Backfire, wont start.

carguy300

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I am back again, and stuck. I have replaced old harness with correct evans update. 1968 300 with 1970 solid state v.r, electronic ign. Replaced starter relay, igniton kit came with distributor, module, 12v coil and resistor. Replaced plugs and wires. Has new ign switch and updated alt. I believe i have everything correct, verified #1 on cap, tdc on crank, firing order right. Kept turning over, tried several minutes, has fuel. Twice when I let off the key it acted like it wanted to start, on the third time it BACK FIRED!, ran the doves out of the woods. To chicken to try again yet. Can someone tell me what voltage I should have, where with key off, in the on position and in the start position, what should i have at resistor and the coil terminals. I am not good at all with wiring aspects, this is killing me. the motor turns over perfect, no wires have smoked or melted. Please any help.
 
Sounds like the classic distributor 180 degrees out problem.

If you brought it up to TDC on #1, was it on the compression stroke? If you aren't sure, I'll bet that's the problem.

Easy fix, just take the distributor out and turn the rotor 180 degrees and reinstall.
 
I cant read the timing marks very good, there is a hole stamped about in the center of the mark. would that be TDC?
 
Also, how much should I be able to turn crank oppisite direction before rotor starts to move?
 
With key on position, what volts should be at resistor and coil, in start position what should there be?
 
I cant read the timing marks very good, there is a hole stamped about in the center of the mark. would that be TDC?
The engine comes to TDC on #1 twice for every one turn of the distributor. Read that again if you need to...
So you can be at TDC on #1 and the rotor in the distributor can be pointed at #6

It has to be on the compression stroke. The easiest way to verify is to pull #1 plug and turn the engine over while trying to keep your thumb on the plug hole. You'll know when there's compression starting. When that happens, just bring it up so the marker is aligned.
 
If im at TDC, with # 1 plug out, I should be able to touch top of piston correct?
 
If im at TDC, with # 1 plug out, I should be able to touch top of piston correct?

Also remember the piston at the top of the cylinder might also be at the end of the exhaust cycle. Piston goes up and down twice for each firing cycle. If you are confused , you can always remove the valve cover over #1 to see if both valves are closed, that will be the true TDC to fire the cylinder.

Dave
 
Just feeling the compression blowing out of the spark plug hole with a finger is far easier than removing the valve cover unless they need to come off anyway.
 
Intake-compression-power-exhaust. the 4 strokes. You want the piston at the top between compression and power stroke. The rotor at #1.
Use some chalk or a paint pencil to mark the damper timing mark.
 
Are you extremely certain that the distributor is actually installed correctly and not a tooth or 2 off from where it should be??
Remember that wise man is NEVER sure, but a fool is always POSTIVE! Good Luck
 
I am back again, and stuck. I have replaced old harness with correct evans update. 1968 300 with 1970 solid state v.r, electronic ign. Replaced starter relay, igniton kit came with distributor, module, 12v coil and resistor. Replaced plugs and wires. Has new ign switch and updated alt. I believe i have everything correct, verified #1 on cap, tdc on crank, firing order right. Kept turning over, tried several minutes, has fuel. Twice when I let off the key it acted like it wanted to start, on the third time it BACK FIRED!, ran the doves out of the woods. To chicken to try again yet. Can someone tell me what voltage I should have, where with key off, in the on position and in the start position, what should i have at resistor and the coil terminals. I am not good at all with wiring aspects, this is killing me. the motor turns over perfect, no wires have smoked or melted. Please any help.
Question on something you mentioned... You say you have solid state ignition...AND a 12v coil with a resistor? If you're running a Pertronix or even a full conversion, you shouldn't need a resistor in that system. It should be bypassed. At least for a Pertronix is needs to be. What system did you install? Sounds like you're not getting enough spark..or cutting out the coil.

If you're running a true 12v electronic ignition, you should have 12v at the coil, because again, the resistor is supposed to be bypassed.

Confirm the position of the distributor, then tell us more about the ignition system you have installed.
 
Are you extremely certain that the distributor is actually installed correctly and not a tooth or 2 off from where it should be??
Remember that wise man is NEVER sure, but a fool is always POSTIVE! Good Luck

How is that possible? On my 383 dual point it's just a slot... Aren't they all the same? I used to hate that issue with my 66 Nova... GM sucks for that problem. Mopar made it super easy...can only be 180 off. Can't even screw up the rotor as it's keyed one way.
 
Have an update... timing was right. Was not getting 12v to start circuit, neglected to rehook ign#2 through new bulkhead. Learning as I go! After that crisis she fired right up, but....oil pump does not act like its pumping. Lifters would not quiet down, oil light staying on. Tried 4 times. let it run 15-30 seconds, car has sat several months. Running Amsoil, new, Wix filter. Does pump need priming?
 
The complete ign upgrade was bought through recommended cbodies vendor, came with dist, coil, resistor. Upgraded harness from bill evans, era correct plug wires also through cbodies vendor. Champion plugs.
 
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