View Full Version : What Should Fuel Pressure Be?

07-15-2011, 07:51 AM
I've seen many recommendations to check the fuel pressure to determine if the fuel pump is good. However, what should the fuel pressure be? Fuel pressure regulator on pump assembly has a 40 psi sticker on it. Does that mean it should always be 40 at the schrader valve?

At key on engine off? had 14 psi
Idle? went from 14 - 37 very slowly (took about 10 sec)
2000 rpm, under load?
Wide open, under load?

These readings are with a NEW fuel pump assembly and the engine still died while testing.

1999 Maristar 210 Indmar 330 EFI

Help is appreciated

07-15-2011, 08:16 AM
Constant 58 psi is what I have

07-15-2011, 03:13 PM
Does anyone know what the pressure should be? I'm going to be at the boat this afternoon and want to know if the pump is working correctly.

If the pump is working but the pressure is low, what's the problem? Fuel relay?

07-15-2011, 03:28 PM
Mine is 55 and I think yours is the same. It should go up to 55 instantly and hold there. When yours went to 37 did it stay there or did it leak down? It sounds to me like a leak in the fuel delivery somewhere, or maybe the regulator. Is this the same problem you had with the old module?

Just to clarify, did you replace the whole $500 module, or just the pump inside?

07-15-2011, 03:48 PM
Same problem I had with the old module. When it hit 37 psi it stayed there, even when I shut the engine off.
Replaced the whole $500 module so I could rebuild the old & have a spare

07-15-2011, 06:47 PM
The only other thing I could think of is a leaky injector, but at this point I'm sort of just guessing, maybe JimN will have some ideas.

07-15-2011, 07:50 PM
fuel filter?

07-15-2011, 10:29 PM
Is your fuel pump in the tank, or external?

07-16-2011, 08:13 PM
My dealer told me that mine should be 60 psi. Once the key is turned to the "on" position, the fuel pump turns on and brings pressure up to 60 psi in preparation for ignition. He made it sound like it would maintain a constant 60 psi while running. 07 350 MCX.

07-17-2011, 10:51 AM
Just checked mine last week and mine was 60 psi at key on, 60 psi at idle, and 60 psi at WOT. Also when key was turned off it maintained 60 psi. Had a few issues on vacation so I bought a pressure tester from auto parts store best 40 bucks spent. Tester also has a purge port to get rid of any air in the line and also get a fuel sample at the same time.

Problem turned out to be grease I used to try and keep corrosion out of the ECM connections.
Engine is a 99, 330 LTR Indmar.

07-18-2011, 09:19 AM
Fuel pump is in the tank.

Tried taking the boat out this weekend. Starts fine but at 2500 - 3000 rpm starts to bog down (ie. RPM's drop a few hundred then increase, then drop, then increase etc.)

All of the electrical connections were cleaned & tightened. Mechanic has a call into MC to try to get some ideas.

Ever tried to pull a wakeboarder with a kayak?

07-18-2011, 09:25 AM
I've got the same problem with my 209 right now. It will be fine for 2 days then sat I ended up limping home. Just would not get over 2500 rpm before setting me into prot mode.

07-18-2011, 09:26 AM
Dirty / Greasy ECM connection? That's one connection I don't think was touched. Just pull it apart & spray in some electrical connection cleaner?

I have a pressure tester. Think I'll try cleaning the ECM connection. Is it ease to pull apart or are there any clips to undo?

07-18-2011, 08:03 PM
My ECM never had a cover over it and it would get moisture thru the connectors even though they were weather pac type. I had removed them and cleaned them put a cover over them and the grease I used actually caused problems. So I cleaned the connectors again and removed the ECM cleaned it all out and all is well.

If your ECM has a cover you will probably have to remove the cover to get access to the connectors. If you squeeze the sides the connectors will come right off. Best to disconnect the battery before you do this though.