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  • possible mechanical issue

    I have a 18 ft diamondback airboat with the 8.1 levitator fuel injected engine.
    last fall while hunting it would not start . not realizing my water was a little low
    we stood on the left side of boat cause I thought maybe I was not picking up gas out
    of the suction of the fuel tank. the boat started immediately.

    I started looking at engine and noticed a sensor in the head
    between the 2 and 3rd cylinder and am wondering if this is a water sensor. the other side of engine
    has the temp sensor. I cannot find any info from the engine dealer(pleasure craft) or the
    scanner or service manual.

    has anyone heard of this or knows anything about it?? all of my starting issues last fall seem
    to point to this problem.

    thanks for helping.



  • #2
    I Have A Service Manual For The Levitator If You Can't Find On Give Me A Call My Name Is Skip 907-322-3291

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    • #3
      Just how many starting problem did you have last year? :eek: :eek:

      I would be surprised if your engine had a low water sensor if it does all you need to do to test it would be to remove a couple of gallons of water and see if your engine will start.

      I would also call Diamond Back and talked to them they are very helpful people.

      Comment


      • #4
        I talked with a mechanic yesterday on line and he said one sensor is probably an alarm and one is the temp sensor.
        they do not have water sensors on the engines. I may give you a call. appreciate it. thanks

        Comment


        • #5
          On an EFI engine there is a Temp sensor for the gauge and there is an ECT otherwise known as the Engine Coolant Temperature sensor, either or both can be located in a cylinder head/s or intake manifold water jacket. If the coolant is low enough to NOT make DIRECT contact with the ECT it will send an erroneous value to the ECM, the ECM uses that value to determine fuel ratio on start up and running. Without direct contact the sensor typicaly reads well below actual coolant temp, this creates a value/ratio richer than required, if the difference is enough the ratio will be such that the spark plugs become fuel fouled, example; if the sensor were unplugged/shorted/broken wire, the value would indicate -40F, obviously far too rich.

          If the amount of time between starts was brief enough that the sensor did not equalize with actual coolant temp via conduction, there is a good possibility that the fuel ratio was rich enough to wet the spark plugs. In the meantime, while investigating the cause, there may have been enough residual engine heat to evaporate the fuel accumulated on the plugs along with the topping off of the cooling system so that direct contact with the sensor was restored, the value corrected to allow the engine to start as normal.

          It is very easy for there to be a 100F+ difference between the ECT and actual engine coolant temp in such a scenario, and that is enough to create such a problem.

          Food for thought based on the given info.

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          • #6
            that makes the most sense of anyone I have heard. really appreciate the info. at least I know how it works. it is hard to troubleshoot when you do not know why or how. I have a scanner along with the manual. I have a lot of reading to do.
            thank you very much.
            gas hogg

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            • #7
              Have you scanned it yet, and did the ECM have any codes stored ?

              Your Welcome

              As you get more info just post it and I will try to be of some help if possible.

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              • #8
                gas hogg,
                what did you find out?

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                • #9
                  all codes are cleared

                  So far all codes are cleared and boat is good to go. seems to start and run fine. debating whether or not to take a computer and scanner with me when I go upriver a 100 miles. seems like a good idea.
                  hopefully no more trouble. instead of up a creek with no paddle, it is up a creek with no computer.
                  the modern times we live in.
                  thanks gas hogg

                  Comment


                  • #10
                    What were the codes ?? The fix?? Your killing me here:confused:

                    Comment


                    • #11
                      been offline for a little bit .

                      the scan keeps coming up with crank sensor fault. My mechanic kept trying to figure out what was going on. I had to call pleasurecraft parts and got a hold of guy that has actually worked on this engine. the crank sensor is between the prop drive and the back of the engine. about 3 inches to work with. the crank sensor is just inside held on by a bolt. hopefully when I get it we can change it out. all this time we were on the front of the engine where the cam sensor is thinking that was it.
                      this is driving me nuts. I will let you know next week when we work on it and see how it runs.
                      sorry about not being online. I had a major crisis at my job and took all my time. getting back on my feet.
                      gas hogg

                      Comment


                      • #12
                        what does the crank sensor do? definition and how does it work for this engine? .338mw do you work on efi engines or just have experience with them?
                        later,
                        steve

                        Comment


                        • #13
                          I am learning as I go. here is what I know from my mechanic buddy. technically the crank sensor takes care of ignition and the cam sensor takes care of fuel issue. they work together to make engine run. when one fails , the other kinda helps the other one . engine will not run good tho. according to the airboat manuf. they have not had any problems with engines. my theory is maybe the cold temps and moisture in the winter time plays havoc with the wiring and connections. one more thing I am going to do is put some electrical stuff on all the connectors.
                          when these engines run they are unbeatable, but when you get problems you better have a scanner available and be ready to have parts. hopefully for me no more trouble.
                          gas hogg

                          Comment


                          • #14
                            Originally posted by gas hogg View Post
                            I am learning as I go. here is what I know from my mechanic buddy. technically the crank sensor takes care of ignition and the cam sensor takes care of fuel issue. they work together to make engine run. when one fails , the other kinda helps the other one . engine will not run good tho. according to the airboat manuf. they have not had any problems with engines. my theory is maybe the cold temps and moisture in the winter time plays havoc with the wiring and connections. one more thing I am going to do is put some electrical stuff on all the connectors.
                            when these engines run they are unbeatable, but when you get problems you better have a scanner available and be ready to have parts. hopefully for me no more trouble.
                            gas hogg
                            The crank sensor... Crank shaft position sensor send a signal to the ecm so that the ECM is aware of TDC (top dead center) of each piston and RPM, the camshaft position sensor provides a signal to the ECM so that it aware of valve position per cylinder.

                            The ECM compares the information between the 2 sensors to determine (in basic terms) ignition timing and fuel injector pulse. For example; at TDC cyl.#1 both valves are closed after the cylinder has just been exhausted and intake stroke is beginning. The ECM knows this by the signal sent from the cam and crank sensors, as the piston travels down for the intake stroke the ECM knows to trigger a injector to introduce fuel into the process, at this time the ECM sees cyl.#8 coming to TDC and the same things happen down the line. Piston in #1 travels up for compression and signals from the two sensors>ECM, program is for ignition @ 12BTDC, combustion occurs>power stroke and back up for exhaust and TDC to begin the process all over.

                            Without the signal from both sensors the ECM is unable to determine when ignition and fuel injection is to occur.The fact that your engine runs at all without a functioning crank sensor is very unusual...

                            That is it in a nutshell. Often but not always, crank sensors exhibit an intermitant symptom; cold start up is normal then failure after a hot soak, once it cools back down the engine starts normally again, sometimes a severe erractic engine miss is evident also. Heat and vibration are usually the cause for failure on crank/cam sensors.

                            When you replace the sensor be sure to coat the outer portion that is inserted into the bore with anti-sieze or grease (if it fits into a bore).

                            Comment


                            • #15
                              Originally posted by AK.airboater View Post
                              what does the crank sensor do? definition and how does it work for this engine? .338mw do you work on efi engines or just have experience with them?
                              later,
                              steve
                              22 years experience on EFI engines as a professional mechanic

                              Comment

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