New Holland/Ford 3930 Fuel Solenoid

[jgriswol538802]

I have a 3930 with about 680 hours. I had a problem with mice chewing the wires to the instrument panel. I put the wires back together with splices and was able to get the tractor running again, although I still don't have it completely right as the gauges aren't working correctly.

However, it would crank, run, and shut off. Over time it started to take longer to fire. Sometimes it seemed to only fire when I let off the starter. Other times it would crank and fire as normal. Then after a while it wouldn't fire at all.

I checked the fuel solenoid. I could not hear the solenoid click when the key was turned to ON ( never claimed to have good hearing ), but I checked for 12 volts at the solenoid when the key was turned to ON and had 12 volts every time. I pulled the solenoid out and grounded it, then applied 12 volts. The plunger was actuated and pulled in each and every time. The plunger felt a little rough as it moved in and out, but again it worked every time voltage was applied. It appeared to work so I moved on.

Since I did not know when the fuel filter was changed and the glass bowl looked pretty dirty, I replaced the filter and cleaned the bowl, which had a fair accumulation of black crud. I reassembled everything and used the bleed screw to fill the bowl and filter. I cracked the lines at the injectors and cranked the engine over. I cranked for quite a while without seeing any fuel come out of the lines.

Since I still could not hear the solenoid and couldn't see it working, I pulled the solenoid and removed the plunger. I reinstalled the solenoid without the plunger. After cranking for a while I saw fuel being pushed out of the injector lines, the engine fired and ran. I closed the lines and the engine ran fine. I used the tractor to do some work to let it run for a while. It ran fine. Only problem was I had to stall the engine to shut it down.

I thought I had narrowed the problem down to a bad/weak solenoid. I ordered one off ebay. I put it on tonight and attempted to crank the tractor. No luck, Assumed that I had air in the system so I bled it again. I never saw any fuel come out of the lines. I pulled the new solenoid and grounded it while I turned the key on. The solenoid worked each time. I put the old solenoid body with no plunger back in, bled the system and it cranked again. It took a while to get fuel to come out the lines, but I have little to compare to since this is the first time I have done this.

Any ideas on what else to do? Should it be a lot harder to get fuel to the lines with the solenoid installed. I cranked for quite a while with the solenoid installed and never saw fuel. I did not want to burn up the starter by running it too long. Is there another place after the solenoid but before the injectors that I can open to see if fuel is getting past the solenoid? I got an aftermarket solenoid. Was that a mistake? It looks like the original and seems to work as it should.

Thanks for any ideas or help.

 

[Harry in Ky]

Okay, so you have 12 volts(+-) to the pump coil with the key on? What do you have while cranking? It's quite possible, and not uncommon, for the coil to somehow end up being powered from a circuit that goes dead while start circuit is engaged. That will give the symptoms you described.

 

[kydick]

have had that problem. could be a bad ignition switch. tried a new one. when switched on a connection made but when it cranks it might lose connection. didnt help. wired a wire with a fuse from the switch to the solenoid and that would start and stop the engine. also some diodes in the dash that might be bad. that was my problem think there was 2 that was bad. replaced them and took the fuse out and put the original wire back on the solenoid and so far so good. if it happens again just have to put my fuse back in and reconnect to solenoid.

 

[jgriswol538802]

You are right on it. I had not checked for voltage once the switch moved into the start position. The voltage drops to less than one volt, but not zero. Of course, that would be a reason the solenoid would not stay energized.

Is there a way to test the switch without replacing it?

I know where the diodes are that you are talking about. They are in the wires behind the instrument panel. ( The wires that were chewed by the rat. )

Is there a way to test the diodes? If they are bad where did you get replacements?

It could also be that I don't have the wires connected properly. I found the wiring diagram on line but working on the wires without removing the cowl is hard as there is very little room.

Thanks for your help.

 

[kydick]

took the ignition switch out and used a ohm meter to see if it was connecting to the different terminals when i turned the key. i dont know how to check voltage. think i watched u-tube about the diodes. with a ohm tester you get a reading and switching the probes around you might not get a reading. if i remember right i think you need a reading both ways for it to be a good one. i got my diodes at the new holland dealership.

 

[jgriswol538802]

I worked on this again this weekend and straightened out the wiring so that all the lights and gauges appear to work correctly.

In the process I checked the two diodes that are part of the wiring behind the instrument cluster. Both checked good as they will only let voltage flow in one direction ( my multi meter has a setting for diodes ). The wiring diagram shows a total of four diodes, but there are only two behind the dash. You said you replaced the two behind the dash. Do you know where the other two are located?

On my ignition switch nothing happens when you turn it to the first position ( I assume that is the ACC position ) but it has always been that way. IN the next position the panel lights come on and the gauges function ( the IGN position ). At that point there is 12 volts at the fuel solenoid. In the next position ( START ) the starter is engaged, but I lose the 12 volts at the fuel solenoid.

I haven't tried taking the ignition switch out to test but plan to do that as soon as it quits raining.

 

[Harry in Ky]

Testing the switch next is a good plan. There may be an issue there, or you may find an unused terminal with power available in the start mode. Who knows? There are a number of different switches out there, not all of which have exactly the same configuration and circuitry.
I've found this problem on more than one occasion. The solution can be simple, but not always. The 30 series came with a much more complex electrical system than the earlier models. How much time and effort you wish to invest in tracking down your problem and what you're willing to accept as a solution is entirely up to you. What I have done on some occasions is to add yet another relay. The relay is wired to supply battery voltage to the fuel solenoid when energized. The control circuit is supplied from the start/crank signal circuit, thus while cranking, the fuel pump is turned on. This goes dead when the start switch is released and the ignition switch "run" position takes over.

 

[kydick]

no its been several years ago and i just cant remember all the paticlers about it. but just keep trying and i think you will figure it out.