Need Help Dont No What Else To Do
 

Hows everyone doing i got a problem with my 1971 chevy c20 350 sbc so recently after this snow storm in north carolina the truck would not turn on so me and my son did i tune up changed the cap,rotor,igniton module,spark plugs,wires the truck turned on we went down the road and all we got was horrible backfire so we thought it was the carb so we changed the carb and it still did it but it got better until u gave the truck alot of gas and it was back to backfiring i dont no what else to do if someone has some advice that will help us out a lot because its my sons daily driver!!

Re: Need Help Dont No What Else To Do
 

Timing is off, or maybe fuel line/filter is clogged up.

Re: Need Help Dont No What Else To Do
 

Check for vacuum leaks, maybe .

Re: Need Help Dont No What Else To Do
 

Check your firing order on the plug wires

Re: Need Help Dont No What Else To Do
 

Check fuel pump--filter--line

Re: Need Help Dont No What Else To Do
 

Replaced the filter already i havent checked the line will check tommorow

Re: Need Help Dont No What Else To Do
 

replaced the fuel pump already and the filter havent done the line yet

Re: Need Help Dont No What Else To Do
 

alright im goona check again for this but wouldnt it always be back firing if the fireing order is off?

Re: Need Help Dont No What Else To Do
 

im goona look into this tommorow

Re: Need Help Dont No What Else To Do
 

Check the firing order, also make sure the distributor cap is seated properly. It depends on which wires are crossed as to how it will or will not backfire.

Re: Need Help Dont No What Else To Do
 

the firing order seems to be ok im goona check it again tommorow and im also goona check the cap and see if its sitting right

Re: Need Help Dont No What Else To Do
 

Any unusual engine noise? How many miles on engine?

Re: Need Help Dont No What Else To Do
 

nah no weird noises never had any weird noises once the storm hit it all hit the fan idk whats wrong with it

Re: Need Help Dont No What Else To Do
 

Can you elaborate on "would not turn on"? Would not crank? Would not fire/start? I assume the latter since you got backfiring (guess I just answered my own question, sorry...) The items you initially changed out sound like you had indications of no spark. You mentioned after a storm and ign module (as in HEI module?) - perhaps struck by lighting? I think if you changed the HEI module, it'd take care of any lightning damage. Hmm. More details please. It the backfiring load-dependent? Like, only when you let off the gas, for example? Or only when you step on the gas, etc? Sure sounds like a timing issue to me - but that wouldn't just change overnight after a storm. So, you may have two problems - perhaps module went out, and then, during reassembly, the plug wires or timing got crossed/set wrong(?) Backfiring is "normally" a timing/ignition issue - not a carb or fuel issue. Did you replace all the ignition components at the same time and then try to start, or one at a time and try to start? (I'd have done them all too... but that is how compound/self-induced issues can be masked). If it wouldn't start AT ALL (as in no ignition, but it did crank over) and then you changed all the ignition parts and it starts but backfires - my guess is something was messed up in the replacement process while the root problem was fixed.

Re: Need Help Dont No What Else To Do
 

How often does it actually get cold enough to snow there? Did you let the truck warm up, is your choke working?

Re: Need Help Dont No What Else To Do
 

It backfires when i drive it mostly not when i start it turns right on no problem im running out of ideas

Re: Need Help Dont No What Else To Do
 

not much dont snow much either but im running out of ideas im thinking it might be the distributor going

Re: Need Help Dont No What Else To Do
 

checked everything you guys told me check everything is good the only thing left i can think of is a warped manifold or a bad distributor

Re: Need Help Dont No What Else To Do
 

Is it a points-type distributor or HEI electronic?

Re: Need Help Dont No What Else To Do
 

hei

Re: Need Help Dont No What Else To Do
 

If you have a points distributor, you could have a bad condenser. I had a condenser go bad once, the truck backfired so hard it blew the end of the muffler off.

Re: Need Help Dont No What Else To Do
 

im runnning hei

Re: Need Help Dont No What Else To Do
 

Dist gear could be warn, and it could have jumped a few teeth.

Re: Need Help Dont No What Else To Do
 

hm i didnt think of that it is a offbrand distributor

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A backfire strong enough to blow a muffler means unburnt gas was in the exhaust. this is because the engine was turning, but not firing. When it started firing again, the hot exhaust ignited the unburnt gas in the muffler. We used to do that on purpose when we was kids.

Since the last thing worked on seems to have been the ignition, time to go over the distributor very carefully, in an organized way. Is the wire from the coil connected correctly? Is the rotor seated on the plate on the top of the shaft. Is the centre contact in the cap there, and in good order. Is the centre contact on the rotor in good shape. I know these are new, but they can get out of whack.

Next, is each plug wire firmly seated in the cap? And at the plugs? Are the wires in good shape, with no issues with the insulation? Etc.Etc. Etc.