Hard Start after Warm looking for suggestions

[steve-cook]

I am having a problem starting my 1940 Ford after it is warmed (not overheated) it starts right up when cold no problem it cranks fine.

It seemed as if it was not getting spark I originally thought it was the timing verified to the best of my ability it was correct replaced points condenser still had the problem, replaced coil and plugs/ plug wires same problem after that I rebuilt the carb I notice the new accelerator pump leaks slightly and needs to be repaced but no change in the problem, in frustration most reciently I started pumping the gas while adjusting the choke it started up and then ran, drove home from the gas station shut it off and of course waited a minute or two and it would not start.

Any suggestions would be greatly appriciated.

[4dFord/SC]

Two things come to mind. First, what is the replacement coil? Even new ones can go bad, and NOS are even worse; condensers are the same. IMHO, the only sure thing is a coil rebuilt by Skip Haney and an IH-200 condenser.
Second, check your ignition switch--the contacts may not be making a good connection. JMTCW

[Brendan]

Bad electrical conections? on my 36 it would crank right up when cold then
it would start very hard when hot. ther was a bad conection on the starter switch
cleand tightend them all up and it would start right up.

[imnezrider]

Originally Posted by steve-cook

It seemed as if it was not getting spark.

If that was before you replaced the parts, how about now? Good spark or not?

[ajohn]

So many things could cause hard starting when hot.I have seen the following causes over the years:Carb leakdown,bad coil,starter fields swellinhg when hot,loose ignition connection,distributor not properly grounded(caused by freshly repainted,rebuilt engine,distributor not grounded,same with coil.Many items can cause your problem.Don't panic,work one thing at the time till the problem is gone.

[Frank The Plumber]

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Corrosion, causes resistance and increases heat, heat causes more electrical resistance, snow balls till failure. May need to slightly retard timing. Try cleaning all connections and apply dielectric grease or anti oxidant compound to all critical connections of electric conduct. This will of course also apply to the grounding system. Ionic return to the battery is critical.

[G.M.]

Steve it takes three main things for the engine to start, air, gas and spark. Check the spark when the condition occures by jumping a spark from the plug wire to ground NOT to a spark plug connector. Jump the spark to a head nut or the grounded base of the plug. You could also do this test cold to see if you have a good spark and what a good spark looks like. It should jump a 1/2" be steady and show a crisp blue spark. When it's hot and the problem starts do this same test and if it has a good spark then the problem is a blocked air filter, spark plugs or gas. If you flood the engine with too much gas it won't start or even try to start. When checking the spark when hot if the spark becomes weak, don't jump the 1/2" is yellow in color then it is the coil or low voltage to the coil due to bad wiring, resistor, ignition switch, low battery, wires and connections or bad ground. Most stock old Ford coils when hot the spark will get weak and the hotter they get the more the insulation leaks and the weaker the spark. The sparks gets down to a fuzzy little yellow ball. This type spark isn't strong enough to jump across the electrodes of the plug with the air from the compression blowing it out like a candle. Always carry a can of starting fluid which will start with a weaker spark. If you have a good spark and it will only fire on either then you have to check the gas supply. G.M.

[CWPASADENA]

If you have checked out all your connections etc, try shorting across the resistor for the coil when the engine is hot. Often time, it will start right up.

When the resistior gets hot, there is too much voltage drop across it and the coil is not getting enough voltage during cranking to produce a hot enough spark.

When everything is cold, there is little voltage drop across the resistor and the coil will get enough voltage.

This is not uncommon, even in the "Old Days" if your electrical system, coil, starter or battery were at all marginal.

My experience, Chris.

[steve-cook]

I appears that the spark starts out strong and weakens as the temp increases (it does not take long) I will take a look for a bad ground this week and follow up with what I find. The replacement coil was a china replacement from MACS I do not think that is the problem I will play with it this week and follow up with what I find. I believe I will also purchase a new coil resistor.

[Charlie ny]

Steve,
Skip Haney...Punta Gorda Florida the coil guy, get one of his coils.
If the china coil isn't the problem today it will be very soon when
least expected.
Charlie ny

[steve-cook]

Would it be better to put a coil adapter to run a newer style coil?

[CWPASADENA]

Originally Posted by steve-cook

Would it be better to put a coil adapter to run a newer style coil?

Have Skip fix your original coil, it will work just fine.

[G.M.]

Before you waste a lot of time measure the voltage at the wire from the resistor at the top of the coil. Turn the switch on and measure the voltage from the wire terminal to ground. If the points are open it should read close to the battery voltage 6.2 to 6.4 measure across the battery before you start and make sure it is over 6.3. Now you need to get the points closed, when closed the voltage will drop and should be in the 3.5 to 4.2 range. Jog the starter until the voltage drops and then the points are closed. If the battery is 6.3 and the coil voltage is in the 3.0 or less range when the points are closed there is a loose connection in the switch and resistor line. A dirty arced ignition switch will cause a voltage drop. Also the battery shut off switch with the green knob go's bad in time and causes a voltage drop. WHEN YOU ARE TESTING THE COIL VOLTAGE AND THE POINTS ARE CLOSED NEVER LEAVE THE SWITCH ON LONGER THEN 2 MINUTES. When the points are closed and the engine isn't running the winding of the coil becomes a resistor dead shorted across the battery and in about 7 or 8 minutes burns the insulation off the wire and melts the tar or potting material in the coil. G.M.

[Terry,OH]

I have found that Mac's ignition components are bad when sold. I replaced a couple of new condensers to find all were bad.

[George/Maine]

If you are giving it gas you maybe flooding after a hot start.If you think its a coil problem something to try.
Mopars don't seem to have starting problem,you may want to try a old plymouth dodge 6 volt coil no resister is needed.

[steve-cook]

The wiring on this car is scary I did the voltage drop test at the wire on the coil at one point I was able to get battery voltage but it appears when the points are open then I get almost nothing would this be the condensor not holding a charge?

[flatheadernie]

no load when points are open , normal . ernie n Tx

[Jack E/NJ]

Hello Steve:

Re-check GM's post above. Full voltage should be seen at coil terminal when points are open. Seems like a coil problem. But another unlikely possibility is that a point arm or spring is somehow touching a ground when the points are open and warmed up.

Jack E/NJ

[G.M.]

Steve you will get battery voltage with the points open. If the points are shorted to ground or adjusted so they don't open you get a 3.5 to 4 volt reading all the time. I don't get the part where you said you don't get nothing?? If that means you don't get nothing at the coil wire when the points close that would indicate you had voltage to the coil when the points were open. There is no amperage draw when the points are open. When the points close then there is about a 3 amp load. If you have a REAL BAD connection or a realy dirty, arced switch this bad connection would make the volt reading at the coil wire drop very low. Leave the POS side of the meter grounded and check the the voltage at the coil side of the resistor with the points closed it sould be in the 3.5 or 4 range. Move the probe to the ignition switch side of the resistor and it should be 6, move to the ignition side of the switch and should be 6 now go to the battery side of the switch and it should be very close to 6.3 or the battery voltage. If you have 6.3 on the battery side of the switch and 5 volts on the ignition side of the switch the switch is dirty and arced. Anywhere the voltage drops below battery voltage before the resistor indicates a bad connection between where you are testing and the battery. These tests all need to be made with the points closed. Remember not to let the switch on longer then 2 minutes with the points closed or the coil will have a melt down. A one to three tenth of a volt drop across the switch is normal. G.M.

[OldDad]

Mine will percolate gas out of the float bowl when it's hot and flood the engine. Checked float level when hot, and tried lowering it to no avail -- new gas? Since I have an electric fuel pump, I tried shutting off the pump before turning off the ignition in order to lower the fuel level in the float bowl so that it couldn't percolate out and flood the engine. Worked for me, but of course no guarantee for your problem -- particularly if you are running a mechanical pump or electric with no switch.

[ford1]

im not sure if the earlier ford v/8 intake manifolds had the heat cross over passage , if it does plug them with real copper pennies in the block under the manifold, not the new pennies, will keep the carb from being heated by exhaust gas, put in a 1/2" carb spacer under carb to keep it away from the manifold and it will help keep it cooler

[OldDad]

Yes, good advice Ford1, I will try this on mine before the weather heats up again. Have one inch spacers on an Evans 2x2 with 97's, but the spacers are aluminum, and conduct the heat beautifully!

[hotrod8]

had a 46 mercury did this when i was a teenager, whn warm i could push it ten feet ,pop the clotch and it started , valves were burnt up !!!!!!!!!!

[G.M.]

hotrod8 Why did you have to push it 10 feet? I suspect the battery was low and wouldn't turn it over with enough power to start. Plus a weak battery running the starter pulls the voltage to the coil down so low there is not enough spark to fire. Pushing the car is no differant then the starter turning the engine over EXCEPT the starter isn't pulling the voltage down and even a weak battery will start the car if it rolls 10 feet. G.M.

[DICK SPADARO]

I have the same issue with my flathead on hotter days 80-85+. Engine starts on 1/2 roll of the starter everytime when cool. Take it for a moderate drive and get everything heated up, stop and set for 2-5 minutes, starts difficult. Most suggestions are ignition related and are valid topics but I have fiddled with this issue all summer and I feel that if your engine fires easily its not an ignition problem.

Again I have addressed the fuel as the suspect of hard starting. This eco friendly new ethanol fuel is not old car friendly. The ethanol additive makes the fuel vaporize too easily and it is my opinion that the fuel is evaporating out of the hot carb, lowering the accellerator pump fuel level and making the car hard to start. If you crank the engine over a couple times to get the fuel bowl refilled then the vehicle starts. This take 4-5 complete spins of the engine and grinds down the battery and taxes the starter.

You can check this buy operating your vehicle up to temp on a hot day, stopping and letting the engine heat soak for 5 minutes or so, then squirt some starting fluid in the carb. Attempt to start the engine, if it fires rightup you can eliminate any ignition problems and the fuel system is suspect. It is also important to have a good fuel pump diaphram not over 2 years old, the diaphram stretches out when setting idle and the efficiency drops excessively as they age. It is a good idea to replace the fuel pump diaphram every spring if you are using ethanol fuels.

To help eliminate the evaporation issue I have raised the float level in the carbs so they contain extra fuel and make the evaportation process slower when the carb and engine is hot. This seemed to help remedy the issue but not totally eliminated the hard start on super hot days.

My sugggestion would be to first check the condition of your fuel pump, diaphram and then reset your float level to a position higher than normal to retain more fuel in the fuel bowl to overcome the evaporation issue.

[G.M.]

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Dick as you know I never believed in vapor lock and couldn't make it 6 or 8 years ago on a HOT 38 ford on a 95 degree day. A friend had had problems after resetting the points 3 or 4 time after driving 25 miles. The problem turned out to be someone put extra springs under the point springs and would wear the shoe riding on the cam. He came by with it and I heated the carb, fuel pump and fuel line until the gas in the pump filter bowl was boiling. Could turn it off wait a few minutes and it would start right up. He left the car and in about 20 minites I had a small red rash all over my hands and arms, 20 minutes later the rash turned to burn blisters from just bumping anything on the engine. This summer I drove my 39 to Pa. and drove it every day up there. On 2 or 3 mid 90 days I stopped for maybe 10 minutes. It didn't start on the first turn, maybe the third or forth and I started out and in a 100 or 200 yards it gave a few chugs like a gas problem. One time after 200 or 300 yards it it died and still coasting I let the clutch out and it caught, struggled a few times and was OK. Driving back to Florida my battery went bad 800 miles from home, not enough power to crank start, had to kick start or use the battery pack. Just above Tampa I stopped for gas, the station was filled and I stalled the engine, got the battery pack, started it and turned the Idle screw up 2 turns. Waited and got to a pump and left the engine running while filling the tank. It was in the low 90s and I pulled out of the station, turned right to make a U turn to get back on I-95 and it stumbled and died. I coasted to the middle lane which was marked off for no traffic. I got out and opened the hood and before it was up a young sheriff puled up behind and asked if he could help and I said I didn't think so I would get it running. Got the battery pack and cranked it to the starter with 12 volts and no go. I have a 4 lb pressure gauge in the fuel line between pump and carb. I cranked it and asked the sheriff what the gauge said and he said almost 1 lb. I could see bubbles in the filter bowl. I have the gauge on testing a pump diaphram and thought maybe the test wasn't turning out so good and would have to change pumps. I gave it a few shots of either and got it running with a squirt of either once in a while to keep it running and the pressure came up to 2 lbs. It had been running at 3+ and thought the diaphram was streatched a little but I only had 125 miles to go. It kept running and I made a left througt the red light and the cop looked away. It started acting up and I had to decide do I want to change the pump on I-75 or here. I turned right on a small side road and went 300 yards and it started clearing up so I turned around and got on I-75 and it ran perfect all the way home. Next day I put in another Optima and it started on the first turn and had a little over 3 lbs pump pressure. The tank was down to 2 1/2 gallons before getting gas and with the heat from the dual exhaust pipes, hot road and engine heat comming back I wouldn't be surprised if the gas in the tank wasn't boiling and after filling the tank and took a while to cool. I don't think it took much over 5 minutes to get started when it quit so it was still hot. Please don't tell anyone I mentioned VL. G.M.

[OldDad]

For what it's worth (probably not much), here's what I've determined with my hot start problem. Starts right up cold, but cranks over repeatedly hot (after sitting a few minutes) and will usually start if I hold the throttle on the floor (flood treatment). But sometimes on a hot day, no start at all, unless, as Dick suggests, I hit it with ether, and then it will start right up. I found if I parked it in the garage when hot, I could smell gas quite strongly, and one day noticed some fuel dripping from the throttle shaft of the front carburetor. I attributed this to percolation out of the float bowl, but it could be from another source. I had set the float level cold, so I checked it again when thoroughly hot, and found no difference. Lowered it a bit, but this made no difference in the hot start/fuel odor problem. If I turn off the electric pump (no mechanical pump) and allow it to run until the bowls are lowered or empty, it will start up hot, after of course allowing the bowls to fill before cranking. So, I speculate that you could end up with both lowered/empty float bowl and a flooded engine due to percolation at the same time. As Dick said, try the ether to take the ignition out of the equation. A frustrating problem which makes it difficult to use the car at all on hot days. And a long trip in the summer . . .

[BOSSY]

Some thing to look at. I had a 48 Mercury that would start right up cold but when it got warm would bearly crank over. What I found was a bad starter solenoid, it would have a very hot terminal on it. When I changed it ,it started like new again.