Hello,
I have a 1996 PSD Dually, Crew, 307,000 miles, all stock. I have owned since 200,000 miles. Standard oil & filter changes. Radiator flushed last year, transmission rebuild 40,000 miles ago. New Glow Plugs this past fall. Basically a stock truck that is very dependable. Issue I see now is when I start the truck first thing in the day, it takes 10 - 15 seconds for the dash oil pressure reading to come up. The needle sets all the way to the left, then suddenly comes up. After looking through threads here, I checked the HPOP (I believe that is what I checked, front top of engine) and level was down about an inch. I topped it off, and started, the truck, same behavior. Looking for guidance on where to check. If I pipe in an external Oil Pressure Guage, where do I connect in? What else could be going on here? The truck runs great, want to keep it that way, plus a long trip pulling a cattle trailer this summer, so want to make sure everything is as it should be.

 

You can remove the stock sending unit (pressure switch) and plumb a test gauge in the hole right there. It may be nothing more than a faulty pressure switch. That gauge really only has 2 positions, on (in the middle) and off (to the left). It really just a glorified dummy light. That being said, with that many miles it is possible that the LPOP is getting weak, so it would be a good idea to put a gauge on it and test it.

Also, how long since the last oil change? Did this happen to start right after an oil change?

 

my guess is pressure switch. mine did the same thing. how long have you let it run with the gauge on zero? did you take it for a drive?

the truck needs to see a minimum of 7PSI to even start so its getting oil.


Best bet is buy a gauge. i got a mechanical one for $13.99 at the local parts store. there is a port on the side of the rear oil cooler housing(right above oil filter) it threads right in. you can even just thread it in and too the gauge and then just set the gauge on the front tire and fire it up to check before going through the hassle of routing the gauge through the cab. Be careful not to kink the white hose if you are buying a cheapy mechanical one.

I have had mechanical gauges for 3 years and never failed me. Dont let these worry warts tell you not to run oil lines into your cab. $14 gauge works fine.

 

If it's staying running for 10-15 seconds with out the oil pressure gauge coming up, my guess is that the oil pressure switch is the culprit.

If it really did not have oil pressure, it would only take 4-5 seconds for it to completely empty the HPOP rez and die. The LPOP has to be filling the HPOP rez at least at a reasonable rate for it to continue running and not start running rough or anything at start up.

If it were me diagnosing this issue, I'd pull the plug out of the HPOP rez and plumb a mechanical oil pressure gauge in there (since the switch for the dash gauge is in the HPOP rez also. Start the truck and see what the mechanical gauge says is really going on. If you start it up and pressure on the mechanical gauge reads good while the dash gauge is still saying nothing, I'd replace the oil pressure switch.. Once you're done with the mechanical gauge, pull it out and put the stock plug back in the rez.