Engine misses, runs then stops

[class87]

From: Derrek  (Original Message)
Sent: 5/26/2003 9:15 PM

Hello everyone

         I have an unusual problem that I just cannot figure out. My 440 has been missing and I cannot find the cause. I have changed the plugs, wires, cap, rotor, distributor, ignition module, ballast resistor, and coil. While road testing, it died, but when I turned the key to the start position while still coasting the engine would regain power. If I released the key and allowed it to go back to the on position it would die again. This led me to believe I had a bad connection at the ballast resistor, due to the fact that in the start position power is fed directly to the coil. I checked the connections and replaced a few connectors. While road testing it tonight it died and instead of going to the start position I tried turning the key off and then back on again. The engine fired back up and ran smoothly for a few moments and then died again. Cycling the key again brought the engine back to life and the cycle would begin again. I would think that this would rule out the possibilty of a bad wiring connection. It almost seems as if the ignition system is reset when the key is cycled and is Ok for a few minutes until it must be reset again. I have checked the connectors under the dash and tried wiggiling the key to check for a bad connection in the ignition switch, but this does not seem to be the case.
--------------------------------------------------------------------------------

     Have you checked the timing?   You could have a worn timming chain or gear and it has jumped timming.   This would cause it to run rough or miss.   I would put a timming light on it and see how close it is to the mark where it is supposed to be.   
Rick (rshaw500)

--------------------------------------------------------------------------------

     Just wanted to give you guys an update. I tried swapping carbs with no change. I pulled the intake manifold and installed an Edelbrock performer non-egr manifold to eliminate the possibilty of manifold leaks or EGR valve leaks.
     After road testing with the new manifold and the MSD ignition I could tell a big difference in low end power but the engine is still not running right. The miss is not as noticeable in the low rpm range, but while cruising at 55 the engine will run smooth, then begin to sputter, run smooth, then sputter,..........ect.
     I do not think that the engine jumped time because this would effect all rpm ranges and would not be somewhat intermittent as this problem seems to be.
     At this point I have gone from troubleshooting to simply guessing. I have been consulting with a local gentleman who has a shop where he specializes in building big block Chrysler racing engines and had worked on this motorhome when it belonged to the previous owner and even he is stumped.    Dk73brave@yahoo.com

--------------------------------------------------------------------------------

     Seems like you have replaced all of the ignition as well as the carburation.  Doesn't leave much more.  I wasn't saying the timing had jumped.  I was saying that the timing chain may have streched which means the timing would change depending on engine load.  Checking it is requires nothing more than removing the distributor cap so it isn't anywhere near the amount of work you have already done.  You also may want to have a dash mounted vacuum gauge so you can see if the problem can be associated with a certain engine load.  Another trick, is to drive at night with the engine cover off to see if you have any plugs or wires jumpping spark.
Dave76Chieftain

--------------------------------------------------------------------------------

     When my timing chain slipped a notch I was just fine until it reached a certain temp then....misfires,stumbles,backfires, etc.Ran just fine cold.Mine slipped at 40,000 miles,got a bad tank of gas at Pilot in arizona at colorado river,pulling out of station got a couple backfires,chain jumped,the rest was history as they say.  BooBoo

--------------------------------------------------------------------------------

     Lets try this (Note: lot of this is from:  Instruction Sheet DCF-194CC MOPAR PERFORMANCE ELECTRONIC IGNITION KIT with VACUUM ADVANCE DISTRIBUTOR (Part Numbers P3690426, P3690427 & P3690428)

1.  Check the timing chain slack per the previous post.
2.  Verify initial timing advance  (engine at normal operating temp):  I think it should be around 5° ± 2° BTDC.  Thats with the distributor vacuum line disconnected and plugged (carb side of the hose).  At idle, you should have somewhere between 16 to 22 hg of vacuum.  That would be around the good/decel break point on the gauge.
Note:  Your MSD distributes multiple sparks (not just one) across a 20 degree window at lower RPM.  I believe you want the first spark point as your ref point.  At higher RPM (above 2000 I think), the number of sparks the MSD generates is fewer because the duration "firing window" (in time that is) is smaller.
3.  Check mechanical advance (engine at normal operating temp):   With the distributor vacuum hose still disconnected, start the engine, set the engine RPM to 2000 RPM and verify the total mechanical advance is around 35 degrees.  Hmm, without a timing tape on the crankshaft that could be ahh difficult LOL  Use the ole eyeball at least.  Idea is to verify the mechanical advance portion of the distributor is working properly.  Place a chalk mark at the approximate point on the harmonic balancer where the crank was (30 degrees would be twice the distance of the 15 degree mark on the indicator).  Idea here, is to give you a reference point so you can see how much "farther" the timing is advanced (total advance) when both mechanical and vacuum advance kick in.    You have a new distributor so I would expect mechanical advance to be ok.
4.  Now this is a little tougher, what you want to verify that the total advance (mech + vacuum) is somewhere around (I think) around 45-50 degrees.  You rev the engine up slowly until you find the maximum vacuum indication at the gauge between 2000 to 4000 RPM.  At the max vacuum point, you verify the total advance is around 45-50 degrees.
     At idle, you should have somewhere between 16 to 22 hg of vacuum.  That would be around the good point on the gauge.
     The poor/fair break point is around 6.5-7 hg of vacuum.  Thats the point where the carbs power enrichment circuit kicks in.  A lower vacuum (poor) means the carb secondary's are kicking in.
     The fair/good point is around 9 hg of vacuum I think.  Higher the vacuum, the better.  It just means the carb is running in it's normal cruise circuit mode (air/fuel mix around 14.5/1).
      While the mechanical advance is a constant, the vacuum advance changes to help prevent pre-detonation (knock) by decreasing the timing.  When you give it gas, the manifold vacuum decreases.  Once a balance is reached (all functions healthy), the vacuum increases towards good on dash meter.    If the timing chain has streched, the cam and the distributor firing points would not be in sync with the piston travel resulting in the late opening/closing of the valves even though the time of fire is in sync with the crank when the chain is tensioned.  If the slack in the chain gets up to 15 degrees (measured per the previous post), the engine will not run.  9 Degrees or more says the chain/cam gear should be replaced.
     Most of your indications really point to the timing chain Derrek.  Especially after replacing all of the things you have.  The "but while cruising at 55 the engine will run smooth, then begin to sputter, run smooth, then sputter,..........ect." could easily be the chain tension.  As the carb reaches a load balance point (maximum efficiency for the given accel pedal position), the chain slackens causing the cam and therfore the distibutor to get out of sync.
     The only other thing that could casue all this is a vacuum leak.  The PCV valve good?  Either brake booster leaking vacuum?  Please take note that the EGR valve does help to reduce combustion heat by recirculating exhaust gas.   I take it you eliminated the (CA only) speed sensor vacuum solenoid vacuum line with the carb change.   Are all unused vacuum connections on the new carb plugged?
Dave76Chieftain
--------------------------------------------------------------------------------

1] you might have to put the egr back in, when out will usually ruin the performance
    and soon ruin the engine
2} replace all vac lines
3] replace pvc and breather [one on one valve cover, the other on the other valve
    cover]
4] if the float in carb is old, and if metal, then probably it has sunk due to a leak     
    filling it with gas,,,,, if you change this, put plastic float in, takes forever to leak
5] the sputtering probably means carb not flowing gas,,,, disconnect fuel line from
    carb, look into inlet of carb and if any gunk, then clean it out with carb cleaner
    spray, until gone, and then some more. this would free up inflow.  similarly check 
    the inlet and outlet of fuel pump, if clogged then clean similarly, make sure fuel
    filters, all, are clean and free flow, if any doubt replace note condition of fuel lines
    from gas tank ,,, the rubber ones often deteriorate and have to be replaced,
    because deterioration is junk that clogs the lines.... same with inside the gas
    tank, if has any filter inside the tank or other as to flow of gas out of tank, and any
    of that is junked then you gotta clean or replace.
6] the sputter could be via the distributer, any of the electrical, the spring loads, and
    or the shaft wobble itself, you can check this at standstill by wobbling the shaft
    and take a look at springs see if opening etc easily or at all.... if old, is cheap to
    just buy another.... go ahead and put new rotor and cap on anyway, they often
    have shorts you can not see, especially on big engines
7] those big engines get hot enough to melt the spark plug wires within 10,000m.
    probably might improve if you switched to jacobs wires which are hard to burn;
    those that use jacobs system on big engines swear by them
8] if you dont change pvc and breather about every 10,000 m, you build up back
    pressure, can be severe enough to stall the engine at any rpm; similarly, cat
    convert, if you have one, gets overly blocked, again, stalling at any airspeed
    similarly, older, especially stock, mufflers get blocked and hi back pressure.
    if you got the bucks, replace or eliminate the cat converter and put in lo back
    pressure mufflers, worth the price because automatic increase of about 20 hp, and
    thus a tad more mpg
9] switch, now to valvoline max life engine oil, will decrease drag

robobob