Hey guys,My boat is shutting down after 10-15 sec. WOT.Boat just shuts down. It will fire right back up.Had a friend watch the gauge he said its doing alot of bouncing around.
I am running a holley black pump set at 7 psi,holley 950 hp. with -6 line,and its going thru a dual switch for the tanks.Witch I believe is 3/8 in/out ports.My question is could the line be to small? Roughly 600 hp/600 tq I'm running a AA imp. to 5100. Thanks in advance!
I believe -8 is recommended at your power level. But I'd check other more likely causes of fuel starve first. Like line blockage from tank to fuel pump. Fuel filter. Check valves, if installed. Carb float level and needle valves.
jer
[ July 28, 2002, 11:11 AM: Message edited by: LVjetboy ]
Travis,need more info. Is it the fuel pressure gauge you are talking about? Does it die instantly
like turning the key off or does it sputter down and die. Open your gas caps and try running it. Your tanks may not be vented enough. Jethro
Yes its the fuel psi gauge. I'll get a few surges like I'm running out of fuel.If I stay in it. Its done 2-3 surges and it shuts down.The time span would be my buddy went by at wide open throttle 21 day druiser 425 hp sbc I/O.From a dead stop I can chase him down and as soon as I get next to him it surges.I make it by him maybe 5 boat lengths and engine shuts down.But fires right back up?????What else is going on jethro?Still have those parts.PLanning on bringing them to tower park the 24th.we are going to try and make it up for sat.If you need them imediatly let me know.
I'm no JEThro, but still think your guess of fuel starvation is a good one jstwkd. Surging is typically a lean condition, though not always.
But as you describe, very likely.
Fuel pressure flux is also no proof of a starvation problem, as opening and closing needle valves during normal full-throttle conditions, along with normal pressure regulation flux can cause a fuel pressure flux for a running engine...depending on how much and at what rpm and pressure. I also have a pressure gage "flux" but no shutdown as you describe.
"Fires right back up" is also no mystery as the fuel delivery at startup and idle are significantly less than full throttle and no challenge, even for a partially blocked system that has a full throttle fuel starvation problem.
So to say again, if I were you jstwkd, I'd check the suction side of fuel delivery first if you haven't already. Verify you have full flow to your Holley, before upsizing the lines. I had shreded bits of rag or paper towel jammed in my tank valve once that caused shutdown, and was hard to find.
Then check the pressure side as in needle valves. Not that -8 line is overkill, just that with good supply pressure, a -6 such as what you have, shouldn't cause "surging" with 500 or even 600 hp, unless something else is wrong. In which case, upsizing is a bandaid fix and no solution at all.
And lean surging can damage you engine, so a good thing to fix soon.
Just thoughts of a BRF,
jer
[ July 29, 2002, 05:29 AM: Message edited by: LVjetboy ]
Thanks LV,
I'm planning to check the fuel lines for the check valve.I may still have it in. I bought the boat from the original owner.I dont think he made that many changes.I,ve allready lost three pistons.I beleive to a lean condition but my machinest disagrees.He feels it was lack of water to that side of the motor.I'm also going to remove the dual tank switch and feed off both tanks at ounce.I beleive thats the norm.Thanks again.
WKD
I run -8 from each tank to the pump and to a fuel block and then run-6 to each bowli am running a pair of BG 850's.But if it was'nt doing this before and then all the sudden started it u need to find the problem not just start changing lines that gets spendy and u will probably still have problems.Thats just my 0.02 cents i mean im no LV JET my boat doesnt even have a stereo in it or a blender,allthough im still working on it!
You say your using a holley fuel pump,
Have you ckecked it?
I've seen lots of problems with them.
-6 is border line you should have -8 but that's not your problem.
Also look inside the hoses to make sure there not deteriating from the inside out as they often do.
I think you can not get a fuel line to big. I build
lots of drag cars and only run -10 pump to regulator. Look at the regulator some neck down
to 3/8's way small for a hot big block.
It is hard to tell if braded line is soft of old
so if you do not know the age replace it. We replace it every 4 years. The pump may be to high. Most aftermarket pumps like to be gravity feed.
a hard thing to do in a boat. A high output
mech. pump may help.
Guys thanks for all the input.I think I found the problem.Found some crap in the filter and both tanks still had the check valves.Removed those and ran it had no stumbling or shut down but i did have a ton of pinging couldnt get it to stoip with timing.I've re-jetted again 86 / 99 now it has to be rich.Let you now thurs. Thanks again.
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