1955 plymouth V8 does not start when hot

[DutchEdwin]

I'm having troubles with starting my 1955 Plymouth Plaza suburban P27 (V8) when hot.
When the car is cold, she starts quickly. Starter motor is turning quick.
When I drive for about 10 minutes, so the engine is hot, and I shut the engine down...after 5 minutes the starter motor is turning slow, thus the car will not start.
I have a good spark, and enough fuel. Also spraying fuel into the carb will not work. Only 1 thing works, letting the engine cool down.

Who knows what is causing this?

I still have the car running on 6V
What I've done so far:
New coil
New spark plugs
New plug wires
new distributor cap
new points
rebuilt of the carb
insulation of the fuel pump to the block by adding 4mm of nylon between the pump and block
very thick wires to the starter motor (used the cable of a welding torch)
rebuilt of the starter motor (a little oil in the plain bearings, cleaning the brushes and rotator, checking the pressure on the bruches, having the rear cap on the motor good aligned when assembled so the motor rotates easy by hand.

[plymouthcranbrook]

Timing?  Have you checked that?

[keithb7]

Exhaust valve clearances? No idea. Never owned an 8. Sorry, I'm throwing darts. I'll follow along to learn. 

Edited September 8, 2017 by keithb7

[greg g]

You might want to try fabricating a sheet metal heat shield that will protect the starter from heat generated by the exhaust manifold.  If the tolerances in the starter are tight when cool, heat transfer from the manifold or exhaust pipe can make them tighter she hot.  This will cause drag within the starter.  You may also want to take a look at the internals to assure the armature shows no signs of dragging against the field windings.  But it seems that excess heat might be the culprit, especially if it works as it should at ambient temperatures.

[knuckleharley]

The first thing I would do would be to run a load test on your battery to see how many amps it's  putting out. You can have a fully charged battery with  check the grounds on both the positive and the negative battery cables by cleaning the connections of all corrosion and using new washers and nuts to tighten them down after cleaning.

While you have them off,check them volts,but if  the plates are corroded inside the battery you won't get the amps you need to operate your starter.

Next,check your battery cables to see if they look burned or brittle. If there is any doubt,replace the correct "0" gauge battery cablles. It MAY be "00" gauge,but  I am sure someone will pipe in and correct me if I am wrong.

Battery cables fro 12 volt vehicles just  won't stand up the amp load.

If the cables seem fine,clean the ends and the area where they bolt to the starer or the ground,and then use new washers and nuts when re-attaching them.

 

 

[DutchEdwin]

thanks all for helping out.
- Timing....I have the timing set to the max vacuum I dare to set, 10 btdc. still only 18 inches. but the car is running great. on the old '50 fuel it should be 4 btdc. Discussed this on this forum years ago, I think this was with Greg g, him being a car nut....must be ok then.

- Exhaust valves: the engine is completer rebuilt, including the head, and new cam. Only did about 2000 miles since then. So I think I can rule that out.

- Heat shield around the starter: The exhaust is far away from the starter at this V8. But I did built a heat shield around the motor from reflection aluminium sheet, leaving a gap of 0.25 inch between the motor and the shield to let air pass for cooling. but the bendix housing is still attached to the bel housing, allowing heat transfer to the motor. but direct radiation from the engine is covered max. Greg, I was also thinking about tolerances between the plain bearing and shaft being a bit on the lower side of the bearing gap. But when metal heats up, is expands. The bearing is in the housing, so it heats up first, giving more clearance between the shaft and plain bearing. The only thing I could come up with is that the side of the motor being near to the motor heats up and expands, the side not facing the motor does not. So the motor housing will be a bit banana shape after that, giving a bad alignment between the housing with bearing and the still straight motor shaft. But how can you be shure.

Greg G, Do you know the spec on the needed clearance between the plain bearing and the motor shaft?

The internals of the motor have a lot of room to move around. so no problem there.

Is there a posibility that the heat is messing with the resistance of the motor (higher temp. is higher resistance)? 

- battery cables are the thickest I could get, from a welding shop for a welding torch, about thumb thick. also no corrosion. I cleaned the battry poles and all electric connections. I do have a little copper based grease in all the connections to prevent corrosion. I think I'm good there.

The battery is full. It is a 6V 700CCA. I can start a few minutes on this one without draining it dead. In fact never reached that piont.
 

 

 

Edited September 8, 2017 by DutchEdwin

[maok]

Have you checked your generator/alternator, it may not be supplying enough charge to your battery enough while running.

[greg g]

I do not know the specs for bushing to shaft tolerances. If your pieces are all nicely coated with fresh paint you might try running a dedicated ground wire from the starter to the frame or engine,just to see if it makes a difference. Or get a big star washers for the bolts attaching the starter to the bell housing.  Stranger things have happened than Fresh paint causing weird ground paths.

[busycoupe]

Is the engine itself binding up? Many years ago I had a friend in college who had a 66 Mustang.  The motor was so worn that it would seize up and stop after about 5 miles.  If he let it cool down for a half hour it would start right up again.  

[DutchEdwin]

I drove my car to the Classic USA car festival last Sunday. Only 20 km, or about 12 miles from my home. The car was not starting after I turned off the engine when I arrived and tried to start after 5 minutes. The battery was filled with a charger for two day's. After 4 hours letting it cool down the starter rev'ed quick and the engine started immediatly. So the battery was not the problem I think.

 The engine binding up sounds unlikely. it is completely overhauled 2000 miles ago. When I try to start up immediatly after I turned it off it starts.

I could try to find new star washers. They are still the original one's from '55. But I was carefull not to paint the filling of the housing where the starter goes in to or any point that . There is no star washer there, putting one could not harm though. Also Running a lead wire to that point direct from the battery should double the capacity for the current to run through the metal of the engine or lead wire. 

A friend of mine mentioned to put a shimm at the rear end under the cap of the starter on the "cold" side of the starter. By putting it on one side, counter balancing the thermal expension of the starter when hot. The shimm although must be small, not blocking the starter when cold. 

I let you guy's know if anything works. 
If not, I probably shoud try making the bearing gap a few microns larger. though I'm a bit afraid doing so, trying not to ruin the starter.

[Don Coatney]

9 minutes ago, DutchEdwin said:

A friend of mine mentioned to put a shimm at the rear end under the cap of the starter on the "cold" side of the starter. By putting it on one side, counter balancing the thermal expension of the starter when hot. The shimm although must be small, not blocking the starter when cold. 

I let you guy's know if anything works. 
If not, I probably shoud try making the bearing gap a few microns larger. though I'm a bit afraid doing so, trying not to ruin the starter.

I would not do either of the things you mentioned. What size are your battery cables? How clean are your battery to cable terminals? When hot and not starting are the battery posts also hot? Are the cables going to the starter hot to the touch?

[Young Ed]

I wonder with only 2K miles since the rebuild if the engine is still so tight it is causing issue. 

[DutchEdwin]

Don, I never checked if the cables are hot, indicating to small size. But the cable to the starter is thumb thick, normaly used for a professionall electric welding torch. They are running bigger then 50 amps. I'll check if they run hot.
All contacts, from battery to the starter are cleaned and grease with any seize (copper based grease) last week.

I'm triggered to the idea of shimming because when I bolt the starter together I can let it turn easy by hand or tough by moving the rear sheald radial before bolting it down. There is a little radial play between the rear sheald with plain bearing to the starter housing of about 0,1mm to 0,2mm (0.004 to 0.008 inch)

[knuckleharley]

On 9/8/2017 at 6:31 PM, DutchEdwin said:

The battery is full. It is a 6V 700CCA. I can start a few minutes on this one without draining it dead. In fact never reached that piont.
 

 

 

Yes,but did you run a load test on the battery to make sure it is producing the amps needed,and to see how quickly the amp "surge" falls away under load?

I have seen fully charged 12 volt batteries that would read fully charged all day long with a voltmeter fail the amp test. They seem to have plenty of power at first,but after they get hot from being drained to start while cold,and then getting hot again as the charging system works to try to restore them to full power,they will NOT start a car that just shut down and is hot.

IF you have had someone run a load test on your battery and the reading shows it will throw out a full load of amps while under drain,ignore everything I am now writing.

If you haven't done this yet and are just relying on a voltmeter to tell you that you have 6 volts,have your battery checked with an amp meter under load.

[Pauls_Plymouth]

Did you think about having your starter checked out?  Worn electric motors (brush springs?) will not turn when hot. But spin when cooled down.

 

[DutchEdwin]

I checked / refurbished the starter myself. Brushes are still good. Brush springs have good force, the commutator is cleaned and polished, the bearings have a little oil, the electric contact cleaned and the bendix is new.

[Pete]

HI.

I have a similar problem with my '39 Plymouth and my '38 Dodge pickup. Filling the gas tank with non-ethanol gas makes it go away. Apparently the higher volatility of the ethanol causes it to boil at a lower temp  than pure gas. Not sure if you can get non-ethanol gas (or even gas with ethanol) where you are located, but it's worth a try if you can.

Pete

 

[MackTheFinger]

@DutchEdwin I agree with KnuckleHarley, have your battery load tested before getting too involved. If the battery passes a load test you might back off the timing a little and see if that helps. 

[Silverdome]

Battery load test, starter load test and timing would be what I would check to start with. I know you stated that you rebuilt the starter and I don't doubt your abilities but if you did not check the resistance in your field windings and armature there could be a problem there that's not visible to the eye.

[janan5243]

It sounds like the battery is dragging when hot. It was common in older starters, 6 & 12 volt. Usually means starter has to be rebuilt. I know you said you replaced brushes & cleaned armature but there could be a problem in the windings that happens when it's hot.. There is an old time gauge used to check the ampere load used by the starter. it would be held on the cable going to the starter. check load when cold & then when hot. If it draws a lot more amps when hot, then starter is bad. I believe you can still get the gauge at an auto part store or maybe a friend has one. Simplest way to check starter.

[wayfarer]

Everything that I have read in this exchange points me to the starter.  As mentioned above, a load test comparison will either confirm or deny.