420C starting issues

[JD Floyd]

Hi all:
I have a 420C that sat for many many years without being started. A few years ago I drained the oil, filled with Marvel Mystery Oil, and made a handle to try and unstick the engine gradually. After a few months of inching it along the engine freed up. This was my grandfather's machine that he bought used. The person before him painted it all industrial yellow without any disassembly or masking including the wiring. I bought new ignition switch, voltage regulator, wiring harness, rebuilt carb, cleaned fuel tank and lines(and added some premium non-ethanol back to the tank), checked starter to be ok, and had generator rebuilt. Then I got new points, condenser, distributor cap, plugs and plugwires, and coil. I bought a service manual and had a mechanic help me time the distributor per the manual. We have checked and have good spark at the coil, distributor, and plugs. I bought a new 6v battery(positive ground system) and tried firing this bad boy up. It turns over and will pop a little, hiss some, and even throw up some smoke from the exhaust and carb. I keep running the battery down trying to start to the point that it seems fried. I have a jump box that I used to try to give it some extra pep when trying to start. I also have tried putting the charger on high boost for engine starting. Nothing seems to make it turn over fast enough to make it fire up. Does anyone have any suggestions?

[mini kahuna]

I would check the compression of the cylinders, without compression it will not run.
with the engine being stuck that long even though you have gotten it to break loose the rings and cylinders will still have to make a good seal.
take a compression test and let us know what you get for psi.

[Stan Disbrow]

Hi,

These things can sometimes be a bear to start. They flood very easily. The trick is to close the throttle fully, then look at the butterfly while tapping the throttle open until you see the butterfly just start to move. Now, grab the choke but don't pull it yet. Pull the starter and after one rev pull that choke. Be ready to push it at least halfway back on the first pop.

Got all that? You might not flood it this way.

Once they flood, it gets harder to start.

When they sit, it gets worse. Then they tend to be too lean using the above steps. Then, they want to pop once in the backwards direction. That throws half burned exhaust back into the intake.

I just went thru all this a week ago after mine sat unused for three months. I pulled the plugs, opened the throttle, spun it a couple revs and then put a low current (5-6 amps) 6v charger on and went away for two hours. Came back and squirted some carb cleaner down each hole and put the plugs back in. Reset the throttle to barely open and cranked. One turn and it was running.

Actually, had to do this to both my M and my 420 two days apart. Man, I like diesels better. I know, other guys who have IP issues don't!

Anyone wanna trade a 58 420 for a 68 350 diesel?? (!)

Anyway, these can be bears sometimes, and they didn't have to sit long, either.

In my experience, battery boosters and fast chargers literally warp six volt batteries. You might need a new one. And, gotta use the fat cables, or double up those Number Two wire ones Tractor.Supply sells.

Too bad you are in Bunn and not Bunnlevel. I am a lot closer to Bunnlevel...

Stan

Edit: it says Raleigh because folks have heard of Raleigh. No one has heard of Lillington.

[notmeu]

If you do the compression test, you should have around 110 psi. Most importantly the cylinders should be close to each other.

[gregjo1948]

Use a 12 volt battery to get in running and then go back to the 6 volt. gregjo1948

[Stan Disbrow]

Hi,

That might help.

But disconnect the original wires to the machine and jumper a new wire from battery to ignition via a new switch. After also pulling the original wire loose from the distributor. Or, the generator and voltage regulator might not be in good shape after.

The coil won't heat enough to matter when the voltage drops while cranking. Cut it off after a few seconds once it starts. Then, you can go back to 6v battery and hook all the original wires back up and you should be good.

With 12v on the starter, watch your cranking time and heat of the starter.

Stan

[JD Floyd]

I went to Autozone today and got a loaner compression tester. I get 60psi #1 & 45psi #2. I guess that will explain the starting issue? Or would it run just rough? Anyone know a good place to have the engine work done in NC?

[gregjo1948]

That's too low to run. Was that a dry test? I would say if they were both 70, it would probably run but, might still start a little slow. gregjo1948

[Stan Disbrow]

Hi,

Squirt some engine oil in the holes and run it unloaded on the starter a few revs then measure compression again.

It may be just fuel has washed away the oil film on the cylinders. So, this is easy enough to check.

The rings may be sticky in the grooves. Running tends to fix that, but you have to get it popping first. Oil also helps if this is the case.

Might be valves, but you have to pull the head to figure that part out.

Finally, it might be worn bores, but that requires even more yanking apart to figure out.

As far as JD 2-cyl shops, I don't know of any. I will ask around.

Stan

[JD Floyd]

It was dry. I will try the wet method to see what happens.

[jtrichard]

I would put a few table spoons of Marvel Mystery Oil in each CLY. and with the plugs OUT crank it over a few times let it set for a few days then try to get her to fire as stated above the rings very well could be stuck in the lands (grooves)

[Stan Disbrow]

Hi,

What tends to happen, is the cylinder walls wear into a somewhat lopsided hourglass shape. So, as the pistons go up and down, the rings move within the grooves to follow the cylinder shape.

So, there is always some oil making its way past the bottom oil control ring. This lubes the compression rings. This, of course with a running engine.

After they sit, or after a good over-rich flooding, that oil goes away. Then, there is no lube and the rings don't seal well and - low compression.

In this case, sounds like there was sitting, then maybe flooding, and a double wammy leading to way low compression.

So, some oil, and Marvel is really good for this, down the plug holes followed by some piston motion may just straighten all this out. I have resurrected many an old engine that would not start this way.

Now, when I go to try firing one up, I squirt a couple pumps of 100 octane gas out of an oil can into each plug hole before putting the plugs back in. This means I would get some combustion regardless of what is happening in the carb.

Those explosions coupled with the oil work wonders for freeing up rings. But, I doubt you have any 100 octane on hand, so a quick shot of carb cleaner will also do.

But, use some oil and then recheck compression first. If you can't get it up from where it is, it isn't going to fire.

Stan

[JD Floyd]

Ok thanks to all for the advice! I added a couple of shots of Marvel Mystery Oil to each cylinder, let it set for a few minutes, then turned it over 3-4 times with no plugs in. I tested cylinders again and got 110 psi #1 and 90 psi #2. Is that close enough to run? Seems like to me that is close enough if I get enough juice to turn it over.

[original possum]

A quick boost using 12 volts won't hurt anything. You can leave everything in place except the hot (negative) booster cable. Engage the starter using the 6 volt system, and while it is engaged touch the hot lead directly to the post on the starter. You can do this for a few seconds of fast spin without hurting anything. Just be sure to keep the starter handle pulled while the 12V is on the starter.

[Lavoy]

Keep in mind an oil test for compression is primarily to determine if compression loss is rings or valves. My bet is as soon as the Mystery Oil burns off, you will be right back to where you were.
Lavoy