The Stovebolt Site Forums The Shop Area Engine Shop engine will not start when hot

have a 55 235 enginge in my 46 chevy, still on 6 volt system. Will start fine with when cold, appears to be charging, but when you shut it off when the engine is hot, it wont restart. you have to wait for the engine to cool down, and if you dont kill the battery it will restart. Noot sure where to be looking for the problem

mine would do the exact thing. the previous owner had the alternator hooked up worng, and it was not charging.
once i fixed it, it now starts when hot.

leonard

dont have an alternator have a generator, 6 volt

"Does not start" covers a lot of possibilities. Exactly what does it do? Does it crank too slowly? Does it crank OK but fail to fire? If it cranks OK but fails to fire does it try to fire but won't catch? Does it fail to fire at all? A bit more specific info will help us help you.

If you are not certain of the gauge of your battery cables, you could start by replacing them with 0 or 00 gauge battery cables. A large-truck shop, Tractor Supply, or a welding supply can make them or might even have them made up. I'd bet that over half of the starting problems people have (cold or hot) is due to 12v cables being put in as replacements over the years.

The starter gets less efficient as it heats up, so a weak starter shows up when the engine is hot.

An outside problem is the engine might be tightening up when hot.

The generator/voltage-regulator and the battery are other possible culprits.

The first thing I did for the last three old trucks I bought was to buy battery cables. All three previous owners had different theories about why they were hard starting (or non starting, when hot). Problems solved with proper-sized cables (both battery cables).

Also, as soon as an old battery dies I spring for 6v Optima Red Top battery. My oldest is now 5 years old. It sits in the unheated truck all winter and starts right up every spring.

we took the generator in and had it checked out, and they told me it was good. They replaced the volts regulator at that time, as for the battery, not real sure. its not that old maybe 2 years, but has been charged alot. Just got a 6volt battery from local tractor supply company.Not understanding the 0 or 00 guage wire your talking about. What would be the difference. Think i just got battery cable wire and made them up. Does 6 volt wire for the battery different that 12 volt battery cables?

Take the starter in for a check. I had to replace mine twice.

the engine cranks real slow, the odd time it will still start, but usually not. Have to wait for the engine to cool down, before it will start again.

where do you buy a 6 volt optima red top battery.

Just another option to check out....I really hate to beat the drum too much on this E10 fuel we're being forced to use in our older vehicles, but we've had some identical issues since our first tank of the blended stuff.

If your ignition system is in good shape and the engine fires immediately when cold, I'd take a closer look at your fuel line routing. We've noted, in a variety of different vehicles, that when you shut the engine down (with the hood closed) and tried to refire the engine after say 20 minutes....it would crank fine but stall out as soon as the float bowls emptied. As we dug a little deeper into the issue we found that the engine was "heat soaking" and the temperature of the fuel lines, between the mechanical (or electric) fuel pump would climb to nearly 150 degrees. Being that E10 seperates at 128 degrees, we noted that our fuel pressure gauges would read "zero" psi when we tried to restart the engine. If the hood was raised upon shutting down and engine compartment heat allowed to escape, the chance "phenomomem" occuring was reduced....dependent on how long the engine was allowed to cool. I just run my a/c supplimental pusher fan for about 5 minutes.

In addition, if a wet rag is applied to the fuel line between the thermostat housing and the carbs before the engine died, fuel pressure would immediately be restored. Several have rerouted their steel line from the pump straight up and over the top of the valve cover and added a small aluminum heat shield deflector under the line, on top of the exhaust manifold, to aid in shielding the line from the radiant heat generated when your engine is shut down.

Once the temperature in the line exceeds the 128 degrees in a system that has no return line to the tank, the classic vapor lock might be your problem. Draining the tank and adding 5 gallons of straight gasoline or Av gas corrects the issue immediately.

The modern injected vehicle with an electric pump that returns hot fuel to the tank and flushes the lines with cool fuel don't seem to have these issues. The next time you have this problem, just run a wet rag over the fuel lines where they pass between the thermostat housing and the valve cover and see if this doesn't bring the line temperature down to where your engine will fire and continue to run. It won't cost you a penny and might just let you get your rig back under power.

Dave

I had a similar problem on a truck I used to have,I replaced the wires leading to the coil, they were brittle and were not delivering enough juice when hot.
Definitely install beefier battery cables, a 6 volt system requires twice the amperage than a 12 volt system, smaller cables won't effectively deliver the amperage, especially when hot.

the wires to the coil are new, have been replaced already. but the cables to the battery, starting to think they are for a 12volt system. Will have to look at that further and maybe the starter

maybe its not charging

leonard

A 12 volt starter pull a lot less amperage than a 6 volt so it needs smaller cables. If I remember right 12v cables are about a 4 gauge. 0 or 00 would be much thicker. I think a 1 gauge would be OK since that's what I use successfully. Since the issue seems to be cranking speed I would do the following in the order listed:

1: Make sure your battery is fully charged.
2: Clean all ground connections @ the starter and battery cables.
3: Make sure your battery cables are 1 gauge at the smallest.
4: Check your ignition timing (too far advanced can cause slow cranking).
5: If that doesn't fix the problem have the starter checked.
6: Buy an Optima Red Top 6v battery (any parts house should be able to order one & hold on to your wallet they aren't cheap).

If you do all of the above and still have the problem of slow cranking speed I'm out of ideas. I've never seen a slow cranking issue that wasn't fixed by following one or more of the above suggestions.

have your battery checked. May not be as good as
you think it is.

well, i think im gonna start by replacing both battery cables with heavier ones and get the battery tested, and see if that solves the problem. if not ill use your guys other suggestions. Ill let you know what works.

Starter!... Guaranteed.... or you don't have to pay for this diagnosis...

Make sure you polorize your generator, and check your timing.

I have also heard of people using an 8 volt battery. I've been told that will help spin the starter a little better and the generator will charge it enough to work well. Maybe some of the other bolters can comment on this. Guys?

Back in the day we always used 8 volt batteries on our 6 volt systems. Never had a cranking issue.

Mine did the exact same thing and it was the Ignition timing. It was too far advanced. I put a timing light to it and put the timing to factory specs and the problem was solved.

skmkr, as mentioned above, check the ground cables size and for good contact. I had this same problem with after market braided ground cables which were not heavy enough. Everything was fine until the engne got to operating tempature, then it was if I had a dead battery when attempting to start when hot. If it was a timing issue it would happen hot or cold. I changed out the ground cables and everyting was fine. To test this, put a jumper cable from the ground on the battery to the starter, (when engine is hot) that will tell the story.

I have the same problem in my 49 deluxe where it would crank real slow once it got warm. I solved it by putting a 8 volt battery in it. Now it starts right up.

One thing that hasn't been mentioned but may be the problem is the heat generated by the exhaust. I have had this problem in the past, basically the starter gets hot and won't work properly, a heat shield can help with this.

Heat from the block, maybe. The starter is on the opposite side of the engine from the exhaust system - designing a heat shield might be a challenge.

Regarding the 8 volt battery "solution": this might help and might actually be cost effective, if you have a free 8-volt battery laying around. Years ago, this was called a "farmer's cure" for slow cranking, because 8v batteries were readily available in-use on tractors (I dimly recall).

The 8 volt "solution" might also decrease the life of light bulbs and might cause a problem with 6v electronic ignitions (especially if the voltage regulator is adjusted to deliver 8v).

If you do not have an 8v battery, you might as well try the higher probability-of-success solution: get 1/0 or 2/0 battery cables (replace both the power lead and the ground lead). Farmers (and almost everyone else after the '50s) would have used 12v battery cables as replacement cables.

I replaced 1/0 cables on a '54 Pontiac straight 8 with 4/0 cable we had at work. It made a world of difference, the others had loose ends and were getting oldm I say the bigger the better on 6 volt systems! Joe