Back firing/ running on 3

Last night it was running brill. turned it off and turned it on 5 minutes later and it ran on 3 cylinders, still is and i cant find the problem, changed the ht leads, cleaned the plugs, swapped them round ect ect, cleaned the dizzy (which is brand new as well as the pionts and rotor arm)

Also it is poping ( back firing) through the carb.

If i take off the connection to the jet it still runs, if i turn the fuel screw all the way it still runs…

Could anyone point me the right direction?

It could be timing? Overfueling? or even sticky valves (my brothers nova did this, turned it off and put it back on and all was well, really weird) Try take out one HT lead off at a time while running and see which cylinder isnt actually firing respond back here, im sure someone may able to help u.

tryed the ht lead trick, turns out number 4 isnt fireing( cam belt end)  but there is a spark.

i recon it could be the valves sticking, someone else said that to me to.

Head off job then - yay

Haha, let us know how it goes and what the actual prob is, its good to know these things to help others, i also have a 1300 driver.
Gd luck

if it were a sticky valve your piston would of hit it = loud baning and knackered

also you would have nasty noses from the head as the cam is slapping the follower

could be head gasket,

get teh compression tested and go from there

are you sure all the plugs are firing,

running too rich would cause it to be lumpy on all cylinders, but would fire up on 3 when starting

oil and water the right colours?

Everything is right mate, no oil in water, no water in oil ect, had the rocker cover off and no sighns of the head gasket gone.

Stripped the carb down and its fine, the jets arnt blocked and theres no dirt in it.

Im getting a spark to all cylinders too, i think the inlet valve in cylinder 4 is not seating correctly due to carbon build up or a split collet breaking.

Ive tryed running red-ex through the tank and down the carb to see if it frees the sticking valve if it is that. Tryed wynns oil treatment ect and still no joy. Tryed different plugs, put new ht leads on, checked dizzy again, rotor arm again, couldnt be the points could it? Only recently had new points…

I will do a compression  test on monday and see what that says. Otherwise i think it Looks like a strip down… yay!

Driver-Matt said

tryed the ht lead trick, turns out number 4 isnt fireing( cam belt end)  but there is a spark.

Just for information ;

Cam belt end is No:1 not 4

Could be the points or the timing, the small block engines are VERY sensitive to points gap setting. Are you setting it with a feeler guage or with a meter measuring the Dwell Angle - Dwell is the only way to go IMHO.

Check the vacuum hoses especially between the carburettor and the distributor advance unit and test with a timing light that that the vacuum and mechanical advances are working.

The compression test might tell you something but I wouldn't do the strip-down until you've exhausted all other possibilites (could even be the coil). Just buy a compression tester and do it for ?15  :dontknow:

Finally (and please don't take this the wrong way), double double check that the plug leads are correctly ordered at the distributor cap, sound obvious but I've seen it so many times when people put new leads on.

Have Fun
 8)  8)  8)

It can be the intake manifold. I have the same problem. A change everything and take off the head and nothing. And then checked the intake manifold and had a little hole in it and exhaust gases are getting in the intake,so i have changed the manifold and everything was OK after that.

I dont know did you understand what I want to say,my english is not the best.

Cheers!

Remus - your english is fine  

Andy

MKone said

Driver-Matt said

tryed the ht lead trick, turns out number 4 isnt fireing( cam belt end)  but there is a spark.

Just for information ;

Cam belt end is No:1 not 4

Could be the points or the timing, the small block engines are VERY sensitive to points gap setting. Are you setting it with a feeler guage or with a meter measuring the Dwell Angle - Dwell is the only way to go IMHO.

Check the vacuum hoses especially between the carburettor and the distributor advance unit and test with a timing light that that the vacuum and mechanical advances are working.

The compression test might tell you something but I wouldn't do the strip-down until you've exhausted all other possibilites (could even be the coil). Just buy a compression tester and do it for ?15  :dontknow:

Finally (and please don't take this the wrong way), double double check that the plug leads are correctly ordered at the distributor cap, sound obvious but I've seen it so many times when people put new leads on.

Have Fun
 8)  8)  8)

Cheers for that matey, i will have a look tomorrow and let you know how i go on!

plus - Would the backfiring through the carb have anything to do with the points or coil being faulty?

I can understand what to look for if its just running on 3 ect, but i cant put my finger on the backfiring.

It ran on 3 ok but i drove it less than a mile to my house from my mates an it completley died and will not start or run now, could it be the coil? or condenser ect?

The point by Remus is good too - a leaking inlet manifold can exhibit these symptoms too.

Check it is firmly bolted to the head (but not toooo tight) amd the tha gaskets, plates between the manifold and the carburettor are good and that the carburettor bolts are tight.

Andy

Had another hour or so on the car today. took the rocker cover off and turned it over to see if there was any clearance after the cam hit the tappit and it was all ok.

Another thing i found - its not running on 3 cylinders, its running on 2!!!

It still idles! If i take plug lead 1 and 2 off then it runs still!  but if a take  3 and 4 lead off then it doesnt start or run.

I will get the inlet manifold off tomorrow

Had another look yesterday. Tryed a new coil and i still have the problem.

I had a thought not so long ago. …

It burnt 2 plugs out, blistered the ceramics and melted the tips.

Also my mate had a look at it and checked the fuel/air mixture - it was running lean. Plus another thing, the timing had been advance by a stupid amount on the dizzy - reset it and put new plugs, richend the fuel mixture and it ran better than it ever had done before.

Do you think it took its tole on the valve and burnt them out maybe?

matt

Matt,

What did the compression test show ?

Andy

MKone said

Matt,

What did the compression test show ?

Andy

not done one yet, just eliminating what i can do with out one as i havent got one.

But… ive just checked the engine timing - Its out a tooth on the cam sprocket

Could that be the problem maybe? I got a new cambelt with the car that wasnt fitted so maybe it was ready but the previous owner didnt do it.

Thers a few little lines across some of the teeth and its a wee bit slack - it looks old.

Matt

if the belt was too loose it would jump a tooth

put a new water pump in there too!!!

a tight bearing can cause stripped teeth or stretch the belt

Yeh i will put a new wter pump on although it looks new,

So if it had slipped 1 tooth then do you recon thats whats causing my problms?

Hello Matt,

It is possible that the belt slipping one tooth is not helping your engine but I don't think that is the whole problem.

One way to find out though - set it correctly. However sometimes you can't get it to exactly line up with the belt on and it is a bit out. The old belt may have stretched rather than jumped and hence be out by a tooth.

If it were me I'd fit the new belt, time and tension it correctly and see how it went then.

Also the compression test is best done with the cam timing spot on, it will tell you if it's a sticking valve. The test dials are pretty cheap from Machine Mart and the like.

Good Luck

Andy

Top man Andy!

I will purchase one tomorrow and give it a go.
Oh and with it being a 1300, the water pump acts as the tensioner? correct me if im wrong so i will need to replace that too?

Cheers

Matt