Ford New Holland 1920 starting issue

[Soundguy]

my comment ont he stuck clutch was aimed at the screwdrivering comment by the prev poster... starting the tractor fromt he ground is a great way to become a statistic..

 

[RobertBrown]

my comment ont he stuck clutch was aimed at the screwdrivering comment by the prev poster... starting the tractor fromt he ground is a great way to become a statistic..

Oh...I didn't notice that post.....
I don't do the screw driver thing, Sparks are bad....Sparks scare me...but thanks for the information.
Hopefully I can keep the safety switches in tact as I can be easily distracted and I'm a firm believer in Murphy, his law, and statistics

 

[RobertBrown]

After lot of testing, dis-assembly and deduction I have arrived at the following:
The problem lies with the safety start relay. This is the culmination of the circuit containing the neutral switch and the P.T.O. safety switch. This circuit operates a relay and closes an n/o switch that allows the starter solenoid to operate.
I have tested and re-tested all of these safety switches, the relay and the ignition switch. All switches/relays function as they should when tested with a meter, and meter with a power source.
The really weird part is the relay works when tested with a power source but will not when plugged into the connection provided. I tested the connection with my meter when turning the ignition switch and I have 12 VDC, but the relay does not operate. it took me to long to figure that out. I am now a lot more familiar with my machines electrical system, but I'm not sure if I should replace the relay or not.
I have located the part. It turns out that same relay is commonly used by an import car maker. The manufacturer is still around but like most it now has a different name. The really cool part is I can get it at Rock auto for about 27$ plus shipping and it will plug right up.

So...why would the relay work with a separate power source and alligator clips but not when plugged into the receptacle provided?
first thing that comes to mind is negative ground. When I tested the receptacle I grounded the meter to the battery. I don't know how the relay is actually grounded during normal operation. Perhaps the problem lies there.

I have a wiring diagram for that machine and it indicates that there are 3 safety switches...... I can only find 2. The manual indicates there are only 2.

 

[PoorPlowboy]

Check mouser if you have the info on the relay. They save me a lot of money.

 

[RobertBrown]

Check mouser if you have the info on the relay. They save me a lot of money.

tried it...no luck. Probably because it's an automotive application?

 

[Soundguy]

the meter has a megaohm input inpeadance at least.. probably more. that line will show as 12v on the meter to the relay. but under the real load from t he relay.. it like drops off.

could be a bad safety switch contact ( either of them ).. or bad wire connector.

to test this. hook relay up and keep meter on the line that goes 12v. then operate tractor as you would. see if you still get 12v there.. or something lower.. like 0-8

 

[RobertBrown]

So your saying there may be voltage but no current or insufficient current, not apparent by the using the meter.
I suspect the neutral safety switch and I plan to dissemble that next weekend. At that time, I will post photos.

 

[Soundguy]

Exactly, the meter could see 12v nut the line may not carry it under any real load, its at least something to test since you say the relay operates fine if you jump power to it externally, and the trigger line to it shows 12v on a meter, that would be my next check, voltage under load, I'd it is too low, relay won't pull in

 

[RobertBrown]

During my testing I noticed some significant voltage drops and some warm wires as I was turning the key and starting the glow plugs to test the circuit. Eventually I removed 3 wires from the Ig. switch so that I didn't blow a fuse or kill the new battery. So I was thinking that the glow plugs may be the culprit or something in another circuit that brought this whole thing on to begin with.
I'm wondering if I can't just remove the plugs from service as I think the machine will start fine without them. I may have a problem with the the timer.
The machine would not run without all 3 of the wires connected as 1 of them went to the fuel shut off (2 of the wires joined immediately after the switch). That makes me think the switch is not the correct one although the installation looked like factory....to me

 

[Soundguy]

i think i'd leave glow enabled.. as it should still help it to start easier.

if you are worried about the draw thru the control ckt. rig it with a push button and solenoid