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Could use some advice - New 2.8 V6 - Initial Start - Low/No Oil Pressure?

Bronco648

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I'm in the process of putting an '85 RCLB back together.

I have a newly rebuilt 2.8 V6. I spun the engine with the starter to get oil circulating. I could not get any pressure to register on the gauge. I verified that I am getting oil to the heads (by popping off the passenger side valve cover). I verified that the gauge works by testing the wiring per the shop manual. I am on my second, new oil pressure sending unit (can two be bad?).

I started the engine and it runs nicely. I watched the oil pressure gauge jump to the upper end of the scale and then slow sink all the way down, until the needle bottomed. The engine has not run for more than a minute or two. It's got an open y-pipe but I cannot hear any noises that would indicate a lack of oil pressure. I removed the passenger side valve cover again and verified there's more oil up by the rockers but I don't know how much oil to expect.

I'm hesitant to run the engine more for fear of ruining bearings/cam, etc.

What else can I do to verify oil pressure? I needed this truck to be running and road-ready about a month ago. I'm getting sick of not making any progress. TIA.

UPDATE: After re-installing the passenger side valve cover, I can see oil on the rockers, it's pooled on the keepers and it's pooled on that sheet metal 'tray' that sits between the rocker assembly and the head (it seems to be there to re-direct oil to the push rod holes to facilitate oil draining back to the sump). I can also see where oil has been flung onto the underside of the valve cover, from two or three of the rockers. Is that sufficient? Am I expecting there to be too much oil in the area under the valve cover?
 
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rusty ol ranger

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Hook up a manual gauge. You probably have a gauge/sender/wireing issue
 

Bronco648

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RonD

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1985 should have a real oil pressure sender(PS60) and real gauge, variable ground

Disconnect spark and crank engine with oil pressure sender out, so oil can come out the hole, put a pan down to catch the oil, could have some left over debris in the main passage, long shot
 

rusty ol ranger

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1985 should have a real oil pressure sender(PS60) and real gauge, variable ground

Disconnect spark and crank engine with oil pressure sender out, so oil can come out the hole, put a pan down to catch the oil, could have some left over debris in the main passage, long shot
The "real" pre mid 87 gauge still relies on wireing and a sender though.
 

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Yes, he said he test that, I assume he grounded the wire on the sender and gauge went up to maximum, same as testing Temp sender wire
 

ford4wd08

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What brand sender are you using? I will only use the more pricey motorcraft replacements after been burnt and chasing my tail with cheaper aftermarket replacements.

I agree on a additional gage setup for start up to see what's going on.
 

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I would agree a mechanical gauge would be good for testing, but...............if oil pressure is actually dropping to under 3-4psi you will hear valve train noise for sure
So I think this is a sender/gauge issue

+1 on OEM senders
 

Bronco648

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1985 should have a real oil pressure sender(PS60) and real gauge, variable ground

Disconnect spark and crank engine with oil pressure sender out, so oil can come out the hole, put a pan down to catch the oil, could have some left over debris in the main passage, long shot
I did that previously, when I thought the first sending unit was bad. There was oil in the extender (hex) tube.

UPDATE: I pulled the sending unit and oil pours out of the extension, almost a shot glass full. So, I don't think the extension is clogged.
What brand sender are you using? I will only use the more pricey Motorcraft replacements after been burnt and chasing my tail with cheaper aftermarket replacements.

I agree on a additional gauge setup for start up to see what's going on.
First one was a Standard Motor Products unit (the bigger one, that kind of looks like a bell). This one is a PS60 from Auto Zone.

I think I'm just going to go with a mechanical gauge and be done with it.
 
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Bronco648

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After re-installing the passenger side valve cover, I can see oil on the rockers, it's pooled on the keepers and it's pooled on that sheet metal 'tray' that sits between the rocker assembly and the head (it seems to be there to re-direct oil to the push rod holes to facilitate oil draining back to the sump). I can also see where oil has been flung onto the underside of the valve cover, from two or three of the rockers. Is that sufficient? Am I expecting there to be too much oil in the area under the valve cover? I'm used to a high pressure, high volume oil pump that moves LOTS of oil (in 289/302 race engines).
 

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Oil pressure is no different than blood pressure, too low is bad, too high is bad, lol

Oil pressure is measured on the Main passage from the oil filter out to the bearings and valve train
So the oil pressure you see is the Back pressure, the oil that is building up because it can't all flow out to the engine
Above 5-6psi can overcome Gravity to lube/cool the valve train
Over 70psi can cause "washing" at the bearings, the oil is spraying out so fast it actually "dries" out the bearing causing overheating and failure

Most oil pump pressure release valves are set at 80psi, which in my opinion is too high
 

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I used an old distributor and a 1/4 socket made a tool to turn oil pump in my new 2.9 I had issues "building" pressure as well. Verify oil type/viscosity. And I highly recommend making a tool to avoid spinning engine with little/inadequate pressure. I had a manual gauge in the port and LH valve cover off to watch rockers. I primed with a drill on the tool and it took probably 20-25 sec of turning to achieve pressure and oil pumped for a while at the rockers. All passages have to be filled to get a good pressure reading. I was running 15W-40 FYI.. good luck.
 

Bronco648

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I think I have a bad pressure sending unit. I tested it and it has continuity without pressure. When I blow compressed air into it, I still get the continuity signal from the multi-meter but it sounds like Morse code. ???

And, looking at the unit itself, it says "3-8 PSI" on it. ?!?!?
 

Bronco648

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Tire Size
14"
I was running 15W-40 FYI.. good luck.
I've got 5W-30 semi-synthetic in the sump. I think I have oil pressure, I don't think I have a working oil pressure gauge system.
 

pjtoledo

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is it possible the oil isn't draining back to the pan?
 

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