Stevenb
New Member
I have swapped them all twice just in case it was that. No change. I’m wondering if it could be a bad inertia switch?
OK. Let's get this fixed.With the key on. I run the two pump system and the low pressure pump by the tank runs almost constantly normally. The wire from the bottom of that relay kicks on at 12v for only maybe 1/10th of a second. Then drops. It does it every time you turn the key on. The relays all click back and forth then stop. I will try unplugging the inertia switch tomorrow to see what it does.
Pizzas were a huge hit. Then we got super busy and had bad weather. But today the sun is out. So here goes. My system is the two pump system from BC broncos. I swore that the rear pump (low pressure high volume) used to run almost constantly, but I’m guessing the was with the truck running. I know I could always hear it when I turned the key on.OK. Let's get this fixed.
What are you saying? "With the key on, the low pressure pump runs almost constantly normally.." That is gibberish. If the low pressure pump is measuring 2.9 Volts, then it isn't "normal." If it runs constantly, that is also not "normal." How is the low pressure pump wired?
How are you establishing a constant fuel pump signal? When you turn the key from "off" to "on" the fuel pump only runs for 1 second, and then the computer turns it off. What kind of volt meter are you using, and how are you establishing your measurement? You only get to count to "one-mississippi" and it's all over. When you say that you are seeing something at 12V for 1/10 of a second...WHAT wire are you measuring?
Type slowly, and assume that I am an idiot. (or maybe just assume that I'm in 3rd grade) You won't hurt my feelings.
a. Unplugging the inertia switch will do nothing.
b. It is not the computer.
c. There are four wires on the fuel pump relay. They are Red, Pink, Orange, and White.
1. What is the voltage profile of the Pink wire measured at the relay when you turn the ignition switch from off to on?
(You should see 0 volts, then you should see +12V for 1 second, then you should see a fast decaying, noisy, counter EMF back to 0VDC.)
2. What is the voltage profile of the Red wire measured at the relay when you turn the ignition switch from off to on?
3. What is the voltage profile of the White wire? (probably don't need this, but since you are there...might as well measure it.)
That should be enough to get you working in the right direction.
Fuel pumps were wired as the old RJM manual showed, Pink wire front high pressure pump, Green wire to rear pump. It’s ran great for ten or more years until now.OK. Let's get this fixed.
What are you saying? "With the key on, the low pressure pump runs almost constantly normally.." That is gibberish. If the low pressure pump is measuring 2.9 Volts, then it isn't "normal." If it runs constantly, that is also not "normal." How is the low pressure pump wired?
How are you establishing a constant fuel pump signal? When you turn the key from "off" to "on" the fuel pump only runs for 1 second, and then the computer turns it off. What kind of volt meter are you using, and how are you establishing your measurement? You only get to count to "one-mississippi" and it's all over. When you say that you are seeing something at 12V for 1/10 of a second...WHAT wire are you measuring?
Type slowly, and assume that I am an idiot. (or maybe just assume that I'm in 3rd grade) You won't hurt my feelings.
a. Unplugging the inertia switch will do nothing.
b. It is not the computer.
c. There are four wires on the fuel pump relay. They are Red, Pink, Orange, and White.
1. What is the voltage profile of the Pink wire measured at the relay when you turn the ignition switch from off to on?
(You should see 0 volts, then you should see +12V for 1 second, then you should see a fast decaying, noisy, counter EMF back to 0VDC.)
2. What is the voltage profile of the Red wire measured at the relay when you turn the ignition switch from off to on?
3. What is the voltage profile of the White wire? (probably don't need this, but since you are there...might as well measure it.)
That should be enough to get you working in the right direction.
No harness yet. I will be installing one soon, but right now the only new wiring is the RJM harness under the hood. By new I mean ten or so years old.OK, I went out and tried to verify the Green wire on the low pressure pump. I dug out my old Ron Francis wiring installation manual. Where are you seeing a green wire? I can't find any refernce to a secondary fuel pump on the ron francis TDZ-Bronco 75 Ford EFI harness.
Now I DID find a green wire as an auxiliary power wire in the Centech Body Harness. Are you using a Centech harness in conjunction with your Ron Francis EFI?
If so, then yes... the Centech harness has a green wire that is under the hood and is a switch ignition power source. It will be Hot at +12 in the ON position only...not ACC.
I’m measuring under the relay on the pink wire as well as by the pump.Yep, I could see where you were headed in your thought process. But remember that all of those Ford inertia switches were mounted in the trunk tail light panel, (near the tank) and the relays are mounted up front. So they do indeed sit on the load side of the relay and carry all of the fuel pump current.
The OP was asked to measure the voltage on the relay (line and load side) back in post #8 in the thread. Until he does that, I can’t help.
I make my own dough, sauce, and sausage. It’s basically Nick and Vittos pizza from Chicago with finely diced green peppers added so it tastes closer to a Howard’s special from Great Falls, MT.Just what is more important here? Pizza or Broncos, boy you gotta get your priorities straight. You need your Bronco running to deliver 17 Pizzas. You have a Pizza oven in your Garage? Damn kids always get in the way. Have fun 17 pizzas is allot of Pizza. you use a rising Dough? I sure miss a good pizza. California cant make a good pizza.
So I looked at my instructions from forever ago. I must have spliced the green wire into the pink to run the two pumps. I have to chase down that splice. I know I soldered and heat shrink tubed every connection as well as used dielectric grease on them. As far as the orange wire floating, I’m not sure how to fix that. You guys are all so amazing to help me so much. If any of you ever come to Spokane I’ll make you pizza!No harness yet. I will be installing one soon, but right now the only new wiring is the RJM harness under the hood. By new I mean ten or so years old.
OK, the instructions say to splice the secondary pump into the pink wire.So I looked at my instructions from forever ago. I must have spliced the green wire into the pink to run the two pumps. I have to chase down that splice. I know I soldered and heat shrink tubed every connection as well as used dielectric grease on them. As far as the orange wire floating, I’m not sure how to fix that. You guys are all so amazing to help me so much. If any of you ever come to Spokane I’ll make you pizza!
I'll get you info on the orange wire. It is NOT the dedicated ground. Don't Ground it!So I looked at my instructions from forever ago. I must have spliced the green wire into the pink to run the two pumps. I have to chase down that splice. I know I soldered and heat shrink tubed every connection as well as used dielectric grease on them. As far as the orange wire floating, I’m not sure how to fix that. You guys are all so amazing to help me so much. If any of you ever come to Spokane I’ll make you pizza!