Need help with wiring.

[720axr]

I have a 1986 720 carburated. I recently set up a new battery on her and it seems like she couldn't handle it. Ever since I did that she's been having all kinds of electrical problems. My main problem is no power to my electronic fuel pump. When i turn my key nothing happens. No lights or anything but if I barely put pressure on it from on to start, I can hear my fuel pump kick on. I'm getting power to my starter but not the fuel pump unless I hit the right spot. 

 

Any ideas on what this may be and a plan of attack on how to fix this?

[datzenmike]

I thought the fuel pump came on with the ignition but no. It comes on when in START position and remains on if engine is running. Can you start the engine and does it keep running? or not?

 

 

 

 

1 hour ago, 720axr said:

I have a 1986 720 carburated. I recently set up a new battery on her and it seems like she couldn't handle it. Ever since I did that she's been having all kinds of electrical problems. My main problem is no power to my electronic fuel pump. When i turn my key nothing happens. No lights or anything but if I barely put pressure on it from on to start, I can hear my fuel pump kick on. I'm getting power to my starter but not the fuel pump unless I hit the right spot. 

 

Any ideas on what this may be and a plan of attack on how to fix this?

 

What exactly do you mean. "No lights or anything" Ignition ON will activate the gauges, charge and low oil pressure lights, brake warning light and wiper and heater if they are turned on. START position all of these turn off but the starter and fuel pump

[720axr]

What I mean by no lights or anything,  i mean I'm not getting any power whatsoever to my dash. After I had posted this I was doing some testing on my relays (i believe thats what they are) to see if I had blown any. Under the dash on the passenger side, theirs a relay or solenoid (forgive me for not knowing the correct term) I had cut the power wire and I magically got my fuel pump to stay on. Now that's fine and all but i need power to my dash now. Where should i go from here? I'm very stumped on this one. If you need pictures just let me know and i can upload some tomorrow when it's light out again.

[720axr]

To answer your question, I get nothing as I turn the key, even in the ON position. Once I get into START she runs better than ever oddly enough. Very weird.

[datzenmike]

Do the gauges ever come on? Does it start and run???

 

The ignition switch should turn the first 5 fuses on the left side of the fuse box and the 6th and 7th accessory fuses for radio and wipers. 

[720axr]

The gauges do not come on. I have absolutely no power to the dash. No gauges or anything. It starts and runs fine. I have wipers and lights but no turn signals. All my fuses are good too.

[datzenmike]

Gauges and turn signals are on the same fuse.... 4th over from the left side of the fuse box. Don't trust fuses. It's 15 amp so swap with another fuse that is also 15 amp. See if the problem moves.

[720axr]

Yeah fuses are all good. I'm thinking about just buying a whole new wiring harness just to move past this problem. I'm almost ready to take it to a shop so they can find it. Been searching everyday for like 2 weeks and nothing. Are you aware of a place/site to get a new harness? Just getting fed up with the dead ends if ya know what I mean.

[datzenmike]

I know of no place that sells 720 wiring harnesses. There are wire harness 'kits' but you are no where near that desperate for that abuse. If you have to, find another '86 720 and grab the harness from it.

 

Is there power on both sides of that fuse?

 

There is a Blue and a White 10 pin connector under dash beside the steering column on left side that connect main harness to the gauges. Everything goes through it. Unplug and plug back in to assure that the pins are making contact...

 

There is no common thing that explains everything not working.

 

 

[1001001SOS]

On 11/14/2023 at 7:50 PM, datzenmike said:

There is no common thing that explains everything not working.

 

There's only one possibility...

 

 

 

 

[fiveoneO]

When checking power on both sides of the fuse, put the probes on the metal clips that hold the fuse and not the fuses themselves. Those clips can get corroded and not pass current. The fuse may show its good, but bower is not getting through the fuse block.