At least the plugs look all the same With that you can rule out wires, unless they all went bad at the same time. The coil takes care of all eight plugs, and they all look crappy. But again, the same gas goes to all eight cylinders
Remove the carb flip it upside down and drain all the fuel out of it that you can. Then with the carb still upside down blow with your mouth into the fuel inlet. You should not hear any air entering the fuel bowl, because in this position the float should have the fuel inlet needle in good contact with the fuel inlet seat. next flip the carb right side up and make the same test, but now you should hear air entering the fuel bowl because the needle is off the seat. then flip the carb upside down again and confirm the first test. bolt the carb back on and rig up a way to fill the carb up with known fresh fuel thru the carbs fuel bowl vent(s) Put in a new set of plugs and fire it up. If it runs fine for at least 30 seconds but then dies out, then you have a bad batch of fuel if nothing else. whenever I have a carb off and even if I have done nothing to the carb I make the blow test!
I'm thinking fuel too but reading your first post if you turned the idle speed screw in alot to get it to idle the throttle blades might be open too far and it will be dumping fuel from the boosters- nose bleed...that would turn the plugs black in a hurry. So before you start it back up turn the idle back down.
I talked to Ray on the phone yesterday. I told him it was either bad fuel, weak ignition, or the carburetor was flooding.
Always go back to the last thing that was done, before it failed.. in this case, filled with fuel. Plugs are black, but not wet, so that's fuel.. either the needle and seat decided to take the day off and the carb is flooding over into the engine (you will see that externally around the hole for the accel pump). Or like Mike said, don't go zebra hunting.. replace the fuel and clean or replace the plugs. That is the correct spark plug and heat range for that engine. Plug contamination is effect, not cause. Moving on.. You had an issue last year with stalling when it was warm... how was that resolved? Or did it just "go away".. I am wondering if that heat related issue just took the next step in the chain of failure. The first thing to do is go to the auto parts store, and get a spark tester.. Here is what your looking for. https://www.amazon.com/OEMTOOLS-250...dp/B0014WDFLY/ref=psdc_15707441_t1_B0002STS44 Start with the coil wire, at the Dist cap.. and then check at a plug wire.. both should have very strong spark. If there is any question.. Bypass your entire electrical system with a good size jumper wire with alligator clips, from the Batt + to the Coil + No need to disconnect anything. Due to removal of the resistance, it should show a stronger spark, but not that much different. I believe your answers are to be found in one of these two systems. JW
Later Q-jets have no problem at all with higher fuel pressures. My CV Products pump makes 8-9 psi, and I occasionally see 10 psi. My 1972 Q-jet doesn't mind a bit.
Thanks for coming in, Jim. The hot idle issue from last year was resolved. It was a combination of small vacuum leaks at the carb (bolts too loose) and fine mixture adjustments plus the mechanical advance was on the hairy edge of coming in when the motor would surge to about 900 rpm. I had to make mixture/idle adjustments very gradually and drive the car in all motor temperature conditions to get it right. The mixture screws ended up needing to be almost 2 turns out but different on each side. Engine now idles smoothly hot or cold. 700 in drive and 850 in neutral. (I do have to shift to neutral at traffic lights with a hot motor and the A/C blasting but expected that. I'll install an idle step up relay one of these days) My new plugs (same NGK 7373 as in it now) will be here Tuesday morning. I'll then install them and run fresh gas from a can directly into the RobbMC pump and see what happens. I do like Stevem's idea about shaking all the fuel out of the carb and checking the needle and seat functions but don't think the carb is flooding. I'll post again Tuesday with results.
Needle and seat aren't seating,....plugs should be caramel color and light grey strap,....wayyyyy to much fuel going thru it,....it's been running rich for a bit looks like
I don't believe there is any thing wrong with the gas quality.... Easy test siphon from tank or go buy a dollar's worth at the station you bought it from.... That a paper towel roll it into a wick and light it.....
As a fella who turned wrenches for a living for awhile, and was in the shop for 10 years after, the only time gas quality was ever an issue was a result of sabotage or a nasty jerry can was used. A call to the station would give you a clue, but the chances of 7k gallons of bad fuel making it out to the public is near zero.
Would water in the fuel blacken the plugs like that, or just make it run funky? My plugs looked like that after my E10 went bad over the winter one year.
No one has mentioned a bad float. Could be that also as they do go bad more often than you think. Runs fine one minute like doo doo the next. Just my thoughts. Tom T.
This 1971 QJ doesn’t have as APT. But I am gonna remove the carb tomorrow and check the needle valve and float.
