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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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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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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, 09:30 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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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, 09:34 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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Old 05-23-2011, 10:56 AM
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Quote:
Originally Posted by woobiedmd View Post
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?
Did you remove the cap, to inspect the inside and the rotor? If so, make sure the cap seated properly on the distributor. You said pulling the #1 wire made a difference and 3,4,7 & 8 are on either side of that plug wire, which happens to be right at the hold-down. If the cap isn't seated properly, the rotor won't line up with the inserts in the cap, so you won't have spark to those cylinders.

Again, look on the intake manifold for the firing order- ir should be closer to the distributor than the other end of the engine and may be 13726548
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  #10  
Old 05-23-2011, 12:57 PM
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Thanks Jim. I did not remove the distributor cap or rotor at all. I will check it tonite. Thanks for everyone's input! I appreciate it. I hope to soon put this behind me!
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