Chopped top 1988 B2 4.0L conversion with pics (Fuel pump & line question)


noticz

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Truck is a 1988 Ford Bronco II 2.9L and donor is a 1991 Ford Ranger 4.0L

I'm on a couple last steps of my swap and I seem to have mixed up the fuel spring lock fittings where it connects to the braided lines. Can anyone tell me which of the lines are the fuel line and return lines on the spring lock connectors. If I had to take a guess I would say the larger of the two is the fuel line and the smaller one is the return line?

Also has anyone else had any problem hooking up the high pressure pump to the ECU and it not working correctly? I am pretty sure I have everything hooked up right. From what I think happens is that the ECU controls the fuel relay which in turns fires the circuit with the cut off switch and fuel pump. I have traced everything and all the wires are correct and hooked up to the fuel shut off but I am getting positive signals on both of the relay power leads. I tested the relay and it clicks and hooked the fuel pump directly to switched power on the ignition and it works. Anyone else have any suggestions or insight on the issue?

Here is a picture of the bronco before the swap
 


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RonD

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Welcome to TRS :)

Looking GOOD


So you are using the EEC-IV computer, 1994 and earlier EFI Rangers and B2s used this computer
60-wire connector using OBD1 communications

With key on the EEC relay closes and sends 12volts out to the EEC(computer) and engine systems, i.e. spark(EDIS-6), injectors, IAC Valve, solenoids and fuel pump relay, but FP relay is not grounded so doesn't close

Yes, the Computer operates the Fuel Pump Relay by Grounding it, pin 22 on the computer
But it only grounds it for 2 seconds when key is turned on, its a safety thing, but it does it every time key is turned on
Computer will ground FP relay full time once engine is above 400RPM(started)

If you test voltage at the inertia switch(cut off switch) it will show 12volts for 2 second then 5 to 8volts after that, that 5-8v is monitor voltage from computer, no amps, so not power for fuel pump

1988 B2 may have 2 fuel pumps, one in the gas tank, lift pump, and one in the frame rail under the drivers seat area, high pressure pump.
Both use the same 12v wire from the inertia switch, there is a splice near the frame rail pump, known failure point, just FYI

There is an OBD1 connector on the main computer harness in engine bay, it has an FP Relay Ground slot you can use for testing
Slot is seen here: https://therangerstation.com/tech_library/OBD_I.shtml

Second drawing, that's the slot you can GROUND with jumper wire and when key is on FP relay should close and send 12v to fuel pump until jumper is pulled or key is turned off
Good for testing and draining fuel from the tank as needed, lol.


On my 1994 4.0l both fuel lines are threaded, the IN line is shorter, connects to fuel rail drivers side near PCV Valve, the OUT(return) line is much longer, crosses over to passenger side under the throttle body to connect to the Fuel Pressure Regulator(FPR) behind alternator, lower intake

Thread sizes are different as well, IN is larger

Not sure how the B2 fuel lines ran?
 
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noticz

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RonD, thank you kindly for the help. I can hear the low pressure FP (in tank) turning on when the ignition is switched to on just nothing from the high pressure pump. I will get under there and take a look, ground out the FP test pin and see what I come up with.

As far as the other question I asked about which fuel line is what...I took a picture for explanation. After cutting everything off the donor truck and making my own adapter to plug in to my B2 I realized that I didn't label them and why I am asking which one is the fuel and return lines?
 

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Big is fuel, small is return.
Also, check the connections at the high pressure pump. I've found that the female end gets loose and gets bad connection. Do both +ive and -ive sides. The connectors are behind the rubber boots on the pump. They can be difficult to remove.
 

noticz

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Just wanted to share my update since I hate looking at a post and not seeing a solution at the end of it...My issues was not with the fuel pump wiring at all. After checking out the wiring diagram for the 1991 Ranger I noticed that the EEC circuit and relay controlled the fuel pump power. When I put in the harness from the 4.0L I had to cut the headlight harness from the engine harness and to do that I had to cut the group of wires connected to it by the passenger side power distribution box. In that group of wires was a yellow wire and another yellow coming from a connector. Once I spliced them together the EEC power relay clicked and then the fuel pump relay right after.
 

RonD

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Good work in finding that :)
 

Shran

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Interesting. I'll have to remember that - years ago we transplanted a Mustang harness into a pickup and had issues running the fuel pump off the ECU. As Ron said we'd get around 8v and the pump would never run. We ended up running it off a toggle switch which was OK since it was a race truck anyway but it would have been cleaner to just have the pump powered off the ECU like it was from the factory.
 


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