1984 F250 460 dual tank - Starter Relay wiring problem

['84-460-Project]

I recently got into a 1984 F250 single cab 4x4 with a 460. Its a father and son project truck and let's just say its a little beat up.

We are in the process of replacing the rear fuel tank, rear sending unit/pump, running all new fuel lines and replacing the fuel tank selector value (w/a universal kit)

While we finished the installations and final wiring tests we ran into some issues. As soon as we connect the battery - power immediately went to the rear tank/sending unit pump. No key in the ignition or ignition turned. Steering wheel locked and everything off. After looking around for a couple of days on this site, all the service manuals and rechecking our wiring I found the issue (I think).

There is a fuseable link (T) that when power is applied -powers the Tank Selector Relay. From what I read, after turning the ignition to "start" power travels through fuseable link T to selected tank's fuel sending unit pump to get fuel to the carb to get the truck started.

The Problem: I found Fuseable link T hooked up to the Starter Relay, along with the all the other fuseable links, next to the battery power cable. It gets constant power when I connect the battery.

I'm unsure if it needs to go to another part of the Starter relay or wire that is fed from the ignition. I searched around for another wire that went "hot" when the ignition turned to "start", but when I connected the fuseable link to it, it didn't put out enough power to get the fuel pumps to work. It seemed odd as I read 12 volts from wire with no load. When i connect the fuseable link to the starter relay - next the power cable - and connect the battery the fuel sending unit pump light right up. The problem is they won't stop unless I disconnect the battery cable.

Hopefully this is enough information to get the conversation started.

Any help you guys can provide would be greatly appreciated.

Thanks

[Ford F834]

Welcome to the group! Thanks for joining and sharing your project with us. Gary and Bill have a lot of 460 knowledge and will no doubt comment shortly... and Gary is working on a page for the 460 fuel system 🙂

http://www.garysgaragemahal.com/460-fuel-systems.html

[Gary Lewis]

Josh - Welcome!  

Lots of things to say.....

First, where's home?  We have a member's map (Bullnose Forum/Member's Map) and I'd be happy to add you.  Who knows, perhaps you are right around the corner from one of us.

On the father/son project, I assume you are the father.  How old is your son and what's his name?

As for troubleshooting your truck, that's best done in the main section and not this one as it is usually used for introductions and not as many people will see it here.

But, that doesn't mean we can't respond to your question regarding the fuel pump situation.  The page you probably need is below, which is from Electrical/EVTM/1985 EVTM/Electric Fuel Pump Control.  You can see there are three power sources:

Hot In Start Or Run: Comes from the fuse box and pulls in the Fuel Pump Cutoff Relay that ultimately pulls in the Tank Selector Relay.

Hot At All Times: This supplies power to the Fuel Pump Cutoff Relay that ultimately pulls in the Tank Selector Relay, and then supplies power to the fuel pump when the vehicle is running.

Hot In Start: This is Fuse Link T, the one you were talking about, and comes from the Start Relay's starter side.
 In other words, the side that has power in Start, but not at all times.  But this wire connects to the 2nd small terminal on the relay, not the big terminal.  You can see that on Page 27.

Hope that helps.

[grumpin]

Welcome!

[85lebaront2]

Josh, the correct starter relay will have a total of 4 posts, 2 big ones for battery and starter, a small one for the starter wire and an even smaller one that fusible link T goes on, it corresponds to the old ignition resistor bypass. What has probably happened is either the oil pressure switch on the back of the engine or possibly the relay is bad and it was bypassed to keep it running.

Welcome to our group pf looneys!

['84-460-Project]

Thanks. That points me in the right direction.

I'll try hooking the fuseable link T to the small post labled "I". When I put a volt meter to that post I couldn't get a reading. I wonder if I need another starter relay.

Any recommendations on how to test the Oil Pressure switch or the Tank Selector and Fuel Pump relays?

As soon we get the fuel situation worked out we need to get after a time and tune.

PF Looneys?  

[Gary Lewis]

The "I" post won't show anything except when the engine is cranking.

Testing the oil pressure switch requires pressure.  If you can't get the engine to start you could use air pressure and a regulator.  I think the switch closes somewhere around 10 psi.

And you can test the "Fuel Pump Cutoff Relay" while you have the oil pressure switch out.  Put battery voltage to the red/yellow wire coming from the oil pressure switch and going to the relay and the relay should pull in.  You can hear it pull in, and you should be able to then see battery voltage on the pink/black wire leaving the relay - assuming the inertia switch isn't tripped.

You can check the inertia switch by checking to see if you have battery voltage on the yellow wire going to the fuel pump relay.

['84-460-Project]

I'm beginning to realize I have alot of checking and rewiring to do.

The electronic vacuum trouble shooting manual diagram shows the fuse link T line "hot at start". I assumed this means when the ignition is turned to the position right before the "run" (when with engine starts to crank over).

Is there a terminal on the Starter Relay that sends 12 volts when the ignition is in the start position?

If the post "I" doesn't get power until the engine starts to crank, and I hook up fuse link T to it,  how would the fuel pumps prime the carb (assuming this takes a couple of seconds)  

Additionally, I tested the Aux battery relay (no additional battery hooked up - just a wire feeding it power) and it shows 12 volts all the time. I assume its wired incorrectly as it's should only show power when the ignition is in start, run and acc?

['84-460-Project]

Gary, I missed this post. We are in the Northern Neck region of VA. I'm the Dad in this project and my son is 17.

I'll post a question in the main sections.

Thanks for you help so far.

Josh

[Gary Lewis]

Josh - No problem.  I miss posts all the time.

I've taken your comment as permission to put you on the map.  But the only thing that came up in your area when I typed in Northern Neck was the jail.  So, that's where it dropped the pin.  

Take a look and see if you want me to move it.  But we aren't trying to get precise as we don't want people using the map to show up on our doorsteps.  But, in a place the size of Northern Neck, or Skiatook for that matter, it is pretty easy to find a person.

Anyway, please let me know if you want your pin to be moved.

[Gary Lewis]

And now to your questions:

The aux battery relay should have 12v to it all the time on both of the main terminals.  One side would be the 12v from the main battery, and the other the 12v from the aux battery - assuming it is connected.  Those voltages will be slightly different - until you turn the key to Run.  At that point you should hear a loud CLICK and the relay should come in.  That will parallel the two batteries and essentially make their voltages the same.  Then, when the engine starts the alternator will charge both batteries.

As for the Start position of the ignition switch, that's when the key has been turned all the way and, if all else is correct, the starter is spinning.  And, during that time two terminals on your starter relay will have battery voltage that otherwise wouldn't - the little "I" terminal and the large starter terminal.

Priming the carb doesn't happen until Start.  Yes, that can require a bit of cranking when the carb is dry, but it isn't too bad.  However, some have added a push button switch to that circuit to bring the relay in prior to cranking in order to prime the carb.  You can do that by placing the switch in parallel to the oil pressure switch, and when you push the button when the key is in Run the Fuel Pump relay will come in and spin the pump.  But note that you'll be sending less than battery voltage to the pump since the voltage will be dropped by the .75 ohm resistance wire.  The pump only gets full battery voltage in Start.  But the reduced voltage is easily enough to prime the carb.

[Ferdinand]

Welcome Josh. Love family projects! Working on my Bronco with my girls has been a great blessing. Glad you found us!