BX 16 valve, cranks but won't start. Possible blocked exhaust?
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  1. #1
    Fellow Frogger!
    Join Date
    Nov 2010
    Wollongong, NSW

    Default BX 16 valve, cranks but won't start. Possible blocked exhaust?

    Hello everyone

    Long story short(ish)


    I purchased a 16 valve BX a year or two back. I've been waiting for it to be eligible for historic rego which as of around a week ago it is

    It has been sitting but started and moved every month or two.
    Usually a few hiccups first but generally starts and runs fine.
    Except around 3 months ago when after moving and getting out I noticed very long fiberglass strands trailing out of the exhaust and down the street lol.

    So one of the mufflers has collapsed and dropped it's guts everywhere. I didn't worry too much (yet) and the car still started and ran but wouldn't rev much beyond 3000rpm.

    I am going to go over the whole car for rego anyway so I just added it to the to do list.

    I moved it the other day and it was a bit more difficult than usual to start but got going ok. Yesterday however apart from the occasional cough it's just not happy and won't run. and today it's not even coughing, just cranking.

    It appears to have very healthy spark. I assume it's getting fuel but I have tried start ya bastard also with no success so i'm ruling out the fuel system for now. The plugs are wet with fuel when removed after it's been cranking also. Then there's possible lack of compression but I doubt that will be the issue.

    So apart from seeking general suggestions, my main question is how bad would a blocked exhaust have to be to stop the car starting?
    I can feel air flow if I hold my hand near the exhaust whilst cranking so I don't think it's completely clogged. I've really been procrastinating about looking into it further as without the car running it's much more difficult to jack up and pull the exhaust off.

    Something else I just remembered, is more and more lately when cranking it would feel like it would hit a particular cylinder and pause or hesitate before continuing to crank, kind of like i've heard on other engines when the timing is too far advanced and premature combustion stops the piston dead in it's tracks. In this case though the timing is completely ecu controlled if I'm not mistaken, and i'm not sure if it's related regardless

    Anyway, sorry for the diatribe, but more information is usually better than too little.

    Thanks for your time

  2. #2
    Fellow Frogger
    Join Date
    Jan 2004


    The plugs are probably shorted out by old fuel. It goes off quite quickly. So, perhaps rod out the muffler innards, drain the fuel and clean the plugs. Old fuel can prevent the car starting and you might have enough in the exhaust for some decent backfires = blown muffler boxes and spooked locals!

  3. #3
    1000+ Posts Ken W's Avatar
    Join Date
    Sep 2002
    North Brisbane


    Bad fuel also stops the fuel pump pretty quickly. Put your hand on it to see if you can feel it run for a second or so after ignition switch on and when engine is cranking. We have had to fit a series of new pumps to our fleet of 16Valves.

    I think the injectors clog up a bit too with time not running and poor quality fuel. Maybe you need to factor in an injector clean to get it back to good starting again.

    Cheers, Ken

  4. #4
    1000+ Posts
    Join Date
    Nov 2010


    Years ago a friend had a car in for some panel beating repair. A Mitz Colt with a lot of kms. When he went to pick it up Friday afternoon just on shutting time, it would not start. They pushed it outside and he called me to help get it going and drive home. We worked on it for some hours but no go. Like yours it sounded like it would, just need a bit extra to kick away but would not.

    To cut to the chase. He went home other ways and the next Monday he came and removed the exhaust pipe at the manifold and away it went ! Catalitic converter clogged. Maybe the sanding dust had finished it off during the week in the shop. He had the cat replaced and it went well as we had done a complete tuneup trying to get it going.

    So pull the exhaust off the manifold and see what that does.
    PS you can take out the O2 sensor and put a pressure gauge there and check the back pressure. Not sure what the readings should be as I have never done it, but it is a normal test to check for that problem.

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