| Flatbob | -- 06-27-2012 @ 12:54 PM |
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Cylinders 6,7&8 won't fire. Here's what I've done: replaced plug wires, three plugs, condenser and had Skip rebuild coil and go through distributor. The car starts easily but I still have the same problem. After Skip rebuilt coil I sent the entire distributor to him to see what he could do & here the mystery deepens, the distributor came back & I can see he either replaced the rotor(s) or cleaned them up & new gaskets but there was no bill or explanation. I've since contacted him by email but have not heard from him. Anybody have an idea as to why 6,7&8 won't fire?
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| kubes40 | -- 06-27-2012 @ 1:49 PM |
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It has to be either a bad inner cap(s) and / or rotor OR the wires are not properly seated in the inner cap(s). Double check that. I check with an ohmmeter. It is fairly easy to dislodge a wire or two when reassembling the inner & outer caps. There is an air gap that must be maintained between the inner cap terminals and the rotor. If I recall correctly it is .015". My advice? First, check each and every inner cap terminal to plug wire end for continuity. If all check well, then check the gap between each and every inner cap terminal to the rotor tip. Don't get too frustrated. This is a simple one. I am guessing you have already looked right at it and not seen it. I have certainly done such. Did you send the inner caps to Skip?
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| ford38v8 | -- 06-27-2012 @ 1:55 PM |
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Bob, check your spark intensity. Put your screwdriver near a head nut for that, not a plug. Compare the intensity of # 6, 7 & 8 to the intensity of # 5. This may confirm an ignition problem. Unbolt the conduit and hold it with gloves near a ground point. That would confirm a short inside the conduit. Remove the left caps and carefully separate the two, you may find that those three wires are not firmly installed in the inner cap. Remove the inner cap and inspect inside with a strong light. You may find carbon traces. With the engine warmed up, remove all spark plugs and do a compression test. You may find eratic compression values, and much lower in those three cylinders. Alan
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| Flatbob | -- 06-27-2012 @ 3:09 PM |
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I did send the complete distributor to Skip's along with the inner caps & covers. Do I check continuity with inner cap installed on end of plug wire? What should I see on the meter? Thanks for the help guys. Bob This message was edited by Flatbob on 6-27-12 @ 4:12 PM
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| ford38v8 | -- 06-27-2012 @ 6:07 PM |
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Bob, Kube's got a good idea there. With the inner and outer caps together, both caps off the distributor, check continuity from the contacts insde to the plug clip of the wire. Alan
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| Flatbob | -- 06-27-2012 @ 8:28 PM |
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That's exactly what I'm going to do in the morning, my meter emits an audio sound for continuity which should be helpful when I'm under the car. thanks for the help
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| Flatbob | -- 07-01-2012 @ 12:20 PM |
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Kubes40, I did the continuity check at the inner cap from the other end of the plug wires for 5,6,7, & 8 and everything checks out, yet 6,7 & 8 won't fire. So having had the coil rebuilt, new condenser, plugs & plug wires leaves only the rotor but as I said I've previously sent the entire dizzy to Skip to go through. Really don't know what to do next. Bob This message was edited by Flatbob on 7-1-12 @ 12:42 PM
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| 40 Coupe | -- 07-02-2012 @ 3:44 AM |
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Make sure the plug wires are connected to the proper location in the inner distributor cap.
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| supereal | -- 07-03-2012 @ 6:01 AM |
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I agree with 40. Is there spark at the dead cylinders, or is it at the wrong time ? It is very easy to install the plug wires in the wrong places in the cap. If the other five cylinders are firing, I wouldn't expect the coil to be at fault. Skip knows his stuff, so it is unlikely the distributor, itself, is bad. The fact that all dead cylinders are on the same side is the clue.
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| TomO | -- 07-03-2012 @ 7:54 AM |
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40 Coupe gave you good advice, but I would like to add that make sure that you are counting the cylinders with no 1 on the passenger side of the car and that you are using the correct numbers on the inner cap. Here is a link to the spark plug wiring diagram for a 36. http://www.vanpeltsales.com/FH_web/FH_images/FH_engine-pics/Flathead_Distrbtr-wiring-1932-36.jpg Tom
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| Flatbob | -- 07-03-2012 @ 1:00 PM |
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Thanks for the input. Let me reiterate the situation; cylinders 6, 7, & 8 were firing for 270 miles, those 3 cylinders stopped firing all at the same time therefore the plug wires were in the correct location in the inner cap. The inner cap is clearly marked for wire location & have double checked them for correctness since replacing plug wires. I have every confidence in Skip's ability as well. I don't know what else it could be but a bad rotor........but Skip would have seen that I'm sure.
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| Flatbob | -- 07-03-2012 @ 2:01 PM |
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Super, no spark at the plugs, plugs are wet & clean when I remove them.
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| supereal | -- 07-03-2012 @ 2:34 PM |
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Do you have continuity between the plug end of the wire and the rotor contact inside the cap?
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| TomO | -- 07-03-2012 @ 2:45 PM |
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The rotor provides spark to the right side and if the left cap is seated you should have spark to the left side. A broken rotor should affect both sides. The front rotor arm sends spark to cylinders 1,3,5,6 and the rear aarm sends spark to cylinders 2,4,7,8 Take off your coil and check the clearance between the rotor arms and the cap. The gap should be .015" The caps swell slightly and can be difficult to get seated. Tom
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| Flatbob | -- 07-03-2012 @ 5:03 PM |
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Super, yes I do have continuity from the plug end of the wire to where the rotor meets the contact point inside the inner cap.
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| Flatbob | -- 07-03-2012 @ 5:09 PM |
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TomO, I will check the rotor gap; am wondering if it might be better to just remove the dizzy & check it on the bench. There is so little room am not sure I would have a clear vision of field with distributor installed; what do you think? Thanks, Bob
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| supereal | -- 07-03-2012 @ 6:36 PM |
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The next place to look is the contact ring on the rotor and the carbon brush on the coil, which must make constant contact with the ring. The rotor shouldn't wobble on the shaft. A distributor machine only checks the action of the points, not the transfer of the energy to the cap and wires. This is an odd problem, but since five cylinders fire, we are narrowing it down.
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| Flatbob | -- 07-03-2012 @ 8:41 PM |
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Super, am going to pull distributor tomorrow & put it on the bench where I can see it better. Thanks for the explanation on what the distributor machine can & can't do; as this explains why Skip wouldn't see the problem as it relates to spark. Bob
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| 40 Coupe | -- 07-04-2012 @ 4:36 AM |
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If you remove the distributor you may want to check: Cracks develop across the center brass conductor (ring) of the rotor. The area where the carbon brush for the coil rides. The carbon brush for the coil needs to have spring in and out of the coil body. I believe I would change the inner cap on the side with the problem before removing the distributor. I have never seen a flathead start or run with 3 of the cylinders not firing. I guess with the engine running you could remove the three plug wires and it still runs the same?
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| TomO | -- 07-04-2012 @ 8:48 AM |
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Bob, the reason that I told you to remove the coil and check the gap is that you would not disturb the caps. When you have the distributor on the bench, it is very easy to get the caps seated. As you said there is very little room to check it on the car and the caps are more difficult to seat when the distributor is on the car. If your inner caps have "Made in Argentina" on them, I would start an immediate search for NOS or NORS USA made inner caps. I have no information on the reproduction caps made by Drake, but they may be an option. 40 Coupe, I cannot count the number of time that I have started my car with one of the caps off. It starts very easily and runs very rough on 4 cylinders. It will not idle with one cap off. I agree that the inner cap on the drivers side is the most likely suspect.. Tom
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| Flatbob | -- 07-05-2012 @ 2:19 PM |
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Update: Skip says the dizzy checked out fine on the machine and there was no sign of rotor arcing. He told me to check continuity from center brass band of rotor to 4 end contacts on the rotor. I see 2 contact points being the rotor blades where the other two are I don't know. The two I checked had good continuity. The gap between the rotor blades and the inner cap contacts is approx. .046"; even with this big of a gap # 5 still fires. I believe the inner cap is original, there is is no origin of manufacture on the cap. So, is it the rotor blades or the inner cap that is bad. Would like to post picture of gap but picture size is too big; haven't figured out how to take smaller images with my camera. However, if I email I can reduce the picture size if anyone is interested. The brush is making contact with rotor ring through 360 degrees. Bob This message was edited by Flatbob on 7-5-12 @ 2:21 PM
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| Don | -- 07-05-2012 @ 7:32 PM |
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You need to do a compression check, since everything else checks out OK. Perhaps valves are hanging up. Don
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| 40 Coupe | -- 07-06-2012 @ 4:20 AM |
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The Max. gap between the rotor and the inner cap terminals is 0.0105, Min. gap is 0.0035. This is for the 48-12201 rotor. As per Subject 12000 page 4 April 18, 1948. The plug gap for the #7 plug is 0.025-0.028 The spark gaps add up and increase the demand on the coil to jump these gaps. The rebuilt coil has limits as to it's voltage output. As the spark gap widens the coil can fail to deliver spark at the plugs. As a note the largest spark gap in any part of the spark circuit should be the plugs. If you decide to change the inner caps do it with the distributor removed this way you can see if either of the TWO rotor terminals are touching the eight new inner cap terminals (as well as the proper gap), and make sure the new caps fit properly into the distributor (sometimes the plastic body needs to be sanded to fit properly) This message was edited by 40 Coupe on 7-6-12 @ 4:23 AM
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| TomO | -- 07-06-2012 @ 8:16 AM |
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The Ford caps have the P/N cast into them. The aftermarket ones do not. Some manufacturers are proud enough of their product to put their name on the product. Now that you know that the gap is too big, you need to determine if it is because the cap cannot be seated fully or it is just worn out. 40 Coupe has good advice in checking any that you purchase, on the distributor before you put the wires in it. Beware of the used caps that are sold as new. The contacts should be smooth with no signs of arcing. Tom
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| Flatbob | -- 07-06-2012 @ 11:10 AM |
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Checked the inner caps & they have no Ford PN as TomO suggested an original would have so they must be replacements but fit very well. Ordered two new caps from C&G; Kyle was upfront & told me I would have to "sand to fit." I checked inner cap for passenger side gap to rotor blades and it's much tighter than the side with the problems; hopefully this will solve the problem. Will post the outcome; again thanks everyone for the help. Bob
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| TomO | -- 07-07-2012 @ 8:24 AM |
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Bob, if the caps from C&G are made in Argentina, you may have to file down the terminals as well. Some of the terminal are so long that the rotor will be damaged. The ones that I have seen like this have aluminum terminals that die out after a few hundred miles. Drake makes new inner caps, but I do not know how they fit or last. Tom
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| Flatbob | -- 07-12-2012 @ 3:37 PM |
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Got new inner caps (origin unknown) from C&G and sanded inner caps so they would fit in the outer caps and replaced dizzy. Fired up immediately but then started backfiring out the exhaust,amazing how well it runs on 5 cylinders but will not idle. Don offered some advice to check compression; wish I would have done that earlier. Right now it's too hot in the garage temps. have been 110+ degrees here in Vegas. Maybe tonight after sun goes down will do compression test. Thanks everyone for the help. This message was edited by Flatbob on 7-12-12 @ 3:40 PM
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| TomO | -- 07-13-2012 @ 7:18 AM |
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Bob, you stated earlier that you had no spark to cyl 5,6,7. Is this still the situation with the new caps? Did you check the rotor to cap clearance when you had the distributor out? Did you check the seating of the caps by examining the rotor to cap clearance with the distributor on the car? Tom
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| Flatbob | -- 07-13-2012 @ 9:08 PM |
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TomO, after Skip rebuilding coil & checking dizzy on machine and new inner caps am getting spark like I never had before; I can hold plug wire a good 1/2" away from plug and get a mini lightning bolt between wire end and plug. However, 6,7 & 8 plug won't ignite. Very hot in the garage could only pull the plugs, tomorrow will do compression test on failed cylinders. Maybe compression is too low for charge to ignite? This was the my first flathead rebuild and I have low compression on all cylinders 70-90 lbs. I put adjustable lifters in & am wondering if I adjusted them without the valves completely on the seats. The car previously ran & idled very well despite the low compression. Did a compression check this morning, cylinders 1-5 stayed the same or were slightly up over the last time I checked with 97 miles on the car. Cylinders 6,7 & 8 (non firing cylinders) have dropped 9, 5 and 15 lbs. respectively, the lowest cylinder reading 75 lbs.; I have other cylinders on the other side with reading this low but they fire. Am going to put new plugs in 6,7 & 8 and see what happens; if this doesn't work am going to pull engine and replace with another I have.........am too old for this much aggravation! Replaced plugs with new old Champion plug made in the USA, runs better than it ever did! I don't understand how 3 plugs next to each other could all fail at the same time. Anyway, am a happy man. Thanks everyone for the help. This message was edited by Flatbob on 7-14-12 @ 1:59 PM
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| TomO | -- 07-15-2012 @ 6:26 PM |
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Bob, I am glad that you solved your problem. Only the "Shadow knows" why the new parts that we get do not work as intended. Tom
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