Commer Non-starter

[Rootes75]

We are having issues with our Commer truck, issues in her not starting. She has a 6 cylinder sidevalve petrol engine with the Solex 40 FAIE carb.

We have set the timing, checked all gaps and plugs for sparks, all fine. We found the manifold gasket was leaking so thats been replaced. Next we fitted new fuel lines and cleaned down the carb, we have checked and she is getting a good fuel supply. We have also checked the compression which is good.

So, with a good strong battery she turns over lovely, but thats about it. Once in a while she does fire/engage but never actually starts. She then just floods everytime. It you put her on full choke she tries hard to fire and almost gets there but floods very quickly. Even a shot of easy start didnt do anything.

We are ticking off things to try out but seem now to be going round in circles.

Any suggestions, no matter how simple, anything could help.

[Sean N]

Are you 100% sure you have a good, fat, blue spark? I've had a number of occasions on older vehicles where condenser, or particularly coil, has started to break down, and will give a spark to e.g. the block with the plug out but not under compression with the plugs in. This sounds like similar symptoms.

[Sean N]

You seem to have double-posted this ...

 

[Rootes75]

Whoops, didnt realise I had done that. When I posted it first it threw back an error message so I hit submit again.

I presume its best to close this thread and use the other.

Edited October 19, 2020 by Rootes75

[ruxy]

https://www.amazon.co.uk/Laser-2780-Ignition-Spark-Tester/dp/B003AN1VPW

Use a set of these , or in your case a set + half set would be best , shop around you should find a set for abt.  £8       40 years ago - Lucas Service used to charge approx. £5 for a single tester &  ISTR so did Halfords..

 

[ruxy]

Seems a classic case of starter motor pulling a already weak battery down & nothing left to fire the plugs.

[Rootes75]

I am erring on the side of poor spark at the moment, the spark is quite hard to see. And as many have pointed out it should be a big fat blue spark.

I have a spare coil so I could swap that over at the weekend and see if that makes a difference.

[67burwood]

Try changing the condenser, I had a similar issue with a Jeep, plenty of fuel and had a spark but just wouldn’t fire properly, drove me mad for ages, double and triple checked everything, last resort started changing stuff to eliminate the problem,  new condenser and started on the button. 

[david1212]

On 10/19/2020 at 5:15 PM, 67burwood said:

Try changing the condenser, .......  new condenser and started on the button. 

The key here is new rather than old in age regardless of if zero hours use.

[Rootes75]

Well, finally we have the Commer engine running!

We have literally tried everything so thanks for all sugestions. In the end we removed the starter motor as we thought it may be taking too much power resulting in a poor feed to the coil.

But, when we bench tested it we found that although she spins up the engaging dog didnt travel far enough, so cleaned and oiled etc and we got the right amount of travel. We refitted it but firstly checked the ring gear for tooth wear, it was fine.

Next we connected everything back up and now she was turning over at a really good speed but still not even firing. So we checked the spark at the plugs and it was very weak, then at the contacts and this was good. So, we took a look at the sprung graphite in the cap and we found its movement very small. So, I had a dizzy from one of Hillmans on the bench and we changed the graphite over. This time with everything reconnected she fired straight away on full choke, not only fired but stayed running. Lots of relief and plenty of smiles!

We have to now fit a new downpipe gasket and replace the brass nuts and then hopefully she will run with no choke, at present you can hear her sucking air in so obviously messing up the mixture.