MotorCityCanadian

Hey all, I have my car in the shop right now for a bunch of work, one of which is to install a new Melling HP Oil Pump and the technician is claiming that there is no oil pressure when attempting to prime the pump..

After speaking with Texas Speed and Performance, they claim to think that it's user error by the tech as these pumps are "bullet proof" and very rarely come defective off the production line..

Here is the write up from the receptionist at the shop I'm using.

" Attempted to prime the oil pump before starting, oil pressure never rose above zero. No oil is reaching the oil filter, pickup tube is sealed to the pump. Suspect a stuck open high pressure relief valve in the oil pump. Could be caused by a machining defect. Oil pump should be replaced"

Any advice or input is welcomed

G Atsma

Sounds like pump removal is warranted so it can be inspected for a stuck relief valve.

MotorCityCanadian

Could is be inspected and just need some force to free up the valve? Or would a replacement be suggested?

IGN-1A

Prime the pump, ALWAYS ?
Lance

G Atsma

You might try that and ensure the valve is moving freely, but to do that you might have to polish the valve bore

G Atsma

Read the first post. They tried that with no good results.

MotorCityCanadian

Very cryptic, mind sharing your thoughts?

MotorCityCanadian

Thanks for the advice.. I'm got a replacement pump on route.. hoping that it solves the issue..

Quito195

They won’t make oil pressure on a fresh build off the starter. It doesn’t crank over fast enough. Maybe if you pull all 8 spark plugs…..

KCS

iTrader: (20)

I’ve never seen a bad Melling pump, but I do disassemble, clean, and lube the pump before I install it. I pop that allen plug out and run a brush down the relief valve bore too.

I don’t think it’s a good idea to just install one right out of the box.

IGN-1A

Hi KCS, as do I.
I remember that there was a way to inject oil into the Oil Gallery that would then drip into the pump thus "prime" the pump.

91 Z28

iTrader: (3)

Most of his posts are like that. He's either too smart for this world or something else

Kfxguy

iTrader: (1)

Mine didn't "build pressure" when I turned it over with the starter. I seriously doubt theres a problem with the pump. Melling is top notch. I've been using them for almost 30 years and never had an issue.

MotorCityCanadian

This is what is concerning me, that comment seems to be the going consensus among most people, even TSP was doubting what I was telling them..

The hard part is trying to get the shop to try some other trouble shooting techniques suggested by the customer.. I'm in a weird spot

Kfxguy

iTrader: (1)

crank engine. It should have oil pressure within 5-7 seconds. If it doesn’t, shut it off. You have a problem. If it’s a new engine, I’d prime it from a port on the block. Google which one. If it’s not a new engine, crank it and see if it has pressure within a few seconds. Just spinning it over with the starter isn’t going to tell you anything. You can’t prime these engines with a drill on the pump shaft like an old sbc.

IGN-1A

I would ask if the large oil pump rotor was "centered" around the crankshaft small rotor?

Keith

I haven't been able to get pressure to build with a new pump, using the starter with plugs out. Or in another situation with the pickup off. Thankfully, $14 in parts from summit and a garden sprayer with some hose attaching the two I was able to prime the oil system.

Oil pressure came right up when I started it.

LS1 TJ

Could it be as simple as a damaged or incorrectly installed pick up tube o-ring?

grinder11

iTrader: (1)

This makes no difference. It might make for longer pump life, but short term oil pressure will be unaffected. In my 2000 C5 shop manual, GM doesnt even mention centering the pump.....

brutalzo6

iTrader: (12)

My engine builder told me to pull the plugs and unplug injectors and crank it until it has oil pressure. It took like 5-8 seconds for the pressure to build but it worked.