Announcement

Collapse
No announcement yet.

Back firing

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

  • Back firing

    My engine has started to back fire and will not run long. Has caused muffler damage. Compression. 62 - 66 - 38 - 62. Burnt exhaust valve? Rick

  • #2
    I would do a leak down test next. This will give you an idea of the exact issue.

    Welcome to the site Rick
    3 ~ Tudor's
    Henry Ford said
    "It's all nuts and bolts"


    Mitch's Auto Service ctr

    Comment


    • #3
      Hey Rick C, WELCOME to the VFF!!

      Mitch is correct.
      You wana look waaay far up da road and plan yer route because the brakes are far more of a suggestion than a command!

      Comment


      • #4
        I always refrain from tear down and exploratory surgery. It's best to do some testing before hand. I recently had one that showed a bad valve in one cylinder and excess pressure coming up through the crankcase in another. Here it had a ring issue that i might have missed without the leak down
        3 ~ Tudor's
        Henry Ford said
        "It's all nuts and bolts"


        Mitch's Auto Service ctr

        Comment


        • George Miller
          George Miller commented
          Editing a comment
          I did that one time and had to put it all back together to find the knock.
          George

      • #5
        Mitch is talking about a 'wet /dry' compression test..make a set of compression readings,then squirt some oil in the spark plug holes and do it again..if that 38 reading doesn't come up its a valve,if it does,its rings..

        Comment


        • Mitch
          Mitch commented
          Editing a comment
          Actually i'm not..

          I am talking about a leak down test

        • BNCHIEF
          BNCHIEF commented
          Editing a comment
          This would be a good explanation for the tech section.

        • CM2
          CM2 commented
          Editing a comment
          Excuse me...wet/dry is effective for diagnosis of the 38 pound cylinder,odds are the heads coming off

      • #6
        leak down is the way to go, and this prolly is a good time to put this forth on the VFF. Mitch is the king of leak down
        It could be as simple as a valve lash problem

        Engine new to you? Been happening long? Been driving it anyway? Work recently done?
        Bore scope might let you get a look in there.
        But start w/ leak down

        One of the problems with the 63# flywheel is that you could have a weak cylinder and you might not know it for a while; that massive flywheel is just gonna keep churning away and glide right past the weak cylinder. Were the FW lighter, you'd be more likely to notice the imbalance, especially in a 4-banger

        Keep us posted we'll walk you thru it

        Comment


        • BNCHIEF
          BNCHIEF commented
          Editing a comment
          Bore scope is one of the things in my toolbox when I go to check out a car.

      • #7
        Why doesn't someone explain the leak down test for us that has never done it.

        Comment


        • #8
          Here is a good explanation Tom
           

          Comment


          • #9
            Thanks Chief, that gives a good idea of what it's about. I use shop air sometimes using a hollowed out spark plug. It can be regulated by pinching off the air line.
            The actual tool is nice though, but rudimentary works

            7BC63BC4-F289-4A35-B997-B004187612B4.jpeg2A1FB40A-5F73-4FBC-AC15-7B883D7AC415.jpeg
            3 ~ Tudor's
            Henry Ford said
            "It's all nuts and bolts"


            Mitch's Auto Service ctr

            Comment


            • BNCHIEF
              BNCHIEF commented
              Editing a comment
              I understand Mitch poor guys have poor ways but it spruces it up a little in that cadillac toolbox you have.

          • #10
            Basically you block the wheels/set the ebrake, bring a cylinder to TDC on compression stroke, apply air, and listen for where the air is leaking out. That is the quick version.

            I have several different size plugs that I have busted out the porcelain and welded in an air fitting

            Comment


            • Mitch
              Mitch commented
              Editing a comment
              The one i pictured was brazed

            • tbirdtbird
              tbirdtbird commented
              Editing a comment
              haha you braze, I weld

          • #11
            Thanks bnchief. Now I understand what their talking about. This is sort of like useing a kuhlman guage to test inside natural gas lines.

            Comment


            • #12
              You are most welcome Tom some of us here wrongly assume at times that every one understands what we are talking about. There is a lot of expertise here and Mitch wants what is posted here to be correct and tried and true not just someones theory. With that said thanks for asking that helps some of us understand what others need. Mitch is building a great area to check for help in the different sections he has put together for all to access. There are many here who are in the everyday business and have much to contribute so read some of those sections as well and enjoy the vff great to have you here. Do not be afraid to post something lest you might feel no one will listen, that is important to grow this forum and help others I myself am a newbie to Model A fords and have learned much and enjoyed every minute of it. Have a great day.

              Comment


              • #13
                Ok Mitch did you make this for Ed.:rolling:rolling

                Comment


                • #14
                  It's also possible you have two problems going on, so do a simple spark check to make sure that's good.
                  Hold the coil wire 1/4" from a head nut and check for a hot blue spark.

                  Comment


                  • CM2
                    CM2 commented
                    Editing a comment
                    After you yard off the head and find out why your pulling 38 pounds on that one hole..wet/dry,leakdown,whatever the heads coming off..

                  • tbirdtbird
                    tbirdtbird commented
                    Editing a comment
                    suppose he just has a tight valve

                • #15
                  1. First comment was: "My engine has started to back fire and will not run long. Has caused muffler damage. Compression. 62 - 66 - 38 - 62. Burnt exhaust valve? Rick

                  2. Question A: Was your engine possibly running well before ...... then maybe engine was allowed to sit for a spell without running ...... then when engine started again ..... "my engine has started to backfire and will not run long".? ............ and/or,

                  3. Question B: What may have possibly happened between the time when your engine was not backfiring ......... and afterwards after your engine started to backfire?

                  4. One or more sticky valves in a Model A can make a Model A engine sound like a 30 caliber machine gun firing in a 55 gallon drum ..... a sticky valve can remain slightly open & can also render low compression reading.

                  5. If it is a simple sticky valve ...... it would be a very simple vintage quick fix to remedy without unscrewing bolts and studs.

                  Comment


                  • CM2
                    CM2 commented
                    Editing a comment
                    simple perhaps..for a farmer fix,but to actually repair you need to see the root cause and examine all potential issues arising from it.

                  • Rick C
                    Rick C commented
                    Editing a comment
                    I am listening ! Rick C

                • #16
                  I wonder if there has been any use of MMO, and if not, why not? Granted, you do need to find the cause of the low cylinder, but if it just started like it sounds, I'd say something has collapsed.

                  Was there any note before this started, maybe like running rough, or starving for power, or falling flat on it's face? Say the intake manifold has a leak causing one jug to run lean, that would burn an intake valve.

                  Looks like Henry and I were typing at the same time.....a simple check would be to pull the intake/exhaust manifold. 4 nuts and washers, to look into the valves and determine if one is hanging open in that jug. It cost a whole gasket.
                  Last edited by DaWizard; 01-04-2018, 11:47 PM. Reason: twinkey fingers
                  You wana look waaay far up da road and plan yer route because the brakes are far more of a suggestion than a command!

                  Comment


                  • #17
                    A slow to close valve could cause a low compression reading. I'd do the leak down check to see if you hear air leaking out the intake, exhaust, or oil fill pipe. If the leak down checks OK, then I'd suspect a slow to close valve, and I'd put a can of Sea Foam in the oil, and another can in the gas, to see if that clears the problem.

                    Comment


                    • #18
                      all of the above.

                      we can advise better once the leakdown is completed

                      Comment


                      • #19
                        Relaying Problems to Mechanics and Doctors:

                        I went to one of these after hours doctors last year and told him I had just visited my druggist and my druggist said none of his "over the counter" medicines could cure what I had ....... and my druggist said after hearing my symptoms, I needed to visit a doctor to get some doctor prescribed antibiotic medicine.

                        This senior doctor replied that from his many past experiences, druggist are always 100% correct in diagnosing patients.

                        I asked this doctor why was this?

                        He responded that when we visit a druggist we go into minute details, relating the before and after conditions, tell the druggist absolutley "everything".

                        But this doctor added that when we visit a doctor, we tell him "very little" or "almost nothing" ..... because we have a profound fear that the doctor will put us in the hospital.

                        Appears describing Model A mechanical problems, and asking Model A Forum mechanical questions on Model A Forums, some questions are somewhat similar.

                        Like, "Hey, my Model A won't start ..... what's wrong?"

                        Maybe at times, we all need to be reminded that Model A Forums do not operate hospitals! LOL

                        Comment


                        • #20
                          Welcome Rick C.

                          Comment


                          • #21
                            Wonder if my doctor can prescribe new parts for my model A and if my medicare will pay for them, Mind altering comes to mind it puts me in a good mood.

                            Comment


                            • DaWizard
                              DaWizard commented
                              Editing a comment
                              X10!!

                          • #22
                            The only way to correctly fix an issue is to put your finger,and eye, on the root cause. I'm all for getting lucky with snake oil or whacking it with a hammer and calling it good,if its an 'ice cream runner' Id try it too..but there is only one way to do it right,

                            Comment


                            • Chevmn56
                              Chevmn56 commented
                              Editing a comment
                              X2

                          • #23
                            Something tells me Mr. Rick C. already suspects that the 38 low reading indicates a possible combustion chamber leak through a non-sealing accompanying valve.

                            In lieu of internal combustion of a fuel mixture occurring with less noise inside an enclosed, sealed combustion chamber ......ignited fuel, i.e., combustion is also occurring much louder outside of the combustion chamber ...... and raw non-ignited fuel was pumped inside the muffler such that afterwards, combustion within the muffler caused enough force to damage the muffler.

                            Backfiring suspects could be: Possible burnt valve leaking, possible sticky valve leaking, possible damaged valve spring causing valve leaks, ignition misfires, improper ignition of fuel timing, or something similar.

                            Usually sticky valves occur after engine is not operated for some time.

                            When engine was last operated, and engine cut off, over time, this sticky valve remained open to outside air through the tail pipe; hence, valve stem rust can occur with ambient heat and cold condensation causing rust; and/or volatile petroleum molecules evaporating into outside air and causing sticky varnish on valve stems and valve guides.

                            Maybe because of our high humidity in our coastal area, valve relatedbackfiring is most often caused by engines not operating for a spell associated with easy to fix sticky valves.
                            Last edited by H. L. Chauvin; 01-05-2018, 09:05 AM. Reason: Double prepositions ????

                            Comment


                            • Mitch
                              Mitch commented
                              Editing a comment
                              A little MMO will fix it

                            • Rick C
                              Rick C commented
                              Editing a comment
                              Thanks. Best way to determine stuck valve and remedy

                          • #24
                            OK, now for part two of the problem. Why does it not run long?

                            Comment


                            • #25
                              Oh, now THAT is the easiest to answer. The gas cap vent is clogged! Duh!
                              You wana look waaay far up da road and plan yer route because the brakes are far more of a suggestion than a command!

                              Comment

                              Related Topics

                              Collapse

                              • Corley
                                Clean engine with PCV?
                                by Corley
                                Just wondering if anyone out there has experimented with using a PCV valve in an effort to keep the engine area cleaner by controlling fumes. A PCV valve is more than a hole that shakes and rattles. It provides an orifice set which is matched to the engine, plus a spring which matches the orifice 'leak' to the varying vacuum. Difficult to explain, but it's more than a simple vacuum leak into...
                                01-22-2018, 06:50 PM
                              • dmdeaton
                                Engine Running Bad
                                by dmdeaton
                                Helping a buddy who has owned A's and T's for 60 years. Since my short time in this hobby, I have met some great people. This fellow called me for a little help. Said his A started sputtering during a ride last week and has progressively gotten worse.

                                Good gas, good flow, changed carb and runs exactly the same.
                                All plugs firing, changed rebuilt dizzy, condenser, no change.
                                ...
                                05-11-2018, 09:47 PM
                              • DaWizard
                                Installing Valve Guides
                                by DaWizard
                                Since I haven't found this in the engine section, I will pose the question here and Mitch can move it too the proper thread when it is answered,

                                To the engine rebuilders.

                                How do you install the new one piece valve guides if they are loose or just not a real tight fit?

                                Do you do the same for the two piece guides?
                                07-07-2018, 11:36 AM
                              • Art Ebeling
                                gas valve rebuild
                                by Art Ebeling
                                It's a rainy day so I was going thru a box of parts for my 31 Victoria and found the original gas shut off valve. The valve is stuck in the open position and I can't budge by by hand. I can loosen the handle and the bigger nut under the handle. How are these rebuilt. ?...
                                10-22-2017, 03:51 PM
                              • Tudor31
                                Valve Guide Failure
                                by Tudor31
                                My 31 Tudor had a 20 psi lower compression on cylinder #3 combined with a ticking noise in that area. I started the work by removing the valve cover to check the valves, and as it turns out adjust the valves (didn't know adjustable tappets had been installed). The exhaust valve for #3 did not close at all which of course could explain the compression problem.

                                However, nothing changed...
                                10-26-2018, 09:42 PM
                              • Hook1948
                                What Happened?
                                by Hook1948
                                Anyone know whats going on at the "other" site? Must have been hacked or shut down if my browser is correct....
                                09-29-2017, 09:08 PM
                              • A31Woody
                                Leaky Gas Shutoff Repair
                                by A31Woody
                                Is it possible to fix a leaky under tank shutoff while it is still in the car? I tried to remove mine, but it feels like it will take the threads with it if I remove it. Carb is leaking from time to time even after running the car out of gas by shutting off the valve.

                                My other option is to put an after market valve in the fuel line inside the engine compartment. If I end up doing this,...
                                06-19-2017, 09:59 AM
                              • amccarl
                                31 Roadster "chuffs" when shifting after it is warmed up
                                by amccarl
                                I have a 1931 roadster which, for the most part, starts and runs great. However, after a bit of driving when it has warmed up, it begins to "chuff" (fire, fart, huff - not sure of the correct technical term) each time I shift. It isn't horrible or loud (not a backfire), but it seems like something that is likely slightly out of adjustment or that I'm not doing right with the choke or something....
                                10-11-2017, 10:00 AM
                              • Tim Warren
                                Gas supply fitting in the firewall ('31) that the shut off valve screws into
                                by Tim Warren
                                I removed a leaking shut-off valve. The threads in the firewall fitting are messed up. Does anyone make that fitting? If not, has anyone chased the threads successfully, and if so, what size tap? Thank you.
                                11-02-2018, 01:45 AM
                              • Cape Codder
                                Valve Checking / Adjusting
                                by Cape Codder
                                I want to check the valve adjustment on my engine but am a bit confused.
                                I know a reputable old timer who has told me to adjust both valves to .012" for each cylinder. He says to move the piston to the top and have both valves closed. When complete move to the next cylinder. When I look in the book it is showing a different procedure.

                                How do Most of you do this procedu...
                                10-25-2018, 11:35 PM
                              Working...
                              X