SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: CHROMEY on August 01, 2013, 07:13:45 PM
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850 HOLLEY DP
got 86 jets up front w/ 2.5 powervalve
got 89 jets out back w/ power blockoff
been chasing down gremlins since i got it running LIKE MISSFIRES AND ELECTICAL SHIT
was watching the fuel pressure gauge while woman was driving....
5+ lbs psi @ idle and bouncing around 2.5 to 3 lbs psi at wideopen
PLEASE ADVISE??
PS RUNS LIKE SHIT OFF IDLE :banghead:
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What kind of motor is this? What are the idle air screws set at? What is the timing set at?
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mech or electric. What size fuel line from tank to pump and are you running a fuel/water sep. I chased a fuel pressure issue and what I did was ran -8 / 1/2 fuel line from tank to sep ( sep being 3/8 npt ) -8 / 1/2 fuel from sep to pump then -6 to carb 850 holley dp. I have a mech 5-6 1/2 psi and has spiked to 7 psi and as low as 5 now. Before it would drop to 3 at wot. My pump is a carter rated at roughly 42 gph. I have around 450 hp or just shy of. Has your carb been rebuilt....Might need jet extensions. http://www.holley.com/122-5000.asp (http://www.holley.com/122-5000.asp)
Under 500 hp a 80gph pump is fine with around 5-7 psi and have seen guys run -10 from tank to pump. Also look for bends in your fuel line cause if you have a mech pump it will suck the line closed on bends if rubber line. I also added SS springs inside my fuel line in one tight area to eliminate collapse.
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Ps this is a new problem lately..havnt changed from when it was running good untill end of june...
Bigblock ford ,dual point mallory,mechanical fuel pump.....
3/8 fuel line from tanks to manual tank selector switch
3/8 to fuel water seperator filter (new)
3/8 to fuel pump
3/8 from pump to fuel rail
And -8 fuel rail to carb with non liquid filler fuel pressure gauge
And no kinks from what i can tell
Timing set at 32 deg full advance @ 3k rpms
Runs and sounds great on trailer ...but under a load i have problems
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just going from 1/4 npt(stock) 3/8 line water fuel sep to a 3/8 npt 1/2 line made a diff and they advertise up to 15% increase
http://www.cpperformance.com/p-14588-stainless-steel-oem-replacement-filter-and-mounting-head.aspx (http://www.cpperformance.com/p-14588-stainless-steel-oem-replacement-filter-and-mounting-head.aspx)
Might have something in tank or as said before collapsing line. Didnt see mine collapsing till I was out in 100+ river temps and I have an enclosed engine(added SS springs inside). Having the fuel line larger is like moving your tank closer to engine. Check your breather for tank...could be clogged. Another way is to run a small gas tank next to pump for it to run out of. I used that method to find a clogged line before and even ran it with tank cap off to check for proper breathing. Has carb been adjusted correctly or set up for your build?
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sorry it double posted
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so where should my fuel pressure be @ ? seems like its fadding away
stock style mechanical fuel pump, and a 850 double pumper is my ?
looking for a "hard" number to base my motor off of , thanks!
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so where should my fuel pressure be @ ? seems like its fadding away
stock style mechanical fuel pump, and a 850 double pumper is my ?
looking for a "hard" number to base my motor off of , thanks!
The seats in that carburetor are good to 8psi, no more. It takes 5psi to sustain good fuel flow.
So I guess to answer your question, 5-8psi.
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Try a new separator filter and see what it does after that
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