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Tech501
Tech501, Auto Service Technician
Category: Car
Satisfied Customers: 747
Experience:  38 years exp, ASE Mastertech with L1 Advanced Engine performance
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Customer Question

i have 1988 ford bronco 2, 2.9 eng. at 4x4, i have replaced transmission and it won’t start. i have spark at plugs but fuel pumps have no power, i replaced both fuel pumps,fuel pump relay,fuel filter,eec power relay,icm,distributer, dist.cap, rotor,sp wires, coil,plugs,engine control computer,battery,cables,solenoid switch,starter,and other parts i probably forgot to list. i haver checked voltage at fuel pump relay i have 12 volts going in but nothing coming out? i checked all wiring in engine compartment. i also checked inertia fuel pump shutoff switch it is ok. tried bypassing it also, still no power to fuel pump. is some other fuse or switch i’m missing? when ignition is turned on you don’t here fuel pump coming on,only thing you here is a clicking sound after a few seconds.
Submitted: 11 years ago.
Category: Car
Expert:  Tech501 replied 11 years ago.

 Do your testing at the fuel pump relay with a computer safe diode testlight that shows ground or power. You should have 2 sockets with power with the key on. One will be to the pump and that should read ground also. The 4th terminal will be the trigger ground from the computer. that's the signal that turns on the pump. You should get a ground signal at that wire for 3-5 seconds when the key is first cycled. That's the only period of time that the pump turns on when you turn the key on. You can test you pump by just jumping the power with the terminal to the pump and it should run. I'll look for a schematic for you for color codes.  OK, as you can see the wire to the Inertia switch and then the pump is Org/LtBlue. The feed power comes from a fusable links and is yellow. The control power lead is red and comes from the EEC relay, and the computer trigger is Tan/Lt Grn. Jump the yellow to the Org/LtBlue to test the pump


 


Customer: replied 11 years ago.
Reply to Tech501's Post: still no luck,i checked all wires connected to the relays computer, and pumps. both pumps will run off of yel wire from relay. i checked volts with key on nothing coming out of pump relay at any time. checked with key on red wire 0v,tan/gr wire 0v,and or/gr wire 0v. checked eec relay with key on red/gr wire 12v,red wire 0v,and blk/gr wire 0v. both relays had power to them from yel wire. checked volts at computer 12v coming in on yel wire, 12v going out on red/gr wire. could computer control be defective, i just purchased at auto parts store? what tells computer to send volts to relay?
Expert:  Davo replied 11 years ago.
Check for ground at the pcm connector terminals 40 and 80 with the connector removed.Also check the black/lt grn wire at the EEC relay for ground.If one is open you need to find it.Maybe a wire was left off during the trans replacement.If this helps give tech 501 the accept its his schematic.Make sure the body and engine grounds are good also.
Expert:  Tech501 replied 11 years ago.
 Did you read what I said? There's not supposed to be and voltage coming from the computer. I told you to use a computer safe, ground reading testlight.. The EEC relay supplies power on the red wire with key on. The computer supplies trigger ground on the Tan/LtGrn wire and that is only for 3-5 seconds when the key is turned on. The pump is not supposed to run continuously with the key on, only for 3-5 seconds. It appears you have a problem with the EEC relay or it's controls because you have no power on the red wire with key on.
Tech501, Auto Service Technician
Category: Car
Satisfied Customers: 747
Experience: 38 years exp, ASE Mastertech with L1 Advanced Engine performance
Tech501 and 6 other Car Specialists are ready to help you
Customer: replied 11 years ago.
there isn't ground at terminal 40 or 80 at pcm (blk/ltgr wire)or at eec blk/ltgr wire. i checked all wires for continuity they were okay.i realize that there is only power supplied to pump relay for 3-5 sec when key is turned on.there is power to pcm supplied by yel wire but nothing is coming out of pcm.
Expert:  Davo replied 11 years ago.
 Run temporary wires from the battery to those terminals and see if it will run.Let us know what happens.The connectors have to be plugged in of course just make sure your connections are good.
Expert:  Tech501 replied 11 years ago.
 Why aren't you reading what I'm telling you? THE PCM DOES NOT SUPPLY POWER TO THE FUEL PUMP RELAY! It supplies trigger ground. The EEC relay supplies the "key on" power on the red wire and the yellow wire is coming directly from a fusable link with power all the time. You need to trouble shoot the EEC relay until it supplies "key on" power at the red wire.

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