If you have a mechanical gauge then ignore the factory gauge.  The factory ones are a joke and when you combine them with Chinese made sending units they are worthless at best. The last sending unit I got was from NAPA and seems ok. I think it was made in Mexico.

 

your oil pressure is according to fsm acceptable , according to me , low after warming . the drop at a stop light is normal but low , I would try a different brand oil , different brand oil filter , and depending on location and what's in it now a different weight oil . The concern is not that you don't have 10 psi per 1000 rpms at that stop light , the concern is when you take off quickly how fast the pressure comes up to match the 4 k you rev it to . When idjut lights come on after several senders , and your gauge reads 15psi when the oils been worked hard for a while its time to change something besides the gauges . Maybe just a change in oil used .

 

I got almost no oil pressure reading with the 2 different senders.

Even if the sender unit is unplugged, the oil light never comes on.

Something tells me that it gets it's signal from somewhere else.
Why the 2 different brands of senders do not work is beyond me

 

Is your sending unit screwed directly into the block or is it screwed into a hex shaped tower looking thing that mounts the sending unit at an angle?  If the latter is the case, look for a switch with a 3 prong plug screwed into the side fo the tower looking thing.  My listing shows you should have just the new style plastic, two terminal sending unit which is listed as both the sending unit and switch but if you have the old style "bell" sending unit for some reason, the switch should be a separate part.

 

My ' 91 was reading low, changed the sensor and bingo, gauge and light were back where they should be.  Those senors are getting old now, may be time to replace it.  Took all of 5 minutes to replace using the correct sending unit socket.  The sensor cost about $16 at carquest.  Well worth it for the peace of mind.

 

  I've had the gauge sit on zero with no light and the light come on when it approaches the bottom of the normal range. No clue why. Same truck different sending units.

  The power flows from your gauge to the sending unit and then gets grounded by the amount of pressure.
    One test is to ground your wire to the engine. The gauge should move to max pressure. If it doesn't jump to the top then there could be a problem with the wires or gauge. Because the ground has to pass through the threads don't add any sealant or tape.

 

Rule of thumb 1 psi for 10 rpm... use a mechanical temp and oil pressure gauge... try different oil viscosities... I run 20 50 in the summer... if I don't my oil pressure is in the dirt

 

And be sure to clean the connector at the temp oil pressure sensor. They often get oily back there and that'll cause a low pressure reading when you get extra resistance through the connection.

 

And be sure to clean the connector at the temp sensor. They often get oily back there and that'll cause a low pressure reading when you get extra resistance through the connection.

I have the 2 plug connector. When you say temp sensor, I assume you mean oil sender?

The 89 B350 ram van doesn't have a RPM gauge

Doe anyone know what part# will for a fact will work with my vehicle?

 

5227914 is the original Mopar Part number.  RockAuto has several that cross over to that number.

 

Rule of thumb 1 psi for 10 rpm... use a mechanical temp and oil pressure gauge... try different oil viscosities... I run 20 50 in the summer... if I don't my oil pressure is in the dirt

Don't quite think that rule of thumb is correct. If so, that would mean 100psi at 1000rpm. Sure you're not thinking 1psi per 100rpm? I've always heard the 10/1000 rule myself.

Now, senders. Well....

I went thru 4 senders on my 91 when the original one would randomly drop the pressure gauge but no oil light came on. First 3 were from the dealer (I worked there, returned under warranty). All 3 of those, light worked normally, gauge didn't read anything. Return to the original sender, worked fine. Verified pressure with a mechanical gauge, everything was fine. Finally tossed in a chain store sender, been working ever since. Now, working and accurate are 2 different things. It's far from correct compared to the original one, with the second notch on the gauge (top of the first segment) being 85psi. Original sender would have it top of the second segment. Given I can adapt my brain to the skewed readings I just left that sender in there.

A quick check as mentioned is ground each pin in the connector manually. Grounding the gauge should cause it to move. Grounding the light should cause the light to come on. With the connector unhooked you won't get a light since the sender grounds the light to turn it on, via case ground on the sender.

I would agree with the other comments, might be time to try a slightly thicker weight or a different brand of oil. That's a whole different debate, but my personal preference is mobil 1 10w40 since my rig sees heavy use and we are mostly a warm climate. Given I have a known history on mine since new, I can say it's in remarkably good condition for the miles, so oil pressure is solid. Hot idle is around 35psi, cruise is around 75.

 

the 2 wire replacement senders are notoriously bad . when you state checked with manual gauge are you referring to a gauge with a hose and NO electric ? called a mechanical gauge ? If so your oil pressure at hot idle is within the rule of thumb ( 10 per 1000 rpm ) because idle speed is some where under 1000 when warmed up .

HOWEVER , it is low as far as I'm concerned ( and apparently others as well )

some of there trucks came with 1 just an ijut light
                                                    2 just a high/low electric gauge in dash cluster as a guide to oil pressure
                                                    3 Both the electric gauge AND the idjut light
number 2 is the most common followed by 3 then 1 IMO.

  test for idjut light by turning key to "ON" but don't start engine , look for light on dash says oil or oil pressure
  if there was one and the bulb is good it should light . look at sender area ,for another connector 3 female spades . 

 

Yes I used a mechanical gauge to test

I am not going to waste another 200$ testing out other oil senders that do not work. Obviously the online retailers are all using the same database to determine what sender unit an 89 B350 LA 360 uses which apparently is wrong.

If there is something major like a bad bearing, which is highly unlikely since the LA 360 engine is built like a tank,
it is not worth the money to fix up old camper van like mine.

Personally I do not feel like, 16 psi at idle is going to damage my engine. If it was <10 I would have to throw a hail marry pass, but for now I am going to change to a 10w oil as suggested and see what happens.

If the engine does decide to sieze/die, I guess it was meant to be. No point in throwing 2000$ in parts and labor at a 5000$ van.

 

It's more than likely some fault in the wiring or gauge or possibly a weak pressure relief spring that is letting too much past at idle.  I'd put a mechanical gauge on it and unless it reads at least 20 PSI at hot idle, I'd look into swapping out the pump.

 

Rule of thumb 1 psi for 10 rpm... use a mechanical temp and oil pressure gauge... try different oil viscosities... I run 20 50 in the summer... if I don't my oil pressure is in the dirt

Yeah... not quite....I'm going to claim that this is a typo... but really I was just not paying much attention... what i meant was 1 psi per hundred rpm... THX for calling me on that... notice I didn't use any zeros there....

 

oil pumps are the stich in time saying , pump less than 70 dollars , gaskets 25 dollars , even new rod and main bearings are ? 100 dollars if that . and it can be done in the truck . about the same cost as a brake job .