Oil pressure sending unit electrical problem (Knock on Wood, Solved!)

[mopar440cu]

I just had to replace a pressure sending switch and thought I would share the differences. The old dirty one is from a 3500 I am working on. The other is one I ordered through Amazon that crossed referenced with the stock one, but Wow what a difference! It seems to work like the old one when I first bought it in 02 though. Lol

I know some of you are going to say, “put a mechanical gauge in it”. Rest assure I intend to, but it is a waste unfortunately because none of my employees will watch gauges. Lol This is why I like the stock dash gauge because at least they hear the chime going off and then see the indicator light on the dash. Then they just complain to me the sound and light is annoying. Lol

Edited May 21, 2018 by mopar440cu

[mopar440cu]

Ok, after installing it I noticed that the pressure is a slight lower at idle and at WOT. So, I decided not to panic and swap out a stock one from another 3500 and to my surprise its reading better pressure. I understand they are not exactly the greatest for pressure reading like a mechanical , but do you guys think the difference is because of the size of the opening in the sender itsef compared to the stock size?

 

I hooked up a mechanical gauge that I had to recheck pressure at the filter and the readings are good.

[dripley]

The size of the hole should not make a difference. Sounds electronic to me. Dont think I would worry about it.

Edited May 18, 2018 by dripley

[mopar440cu]

4 minutes ago, dripley said:

The size of the hole should not make a difference. Sounds electronic to me. Dont think I would worry about it.

Yeah thats what I thought, but its weird thanks!! I swapped the new one to the donor truck and the readings were the same on it as the original one?? Strange!   I am going to install mechanical oil gauges in the rest of them.

[dripley]

2 minutes ago, mopar440cu said:

!   I am going to install mechanical oil gauges in the rest of them.

Been wanting to do that myself. Other things keep getting in the way.

[Mopar1973Man]

18 hours ago, mopar440cu said:

The other is one I ordered through Amazon that crossed referenced with the stock one

 

China part? Amazon?

 

Looking up on RockAuto they sell Standard and AirTex Wells which both look like what you go in your post. 

 

[mopar440cu]

35 minutes ago, Mopar1973Man said:

 

China part? Amazon?

 

Looking up on RockAuto they sell Standard and AirTex Wells which both look like what you go in your post. 

 

No it’s a Wells

Oops, I forgot to add it was from AutoZone and they double checked to see if it was indeed a Wells. They told me they just repack it in a different box, which is no different than what my aluminum supplier does and other auto distributors do. It looks just like the one from the Wells videos also. 

 

[mopar440cu]

Oops, I forgot to add it was from AutoZone and they double checked to see if it was indeed a Wells. They told me they just repack it in a different box, which is no different than what my aluminum supplier does and other auto distributors do. It looks just like the one from the Wells videos also. 

 

 

 

OK, here is the new dilemma on this  one. I changed out the oil sender to this new one and still had the oil pressure dropping to zero then going back up. I decided changed that one out for another oil sender, that is good on another 3500, and that didn't do any good. It did the same thing. So, I started to test wires on the oil sender plug. From what I am reading off this site from the wiring diagram I know there is one for ground and one for 5 volt supply and one for return. The ground tested fine. The 5 volt orange colored, if I remember, had weird findings. When I first tested it I got 1.91v at the plug only. I know from the wiring diagram that this wire goes from the oil sender gets spliced to the Map sensor then to ECM on the motor. I then checked the Map plug for 5 volts and only got 4.96v. I had to move the truck to my poll barn due to rain, forgot to plug the map sensor in and the oil sender worked like it use to. Here is the part I am confused, when I plugged the sender back in it stopped working properly and was erratic again??   Does this mean the PCM is bad?? I have a temporary mechanical gauge in it until I get my gauge in and the pressure is good, but I need to fix the dash one. Any help or thoughts would be appreciated! I was thinking maybe if I find a true 5v ignition activated source and wire it to the sender maybe that might help? 

 

Thanks,

Steve

 

[mopar440cu]

I was thinking out loud to myself, I said “self what about maybe it could be the map sensor!” Lol What do you guys think?

 

[Mopar1973Man]

Possible... 

[mopar440cu]

OK,I checked the theory of possibly being the Map Sensor and to my surprise it cured it, knock on wood!!!