I just bought a 93 3.0 sigle cab that had a blown head gasket with 175,000 miles. After putting motor back to gether and firing up there is no oil pressure on the guage but the motor sounds good, not smoking, so i believe there is oil getting to the motor. any help would greatly be appreciated!! Maybe the sending unit or bad sensor???

 

try replacing your oil sending unit. if theres no oil pressure, you'd prob be having lots of knocking and pinging and stuff.

 

How long have you run it? they can start and run on assembly lube w/o pressure.. I'd pull a valve cover - see if you've got oil up top. Otherwise use a manual gauge.

 

The factory oil guage was VERY iffy to begin with.

 

I don't know....mines been pretty reliable. But, a used vehicle is a used vehicle. [Whitevenom] Do you know if the gauge was working to begin with? I'd do as dcg suggested....definitely before attempting to drive it.

 

Not to hijack this thread, but do 3.0's make alot of valvetrain noise even when operating normally? I had the same issue with oil pressure after my HG job, but the sender is fine and the mechanic didn't seem too worried about it. My top end is louder than anything after about 15-20 min of operation, about right after that high-pressure cold start oil pressure goes down.

 

I had the same thing happen after doing the HG on my 22RE...turned out the sending unit was disconnected (d'oh!).

 

i replaced the sending unit today and started the motor up. it built pressure on the guage then it dropped and wouldnt build back up. i drove it and didnt hear noise. I am stuck!! any help ??

 

You may have a bad ground some where. There are a few test you can run to check and see if the gauge is bad. If your gauge is good and you just replaced the sender I would bet that there is a poor ground some where.

 

how do I check that???

 

I have heard that if you fail to prime the oil pump on reassembly that it can cause this issue...

 

also... where the sensor plug for the sending unit is there is another plug that has no where to plug it in. is this normal?

 

check the pressure with a manual gauge as mentioned. If you have pressure, run it a while. Make sure the pressure doesn't drop. If you had pressure, I wouldn't worry about it.

If you wanted to fix it, I'd begin by checking all the dash grounds. weird things can happen when they open up.

 

Don't worry about priming the oil pump on a 3.0 its not really possible. If your at all concerned about oil being pumped just reach down while the motor is running and start to SLOWLY loosen the oil filter if its pumping oil you will know it. On my old VW rabbits you would need to loosen the oil filter after you start the motor on a fresh rebuild just to purge the air the first time you run the motor. On those rabbits it would not pump oil until you loosened the filter, You could hear the air rush out quickly followed by oil pressure. I have never had this problem with the 3.0 but thats not saying you don't.

 

Funny thing about oil pressure everyone has there own way of checking to see if you have it. Try this for some easy way to see if the guage is working turn on the key dont start it unhook the guage and groung the wire if the guage is at all working the needle will peg to high oil pressure. If its just a light and not a guage then the light will come on. As for your other question about another plug it should be there they put both plugs there one for a guage and the other for a light.

 

would it matter that the truck had sat with the blown head gasket for over a year before I bought it?

 

3V's never had GOOD oil pressure,hell,5V's too for that matter.But if you have OP cold and it goes to $%&@,it could have several problems.Worn bearings(especially if they ran the truck home with a crankcase full of antifreeze),stuck OP relief valve,wrong oil filter.The single largest problem I've had is the strainer being stopped slam up with sludge!

 

well i checked the pressure with a mechanical guage and its the same. when it starts up the pressure is at 20 then the pressure drops to 0. So I am going to drop the oil pan and check the bearings. any other suggestions?

 

If it starts at 20 then drops I would guess that there is a bunch of crap around the pick up screen.