How to troubleshoot B7800 fuel delivery issues?

[eserv]

White/ blue wire at the relay should be very close to battery voltage. any less and it won't work ( try temporarily applying power via jumper to white/blue wire with the relay connected) jumper from red to white/blue should energize the relay and so energize the fuel solonoid)

 

[eserv]

The fuel relay is just an electric switch, apply power to the white/blue terminal and the black terminal and it closes the switch so power can go from the red terminal to the white terminal. Simple as that! no need for any diodes!!

 

[ADDfarmer]

Got it, thanks! I'll report back on my findings tomorrow.

 

[ADDfarmer]

The fuel relay is just an electric switch, apply power to the white/blue terminal and the black terminal and it closes the switch so power can go from the red terminal to the white terminal. Simple as that! no need for any diodes!!

After all my headaches I've learned a bit more about relays. It seems that the use of diodes is more pervasive than not. The reason diodes are used is to keep power surges from the collapsing coil from causing more wear on the contacts, as well as back-surging. I'd like to think that none of this conversation would have taken place had the light circuit relays I installed NOT had diodes in them (which wouldn't have cared which way they were wired on the switch side).

 

[eserv]

Many relays have Diodes and maybe those ones should! There ARE two diodes on the safety switch circuit of your tractor between the HST pedal and the clutch switch ( if yours is HST) they prevent backfeed there. I'm just telling you so you know, not that I think they are part of the problem! Usually if either of them fail they short and you'll keep blowing the 5 amp fuse.

 

[ADDfarmer]

Many relays have Diodes and maybe those ones should! There ARE two diodes on the safety switch circuit of your tractor between the HST pedal and the clutch switch ( if yours is HST) they prevent backfeed there. I'm just telling you so you know, not that I think they are part of the problem! Usually if either of them fail they short and you'll keep blowing the 5 amp fuse.

Great! I can't wait for more electrical fun!

Actually, I should probably re-check the fuses! My conundrum started because I'd had lost my dash lights and it wouldn't start. The new improperly wired light relays resulted in blowing the 5amp and 10amp(? dash) fuses. And at first I didn't even know there was a fuse block! (pretty stealthy- long story)

The more info I read on relays it seemed that there was really no reason to not incorporate diodes. I don't think that the diodes tend to fail (unless you hook them up backwards! ), and they're pretty cheap and easy to incorporate into relays (now then, if I can only figure out how I can replace the blown diodes in my initial two relays... at $20 a pop I don't want to pitch them.)

 

[North Idaho Wolfman]

ADDfarmer,
If you send me the relays I'll repair them if I can get them open, the diodes they use are about $1.00 / 100 and I have a ton of them.
Just send me a PM.

 

[ADDfarmer]

Wolfman, thanks for the kind offer. I think that I am able to do the repairs on the Bosch relays- they can be opened; issue/concern is with the light wire on the coil and subjecting the heat from the soldering iron (I've got experience with soldering though).

OK... I ran tests this morning and I find that I get the solenoid clicking when I jumper, on the OPC wire harness (unplugged), the red/white wire to the white/blue wire. I first check to ensure that the continuity on the white/blue wire was sound: I also used a light bulb in-line to act as a fuse (as well as the tester light's) so that I didn't have to worry about messing up the wire.

The good news is that the shutoff relays are good. Well, that they are properly switching at 12v.

The bad news is that the voltage coming through the OPC isn't enough to switch the relay. Again, I'm seeing roughly 6v here.

Is the OPC bad? It seems to be doing everything it's supposed to do (I can mess with the safety switches and cause it to not allow the starter to be engaged), but only allowing 6v (instead of 12v) to the shutoff relay? That seems to be a rather nuanced failure.

I know that I'd removed the tap that I had to the OPC's red/white power for my light circuits and that that didn't have any effect, which would mean that those circuits are not interfering (now).

Could I have damaged the OPC during my screw up with the first installation of the light relays in which I'd had the switching reversed? Again, any such damage seems pretty nuanced: I'd figure that damage would result in an internal short (very obvious).

Any way I can verify the integrity of the OPC? Some resistance numbers I could check against? How much is an OPC?

Is there any mechanical activity in the OPC that might have something sticking? Maybe smacking it might make it work (I need some additional outlet for my frustrations!)?

 

[ADDfarmer]

The OPC is functioning except to deliver the right voltage to the fuel shutoff relay. So... rather than shell out $200+ dollars for a new OPC I decided to bypass the OPC for the switching power to the fuel shutoff solenoid relay.

I cut the white/blue wire to the fuel shutoff solenoid relay and spliced into the red/black power wire going to the OPC (same one I'm pulling power to switch new light circuit relays).

All is functioning exactly as expected. OPC is still handling safety switches (won't start unless all checks clear), the fuel solenoid relay is engaging the fuel solenoid when the key is switched to ON, and the tractor starts and runs fine. Oh, and I have my auxiliary lights! (will be adding more lights )

 

[Frostbyte]

I realize this is a really old thread but I was having some issues with the stop solenoid on my B7800 tractor and came across this discussion.

Just FYI, if you use LED lights you can get a decent lighting set-up without putting in relays and all that headache.

I have a 48-inch single row light bar and two work lights for the equipment attachments in the rear in addition to the stock headlights on the front cowling. The light bar is set up on the ROPS under the canopy (tractor has a fiberglass canopy shade) and the work lights that shine on the attachments are mounted to the back of the rollbar. I didn't have to do anything particular to get this all to work except tap into existing light circuits.

This gives me very good illumination of my work area. I can mow at night with the finish mower if I want to and it's great for moving snow with the loader bucket. It lights up the operator area indirectly with a nice subdued bounce off the canopy and it lights up my implement attachments so I can see to hook and unhook, grease where/when needed, and such type of normal operations.

Everything comes on when I turn on the headlight switch. This tractor never goes on the highway and especially never at night. I don't need a bunch of switches, I just need LIGHT when I hit the light switch. I get plenty of light with this rig.

LED lights don't draw anywhere near the amps that incandescents do. They're not nearly so prone to overload a circuit and they don't pull enough power to mess up the balance with a stock alternator/dynamo and standard battery. It's a LOT easier if you just use LED lights, which probably weren't available in 2013 when this thread was started.

I realized this was the way to go with my tractor because I had done the same thing with my boat, the little alternator on the outboard couldn't keep up with lights and electronics until I switched all the lights to LED.

I also put in a 12v power socket and a phone mount so I can listen to music, use and keep my phone charged while I'm on the tractor.

I realize this isn't what the thread is about but the OP began his way of sorrows when he installed new lighting so ... I just thought I'd throw this in here for anyone contemplating putting lights on their tractor.