240 1978 245L with B21A and SU HIF6 carburettor that has enormous gremlin

I have typed this all out several times but I get to the bottom of the post then everything collapses so I'm going to post it in several parts as comment or something.


I bought a 245L the other day from a friend who bought the car from the original owners at the end of last year. He warned me of an intermittent bog/miss that would happen occasionally but could not replicate it when he took me for a drive. When I picked it up the car idled perfectly for about 40 minutes and drove well for a short time before the problem first happened for me. I drove it about for about 100kms and the car behaved perfectly for most of the drive besides the occasion bog/miss that would make the car shunt briefly before coming good pretty quickly. I drove it again for about 45 minutes a couple days later and again it worked perfectly for most of the time besides a couple of misses but then the problem happened so bad the car coughed itself to death. it tried for a long time to get it started but it wouldn't start up again and had to be towed home. Since then it has started again and will occasionally idle well and other times will hardly run. Each time I have started it again after the time it had to be towed it will cough itself to death at some point.

I will post a bunch of photos and videos in a comment because I keep loosing everything I type when I do so

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Comments

  • These are photos of each cylinders compression

  • It was suggested that maybe the timing belt was loose and causing some goofy things with the timing but it looks fine. This is a video of the condition and tension of it

  • This is what all the plugs look like. The first time I checked them they were much lighter colour than a nice tan colour but ever since then they are black like this. Occasionally they are wet, occasionally they are dry. It has been suggested to try Bosch plugs so I will do that tomorrow. I have checked the spark of the fist two cylinders and they both have consistent spark. The photo of the receipt is a list of all the new electrical parts that were fitted at the end of last year.

  • I pulled the carb off to poke my head in the manifold. I pulled the carb apart a bit and found the main needle is bent at the bottom. Here is a couple of photos and video trying to show it. I spoke to a carburettor specialist that was highly recommended by a few people and he said the bent needle is unlikely to cause this sort of problem.


  • Here is some other random photos


  • To me it looks like plenty of fuel and little oil in the dashpot. I'd be looking at wiring condition (#1, 2 &3), points, condenser and coil.

  • @Roinik Thanks for the advice! Do you mean plug wiring condition for cylinder #1,2 & 3?

  • No, the engine harness and bulkhead connector. Wiring, wiring and wiring. The great 240 nemesis.

  • Good advice. I'm brand new to Volvo's and still trying to learn my way round them. Is there any common things to check for with the wiring harness? D you recall any good threads on here about wiring on 240s?

  • jamesincJames @jamesinc Oz Volvo Ice Fortress
    edited May 22

    As it's a points distributor, an easy way to rule out wiring harness problems would be to just run your own wires between the battery, coil, and distributor (just be mindful of the fact that in this configuration the only way to turn the engine off is to disconnect the wire from the battery to coil), and if the problem completely goes away you know the issue is (probably) in your harness. If the problem remains, you know your issue is in the distributor/coil/leads/plugs or carburettor.

    I'm not sure in the first video why there's fuel blowing out the vent hole for the bowl, maybe the float level is set incorrectly or the float bowl valve isn't closing properly.

    Your spark plugs look okay given all the cranking etc.

    You should sort the bent jet needle out but I agree it's probably not an issue until you get out near WOT.

  • As you're new to 240s, search 'biodegradeable wiring Volvo 240' or similar. It's a problem up to mid 1988.

  • Prior to 1980 should be the better harness quality though

    jamesinc
  • jamesincJames @jamesinc Oz Volvo Ice Fortress

    Yeah I don't think I've ever had any real dramas with the 70s wiring aside from the alternator wires and oil pressure wire sometimes being cooked from exhaust manifold heat.

  • Says nothing for the connectors though.

  • jamesincJames @jamesinc Oz Volvo Ice Fortress

    The connectors definitely get a bit brittle, I think the most common problem I've had to deal with is F-crimp terminals that have fatigued

  • Thanks so much for the advice everyone, I really appreciated it!


    I spent ages on it today getting the carb set right. Once i put the carb back on the problem carried on the same.

    I tested all four spark plugs for spark against the bolt on the side of the block that the battery grounds to. I got my Dad to crank it over for an extended period for each plug i was testing. What I noticed was a strong spark the first couple of revolutions but it appeared to get weaker after that. From memory it was the number 3 plug that started strong, got weaker then stopped sparking all together. They were brand new Bosh WR6DC plugs I bought this morning. Dad and I swapped spots and i sat in the car cranking it over while he had a look at the spark himself. He grounded them to the exhaust manifold though on the other side of the block to where I was grounding them. He said he didn't observe the same drop in spark quality that I did.


    Is there a place anyone thinks I should test first that could cause a decline in spark after the first few revolutions? Everything is at most a couple of months old besides the leads. Is there another more accurate test I could do to test the spark strength besides just observing the spark?


    Once again thank you so much for your advice everyone.

  • jamesincJames @jamesinc Oz Volvo Ice Fortress
    edited May 23

    @TomD have you replaced the condenser? This thing https://www.ebay.com.au/itm/223337798175

    I'd also check you have the points gapped correctly

    bgpzfm142
  • I put new plug leads on today and tested my fuel pump pressure. I thought perhaps the fuel pump was producing too much pressure for some reason and was overcoming the needle and seat.

    I ordered a new condenser but it still hasn't arrived yet unfortunately.

    Does the quality and regularity of the spark look normal in these videos? The ground on the exhaust manifold may not have been perfect as there is the standard rust/corrosion type surface on the manifold which may not have been perfect. I'm a bit unsure whether to go down the carburettor or electrical route now.

    Thanks again for everyone who has helped me so far!



  • jamesincJames @jamesinc Oz Volvo Ice Fortress

    Spark looks alright to me. I dunno it kind of sounds like the carb is the issue. When you're cranking it it catches occasionally, it seems like it wants to run and the spark seems like it's okay, so that only leaves fuel.

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