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Old 07-15-2016
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1990 Ranger 4.0

I would like to get a schematic of just the electrical fuel pump system from battery to the pump..My pump relay energizes as soon as the ground wire is set on the post. Drains battery.
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Old 07-15-2016
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Yes, that would be a problem

Fuel pump(FP) relay has the Green Base/socket
EEC relay has Brown Base/socket

If key is off and it does this then there are two problems.

The FP Relay's coil only has power when key is on, but it has no Ground so shouldn't activate.
Ground is provided by the computer OR VIP(OBD1) connector.

Power for the FP Relays coil comes from EEC relay, so it maybe stuck closed

Battery------EEC Fuse-------EEC relay-----------FP relay coil

EEC relay also powers fuel injectors, spark system and the EEC(computer).

FP relay coil-----------Computer-----Ground
FP relay coil-----------VIP(OBD1)

OBD1 connector is in the engine bay it is part of the main wiring harness and is hanging loose.
Look here for diagram of it: Ford Ranger - Testing EEC-IV Equipped Engines

The fuel pump Ground slot is labelled in that drawing, if key is on and you were to Ground that slot with a jumper wire the FR relay should "click" closed and fuel pump should start running.

Wiring diagram here: http://www.therangerstation.com/tech...0_3_0_1of3.JPG
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Old 07-17-2016
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Thanks for responding. You mentioned ln your reply there would be 2 problems. The eec relay stuck closed but I wasn,t able ti understand the other possible issue' Is that relay used any where else wher I could swap out for tyest purposes? Thanks Ron in advance Jim
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Old 07-17-2016
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Two problems are 12volts and 0volts(ground)

Fuel pump relay, or any relay or device, can't work without both 12v and 0v
i.e. if you hook up 12v to a light bulb nothing happens, even if you hook up the 12v to both connections on the light bulb nothing happens.
For light bulb to work it needs 12v and 0v so electricity can flow, the flow causes bulb to light up.

A relays coil is the same, if it just has 12v nothing happens, it must also have 0v, then electricity can flow and coil becomes a magnet and relay closes.

Fuel pump relay gets 12v from the EEC relay, EEC relay also powers the Fuel injectors.
Turn on the key and test for 12v at a fuel injector, either wire, then turn off the key and check for 12v at fuel injector, should be no volts at fuel injector with key off.
If there is then EEC relay is bad or wires under it are shorting.

A Relay uses a spring to hold contacts open, when coil gets power it pulls relay closed because spring is weak enough to allow that, when coil has no power the spring pushes relay open..............if spring breaks.............relay stays closed, broken relay.

Testing for power at fuel injectors tells you if EEC relay is opening when key is off

There is also the possibility that the ignition switch is broken, not cutting power to the EEC relay when key is turned to OFF, with key off pull out the EEC relay, if you hear it "click" then it was still getting power with key OFF, plug it back in and it will "click" again, that confirms it, problem is in the ignition switch, it is not cutting power

Thats the 12v side of the Fuel pump relays coil

2nd problem
Fuel pump relay Ground(0v)
If fuel pump stays on then this wire must be shorted to ground, wire from relay runs to the computer, computer controls this ground, this wire has a splice that runs to VIP connector, so any place on these wires that is bare and touching metal will be a short to ground.

All automotive relays use the same numbering for contacts, 85 and 86 are the coil connections inside the relay, there is no + or - polarity.
if one is 12v and the other 0v then relay will close, remove either and relay will open

Last edited by RonD; 07-17-2016 at 11:42 AM.
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