# 6610S Diesel New Holland starts won't run



## Price Tuley (Feb 24, 2020)

Previously owned by the county, my tractor was poorly maintained. no lights worked and the horn button was converted to a starter button. Otherwise the tractor runs great. I corrected the wiring problems, rebuilt the safety circuit switches and replaced the light switch and the ignition switch. I made my own wiring diagram as what was available didn't match.
Now the tractor starts (kicks) but won't keep running. I have something wired wrong. There are two relays in the instrument cluster. One is in the safety circuit and the other actuates the starter. Do I have that right? I understand that to stop the tractor engine you remove the power from a fuel valve. My question is: what needs to be activated to keep the engine running? Everything is there when I crank the starter because the tractor fires, but when the ignition switch drops back to the run position it dies. It ran beautifully before I started. Thanks


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## thepumpguysc (Jan 25, 2015)

How many positions does your ign. switch have..
U need 3 minimum.. stop to remove the key.. run to activate the shut off solenoid & 1 more to activate the starter..
U have the starter & the shut off sol. on the same position.
Do u have glow plugs.?? IF YES, there needs to be 1 for them too..
On a Ford, its usually to the left.. so u would need a 4 position switch.
hope that helps.


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## Price Tuley (Feb 24, 2020)

I had a four position ign switch and replaced it with a five position (called for in the specs.) pos 1 is off; pos 2 activates two connections in which I have connected instruments, lighting circuits safety circuit and fuel shutoff. Position three does the same connections as Pos 2 but is the "run position" Position 4 is momentary and 1/2 way to the starter (pos 5). Pos 4 is connected to the thermostart circuit. Pos 5 is momentary and actuates the starter. The thermostart circuit is active with the start circuit. The connections in pos 2 and pos 3 are inactive during thermostart and start but becomes active again when the switch resets to pos 3 (run). No glow plugs. 

The tractor fires but does not run. It didn't do this before I started messing with it. Question: the fuel shutoff valve has to be activated for the fuel to go to the engine. Correct? Does the fuel shutoff need to be activated when the thermostart and starter is operating?


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## Ed Williams (Jun 13, 2019)

I am surprised again. A diesel engine with no ignition system won't run due to electrical problems. I am not familiar with a 5 position switch. The 4 position with the glow plug/ Thermal position to the left of the off position is pretty straightforward. After the heat position on the left, you have an on-off-start switch. Start goes to the solenoid, everything else to the on terminal. Can you repeat this with the 5 position switch? Things would be simpler. Might dummy the extra terminal with a jumper to convert to a 4 terminal arrangement.


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## Price Tuley (Feb 24, 2020)

I know this is messed up. Neither the old or the new ign switch on this tractor has a left of off position. I read about that in the manual. there are two relays with a bunch of diodes to direct the voltage lying loose behind the instrument cluster that I believe are not properly connected during the starting procedure. I had trouble tracing out the wiring, but one is in the saavety circuit and one controls the fuel shutoff valve, I think.

Do you know if the fuel shuttoff valve is active during the thermostart and starting periods.

Attacked are photo of relays in instrument cluster and some of my wiring diagrams. Remember, the tractor ran great before I started messing with it. It is something I have done in the wiring work. Thanks for being patient. I am an old elevator mechanic and have rewired and trouble shot many elevator operating systems, but this is my first tractor.


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## Fedup (Feb 25, 2014)

Seems to me your new switch is your problem. A five position switch should have an accessory and an ignition position. Not sure which is which, but it's positions 2 and 3. The ign should be "on" in all but position 1(off). The acc position will be dead in heat, heat/start. 

On some 10 and 30 series tractors they used a circuit from both ign AND acc to supply activation of the fuel relay with each going through a diode to prevent cross feed between the two circuits. There would also be a diode in the battery charge light circuit to prevent the charging system from keeping the relay energized after the key was turned off. 

I don't know what if any of this applies to your tractor. It's a 6610, yes, but the s models were assembled in Mexico and have a number of subtle differences. Electric fuel shutoff being one of them. I don't have any diagrams specific to the s models.


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## Price Tuley (Feb 24, 2020)

Thanks, I am going to the New Holland dealer today and buy the ign switch they recommend for the tractor. I will pick their brain on how to hook it up and will let you know how it comes out.


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## Price Tuley (Feb 24, 2020)

OK, I bought a ign switch from new Holland dealer and put it on. It worked intermittently. My main problem is that the fuel shutoff does not stay energized during all three: run, heat and start. After another day of intermittent electrical connections , bad fuse connections, and generally running around with one finger in my mouth and the other, you know where, I ran a jumper wire to the fuel shut off valve, thru a toggle switch to 12 volts. It works and I am tired of trying to make it work the proper way without correct wiring diagrams. All the lights work, which was my initial project and I added an LED light beam above cab roof so my son in law bush hog late into the evening or spot deer, his choice. I have traced out much of the wiring for a 1994 6610S New Holland tractor if anyone is working on one and wants to collaborate. Thanks for your help.


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## Fedup (Feb 25, 2014)

You might be surprised (or maybe you wouldn't) at the number of tractors out there with an "extra" switch just for that reason. It has never made much sense to me WHY anyone would need all the tricky parts and circuits just to power a fuel solenoid?


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