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replaced fuel lines on my 8v71's and now no power ?

Discussion in 'Chris Craft Roamer Yacht' started by gibson36, Sep 13, 2014.

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  1. gibson36

    gibson36 Member

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    So we blew a fuel line the other day so I had all new ones made for both motors .. Went out and ran the boat today motors fired right up no problem and ran great till I tried to go over 1000 rpm the port motor would stop making power and fall off ..pull it back let it run for a min it was fine till again I tried to run her up and same thing ?? I'm not a diesel guy so I guess I'm asking if anyone has a clue what's going on I would assume that if there was air in the system she would not run at all but maybe I'm wrong ???

    Thanks
    Justin
  2. Capt Ralph

    Capt Ralph Senior Member

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    Did you use push in hose-ends or captive screw-ins? Sometimes, the captive screw-in inserts will grab the inside of the hose, collapse it and cause a restriction. Can you send a pic of the new hose ends?
    What hoses were replaced? and, on the V-71s, are you sure you routed the in hoses to the in port of the head and both returns are from the outlet from the heads. It may seem simple, but you would be amazed how often it's done wrong.
    Are you pulling vacuum from your primaries? Any vacuum or pressure gauges installed anywhere?
  3. gibson36

    gibson36 Member

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    I took the old rubber ones off both motors and drove them to aeroquip as they were the orginal manufactiors of the lines they just replaced the hose parts and reused the old factory fittings on the new hose .. I'm 99.9% sure they went back on the same way they came off but I will double check that against the other motors that is not having problems.. I don't have any guages to check anything with ...and I have asked around and there is no one in town who will mess with these old 871 motors closest place is Louisville ky about 100 miles down river give or take so that's out .. Do you thinknit could be air in the system ??
  4. Capt Ralph

    Capt Ralph Senior Member

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    Then they are captive screw-in fittings. Did you blow thru every hose? If not, one or more is restricted. I really feel the problem could be here and checked first.
    And yes, I've even goofed doing them myself but always caught it before installing them.

    You may also be drawing air on the low side of the pump. Sometimes those same screw-in fittings crack at the flair contact area. Especially if re-used.

    We don't need a tech yet. We'll get it figured out. There's a few 71 heavys in YF.

    Finding some cheap 1/4", bottom (not back) mount vacuum & pressure gauges could be a help if lines check out. Assuming you have original styled Detroit fuel filters (cartridge primary, spin on secondary), A couple of 1/2" male to 1/4" fm reducers also.

    71s Rule,
    rc
  5. K1W1

    K1W1 Senior Member

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    Hi,

    If it starts and runs it should self purge air, if you have the suction and return lines backwards it might be unable to suck enough to keep going as the return line will be smaller diameter than the supply ( I am assuming the return line will be under the fuel level)

    It is a very long time since I turned a wrench on an 8V 71N they used to be great engines and I love the sound of one bellowing its guts out pulling out logs or ploughing.
  6. gibson36

    gibson36 Member

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    I'm heading to the marina today and will update after I re check everything and take her out on the water. I did blow I the lines before install and every thing was fine I re routed one of the lines so it would not be right on top of the pully "aka the one that rubed and blew out" I'm wondering if the new route has to much of a bend in it and that could be it ... We shall see ...thanks guys I will up date in a few hours
  7. Capt J

    Capt J Senior Member

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    You could also have an air leak on one of the hoses. Also make sure your fuel valves are fully open as well.
  8. gibson36

    gibson36 Member

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    Well it looks as if the filter was cloged up with crap ?? I did put some new fuel in this year soooo ?? Maybe that's what it was she fires right up and is now reving over 1k rpm with out a load on her . I need to wait for someone to come down so I can take her out and really run her but so far so good ..fingers crossed that was the problem we shall see tomorrow... Its always something
  9. Capt J

    Capt J Senior Member

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    Which filter was clogged up? Did you change both the primary and secondary fuel filters on both engines? Didn't you notice the filter was clogged when you added fuel to prime the system after changing lines?
  10. gibson36

    gibson36 Member

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    I only had a replacement for the secondary filter on the boat I will pick up a new sock for the main filter tomorrow the fuel looked dirty but not really bad darker red then I would have expected and the filter was black so I'm sure I ended up with some bad fuel or less then great fuel anyway ...there is no real demand here in Cincinnati for diesel so who knows how long it sits before you get it or it could have been the fuel left over from last season still in the tank that was bad ?? Who knows I hate to drain 250 gallons out and replace it so I may just run it low and then refill with a truck from the fuel depot here in town ..
  11. Capt Ralph

    Capt Ralph Senior Member

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    Yep, Lets budget some vacuum and pressure gauges. The color of the filter can be a hint, You did not mention any debris on the media.

    Lets also make sure were on the same filter page; Primary Detroit filter using a cartridge or sox filter, then the fuel pump, then a spin on secondary filter, then to the heads? Is there a Racor mud filter before all that?

    By the way, I hate those sock filters. When you dissect the secondary, you will find threads from the sock. I've always felt the ends never fit well either.
  12. Capt J

    Capt J Senior Member

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    I thought the sock filter was only used for the crankcase oil breather filter, that's the only thing I've ever seen it used on? I always say paper cartridge filters (or spin ons) for the DD secondaries. I'm sure they make a pleated paper filter for your housing.
  13. ILELBOAT

    ILELBOAT New Member

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    Gib: If you have the same as i have the sock primary and a steel wrapped pleated filter for the secondary. This was the common filter set-up for d.d. By the description you post one of the lines is on wrong, or a bit of rubber from the line being made is in the line! blow them out with air and or push a smooth rod all the way threw them. I know in my dd days i made a lot of these lines! Also test gauges are a good investment. 60lbs over1000rpm is what you need. on the outlet of the secondary. Any Questions contact me.