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Fuel pump (in-tank)only works if I jump the relay


Bill in Arizona

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86 Ranger 2.9 , My in-tank fuel pump only runs if I jump the green fuel relay. I have changed the relay, the ignition switch, jumped the inertia switch, Checked every fuse and inline. Grounds seem to be good everywhere too. I have a code 87 (primary fuel pump failure) code. There is no +12 power at the blk/pnk wire under the dash, or near the bulkhead. When I jump the relay, the pump runs continually, makes em wonder if there is one more relay/switch that sees the fuel pressure is up?
 


holyford86

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you have a bad fusible link, if there is no power at the inertia switch and everything else checks out good
 

Bill in Arizona

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I tested the inertia switch with a test light. To get the light to light, I connect one end to the inertia switch lead and the other to the positive side of the battery. Should it be positive at the inertia switch?
 
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hidesertrat

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If jumping the relay gets your fuel pump to come on, I would think there is a problem with the control side of your relay circuit.

At the enercia switch, you should be able to ground one side of your test light and connect the other side to your lead. With the key turned on, your light should light.

On the relay socket, there should be four contacts. Two are the power contacts, these are the ones you shorted across. They are the ones that apply voltage to the fuel pump.
The other two are the control contacts, which run through a coil within the relay and energize it. One contact will be ground and the other should have 12 volts on it. If you place your test light inbetween these two contacts, when you first turn the key on, the light should come on and than go off. If this doesn't happen, you are not getting voltage to the relay or the ground path is broken.

Post what you find and we can go from there.
 

holyford86

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If jumping the relay gets your fuel pump to come on, I would think there is a problem with the control side of your relay circuit.

At the enercia switch, you should be able to ground one side of your test light and connect the other side to your lead. With the key turned on, your light should light.

On the relay socket, there should be four contacts. Two are the power contacts, these are the ones you shorted across. They are the ones that apply voltage to the fuel pump.
The other two are the control contacts, which run through a coil within the relay and energize it. One contact will be ground and the other should have 12 volts on it. If you place your test light inbetween these two contacts, when you first turn the key on, the light should come on and than go off. If this doesn't happen, you are not getting voltage to the relay or the ground path is broken.

Post what you find and we can go from there.
I should have thought of this, this is why I shouldn't post when half asleep... /jack
 

hidesertrat

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HolyFord86: Trust me, I FULLY understand!!! lol

Just looked at wiring diagram: the inertia switch is after the relay. So if you jump relay and fuel pump works, the inertia switch is good and so is the fusible link.

Go back to the relay. First off, ensure you plugged the replacement relay in the right way. I don't know if you can put it in up-side-down or not, but if you do it will not work. Most of the relays have a diagram on the side of them to show which pins are your control and which ones are your contact.

You could plug your fuel relay into another spot and see if you here it click when you apply power to it. Or use small jumper wires from your battery to the control pins and see if you hear it click. No clickie, no good.

On the relay socket the red wire should be hot (+12V) all the time, with key on. The other side, of the control circuit is a tan/lt grn wire. It comes from the ECU and is what controls when the relay is energized or not. If you place your test light inbetween thest two connections and turn you key on, it should light briefly and than go out. If you crank your engine over, I believe, it should stay lit.

Yellow wire on relay is your power going to the fuel pump, it should be hot all the time (key on or key off). The org/lt blu is on the other side of the relay, going to the fuel pump. These are your relay contacts, the ones you have been shorting together.

99.9% sure your problem is either a bad relay, or somewhere in you control circuit. :yahoo:

Good luck.
 

Bill in Arizona

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Thank you . Here is the latest, I Turn the key ( on ) I have power at the Relay-on the trip wires, There IS ground coming from the computer on the kick panel. Still will NOT activating the relay. If I take the Negative and touch it to ground( The part where the 3 wires soldier together) The relay activates and the pump runs continually.

Still no 3 second pump run prior to starting. Pump Runs continually if I apply ground to the Relay trip wire, Even though it meters to 12 volts when I turn the key. It is like it needs an additional ground. The computer is not controlling the fuel pump, in tank.

The truck runs fine once started. I have bought every wiring diagram, soldiered all my connectors. Tested every wire, it seems. I am beginning to think it is the comp. The one in it says "reman" on it. The relays are new. Ig switch is new, inertia switch is fine, Grounds look good? Thank you for all your detective work... This is a big mystery...
 

Bill in Arizona

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New info,,,, The voltage from the ground output (to the fuel pump relay) of the computer is 0.65 when I test it with a meter. I have a full 12 vlts at the positive trip feed to the relay. Maybe that is why when I touch the negative side to ground, the relay (clicks in) runs?

Other than a poor ground supply to the computer, seems that the computer is failing to provide proper grounding to the fuel pump relay.

Thinking I should just pick up a comp and switch it out? I have spent hours on this problem. Thanks for any further advice.. Bill
 

RayJr

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I dont know if your 86 is the same as my 94, but i just had a similar problem.
no power to 85 pin of the fuel pump relay, if i jumped from the 30 pin to the 87 pin pump ran.
it ended up being the ecm relay (right beside the fuel pump relay)was shot swapped it out and pump functions fine now.
 

militarydave

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I had the same problem with my 89. I replaced the fuel pump, the fuel pump pigtail, all the wires leading from the fuel pump all the way into the engine bay, fuses, new motorcraft relays, and tested the inertia switch.

in my case, all my wires were burnt from the in tank pump all the way into the fusebox. I mean... burnt to a crisp. It finally blew the 30amp fuse and the relays would get super hot.

In my case it was the entire fuel system (pretty much).

sounds to me like a bad fusible link.

-dave
 

Bill in Arizona

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Just changed the computer, the one under the drivers side kick panel. Everything worked as it should. Wow I wasted so much time on this problem... Truck i s running smooth. I now need to re-wrap all my wires. Next find an O2 connector and eliminate the black smoke when reving it up
 

Bill in Arizona

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We are men of action, words do not become us
Solved issue

Replaced the ECM ran great ! Used a non egr from a later model, ordered it on rockauto. Replaced the fuel pump wiring to the pump on the frame rail with a Painless fuel pump wiring kit from Amazon. Replaced the both fuel pumps too This completely solved my problem. Except for a rising and falling idle issue, the truck is running fine now. Just about 30 years old. I plan on replacing everything eventually. Great resources on this website. Thanks everyone
 

Bill in Arizona

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1986 Ranger 4 x
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We are men of action, words do not become us
The Black Smoke

Black smoke when reving the engine inspired me to replace the fuel injectors with some rebuilt ones from EBay. I pulled the old ones out, noticed they were numbered, whoever had disconnected them before had wired them to the incorrect injector. They were delivering fuel at the wrong time. This caused the black smoke.
 

Bill in Arizona

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1986 Ranger 4 x
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ford
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Automatic
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We are men of action, words do not become us
Ultimate solution

Painless fuel pump,wire harness,,with relay, installed to the rail fuel pump. No more issues. A inexpensive reliable solution. Thank for your advice.
 

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