Oil pump priming, a valuable lesson to keep in mind

Glenn Owner/Technician Texas Posted   Latest  
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No Oil Pressure

Hello DN Folks,

I have another post on a project Lincoln Aviator 4.6 32 Valve engine I am working on for my wife, but I thought this subject needed more focused attention. Over the years (decades), I have built many engines both partially and totally. One main component that was always replaced is the oil pump, this job was no different,

Traditionally to prime the oil pump on most engines before install, all that was required was to pour a little oil in it a rotate it around to let the oil fill the machine clearances and when the engine was cranked a suction would be created and new oil pumped into the engine journals and bearings.

With any engine that has a new oil pump just installed, it is best to confirm it has oil pressure, before rushing to finish it. Yesterday evening, I finally completed all the timing components and installed the rockers. Before installing the timing cover and cam covers I wanted to verify I was getting oil to the components and tensioners were pressurized. With the plugs out of the engine, the battery ground was connected and the engine cranked numerous times. 

What! No oil being pumped anywhere? This is a brand new Melling oil pump, I partially filled the oil filter and the pan was mounted loose with 5 fresh quarts in it. I stopped for the evening to let this sink in for a while and do some research.

There were several things involved. First was the engine has been apart over a couple of weeks time while parts delays and mix ups were sorted out (the vehicle is mine, so it was not a rush job). All of the timing components were removed and replaced, the pan was removed and cleaned, the pickup tube cleaned out and the oil pump replaced. Basically all of the oil journals were empty. Trying to prime through the oil sender unit was in vain because of the oil filter, The (new Ford) oil filter has an anti drain back segment designed into it. (Oil cannot reach the pump from there). Even the thought of pressure tank priming would have still not reached to the void inside of the oil pump. The pump was cavitated.

So how is the oil pump primed? Watch the following, this should apply to any of the Ford Modular V-6 and V-8 engines; 

Melling Tutorial for Priming your Ford Modular Oil Pump ! - Bing video

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Stephen Owner
Florida
Stephen
 

Greetings D.M. Another way I've used successfully in the past is to put about two gallons of fresh motor oil in the engine so that the pump is submerged in oil and then crank the engine. Obviously, when pressure is recovered, you'll be draining the excess oil from the pan for re-use. It's a lot easier and judging from the video, a lot less messy. Best Regards. Steve Wheeler

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Glenn Owner/Technician
Texas
Glenn
 

Hi Stephen, That method also work very well to prove when a pickup tube O-ring has failed or the tube has cracked on some engines.

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David Owner/Technician
Pennsylvania
David
 

Thanks for sharing. I have not done any 4.6 yet but will definitely keep this in mind.

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Glenn Owner/Technician
Texas
Glenn
 

Hi David, I recommend pressure priming any engine regardless. A dry start can easily cost an engine. With todays modern engines, many chain tensioners and cam phaser are oil controlled so it is vital that oil is present before initial startup after major engine repairs. All of the Ford 4 cam engines are very complex. Other manufacturers are not any easier.

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David Owner/Technician
Alberta
David
 

Well, that is indeed a “method” that gives some prime to the pump but there is a much better, even gold standard method, by way of using a pressure tank. The pressure tank is filled with up to 7 or 8 quarts, closed up and then a valve controlled hose is connected to any oil passage of the engine. The tank has a pressure gauge on it. Usually use the the oil pressure sending switch port to tap…

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Jason Owner/Technician
North Carolina
Jason
 

Always use a Pressure Tank to push the oil into the system . I have used this method for over 40yrs,

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Glenn Owner/Technician
Texas
Glenn
 

Hi Jason, I have only worked in 2 shops that actually had a pressure oiler. It is rare to have to use one these days. I did make one using a cheap pump up weed sprayer. It worked very nicely. Now I have a pressure oiler in my collection of shop made tools

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Jason Owner/Technician
North Carolina
Jason
 

Hi Glenn, Great job thinking of a way through and finding a way to solve the problem . My first set up was one that I had made out of an old 20 pound propane tank … lol. As soon as I was able, I immediately bought one from the MAC Tool guy , who of course visits you every week. 😒 I would absolutely not start an engine that is either new , rebuilt, or one that has been setting up for over a…

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Glenn Owner/Technician
Texas
Glenn
 

Hi Jason, I know some out there may think this is a trivial subject, but I have seen brand new crate motors crater before they were ever moved out of the bay. And it never fails, some (idiots) think racing a ticking engine will magically suck the oil in and everything will be fine. There are cases that come up once in awhile on here where other overhead cam engines have jumped the chains…

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Jesse Owner/Technician
Pennsylvania
Jesse
 

Hi excellent video, the suction gun get used at my shop a lot , my favorite pressure oiler is a painters pressure tank with removeable lid , got it at harbor freight for about 100. Several years ago, I also use it to bleed diesel fuel systems

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Sherman Owner
Texas
Sherman
   

Back in the days when I had hair (Circa 1978) I worked at a Cadillac Dealer. GM had come out with the downsized DeVille engine at 425 CI. They went to a skinny oil filter, from a fat one on the 472 predecessor. Invariably, many customer would visit the fast lube joint where the hapless technician installed the fat filter in place of the removed original skinny filter (bigger is better, eh?)…

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Glenn Owner/Technician
Texas
Glenn
 

Hi Sherman, When I was a teenager I worked on a lot of those big vehicles. I even put a 455 in a 70's Buick Century that had a 350 originally back in the day. A few trips to the local salvage and that thing was a screamer. That was back when vehicles were easy to understand and work on. I have packed a few older pumps with petroleum jelly in the past, but this crank mounted pump had me…

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Sherman Owner
Texas
Sherman
 

Actually, back in those days, GM had production quality control problems, and the Chevy small block “thud-thud-thud” upon cold start up was related to a line bore problem on production machining of the crankshaft main saddles of the block being ever so misaligned. I had a 1993 GMC Suburban with the venerable “K” engine (350 with TBI) that knocked pretty unpleasantly upon cold start up. GM had a…

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Glenn Owner/Technician
Texas
Glenn
 

Thanks Sherman, I recall several TSB's with varying degrees of solution. As you mentioned quality control was a huge issue back in those days. Some engine had crank line bore issues so bad the cranks would eventually stress break, some had piston slap issues, while others were addressed with a proper filter with an anti drain back valve. That's what happens when people trust automation and…

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Sherman Owner
Texas
Sherman
 

I went so far as to remove the auxiliary oil cooler/ hoses/ adapter, replaced the main bearings, and install a genuine GM AC/Delco filter at 90,000 miles….. and the knock stayed “cured” for 90 days or so. Like I said, it wasn't a longevity issue. It went 200,000 miles before being crushed by a tree…. with the thud having been there for north of 100,000 of those miles, uninterrupted and still…

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