ron francis wiring/grounding question

[nkhd1]

i have the RF TDZ-75/Bronco-75 ron francis harness. I am not getting a full 12volts to the fuel pump. i have remove the relay 4 pack and checking the wiring going to the proper relay. between what should be the positive and negative wires the 6.7 volts same as pump. the "negative" to the relay is a small brown wire that has on it R2 85 VIP 22SPL it disappears in the harness and i cannot find where it goes. the other three relays hava a commpn ground and a common hot wire feeding them. this one is different. i can temporary hook a ground wire to it and i get my 12 volts to the pump. I dont like short cutting the wiring and would like to know what this wire does so i can check its other connection

i will try and call Ron Francis outfit tomorrow but if anyone has run into this i would appreciate any information.

Thanks

 

[ba123]

You need to run a ground wire to the rear and use that as a common ground for anything back there to do it right. You could just connect a ground wire to the body back there, but I wouldn’t.

Not entirely sure that’s what you mean…maybe you mean the ground to the relay is bad and you get full power when you ground the relay?

If so, I’d bet you didn’t make good grounds in your system..

If I look at your harness instructions, I see #13 that should be grounded to your engine.
It looks like maybe #9 goes to battery, but that might just be power.

Other than that, you need a ground from your batt negative to your starter bolt, wire from that bolt to both your head, preferably at that same spot as the harness ground and then also to your firewall of some good piece of body.

Remove the paint from the engine and starter bolt and firewall and use dielectric grease to protect the connection as well as star washers.

You can use a multimeter and measure the resistance between different spots and your goal is 0.00 on every part of your Bronco and it will prob degrade over time but hopefully not if you do it right.

Hope that helps!

 

[nkhd1]

thanks the bronco is fresh painted and putting it back together i expect ground related running a ground to the back is likely a good idea...

 

[73azbronco]

On my resto, one wire I used was a ground wire all the way to the back, fuel pump and back lights use that, another wire to front grill/turn signals, headlights have their own return using another. A third to dash and fourth to body main, not counting battery ground to block, block to frame, Lets say I'm well grounded.

 

[DirtDonk]

Perhaps the reason that that one particular ground wire is different, it’s because the fuel pump also goes through the safety inertia cut off switch.
Perhaps your switch is defective, or it has actually tripped, but is still allowing some voltage to pass through. Which seems kind of strange as well. So maybe I’m just spit balling here.
Have you tried tripping it and resetting it?

 

[ba123]

Perhaps the reason that that one particular ground wire is different, it’s because the fuel pump also goes through the safety inertia cut off switch.
Perhaps your switch is defective, or it has actually tripped, but is still allowing some voltage to pass through. Which seems kind of strange as well. So maybe I’m just spit balling here.
Have you tried tripping it and resetting it?

Worth checking but unlikely that the inertia switch would give partial power…it’s certainly possible. If you just jump the switch, you’ll know if that’s the problem. Or test the voltage on each side of the switch might tell you more.

But…I don’t think power for the pump goes through the relay, just the power side of the switch. I think power comes from pin 22.

 

[DirtDonk]

I don’t know what pin numbers are appropriate, but the only thing the computer controls is the signal to turn on the pump. Doing so through the relay.
Otherwise, there would be no need for a fuel pump relay.

That’s the use of a relay in the first place. The computer wouldn’t like all that current flowing through it to run a pump, so it switches the relay, possibly the negative side, to turn on the fuel pump.
So if the numbers are normal, pin 30 of the relay is from the battery, and pin 87 of the relay goes directly to the fuel pump. Pins 85 and 86 are switched negative and positive.
I’m only guessing that the inertia switch makes or breaks the switched negative of the relay.
But that makes sense to me.

However, what makes sense to me isn’t what matters. What’s in the wiring diagrams tells the tale.

 

[ba123]

You’re right, I think I must doing something else while writing half the correct answer!

Oddly though, I’m pretty sure power runs through the inertia switch and the ecu controls the ground. Power supplied form the battery

 

[DirtDonk]

Sounds like nkhd is measuring the reduced voltage right there at the relay socket.
Interesting that correcting the ground is what gets the voltage back up. Wish I knew where that brown wire went, but I’ve never unwrapped one of the harnesses.
But the diagram should show wire colors, at least, so that might be a start.

 

[ba123]

It’s not a stock harness, it’s Ron Francis and looking at the diagram, it seems like ground wires are missing and that’s why my first post was about grounds and making sure to put them and measuring resistance.



This shows one ground on the battery (#9) and one ground on the back of the engine, it seems (#13) and that’s it. If you just follow this harness, it’s not enough, imo.

 

[DirtDonk]

That number 9 is a positive power source for the relays. Not a ground.
I think the only ground is the one at the back of the engine. But that’s not unusual, and it’s not really like we’re talking about a whole chassis harness here. This is strictly for the computer and the fuel injection, so there isn’t a whole lot of current being utilized through the system.
Additional grounds might not be necessary.

Although I am with you, and think that more grounds is usually better. We’ve been selling our version of this harness for years, and I’ve been installing them since Ryan McCormick put them together originally. And they’ve always worked flawlessly with just that one ground.
Maybe until now!

What is the voltage for the sensors?
I forget the exact amount, but it’s much lower than system voltage. Something like 4.5v?
The computer is utilizing this for a lot of things that don’t take a full 12V like the pump does.

I’m out of my element here. So I’m very interested to hear what the OP finds out from Ron Francis.

 

[ba123]

Yeah, I was kind of assuming they’d have a ground there with those power connections not shown since it just says Battery, but maybe it doesn’t. And you’re right that it would be ok with just the one, but not if your grounds leading to that spot suck.

With this Ron Francis Telorvek panel I’m using the only difference is that I’m making the harness myself and have to tie is all the wires to a panel that connects to the computer instead of being done for you and I have a ground from that panel and two engine grounds (not counting what else I ran).

Most people just don’t understand that a good ground is just as important as the good power source.

I’m not far off from testing my own fuel pump power so we’ll see how mine goes but will be shocked if not good.

 

[EPB72]

That number 9 is a positive power source for the relays. Not a ground.
I think the only ground is the one at the back of the engine. But that’s not unusual, and it’s not really like we’re talking about a whole chassis harness here. This is strictly for the computer and the fuel injection, so there isn’t a whole lot of current being utilized through the system.
Additional grounds might not be necessary.

Although I am with you, and think that more grounds is usually better. We’ve been selling our version of this harness for years, and I’ve been installing them since Ryan McCormick put them together originally. And they’ve always worked flawlessly with just that one ground.
Maybe until now!

What is the voltage for the sensors?
I forget the exact amount, but it’s much lower than system voltage. Something like 4.5v?
The computer is utilizing this for a lot of things that don’t take a full 12V like the pump does.

I’m out of my element here. So I’m very interested to hear what the OP finds out from Ron Francis.

correct #9 has two connections the larger red wire goes to battery power {battery post side of starter relay} the smaller purple wire goes to the starter relay small terminal I for a cranking signal for Pcm. Sensor reference voltage is 5 volt. sensor operation range is usually .3 - 4.7v, there abouts .That way if the signal wire shows below .3 or above 4.7v it will flag a fault as being circuit high or low and set a code accordingly... ...... It appears all four relays share the same common power source,,but each relay has it's own fuse prior to the relay ? { atleast thats what the picture in there instructions show} so if there's a low voltage situation at one relay ? check voltage drop across the fuse.... or any where else in the circuit in question.....as far as inertia switch ford did it both ways inline on power to pump. And less common on the relay power feed for the control circuit.

 

[don k]

I installed a 2009 Crown Vic, front IFS, engine, and transmission into a 1958 Ford F100. I used a Ron Francis wiring harness. I had a few problems but called them and they figured it out and were a great help. Alot more complicated that what you have. Call them.

 

[ba123]

If the problem is fixed with ground, the problem is likely ground. Right?