Re: Hydraulic lifter or rocker problem? 496 HO
Although now it would appear the low pressure fuel pump has stopped working as when I'm switching on the ignition to prime the fuel rail I'm only getting a few spoons full of fuel coming out and no pressure to make it pass the filter..
Do you think the issue with the valves and rockers has ultimately damaged the low pressure fuel pump?
No the valves and rockers would not damage the fuel pumps, this is a separate incident.
Well only that the boat wont start now, and from what I could determine is that the fuel delivery from the low pressure side has failed as I'm not getting fuel pass the filter..
Well I thought maybe because of the constant filling of the fuel chamber (as its happened about three times now filing with fuel) I also suspect when I had the engine running at idle before fitting the engine (it ran fine on the floor with no issue) The moment it gets put under load it was happening..
Which made me think that maybe its damaged somehow the fuel delivery system..
I believe I see/read this as you have removed and refilled the fuel filter three times now? If so, maybe the O'ring has been compromised somehow and it is now sucking air. I would recommend buying a new filter, filling it with fuel and install it and see how it goes.
Haven't yet hotwired the pump.
Alldodge has it right, here is how the fuel pumps work. Upon Key ON, the fuel pump relay receives 12v battery power through the fuses at Terminal 30. The relay powers both fuel pumps and signals the PCM that the engine is ready to start. Listen at key ON for both fuel pumps to run. A malfunction in the fuel pump relay circuit will not set a fault.
Tried to put the gauge to see its output and it wasn't really registering. I'm going tomorrow with a different gauge and some bits so I can make some other readings of fuel pressure.
Does this pump like the high pressure pump have a small screen for the fuel?
Yes there is a screen in the inlet side of the pump fitting. There
should also be a inline fuel filter just before the pump as well. Item number 21 ,
http://www.mercruiserparts.com/Show...6708&bnbr=60&bdesc=FUEL+FILTER+AND+BOOST+PUMP
If so then this may be the cause, my boat was originally powered with a diesel engine and this is the first fuel load put through the tank and that, although it was thoroughly cleaned you never can be sure and maybe something has blocked it, I did attach another fuel can and tube straight to the pump but if it has a screen and is blocked could be the cause..
The pump screen could be clogged up. Another test would be to tee in a vacuum tester gauge before the low psi pump and make sure the vacuum is very low, under 2 Hg. See this thread for a how to if needed.
http://forums.iboats.com/mercruiser...ow-testing-your-boats-fuel-system-283269.html
Diesel engine to gas engine, Hum, If i recall correctly, I believe Diesel fuel tanks use a return line? if so you capped it off? Also make sure the vent line is working properly. Next time your trying to accelerate, try opening the fuel cap cover for better venting to see if you get your power back or fuel pressure back.
Another thing to consider is do you have an anti syphon valve located at the fuel tank that is working correctly. An anti syphon valve is the fitting at the fuel tank the fuel hose would hook up to. It has a check ball inside the fitting that could get stuck.
