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Discussion Topic:
crab cap/rotor issue?
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MICHV8 |
11-15-2017 @ 1:49 PM
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Member
Posts: 448
Joined: Jul 2010
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I’m trying to get that 59AB mentioned in another post running well enough to try Tom()’s MMO approach due to some stuck valves, but I have found another issue. Sometimes the engine starts right away and idles roughly and other times it tries, but won’t fire. I’ve found that I have a spark at some, but not all, plugs. I’m working alone with a button solenoid so it is hard to reach the driver’s side plugs, but plug 2 and 3 have no spark and 4 does. So I took all the wires (which are new and were tested prior to install) off and, per Supereal’s suggestion from years ago, soldered the connections just to be sure. Did the high tension wire as well. Then did a continuity test on all wires and they are all good. Then did a continuity test on the cap and all sockets tested good. I’m using a crab and the rotor slips onto the stem, but not as tightly as others do. Kind of a head scratcher…do I have a runtime arc somewhere in the cap or is the rotor shifting somehow?
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ken ct. |
11-15-2017 @ 2:43 PM
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Senior
Posts: 1513
Joined: Jan 2010
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Check your PM's. ken ct
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MICHV8 |
11-16-2017 @ 10:32 AM
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Member
Posts: 448
Joined: Jul 2010
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forgot to mention coil and condenser are new
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fsacht |
11-16-2017 @ 2:57 PM
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Member
Posts: 71
Joined: Oct 2009
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Your situation sounds familiar. I am running a crab cap on my 48 Merc. chased this for a long time and discovered that the steel strip on the rotor that sends current to the plug wires had twisted and bent to the side and must have been only making intermittent contact with the cap center terminal. I straightened that metal strip and bent it upward from the point it is secured to the rotor then carefully reinstalled the cap. My rotor also has some movement at the center shaft. So far so good.
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MICHV8 |
11-16-2017 @ 3:32 PM
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Member
Posts: 448
Joined: Jul 2010
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I believe that I have a mechanical vs electrical arc issue in that the rotor doesn't appear to traverse a circle when it rotates. It is harder than heck to take photos that demonstrate my concern, but I'll post 4 in a row. When eyeballing it from a level position, it appears that the stem tilts to the side. However, I took a couple junk crabs from the box and they all appear to have a little tilt, so now I'm not at all sure...photo1
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MICHV8 |
11-16-2017 @ 3:33 PM
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Member
Posts: 448
Joined: Jul 2010
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photo2
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MICHV8 |
11-16-2017 @ 3:33 PM
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Member
Posts: 448
Joined: Jul 2010
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photo3
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MICHV8 |
11-16-2017 @ 3:34 PM
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Member
Posts: 448
Joined: Jul 2010
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photo4
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TomO |
11-16-2017 @ 5:30 PM
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Senior
Posts: 7256
Joined: Oct 2009
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Mich, you can use a jumper wire connected to the center terminal of the starter solenoid as a remote starter switch, just ground the jumper wire when you want to turn the engine over. Are you missing the spark at the same plugs or does it move around? Have you tried looking for spark inside the conduits? Is the rotor hitting the cap terminals? Does the point dwell vary when the engine is running?
Tom
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Drbrown |
11-16-2017 @ 6:11 PM
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Senior
Posts: 571
Joined: Nov 2013
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My experience with rotors etc. Have a crab points set-up in my '47 with 59AB. Shortly after purchase, and thinking I was doing a good thing, installed a new rotor from NAPA. The brass arm on the rotor end broke immediately from hitting the lugs on the cap interior. NAPA gave me a replacement and that broke too. The cap on the dizzy was the one that came with the car and it had worked fine with the old rotor. The crab was fitted with a Pentrox module. Sent the whole unit to Bubba's and he got it working explaining that he checks the alignment and clearance between the rotor and cap lugs to meet ford spec clearance. He said he normally has to file the ends of most new rotor arms in order to get adequate/proper clearance. He also checked the shaft to be sure it didn't wobble. Have had no problems like that since. PS: Had tapping noise in valve chamber when purchased. Could have been from prior owner letting engine sit. Put a little MMO in first oil change and in gas. Noise stopped after a little bit of driving. I continue to put MMO in my gas. I use 10w-30 detergent oil; no filter; changing at 1000 miles.
This message was edited by Drbrown on 11-16-17 @ 6:25 PM
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