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Unable to Fire up Motor

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AndyMenon

AndyMenon

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Hi Folks,

I seem to be having problems firing up my motor. I hope someone here has run into this issue before and can help me out. Here are the symptoms and the checks I have made so far:

Start up Symptoms:
  1. When cranked, the motor turns over. The fuel pump comes on, and switches off as I stop cranking.
  2. When the gas pedal is depressed, I can see fuel being sprayed into the carb.
  3. But the carb coughs really bad and the fuel sparks and spurts out of the carb!
Checks made thus far:
  1. I have confirmed that the plugs have been wired in the right firing order (pic 5) 1-8-4-3-6-5-7-2
  2. In pic 2, I have a spark tester wired to cylinder #1 and I can see the bulb light up indicating that the power is getting to at least plug#1 when I crank.
  3. I have a pressure gauge (last pic), and the fuel pressure is between 4-6 psi when I crank.
  4. I unscrewed all the spark plugs and only the #1 plug (pic 1) has evidence of sparking.
  5. These are brand new plugs, and I could see that there was a spark.
  6. But the other plugs look wet (pics 3 and 4) , and the plugs do not have any evidence of sparking. And it's definitely gasoline on the plugs, and not oil.
  7. The electric choke runs extremely hot!
  8. There are no fuel leaks, oil leaks or coolant leaks any where.
Am I missing something here? The motor is a stock GMC 305 V8.

Thanks much!
Andy


WP_001620.jpg WP_001614.jpg WP_001613.jpg WP_001612.jpg WP_001616.jpg WP_001615.jpg
 
Lets start at the basics. Remove #1 plug bring cylinder to top dead center on compression stroke. (Blows finger out hole). Timing mark should be at zero. Remove dist cap and rotor should be pointing at #1 sparkplug wire. Check firing order. Next set plug gap at recommended gap.
I am assuming valves are adjusted.
Good luck
 
Dirt-T said:
Lets start at the basics. Remove #1 plug bring cylinder to top dead center on compression stroke. (Blows finger out hole). Timing mark should be at zero. Remove dist cap and rotor should be pointing at #1 sparkplug wire. Check firing order. Next set plug gap at recommended gap.
I am assuming valves are adjusted.
Good luck
Click to expand...

Yep, the TDC was set with a piston stop. The timing mark aligns when #1 is at TDC. Valves were adjusted in the firing order . The #1 terminal was set to align approximately in the direction of the #1 Cylinder before the plugs were wired.

Looks like the problem is beyond basics :thumbsdown:
 
AndyMenon said:
But the carb coughs really bad and the fuel sparks and spurts out of the carb!
Click to expand...

Here's one possibility. When you cut a new fuel line there are usually small cuttings that fall into the line. If you don't blow them out before hooking up the line they will travel into the carb and get stuck between the needle and seat holding the needle open and causing the carb to spit gas.
 
I had a similar problem years ago. Make sure battery connections are correct. Mine were reversed, engine still cranked and attempt to fire but didn't.
 
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What they said. Take your time, this is what HotRodding is about! Check what they told you. Have you done anything to the Electronic distributor? If not, how long has it been since you've pulled the dist. cap?

If its backfiring out the intake, its either a spark occuring at the wrong time, by whatever means is causing it
( Carbon tracking inside distr. cap, plug wires off either by 1 or 180 degrees out, distr. moved, Rotor button moved or slipped, Centrifigual and/or vacuum advance broke, stuck,or breaker plate loose, jumped time at the timing chain, sheared dist. gear pin, incorrect voltage, bad/weak coil, Broken distr. shaft, etc)
, or one or more of the valves are not fully closed, by whatever means is causing that
( Valves too tight( lifter pumpup, lifter going bad, Adjustable pushrod came loose), PolyLocks slipped, Jomar Bars or stud girdle incorrectly installed, bent or broken, valve hanging, burn or bent valve, broken and or weak valvespring, etc)

Yes, I know you told us its a stock 305 V8, but any or all those things can cause it. Up to and including sucking a rag into the intake, holding the intake valve open....Yes, I've seen it....

Theres alot of other things that'll cause these things. Its best to go slow and methodical on your search for this demon. 99% of the time its either something simple, either something has been done you didn't see or realize.
The flooding will cause this also, also, extreme lean out of the mixture. But, since you got gas popping out of the carb, I don't believe it'll be lean-ness.
The spark is occuring while the intake valve is open, ....good luck....

Could be a good ole simple case of cross firing....
 
Last edited:
Screaming Metal said:
The spark is occuring while the intake valve is open, ....good luck....
Click to expand...

I have been thinking about this in the meantime. I think this maybe the demon.
I will need to check what the exact length of the push rods is. It's possible that I may have the wrong lengths.

As for the distributor cap, I pulled out the cap a couple of months ago when I did all the TDC checks as I had mentioned in my earlier update
Valves aren't too tight either. Because when I adjusted them, I was able to rotate them without any binding.
And no, no rags in the intake. I'm sure about that :)
Distributor - Brand new - Confirmed that shaft or gear is not broken. This is the first time I have cranked the engine.
 
409T said:
Here's one possibility. When you cut a new fuel line there are usually small cuttings that fall into the line. If you don't blow them out before hooking up the line they will travel into the carb and get stuck between the needle and seat holding the needle open and causing the carb to spit gas.
Click to expand...

Agreed. But this is what I did when I cut my fuel lines. Each of the cuts was properly deburred. After the gas line was installed, I cleared it out with an entire bottle of rubbing alcohol to make sure all the gunk in there is removed. I have 2 filters, one before the gas enters the fuel pump, and another before it enters the carburetor.
 
Mike J said:
I had a similar problem years ago. Make sure battery connections are correct. Mine were reversed, engine still cranked and attempt to fire but didn't.
Click to expand...

Confirmed! Connections are not reversed. I just looked once again. Besides, the spark would not occur had this been the case.
 
One thing I did once when my brain was out of gear and I had the same symptoms. Finally figured it out and had a good laugh at myself. I used the right firing order to wire the engine, but not thinking I used Ford cylinder locations on a GM engine.
Ford is " 1,2,3,4 on one side & 5,6,7,8 on the other ". GM is " 1,3,5,7 on one side & 2,4,6,8 on the other. Number one will fire at the right time and the others were totally out of order. Number one was dry and the others were wet.
 
Another thing to consider is the rotation of the rotor. If the wires are in the proper order but backwards you'll only get number one to fire properly.

Jim
 
Duke said:
One thing I did once when my brain was out of gear and I had the same symptoms. Finally figured it out and had a good laugh at myself. I used the right firing order to wire the engine, but not thinking I used Ford cylinder locations on a GM engine.
Ford is " 1,2,3,4 on one side & 5,6,7,8 on the other ". GM is " 1,3,5,7 on one side & 2,4,6,8 on the other. Number one will fire at the right time and the others were totally out of order. Number one was dry and the others were wet.
Click to expand...

Agreed. I have considered this. The way I have wired it is Cylinder#s 1,3,5,7 starting from the front of the car, and moving towards the firewall on the D-side.
2,4,6,8 are on the P-side - again in the same direction.
 
All I can say is good luck. I once battled something similar on an old flat head V8. After about a month of weekends fiddling with it I ended up giving up and selling the the vehicle cheap...the guy who bought it fiddled with it for about 5 minutes and drove it out of the garage and onto the trailer. :sick: That's the only one I was never able to fix
 
and i need a picture of the front of your engine of the timing tab also. A 305 is straight up at 12 o clock and all others are on the side
 
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