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How Do Bad Coils Act?

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54 replies to this topic

#21 grey beard

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Posted 22 March 2009 - 01:08 PM

Just put a SECOND new 6-volt coil on this new 218 - problem still exists. So far we've replaced the coil, condenser, points, fuel pump. checked float level and had the distributor apart twice. Still no top end.

Tomorrow we'll take a carburetor apart - again . . . . . . :(
Dave Erb
New Holland, PA

#22 Young Ed

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Posted 22 March 2009 - 01:51 PM

Just a shot in the dark here but when I first built my truck it wouldn't go very fast either. I don't have a tach to know how fast it was going but anyway it turned out I had mounted the gas pedal funky and it was hanging up long before WOT. Can you run a test with the pedal stuff disconnected and operating the carb by hand?

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#23 Don Coatney

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Posted 22 March 2009 - 02:01 PM

Are you sucking air into your fuel line prior to the fuel pump? Is there a rubber hose in your fuel line prior to the fuel pump that may be collapsing? Are your valve springs new? Any possibility one or more valve springs are broken? Any intake manifold leaks causing a low vacuum condition?

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#24 grey beard

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Posted 23 March 2009 - 05:10 AM

Valves were completely reconditioned - seats, faces, guides and springs. Fuel line is new one-piece steel from the electric fuel pump at the tank to the carb - actually I should put a short piece of flex in there somewhere near the front mount - and the few short rubber connectors at the fuel filter and pump are all brand new rubber fuel line.

I'm hoping to find the problem inside the carb today. I'll let yo knowl. Mebby I did something really dumb in there that can serve as a good object lesson for everyone else.

I'll be the goat . . . . . . :confused:
Dave Erb
New Holland, PA

#25 Big50Dodge


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Posted 23 March 2009 - 07:41 AM

My guess would be either with Young Ed (linkage problem) or Distributor. If you were working great before you changed all these parts, can you replace them one at a time and see what fixes it ? I'm thinking the vacuum advance is not working properly or the weights on the centrifical advance are wrong springs or something. Should be a spec on the vacuum adv that can be checked with one of those 'suction' thingies that bleed your brakes too.
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#26 grey beard

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Posted 23 March 2009 - 05:51 PM

Well, Gentlemen, I have found and fixed the problem - I think. My face is a litle red, my tail is tucked firmly between me legs, and I am appropriately contrite.

Almost missed it. Pulled the carb off this morning and pulled it apart after dinner, this evening. Completely disassembled the critter, even pulled a few of the soft plugs, blew shop air and Brakeclean hrough every passage. Everything was fine. When I put the float back in and adjusted it, I found it to be low compared to shop manual specs, and fixed that.

Last piece into the innards was the little flat metal "C" shaped spring that retains the float pivot pin. Wouldn't you know it but that little devil was deformed just enough that when I slipped it in its slot, one end went down behing the vertical tang on the float arm that is supposed to hit the needle valve. This piece was actually holding the float up against the needle valve, and effectively shutting nearly all the fuel off from the bowl. Apparanly enough gas was entering to allow it to start and idle, but not enough volume to let it accelerate.

Guess I'll know for sure tomorfrow whan I reinstall the carb. Sure hope this fixes the problem.
Dave Erb
New Holland, PA

#27 MBFowler


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Posted 24 March 2009 - 02:57 AM

Nice going GB! Its usually something very simple that is the root cause, but it'll drive you crazy while trying to find it. The Carter BBD uses a similar float pivot restraint-great design right! Hope that does the trick for ya. Mike

#28 grey beard

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Posted 24 March 2009 - 03:51 PM

My high speed stumble/miss issue is fixed. For the first time since the engine was overhauled, it runs full throttle and accelerates nice and strongly. Here’s how I found the culprit.

My buddy, Frank, is a retired Verizon lineman. He’s not a real engine head, but does understand electricity. After he helped me reinstall the carb and we discovered the same problem was present, we discussed it and he told me how he had found bad plug wires using an inductive timing light to move the clamp around and find bad spots.

With that thought in mind, I fished out my own inductive timing light and clamped the secondary coil lead – sorta’ like a poor man’s scope. Watching the timing light and accelerating to higher rpm, I discovered that as soon as the miss kicked in – about 2500 rpm – the light began to flicker and bounce, as opposed to steady firing at lower speeds. This proved to me that the problem was really ignition related.

Pulled the distributor yet again – comes out real easy after half a dozen trips in and out – and found that the breaker plate bearing had separated from the base – the two parts of the plate, movable and fixed, were coming apart. Did you’all know that if someone installs a contact point retainer screw that is too long, it pushes the two pieces of the breaker plate apart? Well, this may have been what caused this problem/.

Anyhow, while fixing this issue, I found that the breaker point spring was very light and puny, hardly enough tension to keep the points from bouncing. Looked at the original points I had taken out and saved, and they had two springs – steel and copper – together, while my new set had just a very light copper spring. Put the old contact set in and – Bob’s Your Uncle – she fired right up and ran like a scalded dog.

The defective point set came from NAPA - Echlin - and is their part #CS725A. I’m going to get a new set to keep in inventory, but I won’t be getting another one of this type, for sure. This miserable problem has cost me nearly six full days of head scratchin’ work and frustration. Glad it’s fixed.

I suppose the moral of this sad story is that you can never safely assume that just because a new part was installed, that it isn’t still the culprit. Go figure . . . . . .
Dave Erb
New Holland, PA

#29 Merle Coggins

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Posted 25 June 2010 - 12:19 PM

I am currently having a similar problem to what Dave had, so I went searching for this thread and revived it.

My truck ran great, but I knew that the cheap Andy Bernbaum points that I had were going to need to be replaced soon. I was running out of adjustment because the cheap nylon rubbing block would wear too fast. So I ordered up a complete set of tune up parts from Napa, including an extra set of points. My plan was to replace the points and keep the rest of the parts on hand as a "spare tune up kit".

So last weekend I pulled out the distributor and commenced to replacing the points. The Echlin points from Napa looked much beefier and better built than the cheap ones that I had. When I was replacing them I noticed that the wire from the condenser had a rub mark through the insulation. Apparently it was chaffing against something in the distributor. So I also replaced the condensor with my new Napa one. Then when I was setting the dwell, like an idiot, I left the rotor in place. I had set it back on to reference which way it was pointing when I installed the dist. However, when you're cranking the engine over, watching the dwell meter, and adjusting the points with a screwdriver, the rotor must be removed. I realized this when it came around an wacked my screwdriver and knocked it out of my hand. :mad: In the process the rotor broke. So, now I also have my new Napa rotor in there too.

I didn't get a chance to go for a test ride at that time but the engine ran great. Then during the week I installed my new electric fuel pump in line between the tank and mechanical pump. This pump is to help refill the carb after it sits for a while. Again all went well and everything appears to be working fine.

Now this morning I decide to drive the Ol' Dodge to work for a test drive before my Dayton, OH trip next week. NOW I HAVE AN ISSUE! The truck won't go over 55 MPH. When I reach that speed (RPM) it acts like I have a rev limiter installed. It will stutter and stop pulling. I first suspected the electric fuel pump was restricting the gas flow so I reached down and flipped on the switch to get it running to. NO CHANGE. I also tried pulling out the choke to see if it was a lean running issue (like running out of gas). Again NO CHANGE. I believe something happened during the "tune up". I have another new condenser and rotor to replace the ones I used. I guess I'll have to get in there and check everything over again. I'll also check the breaker plate as stated in Dave's final fix post.

Any ideas how to check a condenser to know if it's bad? Maybe I can dig out my old one and try it again. Everything was working just fine before the "tune up". ARRGGG!!!


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#30 Dave72dt


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Posted 25 June 2010 - 01:06 PM

Go back and set the points with a feeler gauge. A worn dist shaft can give you false dwell readings and won't let the engine run properly. I've found a "correct gap" more effective than correct dwell. If you can get both, that's great but often as not , that doesn't happen.

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