Help with Ford 3930...no crank

[Jason280]

I've had a early/mid-90's Ford 3930 for years, and never had any issues with the tractor...until several months back. Went through multiple episodes of sluggish acceleration/low power, ultimately figured out I had algae growing in the diesel (clogging the fuel petcock and injector pump inlet screen). I cleaned the tanks/filters/lines, added and cycled through biocide, and *think* I have that issue sorted.

I've gotten in the habit of cranking/running it every couple weeks, just to be sure the fuel is getting cycled around (and isn't sitting too long). Hopped on it a few days ago to crank, nothing. Starter doesn't move, no noise, nothing. I can hear a slight "click", but that's it.....lights all illuminate on the dash, and headlights come on when switched.

The neutral safety switch on the high/neutral/low shifter has been fickle before in the past, and occasionally would require a little "jiggling" to get it to crank. This time, no amount of jiggling made any difference. So, I went ahead and bypassed the neutral safety switch...no change. Checked voltage at the battery, it's showing 12.4-12.5v (battery is less than 1 year old). Just in case, hooked a jump pack in place, still nothing.

Not sure how to proceed from here. It really *seems* like some sort of safety switch is preventing any cranking to proceed. I know it has a PTO safety switch, not sure about a seat switch. I guess I could try jumping the starter solenoid, but that's not anything I've ever had to do before. It's likely something simple, just need some ideas on troubleshooting before I get back to it tomorrow.

 

[TractorTech]

I was going to ask if you checked/bypassed the PTO switch. Jumping at the starter would be the first thing to do after inspecting the PTO switch for obvious problems as it will tell you if the starter and solenoid are functioning.

 

[Jason280]

What's odd, its doing the exact same thing as before (with regards to the neutral safety switch)...its just jiggling (or bypassing the switch all together) now does nothing.

 

[Roadworthy]

A good starting point is monitoring the battery voltage when attempting to engage the starter. If it stays at the same point you have something keeping the starter from engaging. If it drops significantly - say below ten or so - the battery may have issues. Have it load tested. In any case clean the battery terminals well as well as the insides of the cable connectors. Examine the cable connections for signs of corrosion which can impede current flow. Replace connectors onto the battery and tighten securely. If you can move them they're not secure. Follow your ground lead to the frame connection. Clean and tighten there, too. Now you're ready to begin troubleshooting, or you may have already fixed the problem.

 

[Jason280]

Here's what I've been able to check so far...

Battery reads 12.34v with no load. Not ideal, but should be enough to at least engage the starter.

I tried a different jump pack, and was getting 15+ volts to the battery...which dropped to 14.8 or so with the key engaged. I did a load test on the battery, and it reads "good".

Looking at the starter, I'm not even sure how you even begin to jump start/override the solenoid.

As far as the "clicking" noise, I've isolated it to a relay near the battery. Not exactly sure what it does, but you can hear/feel it "click" when the key is turned....but still no starter involvement, just the "click".

Backing up a little to the neutral safety switch, it simply consists of two wires that feed through a grommet in the top of the shifter housing and connect to the switch inside. If my understanding is correct, the switch remains "open" until in the center position (neutral), which closes the switch. To bypass this, I've simply cut the two wires behind the dash, and closed the connection with a wire nut. Next guess would be the PTO safety switch, which will require bypassing as well.

Other than that, I am not sure how to proceed.

eta: I'm considering putting the battery on a charger anyway, but doubtful it will make any difference.

 

[TractorTech]

Looking at the top of the starter, you have to remove the nut on the post holding the plastic safety cover over the solenoid. Once the front of the solenoid is exposed, you will see that there is a small lead, usually on a spade tab. That is what gets energized when the key is switched to start and all neutral switches are satisfied. Make sure the transmission is in neutral, take a jumper wire, from the positive post of the battery and touch it to the spade connector on top of the starter solenoid on top of the starter. If it turns over, then the starter and solenoid are good. Start looking up the line at the PTO switch or, possible the relay that you posted in the picture. Bypassing them until you find the culprit.

Also, your description of the neutral switch in the transmission in correct.

 

[Semper Paratus]

My 3930 in 6 years has been through two PTO safety switches. They are not particularly easy to jumper out without 5 -10 minutes of disassembly. When mounted the switch pinches the weather boot between the switch and the transmission body.

 

[ROUSTABOUT]

I've had a early/mid-90's Ford 3930 for years, and never had any issues with the tractor...until several months back. Went through multiple episodes of sluggish acceleration/low power, ultimately figured out I had algae growing in the diesel (clogging the fuel petcock and injector pump inlet screen). I cleaned the tanks/filters/lines, added and cycled through biocide, and *think* I have that issue sorted.

I've gotten in the habit of cranking/running it every couple weeks, just to be sure the fuel is getting cycled around (and isn't sitting too long). Hopped on it a few days ago to crank, nothing. Starter doesn't move, no noise, nothing. I can hear a slight "click", but that's it.....lights all illuminate on the dash, and headlights come on when switched.

The neutral safety switch on the high/neutral/low shifter has been fickle before in the past, and occasionally would require a little "jiggling" to get it to crank. This time, no amount of jiggling made any difference. So, I went ahead and bypassed the neutral safety switch...no change. Checked voltage at the battery, it's showing 12.4-12.5v (battery is less than 1 year old). Just in case, hooked a jump pack in place, still nothing.

Not sure how to proceed from here. It really *seems* like some sort of safety switch is preventing any cranking to proceed. I know it has a PTO safety switch, not sure about a seat switch. I guess I could try jumping the starter solenoid, but that's not anything I've ever had to do before. It's likely something simple, just need some ideas on troubleshooting before I get back to it tomorrow.

I've dealt with that. It was a crystallized end of a battery cable. Where the lead is molded on the wire.

 

[blehmann]

Multiple times in my life on multiple vehicles having the same problem. It has almost always been the ground cable corroded where it bolts to the frame. Pull it off. Sandpaper the terminal and the area on the frame around the bolt hole.

 

[Jason280]

7/30 Update

Finally had a chance to play around with the tractor again. I pulled the input(?) wire off the starter solenoid, and tested the connector...I get 11.9v with the key switched to the "CRANK" position. Seems like it would be enough voltage to close the solenoid, but not 100% sure. I tried to use my Power Probe to apply 12v to the ignition input on the solenoid, but simply can't reach it...the post itself is recessed enough that I can't get to it with the probe extension, and its pretty well blocked by the filter housing. So, on the plan B. I used a 8ga wire, and jumped the solenoid terminals....turned right over and cranked without issue.

Good news is, tractor ran great. Doesn't *seem* to be any fuel related issues that I can tell, so maybe the biocide killed all the growth. I'm assuming the starter solenoid is bad, so I'll look into finding a replacement today.

 

[Harry in Ky]

The spade on the starter solenoid is always hard to access. I have a number of "home made" jumper wires (short lengths of wire with crimp on terminals on one end and just 1/2" of wire stripped on the other end) Male, female spades, different size ring terminals, etc. I take one with a female spade and push it onto the solenoid. The wire is long enough to reach around and "flash" to the battery positive starter post or connect to a remote start button. Easy to work with.

 

[Jason280]

Any reason to think it's not the starter solenoid st this point?

 

[blehmann]

If you are putting power to the solenoid spade and it engages and the starter turns, it isn't the solenoid. More likely a dirty switch or something else keeping full voltage from getting to the + side of the solenoid.

 

[Jason280]

No, I couldn't get to the spade...I manually jumped the main terminals.

 

[blehmann]

I'm not understanding what pulled the Bendix in to the ring gear if you are saying that you by passed the solenoid.

 

[blehmann]

Let me reword that. I haven't been into my 3930 starter yet so I'm not sure of the set-up. They are all basically the same though. If you were able to jumper to a post on that starter and the bendix engaged and cranked the engine, the starter is functional. Your problem is somewhere upstream on the wire going to the post that you jumpered power to. It could very well be a relay with badly arched contact points. The click you hear is probably the relay closing. The lack of starter relay engagement is because not enough power is getting through the high amp side of the rela

 

[TractorTech]

Still betting the PTO switch or the relay.
The PTO switch could be out of adjustment.

 

[Jason280]

I'm not understanding what pulled the Bendix in to the ring gear if you are saying that you by passed the solenoid.

I have 11.8/11.9v going to the ignition terminal on the starter solenoid. My plan was to simply apply 12v to this terminal with the wire removed, but couldn't access it...its pretty well blocked by the plastic shroud around the solenoid and the filter housing. So, instead of applying 12v to see if the solenoid/relay closes, I simply applied a jumper wire to the main solenoid posts.

The click you hear is probably the relay closing

No, the starter solenoid is not clicking (or making any noise). The relay I can hear closing is the one in the last two pictures on page 1...its some sort of electrical relay, but not sure what it controls.

 

[Harry in Ky]

That's the start relay. If it clicks when the key is turned to START then I'd say the key switch and safety switches are working. Relay contacts are bad or the wire from the relay to the solenoid spade has a problem.

OR the solenoid is bad. The jumper wire connecting the spade to battery positive would have told you that.

 

[blehmann]

I don't think that the solenoid is bad. It started the tractor. Solenoids are either good or bad, no in between. I'm assuming that when you used the 8 gauge wire, you robbed power from the large lug on the end of the starter. If the solenoid has two spades, one is positive input and the other goes to ground. Placing a wire across the two spades would create a short circuit if the positive terminal is powered because the only load would be the resistance of the 8 gauge wire. Touching a hot wire to the negative side of the solenoid would also create a short circuit. You have a problem with the wire or with something in-line on that wire that is reducing voltage or blocking it. As I said earlier, the easiest and first place to check for me is always the ground cable. It is a quick check that probably fixes at least half of the no start issues on equipment that doesn't get used daily.