Question about 1991 Ford F250

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Fuel pump relay losses power to yellow wire

While running power to yellow wire on relay losses power, and that makes no fuel to engine. engine then dies.

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  • rockinem May 13, 2009

    I checked the Fusable link and that was not the problem. Then fuel pumps are new.

    When you start it up it will run for a while then the power to the fuel pumps will be shut off some how. At the relay is where I have found that the power will be lost. The relays are also new.



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If you wired it yourself, note: yellow is a source wire in most wiring systems - red - direct power (battery/fuse box) - yellow, relay switch to part/component (i.e. fuel pump{electric}); then ground.
Ground, if self-wired, can be grounded to the frame,body, any metal.

If the wiring is not the issue, replace the fuel pump relay, if haven't already. If this is not the problem, or has been replaced already, you may need to replace the fuel pump. NOTE: If this is the Ford e F250,350 etc. it may have a secondary fuel pump which would be located on the driver side mounted to the frame just behind the engine. I owned a 90 F250, 2WD, and no such part was installed. At least not there.

I had a similar issue with my truck, would start, sometimes run for a while and die, would drive, then randomly die while driving -

Check the fusable link next to the battery and ensure it is securely locked together - it is a twist and pull mechanism (plastic). This was the issue with mine. I tore the front of my engine apart thinking it was a timing issue, just to find out 4-5 times of doing that, that it was the fusable link - i too, replaced the fuel pump relay, fuse etc. -- check this first as it may be the cause (if carburated, also check all your plugs, wires, cap and rotor - if not carburated, have the coil packs tested - NOTE: the modular (coil packs sit/bolt to this) cannot be tested - look for bubbles, or sign of "boiled" sections. If such marking exist, it needs replaced. Have the coil packs tested anyway just to be sure. If they all test positive, your good to go - if not, replace as need - (also be suire to mark each one in the order they come off ) this doesn't really make any difference when you put it back together, however, this will let you know, in the event the modular is good, (no boils or bubbles etc) ; you will be able to determine which side (if three, left,middle,right) was the bad coil pack. Mark each, from left to right, as 1,2,3, or A,B,C - or however you deem suitable. This will be useful for reference in possible future occurrances.

I hope this information is helpful and you get your vehicle running smoothly. I understand your frustration with this particular issue, as it took me 2-3 months before I realized that the fusable link was the issue - had spent 3-4 hundred dollars in parts ---

Please let me know if I can be of any further assistance. Thank you,


Posted on May 13, 2009

  • Brandon Bruce
    Brandon Bruce May 13, 2009

    On some newer vehicles, if the vehicle is hit it will automatically shut off the fuel system. If this vehicle was equipped with such that may be the problem. I don't think they were; i'm not sure if mine did or not...I'll do some researching and see what I can conjure up.





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90 f150 fuel pump wont come on check relays and reset not getting pwer to the pump

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Well for starters, you need to diagnose the problem before replacing anymore parts. I say this because you mention both the fuel pump and sensors dealing with the ignition system which are 2 separate main things. Basically it takes 2 things to make an engine start, fuel and spark at the spark plugs. You need to narrow down what is missing because it seems since you replaced sensors dealing with spark and then you mention the other need fuel. I'm not sure as to where to start to help until whatever is missing is diagnosed and then find the cause of the loss. There are a couple of things you can check. Below is a picture of the relay box in the engine compartment. With the help of somebody put a finger touching both the fuel pump relay and the EGI main relay. While touching them have somebody turn the key to the "on" position (no need to try and start). When the key is turned on you should feel a "click" inside both of those relays. The fuel pump relay will click for about 3 seconds and the click again to shut off. The EGI main relay should stay on. If both seem to be fine you need to make sure of the fuel pump gettting "juice" and for power to the ignition system like the coils. You can get to the power/juice wire at the fuel pump pretty easy. You can access the connection at the fuel pump by lifting the lower part of the rear seat. Once the seat is lifted you should be able to see a part in the carpet that is cut to be able to lift the carpet up and access the plate covering the access to the fuel pump and/or the top of the fuel tank. Using a test light, check the green and yellow wires at the fuel pump. You should have power at those wire when turn the engine over or if the key is just turned to the on position you should have power there for about 3 seconds. To begin checking for spark or power to the ignition system you need to make sure you are getting power to the ignition coils. The red and white wires at the coils are your power wires. Check those. Also you can check the power at the fuel injectors. When the key is turned on or when trying to start, you should have power to the green wire at each of the fuel injectors. You should have constant power/juice at each of the fuel injectors. This is where I would start to narrow down the loss. Start here with these tests and let me know how the tests come out by replying/commenting here or you can email me directly at ith what you have found out. Once the first tests are done and I know what the results are, we can go to the next step with a couple of other tests to figue the problem out. If one of the relays don't "click" then you have a possible bad relay. The EGI main relay is a common thing to go as well as the fuel pump relay. Don't mind helping and there is no cost to you for it but I don't want to tell you to start replacing parts until the problem is located. Hope this helps get you started.


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Are you getting battery power and ground at the fuel pump connector? (This should have been checked BEFORE replacing the pump)

Other things to check:
1. Fuel Pump relay in the Engine Compartment Fuse Block
2. The relay is powered (Secondary -or- "fuel pump side") by Fuse 0 in the Engine Compartment Fuse Block.
3. The relay Primary -or- "control" side is powered by Pin 37 RED wire at the PCM
4. The relay Primary control (or ground circuit) is operated by Pin 22 LIGHT BLUE/ORANGE wire at the PCM
5. The Inertia Fuel Shut-off Switch located between the fuel pump relay and the fuel pump may need to be reset. The switch is located behind the right kick panel. The DARK GREEN/YELLOW wire at the switch is the feed from the fuel pump relay. The other wire goes to the fuel pump. Some units have the DARK GREEN/YELLOW wire going in and the wire going out can also be DARK GREEN/YELLOW, or PINK, or ORANGE - the wiring diagram for your vehicle does not specify the color of the wire that actually goes to the fuel pump itself.)
6. If none of the above produce any results, make sure that your ground wire at the fuel pump has good continuity to ground. It usually screws to the left frame rail near the fuel tank.

Any of these components (including the PCM) or their connecting wires could be the cause of your problem.

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Starter motor went out on 92 5.0 ho replaced it and new battery, now fuel pump does not work I get a 542 code checked fuel pump relay and inertia switch both good fuse good

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Engine Starts:

· Fuel Pump secondary circuit shorted to power

· Fuel pump relay contacts always closed

· Open in fuel pump monitor (FPM) circuit between ECU and connection to POWER TO PUMP circuit

· Heated Exhaust Gas Oxygen (HEGO) sensor shorted to power

· faulty ECU

Engine Does Not Start:

· Open inertia switch or inertia switch circuit

· Open in or between ECU and fuel pump (This includes open in fuel pump brushes/windings)

· faulty ground connection at fuel pump

The easiest way to check this circuit is to go to the fuel pump relay. If the relay clicks when the key is turned to the "RUN" position, then the inertia switch circuit is ok.

The Pink/Black wire starts from the fuel pump relay and goes two directions. One side goes back to the fuel pump. The other side is the fuel pump monitor circuit and goes to pin #8 at the ECU. This wire should only be hot for a second or two when the ignition is turned to the RUN position.

The fuel pump relay receives power on the Black/yellow wire. It comes from a fusible link at the power distribution center. This wire should be hot at all times.

If all the above is working as designed, them you probably have a bad fuel pump.

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Where is the fuel pump relay located. i have a 2003 honda odyssey 3.5 v6

  • A clogged fuel filter or problems with the electrical system powering the fuel pump can result in symptoms similar to a failed fuel pump. Have the shop verify that the pump is the problem before replacing.
Best Practices
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Common Symptoms
  • A failing fuel pump will not create enough pressure in the fuel system, potentially resulting in a loss of engine power or a "no start" condition. You may also have a lean running condition that can set a diagnostic trouble code and turn on the Check Engine Light.
  • Fuel pumps require replacement if they leak or begin making too much noise, which is a sign of malfunction. the fuel pump relay is located under hood inside a box with alot of other fuses in it and relay it will be maked fuel pump relay

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Did you check the fuel inertia switch in the passenger side kick panel ?

The fuel pump is powered :
the fuse to the fuel pump relay.
The fuel pump relay to the fuel inertia switch
The fuel inertia switch to the fuel pump itself.

At the fuel inertia switch in the kick panel, power from the relay is the Dark Green w/ Yellow stripe wire and the pink w/ black stripe wire is the power. from the fuel inertia switch to the fuel pump.

If you jumper the fuel pump relay, you should hear it run. If not pull the fuel pump relay, and check the pins in the relay socket, pin 30 should be the power from the fuse.


If you have power at pin #30, jumper the relay socket as shown with the red line above, and check the dark green w/ yellow stripe wire at the fuel inertia switch for power.
Press the button on the top of the fuel inertia switch, and check for power leaving the fuel inertia switch on the pink w/ black stripe wire.

This is tests good, check for power at the fuel pump, same pink w/ black stripe wire.
Fuel inertia switch info is in the owners manual, If you did not get an owners manual with your truck ( purchased used ), you can download one from Ford :

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Once you check the fuel inertia switch in the passenger's side kick panel, next is to check the fuel pump fuse, engine compartment fuse # 10.

If this checks OK ( power on both sides ), you can pull the fuel pump relay, and jumper it.

The engine compartment fuse panel is where the fuel pump relay is located at ( relay # 301 ). Pull the fuse pump relay out of the socket, and using the diagram below, with the red line, momentarily jumper the Normally open contacts, you shoud hear the fuel pump run. ( mind the pin orientation when doing this ) :

I had a bad fuel pump relay on my 2001 F-150 @ ~ 36K miles. Replaced with the trailer tow battery charge relay ( relay #302 next to it ) and it worked again.
The symptom I had was a crank no start ( theft light on dash went out ).

If the fuel pump does not run, and power is on pin #30 in the relay socket, next is to check the output of the fuel inertia switch in the passenger side kick panel. The output of this is the Pink w/ Black stripe wire. The connector to the fuel pump inertia switch should be a 2 pin connector, the other color in the connector is Dark green w/ Yellow stripe wire ( that is from the pin #87 in the relay socket in the engine compartment ).

If that circuit has power at the passenger side kick panel, next is to check for power at the fuel pump at the fuel tank. The fuel pump motor is the same Pink w/ Black stripe wire. The connector is a 4 pin connector with black ( ground for the fuel pump ) black w/ orange stripe ( ground for the fuel level ) and yellow w/ white stripe ( to the instrument cluster for the fuel gauge ).
When testing by the fuel tank, make sure you have a good ground for the meter ( extension from neg on the battery or trailer tow adapter ) as that could also be a problem under the truck.

Sorry for war and peace, hope it helps.

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1 Answer

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Sounds like the problem might be in the relay but before replacing that relay, check all fuses and especially any ecm fuses. Do you have a check engine light come on when you turn the key to the on position?I believe that on this vehicle there is a relay that is labeled "eec relay" this is the relay for the power to the ecm. eec stands for "electronic engine control" If this circuit is dead the fuel pump relay will not come on either, but worse than that the ecm stays dead and the injectors are not delivering the fuel to the engine even when you jump the fuel pump manually.
Check these items and make sure that the computer is getting power and I think you problem will be found.

There is a black wire with a connector like thing in it near the battery cable on the negative post make sure that this connection is good ,it is the ecm ground and the same symptoms will happen if it is not connected well.

Good luck. I hope this helps.

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The PCM then activates the fuel pump relay, sending power to the fuel pump.
You should have one wire with 12V for 3 seconds in "run" position. This comes from the fuel pump relay to the inertia switch in the trunk and then to the fuel pump.
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You may have another ground iwre ging to a diode before going to ground.

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