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Delco and other Low Voltage DC Light Plants Antique Generators, Light Plants, Typically 24, 32 or 48 volt although some are 110 volt. DC Lamps, Motors and appliances.

Delco and other Low Voltage DC Light Plants

Delco 751 running problems


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  #1  
Old 08-02-2017, 03:21:39 AM
locknut locknut is offline
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Default Delco 751 running problems

Hi Guys,
I have obtained what I believe to be a Delco model 751 (1927, 32 volts) generator/lighting plant.The switchboard has a light bulb in relay behind it.
I use the red starting lever to engage the engine which then starts and runs ok.After running for a few minutes when I release the starting lever the engine stops! Before stopping the amp meter shows charging 10 amps.
My question is -when the engine starts and runs does the starting lever need to be fixed in the starting possition for the whole of the run period? If so will prolonged running in this possition eg at an engine rally( engine could be running for 6 hours) do it any harm?
The engine has the following numbers on it - HR20L, 2430 , 287662, the Zenith carb is stamped US pat Dec 29-08.
This is an usual engine over here and information is scarce,any help or advice would be much appreciated.Thank you.
All the best,
Kev.
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  #2  
Old 08-02-2017, 01:24:04 PM
FDChief FDChief is offline
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Default Re: Delco 751 running problems

Can you post a few pictures?
I may have a reprint manual for sale.

Thanks
Jeff
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  #3  
Old 08-03-2017, 01:35:21 PM
locknut locknut is offline
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Default Re: Delco 751 running problems

Hi Jeff,
Here is a picture of the engine showing the red starting lever

I will try and get a picture to show the whole engine later.
Thank you .
All the best,
Kev.

---------- Post added at 06:35:21 PM ---------- Previous post was at 06:30:58 PM ----------

Hi,
Here is another view of the engine - I think that it is a model 751 - can anyone kindly confirm that or advise me which model it is?


All the best,
Kevin.
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  #4  
Old 08-03-2017, 09:27:28 PM
FDChief FDChief is offline
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Default Re: Delco 751 running problems

Cast iron cylinder or does it have the copper fins around the cylinder?

---------- Post added at 08:27:28 PM ---------- Previous post was at 08:20:47 PM ----------

Interesting that it has a 750 style flywheel on it
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  #5  
Old 08-03-2017, 11:05:23 PM
Radiomike Radiomike is offline
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Default Re: Delco 751 running problems

I too had problems with a Delco light plant, not sure of the model number now. This exhibited the same symptoms, started fine from the 32Volt battery and stopped as soon as the start lever was released. A quick look at the schematic revealed the cause, the potential coil in the start switch was open circuit. The coil is hidden behind the series coil which is visible.

So get a manual, take the cover from the start switch and check the potential coil for continuity. From memory it was around 250-280Ω.

I think your only option for this will be a rewind, if it is open circuit.

Your may be different from the one I worked on but it does look very similar. The manual will make it all clear.

Mike
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Old 08-04-2017, 09:25:13 AM
locknut locknut is offline
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Default Re: Delco 751 running problems

Hi Guys,
Thanks for your replies.
Here is a picture showing the top of the carb for information :-


Jeff - there are copper fins arround the cylinder
Mike - thanks for that - I will check the coil and advise.I have been able to find a wiring diagram for the engine so should be able to sort something out.
All the best,
Kev.

---------- Post added at 02:25:13 PM ---------- Previous post was at 02:22:31 PM ----------

Hi Guys,
Here is a picture of the top of the engine for clarity :-


All the best,
Kev.
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Old 08-04-2017, 09:48:43 AM
FDChief FDChief is offline
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Default Re: Delco 751 running problems

What is the serial number?
I do have an excellent service manual that covers all of the copper fin models, 17 different models including the automatic start.
The cost is $37.00 deliverd to you.
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Old 08-04-2017, 09:55:20 AM
George Andreasen George Andreasen is offline
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Default Re: Delco 751 running problems

Here's how it works: You lift the starting (red) handle and current flows to both the ignition and cranking circuits. When the engine starts, you wait until it gets to full rpm before releasing the handle. This is to give the circuit a few seconds to establish an electromagnetic "pull" via the two coils inside. Once the handle is released, a separate tab just above the handle is held up by the pull and keeps the ignition circuit complete, while the starting circuit is is disconnected by the (now lowered) handle.

To test:

Disconnect the battery leads and remove the sheet metal cover from the starting switch. Facing the switch you will see four connections, two on the right and two on the left. You want the two on the left.....these are the terminations for the inner coil of the switch.

Check to see if the wires are broken and connections are good. If they look okay, disconnect ONE of the leads with a screwdriver. Use an ohm meter set on the 100 ohms scale and clip the leads on the coil wires. You should get a reading of 300 ohms or so. If you get no reading at all, that coil is open. Unfortunately, this is a common problem with the old Delcos as that coil winding is very fine wire. After decades of vibration and temperature they tend to break internally.

To the best of my knowledge, I'm the only person winding replacement coils for these Delcos, but you can do it yourself with some patience. You'll need a spool of 37 gauge magnet wire, some copper "desoldering braid" (solder wick), heavy paper for a spool, light cardboard for end disks, Duco or epoxy glue, solder and a small soldering iron.

Disconnect all the coil leads inside the switch. Remove the 3/8" cap screw on the top of the switch body.....this will allow you to lower the two coils and the steel core...make note of the heavy insulated washers at each end. Pull the steel core and set it aside. Carefully remove the inner coil. You may get lucky and find the break on the outside, but it's doubtful. Test the outer, heavy coil with an ohm meter set on the "1" ohms scale first. Aside from insulation problems, these seldom give trouble so it's probably okay. Repair any insulation breaks with liquid electrical tape.

Okay, now we're going to wind a new coil.

Measure the overall length of the old coil carefully and record this information. Make note of the insulating washers at each end of the core and leave one of them in place.

Use a strip of heavy paper and wind it in a spiral fashion over the steel core, gluing it as you go. Don't glue it to the steel core....just to itself. After the glue dries, trim the ends square. Now cut two light cardboard end disks with holes in the center, like washers, that are a close fit over the paper. Slide the disks into place at each end and glue them to the paper by running a bead around the inside. Pay strict attention to the length, taking into account the two original insulating washers from the ends. This whole assembly is now a "spool" with a steel core.

Everything dry now? Good. Okay, pull the end of the magnet wire off the spool (careful...it breaks VERY easily) and glue it down at one end of the paper spool, leaving about 3 inches extra. After the glue has set, put that extra off to the side of the spool and begin winding. You want......brace yourself.....2300 turns of wire on that spool. If you're considering a battery drill to speed up winding, well, good luck. The chances are good that you'll break that hair fine wire and have to start over. The windings do not have to be perfectly flat and neat......just keep them as uniform as you can, but an occasional overlap or hump is not the end of the world. Hey, I use a coil winder and STILL get a few humps!

After all 2300 turns (or close to it) are wound, glue the end of the wire and cut it from the spool leaving about 3 inches of unglued slack.....just like the starting end. Carefully.......VERY carefully......use fine sand paper and clean the enamel off the wire ends (you may want to practice this before starting the coil!). Cut two 3 inch pieces of copper desoldering braid and punch a hole through one end of each with a sewing needle. Push the cleaned end of the magnet wire through the hole and bend it over. Heat the assembly with a small soldering iron and flow on ONE drop of solder. When cool, glue the entire soldered assembly to the coil body LEAVING THE 3 INCH SOLDER BRAIDS LOOSE. In addition to securing it, the glue will serve as insulation.

Test your new coil with the ohm meter and it should read 300 + ohms. If it's good, flow Duco cement over the whole coil and allow to dry. Slide some shrink tube over the braided desoldering wick ends, leaving enough braid exposed for eye terminals at the ends. You should now have a coil with braided leads at each end of the coil. Install the eye terminals, carefully slide the coil inside the outer coil and reinstall in the switch. Reconnect the battery leads and see if the engine keeps running after you release the handle. If not, try reversing the inner coil leads. That usually does it.

Last edited by George Andreasen; 08-04-2017 at 05:31:41 PM.
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  #9  
Old 08-06-2017, 01:33:27 PM
locknut locknut is offline
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Default Re: Delco 751 running problems

Hi Guys,
Thank you all very much for your replies - very helpful indeed.
George - Thank you very much indeed for your in depth detailed reply - armed with the information you have provided I should be able to sort the problem out.
Here is a picture of the starting lever mechanism ;-

When it is all connected up and the engine is working ( starting lever held up) there is no 'pull' at all - when the starting lever is released the connection is broken and the engine stops.
I have tested the left hand connections and got a zero reading - so looks like there is an open circuit - I was short of time today so could not investigate further and will have to wait until later in the week to work on the engine again.
Once again thank you all very much for your interest and replies.
All the best,
Kev.
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Old 08-08-2017, 09:47:20 PM
George Andreasen George Andreasen is offline
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Default Re: Delco 751 running problems

Kevin, I must be seeing things.........I swear there are NO wires on those left hand screws. Is it possible the inner coil is completely missing? If so, that would sure explain why the engine stops as soon as the handle is released!

You'll have to pull the coil assembly out for a closer look and let us know!
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