5.7 Indmar Crazy Fuel Pressure

[Rpburns]

I have a 5.7 that has a new fuel pump, filter and regulator put on it along with all the sensors. The engine runs great for maybe 10 seconds after start up an then slowly starts running rough no power.
At the time of start up its at 39/40 psi then goes down fast to in the 20s. Giving it any gas it just spits an shudders. Let in cool complexity down runs great for a 100yrds or so. Wth.

 

[alldodge]

Welcome
To get the folks a bit more info is which Indmar 5.7 do you have?

I'm seeing fuel pressure from 40 to 60 psi

 

[Rpburns]

Welcome
To get the folks a bit more info is which Indmar 5.7 do you have?

I'm seeing fuel pressure from 40 to 60 psi

Multi port.

 

[Rpburns]

Welcome
To get the folks a bit more info is which Indmar 5.7 do you have?

I'm seeing fuel pressure from 40 to 60 psi

My guess is somewhere in the electrical pump wires something is getting hot an dropping voltage maybe?

 

[froggy1150]

Tank vent or suction tube plugged

 

[Rpburns]

Cap off no anti siphon valve.

 

[alldodge]

Multi port.

Really that's all, what year?

Low pressure is either a restriction, bad pump or regulator

Cap off no anti siphon valve.

As Foggy mention, pull the tube from the tank to see if it's clogged
Then check lines and fittings

 

[Rpburns]

Tank vent or suction tube plugged

The fuel pressure drops off after 30 seconds or less of acceleration.
The motor is a new long block multi port in a 2002 Shoal Runner.

 

[Rpburns]

Really that's all, what year?

Low pressure is either a restriction, bad pump or regulator


As Foggy mention, pull the tube from the tank to see if it's clogged
Then check lines and fittings

New pick up tube 3 new separate fuel pumps used same results. New fuel line new filter. New regulator. Only happens after warm up.

 

[alldodge]

I'm going to need to research. A pump pumps X amount of pressure which is more the needed and the Reg lowers to required limits.

Only reason for pressure to not be we're it should be is restriction, bad pump or Reg

 

[alldodge]

1996 to 2003 fuel pressure
Key-on 43-45 PSI
Idle 35-38 PSI
WOT 43-45 PSI

 

[Scott Danforth]

My guess is bad anti-siphon valve or fuel pickup tube filter. Both are inlet restrictions

Run from a portable test tank to verify

 

[Rpburns]

1996 to 2003 fuel pressure
Key-on 43-45 PSI
Idle 35-38 PSI
WOT 43-45 PSI

The only parameters that it hits are idle an its on the low end. Is there any way to pull a vacume test?

 

[alldodge]

Yes, use a hand operated vacuum pump