BillR

I think I may have an issue with low fuel pressure on my 575SCi's and would like some assistance from the forum.

For those of you with 575SCi'S:
What does fuel presure guage read at idle and various RPMS?

Why I think I have an issue:
I bought my Top Gun used; and from day 1 both engines have read 20-21 lbs from idle to WOT. Since both motors were identical and there was soot on the transom, I assumed that was normal for a TG & 575SCi's.

Actually what lead me to the problem is my sea water pump leaking oil. This was happening because the diapham fuel pumps (that are attached to the sea water pump) have been leaking fuel into the oil of the seawater pump and thus trashing the sea water pump seals and leaking oil in my spotless bilge!
Merc "JUST" updated the mech fuel pump to a new/revised design mech pump. They have been back ordered until just recently. So last week I put on brand new sea water pumps and the new revised mech. fuel pump. At idle I am still getting 20 - 21 lbs. At 4000ish RPM it dropped to about 18 lbs. I didn't take the rpm any higher or into boost, as I was unsure of a possible lean condition. (FYI - I still have soot on transom)

I asked the tech to call Merc, and Merc said I should be at about 30 PSI. (SUPRISE! and why I posted this thread) So now the tech will be looking for a problem. 1st thing he is going to do is hook up a mech fuel pres gauge to rail and see if gauges/senders are wrong. (btw - all wires on senders are good clean connections)
If mech gauge shows low, where would you look for fuel delivery restrictions on an '02 Top Gun???

Thanks in advance!!!!!

Scott

Bill,
No help to you but I just replaced my pumps and have to wonder did I get the new or the old? Anyway of knowing from looking a them.
I did have to take them apart and change the direction of the fittings. Way too much Powder coat on the screws

BillR

The new pumps have a different part #
The New pumps are bare - no paint.
They also have alot of black diapham exposed at the joint.
I haven't done a side by side, but I also "think" the new pump is bigger.

JaayTeee

My new ( to me) ride has 575's,
I ordered the service manual for it.

In the tune up spec's, it list 28 psi at idle,
26 psi WOT.

In the repair section, it list 34-38 psi,
with no indication on engine speed ???????.

Either way, 21 psi sounds low.

I've got to think that Cig. wouldn't have
any problems with the plumbing to the
engines.( sizewise)

If the mechanical guage reads low,
the first place I would look is the fuel
filter, ( at the rear of the engine, back by
the ECU) it could be partially plugged.

Next would be the pressure regulator
on the cool fuel unit.

Last, the pumps themselves.

Mine seem to be somewhat cold blooded,
they will sometimes, when cold, stall when
advancing the throttle off idle.

One will occasionally puff black smoke on
start up.

This thing is kind of new to me, and I'm
just figuring out all the nuances with it.

My last ride had carbed HP500's, and they
were not near as fussy as these things are when
cold.

I have read somewhere about a dual IAC
setup, that helps the rich idle problem,
but I can't seem to find that info any more.

When I get done putting the XR drive with
a bad pinion gear back together, I'll start
looking more into some of these
cold blooded quirks.

keep us posted.

mfb357

I have 3, they all run at @30psi at idle and will drop to around 20 at throttle either wide open or half there really is not much difference. I can tell you if you have run out of fuel with these engines you may need to replace the electric high pressure pump. I hit my fuel shut off once and never was smart enough to figure it out,( I was low on fuel and thought I ran out). So I kept trying to start it, maybe 6 or 7 times waiting for the pump tp prime. That pump let go after about another month of use. These pumps are cooled and lubricated by the fuel flowing through them. You could also try changing the high pressure fuel filter on the back of the engine. Good luck.