No announcement yet.

MCX – Good Fuel Pressure, Good Spark, No Start

  • Filter
  • Time
  • Show
Clear All
new posts

  • MCX – Good Fuel Pressure, Good Spark, No Start

    Long story short…we get to our campsite at Lake Powell 30 miles from the marina, set up camp and then go out to do some boarding. Engine starts fine, we idle about 100 feet away from our anchor and the engine sputters and dies. We end up being blessed by some VERY GENEROUS pontoon boaters towing us all the way back to the marina the next day! They used their entire afternoon to help us. He wouldn’t take a dime for his trouble.

    Symptom…and it never changed. The engine cranks but shows no signs of starting.

    First, I thought the fuel we added at camp somehow water got in the cans. We pumped out 10 gallons from the bottom of the fuel tank through the sender hole.

    Next, I bypassed the lanyard switch by shorting the two wires together.

    I have circuit breakers and fuses on my dual battery ACR (automatic charging relay) and they were all fine.

    The fuel pump was running and pressure at the rails was ~55 psi. When we tried to start the engine it bounced from 50-60 psi.

    I pulled each spark plug and added one mL of fuel to each cylinder through the plug hole. I don’t know if this is OK, but I was desperate.

    I did not know of a way to check the injectors so I’m not sure if they were sending fuel into the cylinders. If you could point me in the direction of some good ways to check them, I’m all for it. I don’t recall the smell of gas when I removed the spark plugs but since I was adding gas...

    The circuit breaker on the engine was not popped and I checked for continuity across the bolts on the rear. All good.

    I had a spare cap, rotor and ignition control module. Swapped them in various combinations.

    I checked the spark using a wire off one cylinder with a spare spark plug touching a ground wire and I had a strong spark.

    I swapped the three relays (Fuel pump, ignition, ECU I believe are their functions) to see if one was bad. Fuel pump primed to ~55 psi and nothing changed.

    I looked at the three 15 amp fuses for the relays and they all looked good.

    I looked at electrical connections. I never found corroded leads.

    I pulled the two large connectors off the ECU and they all looked in good order.

    All gauges, stereo, lights, pumps, etc work as normal.

    I don’t know if there are any trouble codes stored. Since the engine wouldn’t start, the “Check Engine” light isn’t any help. I am going to search for codes tomorrow using the procedure mikeg205 posted in #9 of this thread:

    To me it seems like there's a bad connection, a blown fuse, or a broken circuit, I just don't know where to look.

    We must have tried starting it 60-70 times but nothing changed. I had two good batteries but the Interstate battery for the engine never lost power. We enjoyed using the house battery to listen to music on our 6-hour tow back to the marina.

    Any help would be great. We are hoping to take it on another out of town trip in two weeks and I don't trust others working on my boat nor that they can be timely this time of year.
    2004 X-30 5.7L MCX

  • #2
    just a thought.. ignition wire.. see this thread


    • #3
      Originally posted by Coloradodude View Post
      just a thought.. ignition wire.. see this thread
      Thanks for the thought. I went through all the ignition connections and even replaced the rotor, cap and ignition control module with no luck.
      2004 X-30 5.7L MCX


      • #4
        You have fuel, you have spark.. Have you checked compression? (and the ECM fuse block) You have pressure in your rails, but you have not confirmed your injectors are sending fuel into the cylinder. A very light shot of ether into the intake may tell the story if it is a fuel sending problem. It could be the pink Wire 439 to terminal J2-19 on the ECM is a problem or 467 or 468. If it doesn't fire with ether, Id double check spark (all wires). If you've got good spark, Id start hunting compression issues. Look at page 45 of 290 in the manual in this post:

        I have a 2004 MCX and the first thing I did was buy the Diacom software and got the Indmar Technician's manual. I keep a tablet in my boat with the wire connected to the engine. I also keep copies of the PDF's above on the tablet. Although Diacom is expensive, there is another software that does the same and is less than half the price; MEFI Burn;

        I'll say this- having the software eliminates LOTS of guesswork I see many people having issues go thru.

        Before you order (If you are considering) call the guy and talk with him to make sure you are getting what you need.

        The PDF attachments in the link I posted above may be a big help. Good luck.
        Last edited by 37tr3n5k; 06-28-2019, 09:14 AM.


        • #5
          I had an ect that would keep my 5.7 tbi from starting if it sensed higher than 165 degree water temp. If I pulled the ect it would give the computer a default value and fired right up. Might be something to check. It was maddening...I had fuel I had spark I had compression, but the computer must retard the timing just enough so it would just crank...


          • #6
            OK, using the MEFI 4 DTC (Diagnostic Trouble Code) process to pull codes, this is what came out:

            1 - 2 (code 12)
            1 - 2 (code 12)
            8 flashes
            1 flash
            8 flashes
            1 flash

            The MEFI Section 1, page 3 said Code 12 should repeat 3 times but for me it's only repeating twice.

            "Once the MDTC tool has been connected, and service mode or ON selected, the ignition switch must be moved to the key ON, engine OFF position. At this point, the MIL should flash DTC 12 three times consecutively. This would be the following flash sequence: flash, pause, flash-flash, long pause, flash, pause, flash-flash, long pause, flash, pause, flash-flash. DTC 12 indicates that the ECM's diagnostic system is operating. If DTC 12 is not indicated, a problem is present within the diagnostic system itself, and should be addressed by consulting the On-Board Diagnostic (OBD) System Check in the Diagnosis section.

            "Following the output of DTC 12, the MIL will indicate a DTC three times if a DTC is present, or it will continue to flash DTC 12. If more than one DTC has been stored in the ECM's memory, the DTCs will be flashed out from the lowest to the highest, with each DTC being flashed three times. At the end of the DTCs, the ECM will simply go back and start over with flashing DTC 12."

            If I read the flashes right, this is a DTC code 81. The MEFI Section 5, page 100 reads:

            "When a DTC 81 is flashed out using a Diagnostic Trouble Code (DTC) tool, a scan tool MUST be used for further diagnostics. DTC 81 has multiple failures, and are only distinguished using a scan tool."

            So I guess I'm done guessing. Can I use the MEFI Burn software or do I need Diacom?

            I've attached a PDF one pager that I made to make the MEFI DTC Tool process easy to print and reference in the boat. Note, I did use some images off the web from a post by "Dave N" on and some text from "mikeg205" from the post I referenced in my first post.
            Attached Files
            Last edited by Soder; 06-29-2019, 07:04 PM.
            2004 X-30 5.7L MCX


            • #7
              Bob MEFI ECM burn
              Mobile +1 310-991-9072

              You can use MEFI Burn, but call him for your own reassurance.

              Also... Larry at Indmar is pretty fantastic.
              Larry Indmar Customer Support
              Mobile (901) 353-9930


              • #8
                Thanks so much for the references! I ran this past the head technician at my local MC dealer and he was stumped. He said "bring it in and we'll have a look." At $140/hr I'll be doing what I can before I take it in.

                I ordered the $200 MEFIburn cable and software today. I'm excited to get it not only to solve this but for future reference as well.

                However, looking further into DTC 81, since my boat does not have ECT (Electronic Throttle Control), there are only a few causes:

                -Fuel Pump High, Low or Open
                -Injector Driver A Circuit High, Low or Open
                -Injector Driver B Circuit High, Low or Open
                -Recirc J1-32 Fault
                -5 Volt Reference Circuit Out of Range
                -CAN Bus Fault
                -Oil/Catalyst Temperature High
                -Can Bus Contention

                I'll go through the service manual diagnostic procedures to see what I can find.

                The other 20-ish errors are all ECT. I'm going to look into some of these while I wait for my MEFIburn.
                2004 X-30 5.7L MCX


                • #9
                  Im curious how this turns out. I have the same engine. Please update this thread when you get your tool and figure it out. The injector driver circuit is the 467 or 468 I was referencing above. Did you try a small dose of ether on the air filter?

                  EDIT: Wait.. I was reading your post again. Im not sure this makes a difference because I have not referenced those trouble codes you are referencing but I noticed your Acronym "ECT" is not Electronic Throttle Control. Your T and C are switched. Are you sure the ECT code is not referring to "Engine Coolant Temperature"? The ECT sensor is sending the temperature to the ECM. I would not discount this info-- just in case. Perhaps the ECT is sending a false high temp signal and the engine is in a mode not to start. Like I said- Im not looking at the codes, but that would make sense aside from your alarm not lighting up. This would coincide with what the poster (Rossi_the_Heleler) was describing above

                  Just out of curiosity: What does your thermostat say?

                  EDIT 2- Sorry- I went back and it is ETC for Trouble Code 81.
                  Last edited by 37tr3n5k; 06-28-2019, 07:06 PM.


                  • #10
                    Originally posted by 37tr3n5k View Post
                    Im curious how this turns out. I have the same engine. Please update this thread when you get your tool and figure it out. The injector driver circuit is the 467 or 468 I was referncing above. Did you try a snall dose of ether on the air filter?
                    No, I haven't tried the ether. In fact, I don't even know where to purchase ether. Is it called by a different name like "starting fluid?"

                    I'll check 467-468 tomorrow when I get some time to work on this.

                    I will keep updating this thread for posterity of course.

                    I just updated my "MEFI 3-4 DTC Reader Tool" PDF with instructions to clear DTC codes. I wonder if I could have cleared my code 81 at Lake Powell and made it home. I know that risks further damage without fixing the problem, but if the pontoon boat had not come up our little canyon, we could have been stuck there for a while. I've cleared OBDII codes on cars a million times but that's just the emissions stuff and doesn't risk damaging the drivetrain. Maybe it's the same for boats. Please educate me.
                    2004 X-30 5.7L MCX


                    • #11
                      Originally posted by rossi_the_heeler View Post
                      I had an ect that would keep my 5.7 tbi from starting if it sensed higher than 165 degree water temp. If I pulled the ect it would give the computer a default value and fired right up. Might be something to check. It was maddening...I had fuel I had spark I had compression, but the computer must retard the timing just enough so it would just crank...
                      This didn't come up as one of the causes of my code 81 but I'll let you know if the MEFIburn software finds anything.
                      2004 X-30 5.7L MCX


                      • #12
                        Yes- ether is starting fluid. If you have spark and compression, it would cause it to fire. In my opinion, this would isolate it to a fuel issue rather than a spark issue. Many people are scared of ether because it is dangerous to use in high doses. Very, very small doses. Do not keep it running with it.


                        • #13
                          My best guess. Bad crank position sensor, Bad distributor, bad ECM or bad engine wiring harness.


                          • #14
                            Well, I've learned a few things.

                            I went through the service manual procedures for checking 3 of the DTC 81 code problems:

                            -Injector Driver A Circuit High, Low or Open
                            -Injector Driver B Circuit High, Low or Open
                            -5 Volt Reference Circuit Out of Range

                            I checked for 12v and pulsing at each injector and everything checked out fine. My 12V LED flashed when I tried to start the engine. = OK

                            The only other procedure was the 5V check. When I tested the J2 post #2 for the 5V reference signal coming directly off the ECU, I got nothing. However when I plugged in the J2 plug and tested for the 5V at the Throttle Position Sensor and the Manifold Absolute Pressure plugs, I had 5V. I tested for continuity between the J2 plug and the plugs for the TPS and MAP sensors and I had good connections. I can't figure out why I couldn't see 5V coming straight off the ECU.

                            Now I'm really needing the MEFIburn reader.

                            Curiously, a DTC code 34 now shows up in the ECU. DTC 34 = Manifold Absolute Pressure (MAP) Sensor Circuit - Signal Voltage Low. This would make sense if I wasn't getting 5V coming from the ECU. Maybe I don't have a full 12V on my battery when cranking the engine. My battery may be low from all the cranking we've done this week. It's on the trickle charger so that it will have a full charge on Tuesday when the MEFIburn comes.

                            With a DTC 34, I would also expect a DTC 22 = Throttle Position Sensor Circuit Low since they use the same 5V reference signal from the ECU???

                            One more thing I learned is that when I put the jumper in the MEFI DLC (Data Link Connector) to read the MEFI codes from the ECU, the same flashes that are showing up on my 12V LED in the DLC are also flashing on my Check Engine Light on my dash! Literally all I need to read codes is a paper clip!!!

                            I don't know if all MEFI 4's will do this but I'm curious if anyone wants to test it out. Even if you don't have any DTC's, it will still flash a code 12 to show the ECU is "working properly." Here's a link to a video showing the flashing of codes 12-34-34-81.

                            Attached Files
                            Last edited by Soder; 06-29-2019, 06:49 PM.
                            2004 X-30 5.7L MCX


                            • #15
                              MEFI 4 Software and cable came today. Great stuff!

                              Once it was up and running, I looked at my DTCs and my code 81 is not showing. However when I go back to the non-scan tool blinking check, the DTC 81 is still present.

                              It has now been joined by a much less nebulous DTC 43 - MAP Low.

                              I talked with Ken at MEFIburn and he said to check the wire to make sure it's not flaky before replacing the MAP sensor. I did check the center, light green wire coming from the MAP sensor to the ECU J2 plug position 8 and the wire is not flaky.

                              The technical manual page 5-10 says the Typical Data Value for the MAP sensor should be 1-2 volts (29-48 kPa) and as you can see from my MEFIburn dash, it's coming in at 4.00 volts (85.6 kPa). I'll pick up a MAP Sensor tonight so it's ready for my conversation with Ken tomorrow.

                              I'm going to call back tomorrow and talk with Bob (Ken=software, Bob=engine) to see if he can help me determine what's up with the DTC 81 and if it's a MAP or ECU. Ken told me they can test my ECU if I ship it to them before I spend the $1300 for a new ECU.
                              Attached Files
                              2004 X-30 5.7L MCX