Topic: 1950 Merc. engine restart


jeff holland    -- 06-07-2010 @ 7:09 PM
  I just had my 50 Merc engine worked on and tuned up and am still having problems with start-up of a warmed engine.
I had the carb. rebuilt, put in new gas tank,6vt. fuel pump, and tune-up. I was originally having engine fade while driving, but that seems to have been taken care of with the most recent work. However, I am still having problems with easy start-up of the engine after repeated stops and restarts ( maybe after 3-4)after the engine has warmed up. The car will start after several tries of the engine. After the engine has cooled down a bit, it starts right up again.
Any thoughts or advice I can pass on to my mechanic?
Jeff Holland


ford38v8    -- 06-07-2010 @ 8:07 PM
  Jeff, From your description of the symptoms, I would say that your electrical connections are in need of service. A poor connection gets worse with the heat it builds, until the symptoms appear that you describe. Starting with your battery, clean and ream, and use dialectric grease to prevent future oxidation. Go through the system cleaning and servicing connections, and importantly, make sure that your cables are sufficient for 6v. Some dealers furnish cables that look thick enough, but have 12v wiring inside. Battery to solenoid, solenoid to starter, and the braided grounds are the major problem area to concentrate on here, but every connection can and does reduce your voltage if not perfect and tight. Pay particular attention to your battery cables themselves, as they can appear to be good, but have oxidized inside to the point of failure. (I have a wall hanger braided cable that is Show Quality in appearance, but has no continuity end to end!!).

A problem with similar symptoms is the coil and condenser, but try the above service before spending money on parts replacements. Follow through on one thing at a time, as it becomes very difficult to diagnose when multiple things are tried without being sure of any one result. Be aware that if you do discover that your coil is bad, the best solution is a rebuilt rather than an NOS, as the coils do go bad on the shelf just as they do on a car.

Alan


trjford8    -- 06-07-2010 @ 8:30 PM
  Jeff, in addition to Al's advice make sure that the braided ground straps are not oxidized. These straps have a tendency to oxidize(causes resistance) and they no longer make a good ground. If you are not concerned about being 100% stock I would use good heavy duty plastic coated cable for your grounds.


37RAGTOPMAN    -- 06-08-2010 @ 5:45 AM
  Next time it will not start, touch the coil and see if it is very hot,if it is real hot to the touch,
it might be on the way out,
also and make sure your ignition switch wiring is clean and tight, also you can feel the wire if they are getting warm or hot,
also if it is starting hard hot,
run a jumper wire directly to the ign side of the coil [ not the distributer side ] from the battery,and see if it starts better, if it does you have a problem in or around the ignition switch,and have very little voltage going to it, if you have a volt meter you should have 6 volts or better at the coil terminal with the ignition on with points open,[ you can take the cap off and either turn the engine over till the points are open or put a match book paper in between them when doing this test,,,is dash wiring is it new, or old,???
let hear how you made out,!!!!!!!!!>>>>>>>>>><<<<<<<<
37RAGTOPMAN ,,,,,,,,,,,,,,,KEEP ON TRUCKIN,


TomO    -- 06-08-2010 @ 8:34 AM
  Before you start replacing parts, have your mechanic check a few things. All tests are for a 6Volt POS ground car.

These tests will determine the condition of the starter circuit. They should be performed with the engine at operating temperatures.

1) have him do a voltage drop test with the starter cranking. Hook up the COM to the NEG battery terminal and the POS lead to the connection at the starter. Crank the engine with the ignition off. The meter should read .3 volts or less. If it is higher, there is excessive resistance in the starter circuit. Isolate the cause by moving the POS lead of the meter.
2) the ground circuit for the starter should be checked in a similar matter, except the test points will be the POS terminal of the battery and the case of the starter. The meter leads will be reversed. The maximum reading is .1 volt.
3) Perform a cranking voltage test. Hook up the COM meter test lead to the starter connection and the POS meter lead to the case of the starter. Crank the engine with the ignition off for about 15 seconds. The starter should crank the engine at a good rate of speed and the voltage treading should be between 4.5-5.8 volts.
4) Perform a starter current draw test. The starter should draw 150-200 amps.

Next check out the spark when the engine is cranking. Remove the wire from one of the spark plugs and hold it near a head bolt. The spark should be blue in color and at least 1/4 inch.

Check fuel delivery. The fuel pump should deliver 1 pint of fuel in 45 seconds, with the engine running at idle speed. You may have a blocked fuel line and your electric pump is overcoming the blockage most of the time.

If all of the other tests have been passed, check your spark plugs for color. Black sooty plugs indicate a rich mixture and may be due to internal leaking in the carburetor or a failing automatic choke, causing a flooding condition.

Let us know how you make out.


Tom


supereal    -- 06-08-2010 @ 9:15 AM
  From your post, I was unable to determine whether the engine cranks, but doesn't start when hot, or doesn't crank, or cranks very slowly. The causes for each is quite different, as are the fixes. Did the problem begin after the "tune up", or was it happening before? As is often said here on the Forum, it is very important to properly diagnose a problem before replacing parts. That will often change the characteristics of a cause, or mask it, making the job more difficult. Henry Ford was famous for his "Fordisms". One of my favorites was issued on My 25, 1945: "Diagnose, Don't Guess". Another was issued in 1941: "Things don't just happen. There is an underlying cause for every failure. Find it and you will be a better mechanic".


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