Volvo 431 STILL will not start

[Super Blue]

Having carried out a full service my Volvo 431 will not start
I changed the plugs / oil / filters ( fuel and oil ) / rotor arm & plug leads

Fuel is coming through ok and the Carburettor is clear
There is a healthy spark

When I turn it over there is an occasional back-fire
I have the firing order as 1-6-5-4-3-2

Please any ideas would be appreciated. I don't have much hair and I'm rapidly pulling out what is left !!

 

[Aardee]

If you have fuel and a spark I'd start looking at timing - Could you have shifted the distributor while changing the rotor arm?

Edit: Are you 100% sure the leads are correct, it's easy to get it wrong

 

[Hunterlees]

+1 on that.
Also check that the leg on the new rotor arm points in the same direction as the old one. This caused me grief about 55 years ago!

 

[gery w]

.

 

[DavidJ]

I know it sounds crude but have you tried a squirt of easy start. I used to have a 431 in a Sealine 195 and this time of year a squirt did the trick and was ok for the rest of the season. Maybe some damp.

 

[James L]

Years ago on my old Mercruiser I changed the rotor arm as part of routine servicing and the engine wouldn't start.
I put back on the old one and it ran perfect again. Never really bothered looking into why and I sold the boat before I ever got around to doing it again.

 

[Seastoke]

Was it running before you started work on it.

 

[Super Blue]

Was it running before you started work on it.

Yes. But because of circumstances that was about 20 months ago

 

[Bilgediver]

Try taking out the plugs and put a few squirts of oil down the plug holes then wind over on the starter then before putting the last plug back double check that when the piston is about TDC on the compression stroke, ie both valves closed, that the rotor arm is opposite that contact .

 

[Seastoke]

Shit petrol

 

[Billy no mates.]

After 20 months the fuel will be U/S, fresh fuel and probably a carb clean as well. There could be varnish in the jets from old fuel.

 

[Seastoke]

I work on all types of machines and always run it before you touch anything , unless it is broke down .back to problem could you drip feed fuel to carb .

 

[Super Blue]

Although the engine was last run about 20 months ago, the fuel is only a couple of months old and the carb has been cleaned.
It could be a red-herring but I found a 13 amp fuse in the bilge.

 

[fred247]

The firing order is correct, but it sounds like the leads may not have been placed in the cap correctly. find TDC of number 1 cylinder ( front right hand bank from front of engine ) and check the rotor is pointing to what you have as no 1 in the cap, if not rotate the leads accordingly

 

[QBhoy]

Almost certainly bad fuel. You can have 10l of crap fuel in the tank. Add 90l of fresh fuel...and then its usually the case you then have 100l of bad fuel.
apart from that...9/10 times...with these engines...if you’ve put a little bad fuel through the carb...the carb needs to come off for cleaning. It’s a Rochester carb on these. They don’t deal with water in fuel at all. Been there many times years ago. Take the fuel filter off and empty into a glass. Let it settle and see what’s going on. Not much causes these things to not run. Water in the fuel is the usual reason.

 

[Super Blue]

Thanks for all the very helpful replies - I'm off to try again this morning.

Could someone confirm the plug gap ? I have seen conflicting info on this

Thanks

 

[penberth3]

Thanks for all the very helpful replies - I'm off to try again this morning.

Could someone confirm the plug gap ? I have seen conflicting info on this

Thanks

It isn't critical and easy to adjust later so don't let that stop you. Just check you have a good spark when the plugs are out.