95 502 needs help

[whitelightnin]

Hello, I have not posted in a long time, but i need help. try to make this short. I have a 1995 502 that originally had a vs tank. Due to problems with boat operation, I removed the vs tank to have one less headache. The questions I have are:
Regulator on front of fuel rail, fuel pressure reg or pressure dampner. I am getting conflicting info.
Best american made electric in line fuel pump capable of over 50# pressure and at least 40gph flow. The chinese junk I have will not produce over 30# but says it will go to 75.
If the reg on the end of the fuel rail is a fuel regulator, can I add an adjustible reg after the pump but just before the fuel rail.
I have installed all new fuel lines from tank thru 100 micron pre filter to pump to 10 micron post filter and to fuel rail. Also ran a new return line from return on fuel rail to tank. I have replaced plugs, plug wires, distributor cap & rotor, fuel pump relay, many new sensors and new vacumm line from new reg at end of fuel rail. The problem is at about 3000rpm the engine falls on its face, keeps running and after a few seconds recovers but cannot exceed 3000rpm +-. I installed a fuels guage in the main fuel line just before the rail and will not exceed 30#. I know I need somewhere around 40# for proper operation. At low speed and low rpm the boat runs OK.
Any help is greatly appreciated.

rail

 

[alldodge]

originally had a vs tank

If the reg on the end of the fuel rail is a fuel regulator, can I add an adjustible reg after the pump but just before the fuel rail.

The VST 502 should have 37 psi and the cool fuel has 43 psi

Adding a Reg after the pump will do nothing to help, only hurt. The Reg at end of fuel rail is there to bleed off any pressure above 37 psi to the low section of the rail back to the VST.

There is a break in SN for the VST but both use Reg 805227A1 so pressure set at 37 psi

Also ran a new return line from return on fuel rail to tank.

So you plugged the return to VST, correct and sent it back to the tank?

Not able to get and hold 37 psi, this would be a pump or Reg problem. Pump was replaced so must be the Reg

 

[whitelightnin]

The VST 502 should have 37 psi and the cool fuel has 43 psi

Adding a Reg after the pump will do nothing to help, only hurt. The Reg at end of fuel rail is there to bleed off any pressure above 37 psi to the low section of the rail back to the VST.

There is a break in SN for the VST but both use Reg 805227A1 so pressure set at 37 psi


So you plugged the return to VST, correct and sent it back to the tank?

Not able to get and hold 37 psi, this would be a pump or Reg problem. Pump was replaced so must be the Reg

pump was replaced but as I said in my post, the pump I have will only put out 30psi. I feel a good new pump will help. nay suggestions on a pump

 

[alldodge]

pump was replaced but as I said in my post, the pump I have will only put out 30psi. I feel a good new pump will help. nay suggestions on a pump

First a pump can output 1000 psi but if the Reg is set to 30, then all anyone can see is 30

This can also happen if the Reg is bad and will only allow pressure up to 30 psi when it should do 37

In short the pump is not the issue

 

[whitelightnin]

The reg is new and it is oem mercury with correct part number. The gauge I installed is just after the pump but before the rail, which I would think indicates poor pump pressure.

 

[alldodge]

The reg is new and it is oem mercury with correct part number. The gauge I installed is just after the pump but before the rail, which I would think indicates poor pump pressure.

no, it indicates what the Reg is set to

 

[Lpgc]

It'll indicate actual pressure regardless of where it's fitted in the feed to injectors.

Pressure will be limited by the reg or pump, most likely the reg. If the pump can only pump to 30psi you won't get higher than 30psi, if the reg is set to 30psi you won't get higher than 30psi.

 

[whitelightnin]

It'll indicate actual pressure regardless of where it's fitted in the feed to injectors.

Pressure will be limited by the reg or pump, most likely the reg. If the pump can only pump to 30psi you won't get higher than 30psi, if the reg is set to 30psi you won't get higher than 30psi.

Thanks for the input.
I plan on disconnecting the fuel line from the rail and cap it. Then turn the pump on and see where the pressure goes to on the gauge. If it climbs no higher than 30psi, I know I have a bad pump.

 

[Scott Danforth]

New doesn't mean good

 

[alldodge]

Thanks for the input.
I plan on disconnecting the fuel line from the rail and cap it. Then turn the pump on and see where the pressure goes to on the gauge. If it climbs no higher than 30psi, I know I have a bad pump.

If it goes above 60 then the pump is good but might have damaged the Reg