Welcome Guest - Sign Up today
Welcome Guest - Sign Up today
Store Links Mobile - Shop Now

Announcement

Collapse

Help Tip: If you have a question that has not been answered to your satisfaction in the archives, it is always best to start a new thread of your own. By starting your own thread, you will receive the maximum number of views by forum members.

Below are some additional forum policies in hopes of all iboats members will follow, Thank you.

1. Please do not reply to old topics or hijack existing topics. Old topics of a technical nature are like a library book, Please do not write in them.

2. Old topics should be considered archives and used for reference only. Please do not reply to them.

3. Do not take over someone else’s topic (aka hijack) with your own question, even if it is similar. If you have a question that has not been covered to your satisfaction in the archives, it is always best to start a new topic of your own.

4. If you have a question for the original poster (OP) and the topic is over 30 days old, send the OP a PM, he may not even visit the forums any longer, or may not notice your question in the old topic.

5. By starting your own topic, you will receive the maximum number of views by forum helpers that may not even notice your question when it’s posted at the end of someone else’s topic. And those answers will be specific to your particular issue.

6. Please do not post to topics that have been inactive for more than 3 months unless you are the original poster. We have very active forums and any topic that remains inactive for that long should be considered "dead". It is especially confusing when there is an entirely new question posted to an old topic.

7. Posting at the end of any topic is considered to be hijacking the original posters topic which in turn subjects the topic to be closed if it continues to happen thus not making it fair to the original poster in the future had for some reason he/she needed to return for additional information or provide an update of the problem solved which is always welcomed within a reasonable amount of time frame.

8. Please note that you should see a red banner pop up near the bottom of each inactive topic asking you not to reply to old topics. The Red banner will read: Please note this topic has been inactive for 90 days. For the best results, please start a new topic.

Thank you all in advance for doing your part in helping iboats run a smooth ship.

Additional forum rules linked below.
http://forums.iboats.com/forum-rules-guidelines-405/
See more
See less

4.3 pops and backfires thru carb, wont run

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • 4.3 pops and backfires thru carb, wont run

    Its a 2001 mercruiser 4.3 v6, carburated. Had not run in maybe 1 1/2 years. I changed the oil and filter, and fuel filter/water separator, used earmuffs and a hose for cooling, and after some cranking and pumping the throttle, it started, ran for 5 minutes or so, and then it died. I could not get it to start again. Poured a little gas into the carb, and it would start, but not run. I tested the fuel pump, and oil pressure switch, had power to the pump, and when I direct wired the pump, it would not run. I ordered a pump, installed it, and verified that it would run (can hear it run while cranking, and then for a few seconds until the oil pressure drops on the gauge). Again, it would pop, run for a couple of seconds, backfire thru the carb, and die. I went ahead and replaced the plugs, distributor cap, and rotor. I am still having the same issue. I can hear the pump run, and I can pump the throttle, and it will start, but immediately dies, and it back fires thru the carb. Has me stumped. I can understand the fuel pump going bad, but what else? As I said, it was running prior to the pump going bad. I checked the fuel filter at the carb, and its clean. Could plugged jets from sitting with old gas cause this? The gas in the boat is probably 1 to 1 1/2 years old, but like I said, it did start and run for 5 minutes or so, until the fuel pump went bad. I did add some octane booster and a can of Seafoam to the tank. I am thinking of pulling the sending unit off the tank to look in it, in case its a mess in there. Any ideas or suggestions? I have owned the boat since new, and it has always been trouble free and reliable. Hour meter shows 419 hours.

  • #2
    Welcome aboard.

    I would try using a portable tank or other way to avoid using the old gas in the tank. 5 minutes before the pump going bad isn't much and who knows how good that old gas is.
    BOAT SPECS FORUM HELP STARCRAFT FORUM SHOP iboats
    Please, no PM's (Private Messages) regarding boat/engine problems.
    That is what the forums are for.
    Only forum/moderator issues will be answered in PM's.

    Comment


    • #3
      The stuff in the tank is no longer fuel. Go thru your carb, clean your fuel system.

      Your motor is ackfiring because its running extremely lean
      1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - http://forums.iboats.com/forum/owner...988-rogue-2420

      Past Boats
      1970 Wooster Hellion - Merc 9.8
      2002 SeaRay 190BR - 5.0 - A1G2 - "Cheasheads in Paradise"
      1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

      What’s behind you doesn’t matter.Enzo Ferrari

      Comment


      • #4
        So, drained the gas from the tank, it smells and looks O.K., I will put a few gallons of new gas in, and see how that goes. I used the electric pump and a clear hose, and I could see that its is not pumping freely, see some air bubbles. I took out the pick up tube, and blew thru it, and there is a restriction. I pulled it all apart, and there is a hose fitting with a one way valve in it. This valve was sticking, the fitting its in is made out of aluminum, and has that powdery, white corrosion. I think I can clean most of it with CLR, but I am wondering if I even need this valve. I think its there to keep gas from draining back, or if my motor was fuel injected, it would maintain pressure. But with a carburated motor, is it even needed?

        Comment


        • #5
          I have been trying to figure out why my motor wont stay running. I have another post under 4.3 V6 wont stay running. I took out the gas tank pick up tube, and blew thru it, and there is a restriction. I pulled it all apart, and there is a hose fitting with a one way valve in it. This valve was sticking, the fitting its in, is made out of aluminum, and has that powdery, white corrosion. I think I can clean most of it with CLR, but I am wondering if I even need this valve. I think its there to keep gas from draining back, or if my motor was fuel injected, it would maintain pressure. But with a carburated motor, is it even needed? If I replace it with a regular fitting, is there any reason I cant use brass? It would screw into another fitting that is stainless steel.

          Comment


          • #6
            Yes, you need the anti-siphon valve. Replace if needed.
            1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - http://forums.iboats.com/forum/owner...988-rogue-2420

            Past Boats
            1970 Wooster Hellion - Merc 9.8
            2002 SeaRay 190BR - 5.0 - A1G2 - "Cheasheads in Paradise"
            1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

            What’s behind you doesn’t matter.Enzo Ferrari

            Comment


            • #7
              Its the anti-siphon valve. Yes you need it.
              1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - http://forums.iboats.com/forum/owner...988-rogue-2420

              Past Boats
              1970 Wooster Hellion - Merc 9.8
              2002 SeaRay 190BR - 5.0 - A1G2 - "Cheasheads in Paradise"
              1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

              What’s behind you doesn’t matter.Enzo Ferrari

              Comment


              • #8
                Dirt - Merged your two threads. It becomes confusing when we reply and you are getting offsetting advice when members don't see all the responses.

                That's why Scott has the same answer two times.

                On your question about the anti-siphon valve - Yes you need it. And it has nothing to do with carbed or FI engines. The valve is keep gas from siphoning out of the tank in the event of a fuel line failure, not to maintain pressure in the line.
                BOAT SPECS FORUM HELP STARCRAFT FORUM SHOP iboats
                Please, no PM's (Private Messages) regarding boat/engine problems.
                That is what the forums are for.
                Only forum/moderator issues will be answered in PM's.

                Comment


                • #9
                  What he said try running on alternate fuel tank.

                  Comment


                  • #10
                    Looks like I'm behind. Anti siphon valves are a safety item to prevent you from exploding when there is a fuel leak after the fuel tank. Required by the United States Coast Guard! They get stuck and fail, or may not open completely. It could also be the screen below your fuel pump preventing flow.

                    Comment


                    • #11
                      when I reassemble the pick up tube, can I use teflon tape on the threads, or do I need to use a different thread dope?

                      Comment


                      • #12
                        Originally posted by dirtdad View Post
                        when I reassemble the pick up tube, can I use teflon tape on the threads, or do I need to use a different thread dope?
                        Many of us don't like T-tape for gasoline NPTF pipe threads.... It doesn't always seal perfectly.............. Use any good gasoline rated pipe thread sealant like Permatex or equivalent......

                        Just click on the first link in the following google search ....How to properly seal fuel fittings

                        Regards,

                        Rick

                        1987 FourWinns 211 Liberator, Originally OMC 460 King Cobra.
                        Re-powered in 2006 with a 1997 Mercruiser 7.4L Bravo III
                        THERE IS NOTHING LIKE A GOOD OIL "THREAD"!!!

                        Comment


                        • #13
                          I cleaned the antisiphon valve, and drained the gas tank of all old fuel, put in 3 gallons of fresh fuel, took apart the carburetor, cleaned it (it did have the fuel bowl full of gummy looking stuff) replaced needle and seat, power valve, very carefully removed the jets, blew air thru all orifices. Got it running, but after a couple of minutes, it dies out, I think the electric fuel pump (new, quicksilver brand), is sporadically cutting out, and the all of a sudden starts working again. I dont always hear it running, after the motor dies, although the oil pressure is still 40 lbs or so. Does this indicate a problem with the oil pressure switch? Funny thing, it has acted up in this manner when I was trying to start the motor before cleaning the carb, but whenever I used a test light to test if there was power to the switch, I have always found power to the red terminal, but I did ground the other end of the light to a ground source. Does the oil pressure switch control power, or ground?

                          Comment


                          • #14

                            usually power if factory wired, the pressure switch is in series with the fuel pump
                            NO PERSONAL QUESTIONS, THIS IS WHAT THE FORUM IS FOR.

                            Comment


                            • #15
                              Sign up today
                              If you're not sure, I would plumb a 0-15 psi gage into the fuel line and observe the pressure.
                              1987 FourWinns 211 Liberator, Originally OMC 460 King Cobra.
                              Re-powered in 2006 with a 1997 Mercruiser 7.4L Bravo III
                              THERE IS NOTHING LIKE A GOOD OIL "THREAD"!!!

                              Comment

                              Working...
                              X