As the title, my freshly rebuilt engine wont start... It's a Datsun A14 with a 32/36 Weber and electronic distributor.
Short story, I had it running fine for about 30 secs till the fuel ran out of the fuel bowl (due to faulty FPR)
I removed the FPR and now the bastard won't start.
After *much* fiddling I can get it to 'run' but it sounds like it's not running on all cylinders and any adjustment of the distributor makes it piss and fart and backfire out the carburettor. All the spark plugs except for #3 are black as the ace of spades.

I have been thinking it's a timing problem, but I've inserted and timed the distributor as per factory instructions and tried different distributor/leads/coil which as of 5 mins ago has got me thinking that it may be a fuel problem...

How can I tell if it's running too rich or too lean? Being a Weber would the fuel pressure be causing this problem? I'm running an electric fuel pump rated at 2.5-4.5 psi and I've read that Webers need 3.5 psi max... (Keeping in mind I had it running for about 20 secs without the FPR but then the idle kept dropping until it eventually started backfiring out of the carb again)


I'm so fried, at a loss and I think I'm missing something simple so after some fresh perspectives :)


Cheers,
Sam

Backfiring can mean that you have a couple of plug leads in the wrong place, which in this case I seriously doubt, or it can mean a lean mixture.

This seems to be the case however black plugs, particularly if the deposit is dry & 'sooty' are indications of a rich mixture or the wrong heat range.

At this time I'm going to guggest that it might be a lean mix caused by a low float level setting, or a blocked jet somewhere.

Since it was running 'fine' for 30 seconds before exhausting its fuel reserve I would not think that the distributor was a contributing factor in any way.

If the fuel bowl is filling with fuel, then fit the air cleaner, then swap leads on cyl numbers 2 & 3.

This will cause it to backfire & hopefully the pressure wave will dislogge any foreign material in the jet[s]
Allow it to backfire a few times then switch off. Make sure that there is no fire in the air cleaner [there shouldn't be] then re-position the leads to the correct plugs & see if that improves the situation at all.

If so, then just let it run at a fast tickover for a little while, if not, then as long as there are no other issues, it looks like a carb strip & clean.

OK so today I started with a fresh mind. I removed the carb and went through it with a fine tooth comb with the carb cleaner = spotless.
Bolted it all back up, same damn thing, not running on all cylinders.
My uncle came out to help and after much, much stuffing around (including putting in a brand new coil, different plugs, etc) we removed #3 spark plug lead and it ran exactly the same = something wrong with #3.
Came to the conclusion that the #3 exhaust valve wasn't seating properly so ripped the head off and the valve seats are terrible.
I'm not too impressed with the machine shops definition of re-seating the valves.

So I'm off to get some paste and grind them all in again...

I lapped all the valves in properly this afternoon, put it all back together and it sounds like it has much better compression but now it has so much the battery hasn't got enough grunt to crank it over!

I'll see how I go tomorrow...