a domestic sender with similar specs hoping to find a usable substitute that would be more reliable. First I checked the FSM and discovered that the factory unit is poor to start with. At 60 PSI (mid range) it is considered OK if it reads 26 t0 37 Ohms resistance. That is a range of 11 Ohms or an allowed variation of 30% of the total reading. Obviously the factory wants to be sure there is pressure but they are really not concerned with how much. I searched several catalogs and found a few likely replacements but before I could buy one to test, a good friend and Jeep enthusiast suggested I try a new spare he had for a 1978 Jeep CJ7 V8. When I pressurized it with air it read about 10 Ohms lower than the bottom of the Nissan spec at which point it occurred to me that this was a fortunate thing. It allowed me to "tune" the output and easily calibrate it to my car. But first I had to check on the reliability of the design. Polling members of a local Jeep club and trolling a few online forums It seems that they Jeep unit is not known for failure. So at least it seems like it has a chance of surviving longer than the Nissan units. Here is the good part. Because it has lower resistance than the Nissan unit I was able to add a resistor to the wire lead and fine tune it to give a much more accurate reading than the Nissan one ever gave. To do this, I soldered a 20 Ohm pot into the lead and pressurized it with 60 psi of air while it was connected to the lead on my harness. I adjusted the pot to get an identical 60 psi reading on the in dash gauge. Measuring the pot resistance I found that a 1.5 ohm resistor was needed. The Jeep unit does not have a spade terminal so it requires a small lead to be soldered on the output terminal. This makes a good place to add the resistor. I covered it with heat shrink, added a male spade terminal to the end and ty-wrapped it to the sender body. Now my oil pressure reads more accurately than it ever has. The gauge is rock steady and the whole setup was $35.
KKROFFTNow occurs everywhere, simultaneously. But it doesn't have to be experienced the moment it happens. Every now that ever was is still exactly when it was, when it was now.
Then, in terms of perception, is nothing more than all the nows that are no longer now. Thus, the difference between now and then is when. --The Waystoppers Users' Manual 
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Oil pressure sender... - 
