Starting the CMP
 

Hey

So we got our CMP running for the season and it was starting fine. I drove it for about a half hour and then it stalled. When I went to start it, the engine was cranking over very slow and wouldn't start. Had it towed and when it came off the flatbed, I tried and it started fine. It stalled a few minutes later and again when I started it, it cranked over very slowly.

The battery was tested and volts are fine (6 volt battery) and load tested and it was fine. The starter was tested to see if it works and ran fine. the wiring to the starter is 4 gauge. There is also a kill switch for the battery.

Any ideas what might be causing the problem?

Thank

Joel

Ford or Chev?

Chevy

Sorry

Air...fuel...spark.....
 

That's the Holy trinity..... all 3 are needed to make the engine run....

Wild guess the ignition coil may be bad ....as it gets hot it may shut down.
.... do not overlook the cheap little condenser inside the distributor.

When it stalls and you crank it can you smell gas fumes by the carburator????

To quickly check if you haver a sparks problem....after it has stalled..... open the hood, remove the air filter and spray ( using a plastic spray bottle) fresh gas or dribble a little gas ...one or two ounces... in the carb while someone else is cranking the engine...... if nothing happens and the engine does not try to start then you probably have no spark....... if it coughs and sputters you may have a fuel starvation problem......

You could have a fuel starvation problem with...... dirt....swelled rubber lines (swelling is inside the de-laminated rubber tube and may not be visible) allows it to run on what is in the carb bowl but the system is not pushing enough fuel to keep it running.



Start with the coil and condenser........ that is were I would put the money!!

Can you describe what happens when it quits....... gradual sputtering then dies or just plain shuts down......

As a precaution if it has been sitting since last season........fresh gasoline will help.

Good luck and keep us informed of what you find.

Bob C

Have you checked the earth connections are nice and clean? Cold they may still work OK, but as they warm up with resistance, the 'juice' to the starter gets less, hence cranking slows down. I had that problem with a jeep I purchased last year. Cleaned all the connections and installed a direct battery to starter body earth cable, and it now works fine, vehicle hot or cold.

Mike

Make a list
 

Hi Joel

Make a list of all the things it could be. Put the list in order of most to least expensive and time consuming to fix, then turn the list upside down and start with least. I often forget this approach and start taking things apart, only to find in the end that it was something really simple.

As Bob suggest it probably one of the three Air...fuel...spark.....

The cranking slowly though is something I would start with, is it really slower than normal cranking? If so disconnect the battery and charge it while you have it disconnected clean the terminals.

At the bottom of Bob suggestion he hits on one of the really big problems down here in the States "modern gas" goes stale very quickly. I make it a rule that if I can get the engines to run in the spring burn through the bad old gas and put fresh in before trying to fix rough running or do a tune up. Most often with fresh gas and ten miles on the road the problems go away.
Please let us know what it you find.

Cheers Phil

What was the engine temperature like? Something similar happened to me. Started and ran fine until a good run heated it to the point the gas vaporized and perhaps the cylinders/valves got a little sluggish. The rad was full and the temp gauge inaccurate leading me to believe it wasn't heat. The problem was a very old rad that, despite not leaking, had collapsed on its insides and was not cooling by way of the fins as it should. Let is sit and cool for 20 minutes and it started like new. Replaced the rad and the problem went away.

The engine temp sits right below the red on the gauge and then drops a bit then climbs back up etc etc etc.

Once the truck starts, it usually stays running, it sometimes likes to stall when I'm at a dead stop and shifting it into gear.

I was told the spark plugs were all fine and working by the students working on it.

How much suction should there be with the carb off, the teacher said he felt very little.

Joel

What do you mean by 'suction with the carb off'? Intake when you crank?

Weak pressure off the fuel pump (due to an ethanol soaked diaphragm) or spark plugs with too cool a heat range could cause difficulties but probably not after time. Maybe a weak coil breaking down as it overheats?

"Stall(s) when I'm at a dead stop and shifting it into gear" ...is that a learning how to drive standard issue??? :devil:

Like most problems, you'll puzzle and puzzle until you finally find it and kick yourself because of how obvious it was.

Ok, now the next question. Our engine only has a 15" four blade fan and no cowl/shroud. Should I be looking for a six blade and cowl/shroud for the rad? If so, where can I find one?

Thanks in advance

Joel

Did you get it sorted out????
 

Hi Joel

Is the truck running reliably now???

Has the truck ever boiled over????? overheated and steamed????

If not do not worry they were designed that way..... yes some had shrouds and had 5 or 6 blades but usually on gun tractors or heavy working C60........

Cheers

The truck is getting better. We adjusted so the generator is now recharging the battery, it wasn't really before but now we noticed that the starter switch is twitchy. Depending on how hard and where you push the engine starts better and quicker. We are going to replace the switch I'm just trying to find one locally (so we can get installed quickly, need it for a car show) before I go online and wait for like a week for the part to arrive.

We were also looking and the gauge of wire that we have going from the battery to the starter. A 4 gauge is on it, we were wondering if going to a thicker gauge would help. Or someone said hooking up two 6 volt batteries.

Bigger cable better
 

Hi Joel

All three of my Chey CMPs have 6 volt systems and have 0 gauge cable. Made up of welding cable they are no longer than necessary and have soldered ends not crimped on. Even with 6 volt batteries I have no problems starting the bigger 261 and 235 engines.

As to the start switch just take it apart and clean it. The old switch have better metal, many of the "new" are made with recycled brass with impurities.

Cheers Phil

Agreed with taking the switch apart. Most of the time it's arcing/burning on the contacts causing bumps that is the problem. A little sandpaper and off you go. Bren carriers (if original) have close to 15' of 0 gauge cable going from the battery to the dash starter switch to the starter (what, they didn't know about relays?) so clean, soldered connections are critical.

The insulation in the starter switch can fail also, had to replace it in mine and it works fine now.

So we did what you guys said, we looked at the starter switch, it needed to be cleaned and had turned inside the switch so there wasn't a full contact. Then we redid the wiring to the starter with 0 gauge wire.

Now it starts up quick and easily.

Thank you for your help with this.