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Fuel Pump


Lowrange2

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Got a question for you Ranger fellas.

I just picked up another 88 Ranger 2.3 FI 4 banger 5 speed. It won't start. Just spins over. Here's the story.

Dude was askin 1200 for it. I test drove it and it ran great. I brought the wife back to check it out and it started but within 5 seconds cut off. i started it again and it did the same thing... it shuddered like it was out of gas. I left and came back several days later and the guy told me that he had attempted to fix it but had no luck... I gave him 200 bucks and pulled it home.

Now I've determined that the fuel pump in the gas tank is not running when i turn the key on. Its not running at all. I pulled the plug off the fuel pump and tested each wire. My haynes manual says that the pink/black wire should have 12 volts on it when the key is on but it don't. I followed the wires back up to the inertia switch and tested it. The inertia switch tested out ok. I then followed the wire on up to the relay on the passenger side under the hood. When i turn the key on the relay clicks like it should but the pump still doesnt run. I tested the wires at the relay and couldnt get very good readings for some reason... Thats when it got dark and i had to hang it up for the night. Is there some common problem that i should be looking for or do i just keep diggin till i find it? Does the computer have anything to do with this system? Should I try switching it out?

The Pink/black wire shows 0.1 volt at the pump, inertia switch, and relay... Should it all show 12volts?
 


RobbieD

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Yeah, it should show (+) 12 volts. The computer triggers the relay, which then switches battery power to the fuel pump, via the Pink/Black through the inertia switch. Pretty sure about that, off the top of my head, but I can check the EVTM if needed. Good luck getting it going; sounds like you got a sweet deal. And, welcome to TRS.
 

Lowrange2

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Yeah, it should show (+) 12 volts. The computer triggers the relay, which then switches battery power to the fuel pump, via the Pink/Black through the inertia switch. Pretty sure about that, off the top of my head, but I can check the EVTM if needed. Good luck getting it going; sounds like you got a sweet deal. And, welcome to TRS.

I'm pretty sure my problem is that I'm not getting constant power to the relay from the black and yellow wire. What i dont understand is why the diagrm here>>
(http://therangerstation.com/tech_library/EDiagrams/files/Diagram_ElectronicEngControls2_3_1of3.JPG )
shows the DG/Y wire running from the relay to the inertia switch as well as the computer. By this diagram is looks like the Ignition switched wire trips the relay and the pump gets its power from the fuse panel that is hot all the time. Which wires are the grounds for the relay. It doesn't look like I'm getting power from the fuse panel via the bk/y wire. I think I'm gunna try to jump power over to the bk/y wire to see what happens. Keep in mind that the relay still trips properly it just doesn't have 12volts on the other side to send down the line. So i know the pos and neg is tripping the relay properly.


lol Your sig list of rangers looks about like my yard. Since I started drivin 6 years ago i've had 6 rangers... a 91, 93, 94, another 94, 97, and a 2000 4dr 4wd. I've still got all of them except the 2000. This 88 is gunna be my 7th. Plus I've got a couple flipped broncos out in the field.
 
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RobbieD

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I think you're right, about your problem being no power into the relay on Black/Yellow (you do find the relay does trip properly).

The reason for the Dk Green/Yellow running from the relay to the computer is it's just a branch-off of the pump power, to tell the computer that the relay did activate when it was commanded to.

The coil of the relay has Red on one side, and Lt Blue/Orange on the other side. When the ignition key is turned on, the same power circuit that turns on the computer also powers one side of the fuel pump relay coil; what makes the relay trigger is that the computer will switch ground onto Lt Blue/Orange, when it wants the pump to run. That branch of the Dk Green/Yellow just confirms back to the computer that the relay did comply.

I hope that description makes some sense, as you look at the diagram again. To check the pump. you can jumper power over into the Dk Green/Yellow to see if the pump runs. Then do the proper repair accordingly, but you sound like you know what you're doing.

Thanks for the comment. I wish that I still had all the ones I traded in over the years. Sounds like you've got a good collection going.


Edit / Add: Keep in mind that the wiring diagram we're looking at is "typical"; I don't think that it matches your year model perfectly. Good luck.
 
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shadetree

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You say your engine is a 2.3. The pink/blk wire is for a 2.0 carbed engine. Do you know if the engine has been swapped?

Per Chilton's, wire colors for the 2.3 are:

Yellow to fuel pump relay is hot all time thru fuse link to fender starter relay, battery plus side. The power to the EEC relay from the fender relay is also yellow, so make sure you are checking the correct relay.

Red to fuel pump relay is hot when ignition is on. Power comes from the EEC power relay.

tan/lt grn from the fpr goes to pin 22 of the computer.

org/lt blu from the fpr to the inertia switch & pin94 of the computer.

At ignition on, the computer momentarily grounds pin 22 to turn on the pump to prime the system. After approx 2-3 seconds, the computer un-grounds pin 22 and waits for ignition pulses before restarting the pump. The pump will NOT have 12v except for the 2-3 seconds, and when the engine is turning over.

Not shown in the diagrams is a wire going from pin 22 to the self test connector. You can jumper this wire to ground, and the pump will run all the time the ignition switch is turned on if everything is working as it should.

You can do some simple tests with a test light to see where the problem lies. shady
 
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Lowrange2

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Thanks fellas. I'm gunna be home in a short while and I'll make the jump to see if the bk/yellow wire is the problem. I'm thinking there is a broken wire somewhere between the relay and the fuse panel... lol I havent even checked the fuse yet... the previous owner said the fuse was fine... Ill check behind him tonight.
Edit: I should have constant power on the black and yellow wire, correct?
 

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Yes, I believe it's constant power you're looking for going to the relay. I can check the '88 EVTM, but like shadetree pointed out, on an '88 the constant battery power to the fuel pump relay should be protected by a fusible link. The underhood fuse block came along in '89.
 

Lowrange2

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ok here's the update. I jumped 12 volts to the pink and black wire on the pump side of the inertia switch. The high pressure pump ran but the one in the tank did nothing. The relay seems to be working properly but I dont have 12 volts on the black/yellow wire yet. Does this sound like i need to replace the pump in the tank? What are the odds of the pump in the tank going out and the fusible link going at the same time? The black and yellow wire does not have power and when i give power to the pumps only one of them run. Whats up with that. If i hurry i can make it to the parts store and get the pump they have in stock... What do yall say?
 

shadetree

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Two things:
Make sure power is reaching the tank.

The tank is grounded to the frame from the pump assembly, and sometimes the ground wire breaks or becomes corroded. Make sure of a good ground. If there is power, and a good ground the pump should run. If not, it has a problem.

If you have to change the pump it is usually easier to lift the bed. shady
 

Lowrange2

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do you know which wire is ground for the pump? The pink and black wire is obviously pos.
 

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From the '88 EVTM:

Pump
Power: Black/Pink (after the inertia switch)
Ground: Black
Sending unit
Signal return: Yellow/White
Ground: Black (both Black wires are the same circuit).

You've also got an inline pump on that thing, inside the frame rail under the driver seat; it's powered by the same Black/Pink circuit as the in-tank pump. Both pumps also share the same grounding point, G200, which is below the driver's side dash, to the right of the fusebox.
 

Lowrange2

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Alright! I took the pump out of the tank and tested it... it was toast. I went to the parts store and got another one. I installed it and jumped the relay again and put power to the pumps... She fired up and ran excellent... Now all i have to do is find where I'm losing power somewhere between the power dist block and the relay. I assume the fusible link went bad when the pump went bad. Do any of your guys know right off the top of your head where that fusible link is? That would make my search tomorrow much more easy...
 

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I believe on an '88 the fusible links are still all hanging off the starter relay.

If the pump failed via a short (which sometimes happens on coils), blowing a fusible link is a possibility. However, it's a little weird to burn out a fusible link AND burn out a pump. One dying should save the other, at least from a burnout.

A fail-to-open in the pump will not blow a fusible link, as it doesn't generate heat.
 

Lowrange2

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Yeah thats kinda what I was thinking but I still don't have 12v on the pump relay input. Maybe the PO messed around with the other end of the wiring. I still haven't checked the wires past the relay...

EDIT: I may have found another issue. I just went out there looking for the starter relay and found 2 other relay harnesses near what I call the fuel pump relay. There is a Black plug (Thats the one i've been working with), then i just found a green and black plug but both of those harnesses are toast! All bare wire so i have no clue what colors they used to be! this is gunna be fun to fix! Which relay is the fuel pump relay? Black Green or BRown?
 
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RobbieD

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Hey Lowrange2, battery power to the fuel pump relay is a Yellow wire, which has a Blue 20ga fuse link at the starter relay.
 

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