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High Pressure Pump: Does it produce more pressure then the system calls for and...

C

carboncow

Contributing Member
the pressure regulator knocks it down?

I know in another post it was stated that the pressure shouldn't go above 50psi or it can damage the regulator.

While sourcing high pressure pumps I can go OEM for $400-600. Not much comes up for the part number I found 23021433 for my 7.4GiPLKDCE. Many aftermarkets are out of stock. One website noted other numbers and I started to cross reference those and found a pump that the seller states works with the 7.4GiPLKDCE but the specs say 120lbs. Its part number is 3857650. So my thought is either that is incorrect or the regulator knocks it down?!?

Just learning here as I consider my options for my next round of pump(s) bench testing and maybe cleaning/swapping when I get to the lake next week. Some of these parts are approaching 20 years old and one mechanic buddy said I might consider just replacing.
 
That PSI seemed rather high to me too but then they claim it meets the needs for most VP big blocks of the era. I'll most likely got with the OEM you linked when it comes to the HPP as I'm not seeing some options...although I didn't want $50 china pumps I'm not even seeing them. This seller claims their own name on them (out of Georgia) but my guess is that it's rebated china. I won't link to their alternate site but you can see from the photos it's the same pump I got (and most look like) and claims a lot of engines.

I just cannot image that the regulator takes it from 120lbs to 40lbs and I know my injectors are 43lbs. I think AllDodge in one post said I should see 60bs if I bench test it. Fun finding parts for ancient VP MPI systems!
 

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Yes Reg drops pressure but note it's not high volume

Fuel is in your tank with HP pump. The float in the tank keeps the fuel in the tank from getting over full. So no fuel comes into the tank until level drops below float level setting

Motor is running a HP pumps fuel above need and any excess is dumped back into tank. Again tank level does not increase until level drops.

Hydraulics uses liquid because liquids do not compress. So fill a fuel line with gas and apply pressure and the increase is instant. Then Reg keeps things from getting to high
 
Just a follow up of where this project went...

1. New LPP. Still no reading of fuel pressure on low or high side
2. New HPP, but now I can get a rock solid 40lbs with our HVAC gauges but NOT our fuel pressure gauge set. Must be bad although they read air pressure just fine. New HPP had a good sound to it with key on (not started) where I never heard anything before. So maybe it was struggling. HPP also had "gunk" on bottom where I couldn't see, maybe a very slow leak I couldn't smell.
3. So a faulty set of gauges had me spinning in circles and throwing some parts at it but I"m only $200 in and I believe this means my FPR is just fine since I"m seeing 40lbs rock solid on my high pressure side.
4. Bad news is I still got a rough idle but it purrs like a kitten at any speed. Going to see this afternoon if the new HPP will allow me high RPM as I never got to WOT since the new long block.
5. Lastly my marine mechanic buddy (not near me) said the guy who put in the long block may have not got the distributor set correctly to spec when installing and being off a few degrees might be impacting the idle timing oh so slightly. This rough idle will be his problem in the off season.

Thx for all comments and I got a great education on fuel system troubleshooting and all the components of my rather oddball OMC/VP 96-98 big block.
 
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