Re: [Chrysler300] Surprising source of miss in 300 ?
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Re: [Chrysler300] Surprising source of miss in 300 ?

Thanks John,
Good suggestion! 
I did replace that rod  not too many miles ago (-less than 15,000 but many years.) I do have an electric fuel boost pump installed. 
I may just go ahead and put a new rod in anyway. Chuck Hill told me he has had a hard time getting fuel delivery with the mechanical pump and has installed a stand alone electric pump. I really want to stay stock and had to hold my nose to install the boost pump!
BTW, my old pump rod was substantially shorter than the new one. I will certainly be disappointed of this is not the problem, but there is no doubt it is a problem!
  Thanks again John. 
Mike Moore
On Mar 4, 2016, at 8:26 AM, John McAdams <clafong@xxxxxxxxxxxxx> wrote:

Since you now seem to have replaced almost everything in the ignition system.  Before you take it out on the road, I have one more thing for you to think about.
Do you run an electric fuel pump?  If not, have you replaced the mechanical fuel pump actuating rod.  It resides at the front of the engine where the mechanical fuel pump is installed.  It is a short rod, about 3 inches long that rides on the front lobe of the camshaft and drives the lever on the mechanical fuel pump.  Over time, this rod wears down and will no longer drive the fuel pump adequately.  It usually manifests itself by not supplying enough of the foul fuel that we have to buy at the pump these days at the higher RPMs.
Anyway, even if you have an electric fuel pump, or your present problem is/was ignition related.  I always carry a spare mechanical fuel pump rod in my road trip tool box to give to a fellow Club member (or even anyone stopped along the road that is driving a “B” or “RB” engined Chrysler product) who has stopped along the road, in mid trip.  This rod, by the way, should be flat on each end with a slight radius at the outer edge.  If it appears rounded on one end, it should be replaced before it causes a fuel delivery problem.
I am glad that you seem to have found the evil demon that was residing in your car.  Congratulations on your determined and persistent search for that elusive “miss”.  Enjoy your next hundred or thousand mile road trip in your “300 H”.
From Big John Mc Adams
(with my ’62 “Sport” 300 Convertible with Short Rams)
From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On Behalf Of Michael Moore mmoore8425@xxxxxxx [Chrysler300]
Sent: Friday, March 04, 2016 6:55 AM
To: Mike Moore
Cc: Chrysler300@xxxxxxxxxxxxxxx
Subject: [Chrysler300] Surprising source of miss in 300 ?
I have been trying to eliminate a miss in my 300H.

In the ongoing effort, I have replaced the damper, installed a Philbin rebuilt distributor, new plug wires, new plugs, carbs “restored”, coil replaced etc. with no improvement. Even 108 octane gasoline hasn’t helped.

I made arrangements for a visit to a great shop with a Sun engine analyzer (equivalent) , but I had to get it running reliably enough to get down there, and it now ran worse each time I started it.

Judging the problem to be ignition related versus carbs, I decided to strip and replace the entire ignition apparatus from ballast resistor through plugs. I ordered NOS Champion J-12Y plugs (which have always worked well for me), a new set of ignition cables (which are the best I have seen), a new coil, correct Mopar points, and new capacitor.

I began with a new correct ballast resistor and noticed the old ballast resistor ceramic wire wound resistor inside was broken into two pieces. As I hadn’t disassembled the rest of the system, I started the car with the new ballast resistor with no improvement, so I incorrectly dismissed that as the source of my miss.

While waiting for my original new parts to arrive, and after doing a thorough (165# on all 8) compression check (because all the plugs were out, front wheels were off and access was so easy), I disassembled the points from the distributor last night.

I found them badly burned! Aha!

My earlier distributor trouble shooting was to check only the dwell angle since it had recently been rebuilt. I noted the dwell angle had increased to 45 degrees since I installed the distributor when it came back from Philbin.

I now believe what happened was that the ballast resistor failed sometime in past years, allowing the points to burn because of the higher than specified voltage on the coil. In recent years I haven’t driven the car much, but have changed the points entirely too often and haven’t noticed it too much because although it might be only 1500 miles, it may have been 3 years. I am certainly anxious to get it back together.

Thanks for all the help on line and off.
Mike Moore


Posted by: Michael Moore <mmoore8425@xxxxxxx>

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