JD 730D Won't start under own power, will if you p

~On the cable connections,, while that's a possibility, if it cranks good now with the compression release pushed & won't crank under compression it will be easy to find a bad connection [if you do actually have one].. To do that, just try cranking the engine a few times then use your hand & feel all the cable & battery connections.. If you find a hot connection or hot battery cable clamp you have fond a poor connection... If you find a hot connection pull it apart & clean it..

~On the cranking RPM,, I did have that somewhere but can't find it at the moment & I'm not in my shop today... Keep in mind that those 2-cylinder diesels must crank pretty briskly to start cold.. If it is just dragging over on the starter it probably won't start cold..

~From your post above my gut feeling is you have two poor batteries in your battery box..

~If your tractor starts after just a little short pull off there is probably nothing wrong with your fuel system, fuel, or engine..

~Any questions be sure to post back or E-Mail.

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Like John T said, all terminal connections between the batteries and the starter must be absolutely perfect. This system draws tremendous amperage so connections are critical. I would also suspect that the two remaining batteries need to be replaced. You may want to try 2 good 12 volt batteries in series just to test things out. We have one 720 pony start and one electric and have gone to the 2-12 volt arrangement. It seems to be a little less troublesome than dealing with 4 batteries that need to be matched in performance (not to mention all the extra connections!).

I have seen the electric start 720/730's where the starter would not even bump the diesel when the decomp pedal was released, yet if you put the tractor in a lower gear the starter would motor the tractor along with the decomp depressed. That just goes to show you how much it takes to turn that beast over!

Now you know why the pony starting engine was pretty popular in its day! Cooler temperatures always pose a problem for any diesel, regardless of make. That's what begets glow plugs, engine heater, etc. but's let's analyze your problem.

You asked if it a cranking speed problem. The trite answer is that it is ALWAYS a cranking speed problem if the engine starts when pulled but not when using the starter. Either the starter is fine, but the engine is out tune enough that it needs more than factory cranking speed to start, or the engine is fine and the factory cranking system is turning the engine too slow, or somewhere in between.

You said:

~~He (previous owner) trouble shot the batteries and replaced two of the 4 six volts.

Replacing those banked batteries one at a time can be risky. What you can end up with are two new batteries able to yield maybe 400 or 500 CCA, but the old ones, while tesing well, could be limited to yielding 250 or 300 CCA. So your cranking speed will suffer immediately. Only by an exact load test could you tell the conditions of the batteries. It's a series/parallel circuit (2 - 12 volt loops) and the weakest battery will determine the ampere throughput of each leg.

Suggestion #1: Have all four batteries load tested on a quality machine.

~~It still won't start, it cranks at decent speed ( although I don't know how it should sound,...

Does it re-start using the starter after you have warmed up the diesel? If it won't, it's either turning over way too slow, or the diesel needs some attention, which might be no more than setting the valve clearance, adjusting the de-comp pedal linkage, and checking/re-setting the timing of the pumps. Even a poor electrical starting system should spin it enough to start after the big eninge is warm.

In a pony-start diesel owner's manual it says the pony shouild spin the diesel at 200 rpm. Now that's a pretty snappy jog, but I would think your electrical starter should spin it at around 100, so if you can eyeball the tach while it's cranking, you might see what the engine speed reads.

Suggestion #2: Tell us if it starts warm and how fast it cranks.

~~you let out compression release it just stops.

This is probably a good thing. Now we know the compression release relieves the compression enough for the starter to spin it, and when it closes you have enough compression to stall the starter.

Suggestion #3: Re-check ALL heavy cable connections between the batteries and the starter. You gonna need all the amps you can get! The starter might need to be inspected and checked for needing brushes and or cleaning.

~~Well the previous owner pulled it and within 5 feet she started right up.

This is good. Does the engine sound good when it runs? Does it charge? Does it warm up well...no stuck open thermostats?

Suggestion #4:

Get a really full charge in all the batteries. you might still have a weak one if not two. We drove it 1/2 hr home and it ran perfect.

Anxious to hear what you find.

Frank-in-Tallahassee
70D // 855 // VAC
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• F-I-T's webpage.....ALWAYS under construction....

First thing that comes to mind is still the battery bank, and if 2 of the 4 batteries were replaced as you say, unless the two remaining ones were load tested and youre absolutley sure they are in good condition, you may want to consider buying 2 more new ones to match the other. Any single weak battery can affect the 4 in series when a heavy load is called for, and its best if ALL batteries are matched. I recommend the absolute highest rated largest batteries in the frame size so they will still fit in the box. Make sure each and every battery and starter and ground connection is clean and tight (remove, clean and wire brush, and reattach ALL of them is best). I use the lower felt wahers PLUS that red battery terminal protectant, and once all is done that way you should get long trouble free battery terminal performance.

Like posted below, begin cranking with the compression release engaged till she revs and warms and frees up some, then dump the compression and hold ur mouth just right.

A good running and purge of any water or crud in the fuel system can help, and if she still has old fuel in her, you may want to consider a total drain and flush and new fuel and filter change. After that and youre sure ALL 4 batteries are good and all connections clean and tight she may improve on her own.

Good Luck n God Bless ya Joe

John T

How cold is it where you are at? 730s are hard to start in warm weather. You ned 4 good batteries and good clean conections and cables between them.
There should be a heater located in the lower water jacket just before it goes into the block.If it is not there it can be purchased from deere but they are expensive, about $75. Or you can install a tank type heater.That is what I have done to mine. Katts also makes a heater of this type for some of the big diesel trucks. They are 3/4 NPT and about 400 Watts.
Most local dealers that handle the katts tank heaters do not stock the screw in type heaters. I have checked on it and they can get them but they have to order a dozen at a time and they are a little over $30.
I have started mine by using a heavy duty battery charger hooked between 2 of the batteries to give it extra boost. Be very careful in doing this!
I usually get the diesel engine rolling with the compresion released until the oil pressure comes up at least half way on the guage be for I release the compression peddle. From what I have heard from people who have owned these tractors they are hard to start. Especially in cool weather.