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Old 05-22-2011, 05:37 PM
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woobiedmd woobiedmd is offline
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Boat: mastercraft PS190 1988 351
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Rough Running '88 Prostar

I need some help! My 351 Ford was running great until I changed the spark plugs-put in same Autolite 24. Now it's hard to start, runs rough, and won't idle(dies). I pulled each spark plug wire individually to see if one plug was bad/cracked. The back two on each side don't seem to make a difference! If I pull the vacum line off the carb, the RPM's go up and it seems to run better. If I remove the flame arrestor and look down the Holley 4160, I see gas streaming into the back of the carb. What's going on- I'm driving myself nuts!
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Old 05-22-2011, 06:33 PM
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Quote:
Originally Posted by woobiedmd View Post
I need some help! My 351 Ford was running great until I changed the spark plugs-put in same Autolite 24. Now it's hard to start, runs rough, and won't idle(dies). I pulled each spark plug wire individually to see if one plug was bad/cracked. The back two on each side don't seem to make a difference! If I pull the vacum line off the carb, the RPM's go up and it seems to run better. If I remove the flame arrestor and look down the Holley 4160, I see gas streaming into the back of the carb. What's going on- I'm driving myself nuts!
Check your firing order and your plug wires.
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Old 05-22-2011, 07:16 PM
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How do I check the firing order? I checked the resistance on 2 plug wires and they both said about 675 ohms. Is that OK or too high?
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Old 05-22-2011, 08:31 PM
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woobiedmd woobiedmd is offline
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Looked it up and I do have the correct firing order. I'm not sure how to check the wires.
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Old 05-22-2011, 09:08 PM
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Just ensure that they are seated properly on the plugs and the distributor cap.

If the boat was running fine before you replaced the plugs and....
the plug wires are in the proper firing order....
then maybe one of the plug wires is not seated properly
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Old 05-22-2011, 09:30 PM
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Originally Posted by woobiedmd View Post
How do I check the firing order? I checked the resistance on 2 plug wires and they both said about 675 ohms. Is that OK or too high?
The firing order may be cast into the intake manifold. If the plug wires are old, they're due to be replaced, anyway. You may have continuity but that doesn't really matter to high voltage- a spark tester is what needs to be used, not an Ohmmeter.
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  #7  
Old 05-22-2011, 09:34 PM
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I pulled each plug wire one at a time as the engine was running. Pulling 1,2,5,6 made a difference. Pulling 3,4,7,8 didn't make a difference in performance. I checked the resistance of the wires, 1:717 ohms 5:579
6:578
2:677
3:893 7:767
4:880 8:761
The coil to cap wire was 193 ohms. Are these values OK or not? What am I missing?
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Old 05-22-2011, 11:24 PM
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Quote:
Originally Posted by woobiedmd View Post
Pulling 1,2,5,6 made a difference. Pulling 3,4,7,8 didn't make a difference in performance.
I am not familiar with your particular engine, but that looks like problems on one plane of a dual plane manifold. Are you seeing gas in both primaries? Check for vacuum leaks too.

Did you change your wires one at at time, if so you didn't mix anything up.
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  #9  
Old 05-23-2011, 05:16 AM
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rjracin240 rjracin240 is offline
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Quote:
Originally Posted by woobiedmd View Post
I need some help! My 351 Ford was running great until I changed the spark plugs-put in same Autolite 24. . If I remove the flame arrestor and look down the Holley 4160, I see gas streaming into the back of the carb. What's going on- I'm driving myself nuts!
Tell us more about what you see with the gas streaming into back of carb. Are you getting a lot of black exhaust smoke. Does it run better at WOT (wide open throttle)?
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  #10  
Old 05-23-2011, 06:24 AM
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I'm running it in the driveway hooked up to a hose. yes, it runs better at 2K than 800RPM. I wouldn't call it black smoke, but it smells heavily of gas.
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