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  • Mg Montego Turbo Problems

    Having problems with my sons MG Montego Turbo and going around in circles and I'm running out of ideas, so maybe fresh eyes will help. When cold starts up and runs rough gradually improving, Restart and revs freely then pops and bangs before dying, Restart and runs better and revs but sound like a little missing, then clears and revs freely but again dies sometime with a bang and a pop. Sometimes it dies when you try to rev it. As the fuel pump was messing about when I had the welding done, ive also replaced the fuel pump with a proper Lucas/Bosch one. I've cleaned and reset the carb, replaced the O rings, changed the carb gaskets to the manifold, changed fuel regulator, checked the cam belt timing and its spot on, and the usual distributor cap, rotor, leads etc. checked all rubber pipes and no leaks. The temp gauge was running amuck but after changing the fuel ecu for a replacement it now seems to give the proper reading. I've also tried blocking off the vent pipe, nothing I do seems to clear the problem that only started prior to having it welded. I've used my lucas ignition and fast check fuel units and all sensors etc are working. Your thoughts and ideas please as i'm running out of ideas and this is the first time I've not been able to fix a turbo so I must be getting old
    Last edited by Jeff Turbo; 24th July 2020, 14:22.
    1958 Ford Consul Convertible, now being used
    1965 Ford Zodiac Executive. now being used
    1984 MG Montego EFi in black. Digital dash, putting back together
    2004 MGZT cdti. Great workhorse
    2004 MGZT V8. Back on the road. now being used

  • #2
    Well to be honest our Montegos are diesels and I know very little about petrol's. I think the temp gauge uses the same sender as the stepper motor that controls the carb mixture. I don't think fast check can tell if the sender is reading correctly, only that it is in range.

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    • #3
      Hi Robert, it's not the sender as I replaced that, that problem was the fuel ecu as the temp gauge now works properly as does the auto choke. I removed the plenum and put a colour tune on it, was running lean but better now. Still popping while on fast tick over so will do a compression test on it next. The car doesn't die as much as it did do but its still not right. If I can get it running properly as per a normal carbed engine then it should run propely as a turboed one, well that's the theory
      1958 Ford Consul Convertible, now being used
      1965 Ford Zodiac Executive. now being used
      1984 MG Montego EFi in black. Digital dash, putting back together
      2004 MGZT cdti. Great workhorse
      2004 MGZT V8. Back on the road. now being used

      Comment


      • #4
        Did all the trouble start after welding? I once blow the pcb in the master locking solenoid mig welding a Montego, the current inducted to do that must have been high.

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        • #5
          No rob was before that, just highlighted that the fuel pump problem started was bout that time it went for welding. I know that does happen but the welding has nothing to do with it, Its looking like a valve but can't be sure till I've done a compression test, just have to find my compression tester now in between the rain. Am giving this car a rest for now for maybe a couple of weeks as I might be able to come up with a solution in that time.....or not
          1958 Ford Consul Convertible, now being used
          1965 Ford Zodiac Executive. now being used
          1984 MG Montego EFi in black. Digital dash, putting back together
          2004 MGZT cdti. Great workhorse
          2004 MGZT V8. Back on the road. now being used

          Comment


          • #6
            A compression test would be good as the head gasket may have blown between two cylinders, did any of the plugs look black? do you have a strobe light to check the timing is advancing on acceleration?

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            • #7
              Head gasket should be ok as I changed that not so long ago. Will go with a compression test first so to rule out any valves sticking
              1958 Ford Consul Convertible, now being used
              1965 Ford Zodiac Executive. now being used
              1984 MG Montego EFi in black. Digital dash, putting back together
              2004 MGZT cdti. Great workhorse
              2004 MGZT V8. Back on the road. now being used

              Comment


              • #8
                I can't see it being a valve problem. I have had problems with head bolt becoming loose with aftermarket gaskets. In my case it was a diesel but what I did was to mark number one bolt with tippex remove it, oil it and refit it. It was only at 60 foot pounds. I bodged it up by re-torquing to 100 ft lb. I am not saying to do that, please don't. But the fact that two years later the engine is still running well does prove the problem was just lose bolts. If the compression test tells you the head must come off and you fined the bolts are loose, you may want to do an extra re-torquing.

                Comment


                • #9
                  Originally posted by robert1 View Post
                  I can't see it being a valve problem. I have had problems with head bolt becoming loose with aftermarket gaskets. In my case it was a diesel but what I did was to mark number one bolt with tippex remove it, oil it and refit it. It was only at 60 foot pounds. I bodged it up by re-torquing to 100 ft lb. I am not saying to do that, please don't. But the fact that two years later the engine is still running well does prove the problem was just lose bolts. If the compression test tells you the head must come off and you fined the bolts are loose, you may want to do an extra re-torquing.
                  Hi Robert, nothing wrong with the head bolts etc as i've done plenty of headgaskets. Compression test is very easy anyway so thats the next thing to try
                  1958 Ford Consul Convertible, now being used
                  1965 Ford Zodiac Executive. now being used
                  1984 MG Montego EFi in black. Digital dash, putting back together
                  2004 MGZT cdti. Great workhorse
                  2004 MGZT V8. Back on the road. now being used

                  Comment


                  • #10
                    Originally posted by Jeff Turbo View Post
                    the usual distributor cap, rotor, leads etc. checked all rubber pipes and no leaks. Your thoughts and ideas please as i'm running out of ideas and this is the first time I've not been able to fix a turbo so I must be getting old
                    Hi Jeff, Just wondering did you try changing the rotor arm for a known good one? Does the rev counter do any jumping about when it is popping and banging? Did you change the plenum chamber gasket, if so did it have the extra holes for the turbo car? last thing is the metal pipe that is part of the pipe run from the plenum to the FP regulator & turbo waste gate actuator ok under pressure?
                    Cheers Jeff, Gary

                    Comment


                    • #11
                      Hi Gary, rotor arm was from my spares and a NOS item, that made no difference to the running from before and after, when I removed the plenum, which is still unattached, that also didn't make any difference. I was trying to get all set up and running without the plenum attached then go from there. I also changed the pipe that connects to the wastegate etc and again no difference. The rev counter I didn't look at to be honest.
                      1958 Ford Consul Convertible, now being used
                      1965 Ford Zodiac Executive. now being used
                      1984 MG Montego EFi in black. Digital dash, putting back together
                      2004 MGZT cdti. Great workhorse
                      2004 MGZT V8. Back on the road. now being used

                      Comment


                      • #12
                        Hi Jeff
                        OK that's all fine, do have at the look at the rev counter just to rule out a low tension ignition problem. Did you change the inlet / exhaust manifold gasket or just carb to manifold? if not check the inlet manifold gasket isn't drawing air in. Another thought is how old is the exhaust system could that be blocked?

                        Comment


                        • #13
                          Originally posted by G Force View Post
                          Hi Jeff
                          OK that's all fine, do have at the look at the rev counter just to rule out a low tension ignition problem. Did you change the inlet / exhaust manifold gasket or just carb to manifold? if not check the inlet manifold gasket isn't drawing air in. Another thought is how old is the exhaust system could that be blocked?
                          Hi Gary. Inlet manifold is new and I sealed it so it wouldn't leak, I've had that before. The complete exhaust is also new but the rear box it a deisel one. This is why I've run out of ideas for the first time ever. It's probably something silly but I have compression test and rev counter to look at so 2 things I haven't thought of. Would you think fueling or electrical to narrow it down?
                          1958 Ford Consul Convertible, now being used
                          1965 Ford Zodiac Executive. now being used
                          1984 MG Montego EFi in black. Digital dash, putting back together
                          2004 MGZT cdti. Great workhorse
                          2004 MGZT V8. Back on the road. now being used

                          Comment


                          • #14
                            Originally posted by Jeff Turbo View Post

                            would you think fueling or electrical to narrow it down?
                            Hi Jeff.
                            That is the trouble really as it could be either. The pops and bangs you refer to if I am assuming correctly whats going on. are typically associated with air fuel mix still burning towards the end of the exhaust stroke as the fresh charge is introduced causing some of the new charge to ignite whilst on the inlet stroke, this manifest as the popping back through the inlet tract. A weak mixture can cause this because it burns at a much slower rate than normal so it can still be burning towards the end of the exhaust stroke. The same thing can happen if the ignition timing is wrong, retarded or late ignition can cause the same thing.
                            There are other causes like camshaft timing or worn camshafts, head gasket failure between cylinders, bad valves etc.but you more or less have already or going to have those covered.
                            Once you have done a compression test if that draws a blank. I would look at the ignition side first until your happy with that then move to the fuelling side. You could whilst you have the plugs out check out the rotor arm position relative to no 1 plug lead in the cap at TDC no. 1 cylinder. Just in case the rotor arm has spun in its bush, that's if you've not done already. If you have a substitute ignition ecu you could try that, any would do to test the fault but DON'T road test with a n/a ECU as the turbo one has a boost retard map, we don't want any melted pistons etc.
                            Cheers, Gary.

                            Comment


                            • #15
                              Thanks Gary, food for thought there. I have tried nearly all including the replacing both the fuel and ignition ecus but will start again from the beginning after the compression test as I must have missed something for it to do this. I have made significant progress from a few weeks ago when it wouldn't even start, tick over and was over fueling so i'm slowly getting there. My son has given up for the year but i'm not beaten yet so when I have time I will come back to this car later in the year
                              1958 Ford Consul Convertible, now being used
                              1965 Ford Zodiac Executive. now being used
                              1984 MG Montego EFi in black. Digital dash, putting back together
                              2004 MGZT cdti. Great workhorse
                              2004 MGZT V8. Back on the road. now being used

                              Comment

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