temporary relay defeat

   / temporary relay defeat #1  

RobertN

Super Member
Joined
Apr 6, 2000
Messages
8,655
Location
Shingle Springs California
Tractor
New Holland TC40D
My TC40D wont start. I am 99% sure, based on feedback from my tractor mechanic and from here, that the glow plug reley is not working. It has been cool enough around here(mid 20's) that she does not want to start.

The tractor is down in the shed with no power, lights, or room to work around it.

Wonder if I could just bypass the realy to start it and get it to the garage?
 
   / temporary relay defeat #2  
Robert, I'm taking it that your symptoms are the engine is cranking over, but not firing. It could also be bad seat switch that is keeping your fuel solenoid from opening. The solenoid is on the back of your injector pump and you can jump 12 vdc directly to it to check it. I also don't think there would be any problem with jumping 12 vdc directly to the glowplugs and bypassing the relay for a few seconds.
 
   / temporary relay defeat #3  
I do not own that model of tractor but I worked with a fellow how had glow plug problems and he took a lead to the common positive of the glow plugs. It will draw around <50 amps for a 4 cylinder. If you time your jumper the same as you normally do maybe 10-15seconds. I use to check my glow plugs every fall with a special meter to make sure they were working.
Craig Clayton
 
   / temporary relay defeat #4  
Craig, our main fuse on our tractors is 40 amps, and the glowplugs are normally fed from that fuse, through the ignition switch, and relay contacts. I think they are low-current types, probably less than 5 amps each when they heat up. They are only 0.8 ohms when cold, and that would indicate over 10 amps each, but resistance will rapidly go up or we'd be blowing fuses everytime we start our tractors. For jumping power to them, a good heavy wire is surely indicated to keep it from getting hot. :thumbsup:
 
   / temporary relay defeat
  • Thread Starter
#5  
It's blowing plenty of smoke.

It has been persnickety before, but with the cool weather it just did not want to go last weekend. I brouhg the battery to the garage, and put a maintenenace charge on it, after cranking it over a bit.

All the switches were working. I made sure of that previously, since my 16 year old son was doing the mowing at my parents 8 acres. Although I dislike the switches, I want the safety when the kid is on the tractor.

The mechanic/shop I got it from, thought the relay might be getting flaky; I should have replaced it sooner. It has had the glow plug light come on at odd times, but typically not during startup.

Robert, I'm taking it that your symptoms are the engine is cranking over, but not firing. It could also be bad seat switch that is keeping your fuel solenoid from opening. The solenoid is on the back of your injector pump and you can jump 12 vdc directly to it to check it. I also don't think there would be any problem with jumping 12 vdc directly to the glowplugs and bypassing the relay for a few seconds.
 
   / temporary relay defeat
  • Thread Starter
#6  
I was at the fire station all day covering; big structure fire. Didn't go to the fire, but spent all day running other calls while first out engines were at the fire.

I put the freshly charged battery back in the tractor. It spins over real nicely. But all it does is blow smoke.

Little history:
It has been hard starting in cooler temps since I got it last year(Super Bowl Sunday actaully...). It never has had the glow plug light on the dash light up when starting. From what I read, it should be like my pickup; turn the key to ON, and the glow plug light will light up. When it goes out, it should start.

Well, it never has. Although, the glow plug light has gone on at odd times(not very often) for a couple seconds.

So now, we have had a cold(for central Calif) snap. It has been 20's at night, and 30's during the day(it is 38F right now, 1:30 PST). And, it appears I have no glow plug operation.

The schematic I have, indicates I have a glow plug timer, that activates a glow plug relay.

So I am back to the shed, with a couple flashlights, grubby cloths, and a DVM... and maybe a jumper wire...
 
   / temporary relay defeat #7  
To RobertN
If you have smoke then there is fuel being delivered to the cylinders but it has not reached the flash point to fire. What grade of engine oil are you running for your temperature zone, 10/30 diesel should work. If you install a block heater or a lower rad hose inline heater it will raise the engine temperature. Then it will be like a summer time start in the lower temps. You can also add gasoline to diesel fuel to make it flash better, the rule of thumb I know of is 10% max.
Craig Clayton
 
   / temporary relay defeat #8  
Robert, I think you will find that the ultimate resolution is a new glow plug timer (not the glow plug relay). Our tractors, including mine, have history of going through timers. It's $65, but it solves the problem.

In the meantime, I'd get a 12 awg wire and put a momentary on switch inline. Hook it to 12 vdc and the the other end to the glowplug bus. Cycle it for 5 or 6 seconds and your tractor should fire right off.
 
   / temporary relay defeat
  • Thread Starter
#9  
All the fuses look ok(ohm out ok when removed. Two get voltage with the key off. The rest get voltage with the key on.

It looks like, to get to the relays, I have to remove the lower black cover on the left side.

I just came back from the shed to get some sockets and coffee...

So Jim, is this a simple relay? Will we able to use some other relay in 20 years when the part is obsolete, or will we have to change to a momentary switch?

I'm going back in a few minutes, and remove the panel, poke around for some voltages as long as I have the meter out. If nothing else, I will have it ready to swap when the timer comes in(Guessing I will order one tomorrow...).

As long as we don't get snowed in in the next week. Last year we got a couple feet of snow(unusual here). The old Kubota was 30 miles away at a friends that I was helping. The one time I coulda plowed snow. Needless to say, my wife was not impressed :eek:
 
   / temporary relay defeat #10  
Shucks, auto parts stores can supply relays.

Horn or headlight relays come to mind, however the timing function would not be available so you'd resort to counting thousand and one and two etc as you are now the timer!
I rigged my old GMC 6,2 diesel that way due the the high cost of the GM unit.

One gur I knew simply had 2 HD wires under the dash and he'd pinch them together and start counting. Ran that way for some 5-6 years. LOL!
 
 
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