Hot Start 1950 Merc

[Pvmt-Pndr]

I've done some research on this topic but want a little more feedback or reassurance I'm heading the correct direction.

1950 Merc fires up cold like its fuel injected, half a crank and its running.
Electric fuel pump, regulated to 3-4 psi with a kill switch. My battery is 2 years old, load tested good a couple months ago - still 6 volt. I've replaced everything relevant to spark except the distributor itself. New battery ground wire to motor size 00. New factory starter wire and relay from shoebox central. I've pulled the starter, cleaned the brushes and grounds from the pan to the starter. All wiring from the firewall forward is new. I added a 1/4'' spacer made out of garloc gasket material to act as a phenolic spacer.

The only things that I have not done is install a phenolic spacer or move my coil from the motor and away from the heat. These are 2 things I plan to do next.

All of the things I have done were not for this problem specifically, most was done preventively since she lived in a barn for years before I got my hands on it. I do have a 12-volt conversion and a full wiring harness waiting to go on whenever I get time. Id like to solve this while it's still 6 volt as everything is highlighted and I won't be covering up my issue with 12 volt.

Now that you know where I'm at and where I'm heading none of the above has helped with my hot restart issue. I even go as far as to shut the fuel pump off before I park and allow the motor to run out of gas. Before I restart it, I let the fuel pump run for 5-8 seconds to refill the bowl with cool fuel - this has proven to help but only the slightest bit and still requires multiple attempts at starting. I do not touch the gas pedal while trying to restart, I have found not messing with the pedal allows it to restart sooner. It also cranks slower while trying to hot start vs being cold. Any other suggestions?

[drolston]

The most common causes of not starting when hot are (1) vapor lock and (2) coil. With an electric fuel pump, it is pretty safe to say that #1 is not your problem. So, check the coil. Disconnect any spark plug wire and hold the tip of the wire close to any ground. When cranking you should see a white to blue spark that will jump half an inch. If no spark or yellow and weak, try a new or rebuilt coil.

[Pvmt-Pndr]

I suspected the coil also. I needed one for my tractor so I pulled the 2 year old coil off the merc and it works fine on the tractor. I bought a brand new one for the merc instead of pulling one back off the tractor. Same issue to a T

[tubman]

You said : "It also cranks slower while trying to hot start vs being cold."

This indicates that here is a voltage drop somewhere in the system. This means there is also lower voltage to the coil when hot, which weakens the spark. I would make sure all of the cables and connections are good, but I suspect that the starter itself may have a problem when it gets warm. I had a similar problem and changing the starter solved it. The bushings and bearings get worn and you never know what might happen.

[Fritz]

I agree with Tubman's statement. You said you replaced the engine ground cable with 00, that's good. What about the battery ground, battery to solenoid, and the solenoid to starter cables? They should also be 00. When you notice the slow cranking, you will be able to tell one or more of those cables will be hot due to the resistance. I've had cables made by an old local NAPA that went bad quickly.

You can have good cables made for you. I just used batterycablesusa.com, and they are very nice custom made cables.

[glennpm]

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Ditto on what tubman offered. I'd also check your distributor advance, too much also makes hard starting.

[Bill OH]

I have used an analog voltmeter connected from one end to the other of a cable to find voltage drop. I have found that the battery must be connected direct to the motor from the plus terminal (6v positive ground) of te battery. Connecting the plus terminal of the battery to the firewall and at another point on the firewall to the engine promotes resistance - steel does not have the conductivity that copper possesses. And steel terminals on the battery cables also creat resistance - cut the steel terminals off and solder on copper terminals. And you might trying connecting the voltmeter to the positive terminal of the battery and the other lead of the voltmeter connected to the starter frame and then attempt to start motor. And try going from the negative battery terminal to the terminal bolt on the starter and again attempt to start engine. Observe the action of the voltmeter in the two test. And you can limit a test to just a section do the circuit. You should find the problem. Do not rely on crimped terminals - solder should be used.

Another thought - I put about 4 gaskets under the carbs and and blocked the heat risers and engine starts hot instantly, but this makes the car fair weather 50 degs F or above.

[Pvmt-Pndr]

I have replaced all of the cables to the starter, battery and motor. Only the positive ground to the block is 00. All others are what shoebox central sent me. I also upgraded to "military style battery connectors" along with copper connectors anywhere I could install them.

The distributor pointer is lined up with the "bump" on the crank.

Bill I did all these test last year but didn't drive the car near as much, I also only have a digital volt meter. The car failed multiple test so I bought/made more battery cables. After that it passed all test but reminded slow to crank while hot.

When I bought the car the starter only had a couple cranks left in it until it died. I happened to find a starter in the truck, I verified it worked before I installed it and cleaned the brushes. It was surprisingly rust free when I opened it up but I cleaned everything anyway and installed it. I suspect the starter as most of my problem now. I do not see me upgrading to the 12v kit that I have quite yet as I recently bought another house and am getting that livable. I could get another 6v starter and hope for the best for ot when I do upgrade to 12v as I've read a 6v starter will work with a 12v system.

I just want to jump in this car and drive it when and where I want knowing that I'll be able to restart it every time. After my second time of shutting it off once hot now I question if it will restart as it only gets harder to start the more/longer I let it sit as it's hot.

[tubman]

What kind of battery is in it and how old is it?

A long time ago, the only battery I could find in a pinch was a Group 1 (made for Plymouths, Chevrolets, Studebakers, and various tractors). It was quite a bit smaller than the proper Group 2L my '51 took, Even though it was new, I had to leave the hood open on hot days to make sure it would start. I went to an 800 CCA Optima which solved all of my problems.

[Pvmt-Pndr]

This is what oreillys had available when I bought it about 2 years ago or so.

[petehoovie]

Originally Posted by Pvmt-Pndr

This is what oreillys had available when I bought it about 2 years ago or so.

[FortyNiner]

Originally Posted by Pvmt-Pndr

I have replaced all of the cables to the starter, battery and motor. Only the positive ground to the block is 00. All others are what shoebox central sent me. I also upgraded to "military style battery connectors" along with copper connectors anywhere I could install them.
.

There's your problem.

[pistonbroke]

That very battery was my hot starting problem. Go with the optima. Tim

[TJ]

I would look at rebuilding the existing starter. Sounds like you cleaned it up, but did not rebuild it. Rebuild it and add the Optima and you should be good to go.

[Pvmt-Pndr]

I'll be purchasing a red optima today. I guess I'll have a nice optima for my tractor once I do upgrade the merc to 12v. Ill see what the battery does and move onto the starter from there. Thanks guys Ill report back at my findings with the new battery.

[Fritz]

I’m not familiar with what Shoebox Central sells for battery cables, but they all need to be 00.

For the 6v Optima, your only option is the 6v Redtop. They really are by far the best 6v battery.

[tubman]

Originally Posted by Fritz

I’m not familiar with what Shoebox Central sells for battery cables, but they all need to be 00.

For the 6v Optima, your only option is the 6v Redtop. They really are by far the best 6v battery.

I saw a "Yellow Top" ad the other day. It offers a battery that looks just like a "Red Top" except that it's yellow for $138! Does anyone have any information on these? Sounds too good to be true!

https://www.mlperformance.co/product...lowtop-battery

I also thought I saw a 6 volt "Blue Top" in my wanderings around the internet, but can't find it again.

[DFS]

This has been a very through and expert discussion of hot starting issues. Not mentioned, is there a resistor in series with the 6V ignition wire, like my '37, or had this been eliminated by 1950? This resistor is heat sensitive. The resistor cools off quickly on its own when the ignition is off, but if not well insulated from the hot firewall, it's resistance can stay high, the coil voltage will be low, and starting can be difficult.

[JayChicago]

Originally Posted by DFS

This has been a very through and expert discussion of hot starting issues. Not mentioned, is there a resistor in series with the 6V ignition wire, like my '37, or had this been eliminated by 1950? This resistor is heat sensitive. The resistor cools off quickly on its own when the ignition is off, but if not well insulated from the hot firewall, it's resistance can stay high, the coil voltage will be low, and starting can be difficult.

Have to disagree with that.
The resistor's voltage drop change cold-to-hot is only a few tenths of a volt. Not enough to make a difference.
The resistor gets so hot you will burn your fingers. Any additional warmth radiating thru the firewall is negligible.

[tubman]

This discussion is kinda off the point as the post-48 Ford products no longer used that type of resistor.