John, in theory both engines should should spin the same speed when cranking, the 6-71's require decent starter speed to fire up being a two stroke diesel, if your starters were easy to interchange i would swap them and see if the starter speed is now on the other engine. at least start the easy engine first which will charge the batteries and give some boost to the other when you start it.if you swap the starters and the problem now has changed engines, check you cables, diesel starters require alot of amps and any corrosion hurts, also, you can have someone crank and touch the terminals, if they seem to get abnormally hot then there is an issue.i know alot of this is theoretical and can be frustrating, we are just typing words, you're the one actually getting dirty, be systematic and eliminate one problem at at time, on your fuel line, any oily residue around a fitting or valve can be a sign that something is loose, things are easier to check with an electric fuel pump, you can simply turn the ignition on, disconnect the fuel line and dump it in a container, if you see little bubbles then you're sucking in air somewhere... with a mechanical pump the engine has to be running... obvioulsy you cant disconnect the fuel line..you can use the return line and see if you're getting air..of course, im in arizona , its going to be 92 today, any diesel starts in this weather...lol....hope some of what i said helps. Eric
Date: Sun, 8 Apr 2012 09:23:28 -0400 Subject: Re: [UnifliteWorld] Re: uniflite 42 ft question From: [email protected] To: [email protected] Dear Arlen,Thank you for your input, but my emergency shut off valve is correctly set. I will check the lines but don't quite know how to check if it is sucking air. One very important thing I have learned with a diesel engine is that the starter motor has got to put out enough revolutions to start up, it is not like a gas engine which can fire up on half revs. It is just a job removing it in such confined space. Thanks for your input, I really appreciate it. John On Sat, Apr 7, 2012 at 9:31 PM, M/V Arrluk Homer Alaska <[email protected]> wrote: Hi John, I have a 42' with twin 671's. They run great. My fuel filters are in locations that are easy to get to and I think that previous owners have upgrade the original system. I would suggest you do the same and mount your filters in the engine room in a place were you can get to them easily. As for your starting problem, I had a similar problem last year. The port engine fired right up, but the starboard engine would crank over good , and try to fire. I am a mechanic by trade (aircraft), but don't have much diesel experience. After calling several friends that do have diesel experience, I was told about the emergency air cut off. If this valve is stuck closed, as mine was, the engine will not fire up. This is an important part of a diesel engine and must be working correctly. This would be your only means of shutting down a run away engine. If a diesel engine goes out of control, it can actually continue to run even if you shut off its fuel supply. This is because it will suck its own oil supply and that is 5 gallons or better. If your emergency air shut off vale is stuck, you need to fix it to were it will work freely. Also, one time I had a fuel problem to the starboard engine. I could not get the thing to fire and went through the bleeding process several times. I finally found the problem was a cracked fitting on the line going into the secondary filter. It was not leaking but was sucking enough air to keep the engine from firing up. Thanks, Arlen Zacharias 42' Sport Fisherman Extended Cabin Homer, Alaska On Apr 7, 2:58 pm, john hitchcock <[email protected]> wrote: > Thanks EB and Bernie. I have the twin Detroit Diesel > 6 71s and its a terrible job opening up the floors, and having to move all > the furniture to get off the fuel filters. Then I have had to remove the > injector covers and brake them loose to bleed. I dont believe I have a > priming valve or bleed screw as you mentioned. A problem Ive had in the > past is that the port engine fires up immediately but the starboard just > keeps cranking. I took in the starter and they found it was a 24 volt > whilst my system is 12 volt.They corrected it to 12 volt and I put the > starter back on but it still seems to be cranking slower than the port > engine. Do you think this may be the problem why the engine wont start up? > > On Sat, Apr 7, 2012 at 12:44 PM, [email protected] <[email protected]>wrote: > > > > > Eric is correct and John's question is valid because it would seem > > that having a gravity fed fuel system would work better, but then all > > the sediment would be sent through your engine and that's not good at > > all. I have Cummins 903 naturals on my boat and they are very easy to > > bleed. There's a bleed screw at the top of the engine in the valley, > > it's on the fuel pump. The few times I've had to bleed the engines I > > just cracked the screws open a little and turned over the engines > > until fuel started flowing from the screw. While you're still turning > > the engine over, tighten the bleed screw and the engines will run just > > fine. If the fuel lines have a cronic problem of air in them then you > > may want to check the connections from the pick-up tube to the fuel > > pump. If any of the fittings are loose, air will be sucked into your > > system and stop the engine. There shouldn't be too many fittings and > > should only take a few minutes to go through and tighten everything > > up.. > > > Also John, note that you have another fuel line that returns to your > > fuel tank from the engine. That is called the fuel return line and it > > returns unused fuel back to the tank. You may ask, why send more fuel > > than the engine will burn and then return it back to the tanks. The > > answr is, it ensures that enough fuel is getting to the engines but > > just as importantly the extra fuel acts as a coolant and lubricant for > > components on the engine. > > > On your boat you probably have a grouping of ball valves that have > > fuel lines running in and out of them. They are there so you can > > choose where the fuel is coming from and going to. If you need to > > transfer fuel from port to starboard or forward or aft you can open > > and close the appropriate valves to move the fuel around and transfer > > weight. Remember the fuel return line? You can pull fuel from one tank > > and return it to a different one effecting the boat's trim, list and > > running attitude. > > > All the best, > > Bernie > > 1973 42' Aft Cabin > > Cummins 903 > > > On Apr 7, 6:41 am, e b <[email protected]> wrote: > > > the supply outlet is on top of the tank but inside the tank there is a > > dip tube that goes to the bottom, sometimes on the bottom of the tube thee > > is a mesh strainer, usually the strainer and / or bottom of tube is > > slightly above the bottom to prevent dirt / water from being sucked up if > > there is any. depending on tank location / fuel level the fuel might be > > above or bellow the engine the fuel pumps should have no problem priming > > the line unless the check valve in the pump is dirty or sticking. > > > eric > > > > Date: Sat, 7 Apr 2012 09:10:02 -0400 > > > Subject: [UnifliteWorld] uniflite 42 ft question > > > From: [email protected] > > > To: [email protected] > > > > I have the above boat. The engines have not run in months but are in > > good shape. Now that I am trying to start them I have a problem getting > > fuel to them. I know I have to prime the filters but my question is...The > > supply line comes from the TOP of the tanks, not the bottom. Therfore by > > the force of gravity the fuel sould run back into the tank and leave a > > airblock...right?? This would then be a constant problem. Anybody suggest > > anything?? > > > Thanks John > > > > -- > > > > You received this message because you are subscribed to the Google > > Groups "UnifliteWorld" group. > > > > To post to this group, send email to [email protected]. > > > > To unsubscribe from this group, send email to > > [email protected]. > > > > For more options, visit this group athttp:// > > groups.google.com/group/unifliteworld?hl=en. > > > -- > > You received this message because you are subscribed to the Google Groups > > "UnifliteWorld" group. > > To post to this group, send email to [email protected]. > > To unsubscribe from this group, send email to > > [email protected]. > > For more options, visit this group at > >http://groups.google.com/group/unifliteworld?hl=en. -- You received this message because you are subscribed to the Google Groups "UnifliteWorld" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/unifliteworld?hl=en. -- You received this message because you are subscribed to the Google Groups "UnifliteWorld" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/unifliteworld?hl=en. -- You received this message because you are subscribed to the Google Groups "UnifliteWorld" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/unifliteworld?hl=en.
