Backfire through Carb on start up

[GearAddict]

I finally finished off the electrical and took a break from the Road Runner for a month...finally started on the engine....here's the time line of events.

1. Car Started and drove"ok" when I bought it.
2. spent 3-4 months working on electrical and interior
3. Tried to start car after 3 months - no go.
4. Fuel was low (and old) - Flushed fuel line, did not flush tank, but added 5 gallons fresh gas
5. Started, but would not stay running unless reved up to 2K RPM.
6. Shut her down for 3 weeks (vacation)
7. Went back at it....realized vac advance was plugged up to manifold vac. (Edlebrock carb)
8. Had already purchased Holley when bought car, installed Holley, replaced all plugs except #6 (need to remove header, haven't gotten around to it yet.) Vaccum Advance plugged, so I could set timing.
9. Attempted to start, she would start to fire and die.
10. Attempted to start and give a little gas, she started for a second then POW! fireball from carb and die.
11. 2 more times, same deal.

What I have done since then...
12. Simple compression test on all cylinder except #6 (bumped starter and checked with finger). got pressure...assuming that all cylinders checked don't have stuck valve (that nasty #6 still in question).
13. checked that all vacuum ports were plugged. (PCV only thing hooked up) checked visually for cracked hoses.
14. Bumped starter until compression on #1 cylinder, Timing marks around 12 Deg BTDC (no socket large enough to move crank manually to hit 12 deg perfect)
15. Pulled dizzy cap off, rotor dead in between #1 and the one before it.
16. Rotated dizzy to have rotor straight on #1 Cylinder.
17. Check plug wires for correct order.
18. Tried to fire up and POW! same deal.
19. Replaced Cap and Rotor.... Same effect.

One thing I noticed the last 2 times I went to start it (the motor was cold) The Choke was wide open....I realized since I was using a remote starter, I had left the key in the Run position and the choke had heated up fully.....this may have been the case each time, can't say for sure.

I'll let the header bolts soak with some WD-40 and try to get them off tomorrow to get at the #6 plug....outside of that is there anything you guys can see that I missed?

Any comments would be greatly appreciated.

 

[fatecaptured]

I would think the intake valve is open when the plug fires to cause the backfire. But someone will come along and help ya. My opinion is your too advanced on your timing.

 

[RustyRatRod]

Try advancing the initial timing some and see what happens. Advance it until it lugs the starter trying to turn it over, then retard it until it starts (hopefully).

 

[snakeoil24]

Pull the valve cover on cylinder 1. rotate engine until intake valve opens. Then watch it closely, giggle the rocker arm left to right as you rotate engine. You will look for the point where intake and exhaust are both closed. Then check balancer for tdc. Install distributor withrotor facing horizontal. Then check your wire location. If your 180 out you will know .

 

[HEMI-ITIS]

If you never removed the distributor,that rules out that being 180* out.Therfore if it spitting up from the carb,the timing is too advanced,if it were farting out the exhaust it would be too retarted:thinker:

 

[charger360]

spitting farting sounds messy!

 

[Red63440]

It could aslo be bad valve seats.

 

[RustyRatRod]

It could be a bad flux capacitor or plasma conduit, but lets try to stick to the simple stuff to start with. We don't wanna get him in too deep too quick.

 

[JacobEXE]

gas is just made like **** now i dont get it. you used to be able to buy a drum of gas and let it sit for six months or so, go back to it and fresh gas. this new gas onlly takes like three weeks to turn to ****. isnt it supposed to be quality over quantity?

 

[coloradodave]

OP said that it ran OK before so we can rule out a mechanical problem. If you let today's gas sit in your carburetor for 3 or 4 months without Sta-Bil or a similar fuel treatment, the gas will have started to gel and clog your idle circuits. Best advice: drain tank and lines and rebuild/clean the carburetor, paying particular attention to blowing out all the tiny orifices with compressed air and carburetor cleaner. Reset floats and refill tank with fresh gas. (Fresh gas mixed with old gas=more old gas). Check your setting on the choke, making sure that when you push the acceletrator down on a cold motor that the choke closes. As others have said, check #1 cylinder (driver side front) by putting your finger over the plug hole while tapping over the motor with a remote starter (cheap at any auto parts) until the compression tries to blow your finger off the hole. At that point the timing mark should be coming up to the pointer. Get a 1 1/4" socket and turn the crank a little more until the 12* mark is in line with the pointer. Then pull the distributor cap. The rotor should be pointed right at the #1 plug wire. If it's not, move the distributor until it is. Check that the firing order is 18436572 going in a counter-clockwise direction on the distributor cap. Driver's side cylinders are 1357 (front to back). Passenger side are 2468 (front to back). Doing all the above correctly should get you running again. At this point, don't look for trouble in places you haven't messed with.

 

[RustyRatRod]

I tend to agree, Dave. Sounds like you scored anotherun.

 

[snakeoil24]

It could be a bad flux capacitor or plasma conduit, but lets try to stick to the simple stuff to start with. We don't wanna get him in too deep too quick.

That is great

- - - Updated - - -

gas is just made like **** now i dont get it. you used to be able to buy a drum of gas and let it sit for six months or so, go back to it and fresh gas. this new gas onlly takes like three weeks to turn to ****. isnt it supposed to be quality over quantity?

They put ethanol in it and that absorbs water

 

[GearAddict]

OP said that it ran OK before so we can rule out a mechanical problem. If you let today's gas sit in your carburetor for 3 or 4 months without Sta-Bil or a similar fuel treatment, the gas will have started to gel and clog your idle circuits. Best advice: drain tank and lines and rebuild/clean the carburetor, paying particular attention to blowing out all the tiny orifices with compressed air and carburetor cleaner. Reset floats and refill tank with fresh gas. (Fresh gas mixed with old gas=more old gas). Check your setting on the choke, making sure that when you push the acceletrator down on a cold motor that the choke closes. As others have said, check #1 cylinder (driver side front) by putting your finger over the plug hole while tapping over the motor with a remote starter (cheap at any auto parts) until the compression tries to blow your finger off the hole. At that point the timing mark should be coming up to the pointer. Get a 1 1/4" socket and turn the crank a little more until the 12* mark is in line with the pointer. Then pull the distributor cap. The rotor should be pointed right at the #1 plug wire. If it's not, move the distributor until it is. Check that the firing order is 18436572 going in a counter-clockwise direction on the distributor cap. Driver's side cylinders are 1357 (front to back). Passenger side are 2468 (front to back). Doing all the above correctly should get you running again. At this point, don't look for trouble in places you haven't messed with.

Thanks Dave, this is the approach I was taking. But didn't flush the fuel out. I will siphon the gas this morning, blow out the lines and give it a shot with all fresh gas.

The carb that is on it is brand new as of 3 weeks ago... I'm hoping rebuilt not required.

 

[moparmarks]

You said that it ran before you did some electrical work. So back track a bit. What all did you do?

Yes get fresh fuel in it to start with.

 

[GearAddict]

You said that it ran before you did some electrical work. So back track a bit. What all did you do?

Yes get fresh fuel in it to start with.

I did a complete rewire with a Ron Francis kit. Front to back.

 

[moparmarks]

I did a complete rewire with a Ron Francis kit. Front to back.

Standard or Electronic Ing?

 

[GearAddict]

Standard or Electronic Ing?

Electronic.
OEM distributor with MSD 6a and MSD Coil

 

[moparmarks]

ok and your fireing order is CCW?

- - - Updated - - -

I'm guessing that it is a big block.

 

[GearAddict]

ok and your fireing order is CCW?

- - - Updated - - -

I'm guessing that it is a big block.

Correct CCW, 383

an update... Siphoned all the old gas out and cleared the fuel lines...added 5 gallons of premium.

made sure choke was closed, and she fired up but ran a little rough and eventually died...no backfire. Maybe 15 seconds of run time.

Started again, ran rough, gave it a little gas and the RPMs shot up to 2k I let it go for about a minute then tried to dial down the idle screw...rpm drop then died.

started again, ran rough and died....noticed magnetic pickup wires were touching the headers...shut down and inspected....wires were melted...don't know when this happened...might have been that way from the beginning of the problem. I will splice and reroute wires tomorrow and give it another shot.

 

[moparmarks]

Good sounds like your making some headway. Eliminate everything that you did as the problem. Is sounding like a fuel problem. A lean condition will cause backfire though the carb.