I have a 1987 Ford F-150 4.9L pickup with about 100K that I use here on the farm. The other day I gave it its fall washing, pulled it up next to the house, cleaned it up and checked the lights and things for state inspection. The next morning that I was to take it to town, it wouldn't start. I listened carefully when I put the key into the ignition and turned it to the on position, and there was no sound of the fuel pump activating. I pulled the fuel pump relay and checked it out and it was OK. I checked the voltage first to the ECC power relay and it clicks and functions correctly. The fuel pump relay has power to the high and low power sides if the relay and I jumpered the fuel pump power terminals and the fuel pump went on. I measured the voltage to the high and low power terminals and they were 12.5 V. I then measured the voltage between the solenoid power wire 361R terminal and the other side if the solenoid terminal 97T/LG and my reading was 10.25V when I turned the ignition key to on pos.. There seems to not be enough voltage to energize the solenoid or to light a test light. I also have continuity between the 97T/LG terminal and the test terminal on the VIP self test connector. Now my question is the following, what is the mechanism that limits the fuel pump to about 2 seconds run on when I turn the ignition switch to the on position? Also another question, Does this seem like a EEC problem or a wiring connection problem although the truck runs with a jumpered fuel pump? The only thing that I see next is to look at the EEC connector at the firewall and see that all connections are good there.

 

Have you checked the inertia switch? These trucks have a little button some where under the dash it may be hidden mine is on the passenger side upper kick panel next to the door has a little notch to where I can slip a finger in there and reset it yours may be in a different place it will have a red button top if you can see it. These are installed to kill the fuel pumps when your in an accident locate it and see if it hasn't tripped.

For you truck an 87, I would look up under the driver side area above the pedals for that inertia switch.

 

have you tried another fuel pump relay yet? good ground to fuel pump relay?


it still sounds like that's where your issue is.

 

It sounds like you already have jumpered the fuel pump test connector and determined that the fuel pump does indeed run when jumpered and that the truck will run with the fuel pump jumpered. Good news is the fuel pump, relay and inertia switch are proven to be in working order along with the associated wiring.

To answer your question, the ECM contains an electronic timer that shuts down the fuel pump if it does not see PIP pulses from the distributor. This is a safety feature designed to shut down fuel delivery to a non running engine. You already noticed that the fuel pump relay has power to both sides of the coil with the key on, but the engine not running. This is because the ECM removes the ground from the relay coil to shut down fuel delivery. The fuel pump test connector is the same point as the relay control output from the ECM and it can also be described as the - side of the relay. The + side of the relay is always live when the key is on and actually gets power from the ECM power relay. Measuring power at the fuel pump relay proves the ECM power relay is working. The test point will measure +12 volts with the key on and the engine not running and ground, or 0 volts with the engine running. Grounding the test point is the same as getting a running engine signal from the ECM and will run the fuel pump continuously.

So what goes wrong? If the pump comes on for a second when the key is turned on without starting the engine, the ECM is functioning correctly. The fuel pump test point should go to 0 volts with the engine cranking or running. If it does not, the ECM may not be seeing PIP pulses from the distributor. This may be the result of a broken wire in the PIP circuit, a faulty distributor or a missing ground to the ECM. Rarely, it can be a faulty ECM. A bad pickup coil in the distributor will cause this along with a no spark condition. Often, the problem is the main ground on the inner fender by the battery. One of those two heavy black wires is the ground for the ECM. On early EFI trucks with a 5.0, the fuel pump circuit returns to a ground via a connection to an intake manifold bolt at the rear of the engine. If memory serves me correctly, the color of the ground wire in this case is something other than black

 

Thank you Zemus420 for your input. I thought that the inertia switch was probably good because my fuel pump would operate when jumpered through the fuel pump relay. I do not know where the switch is located in this truck but I will look for it soon so that I will know in the future.

 

Thank you 68Mercury250Ranger for your reply. I had purchased a new relay and tried it yesterday with no difference from the old original relay. I had taken the old relay to my shop and tested it with another battery (even at 10.5 V) and my test meter and it clicks and works just like it is supposed to.

 

Thank you NotEnoughTrucks2014 for your help also. I only had about an hour today with the truck and disconnected the ECC interface connection at the firewall on the drivers side and blew it out with an air hose and tried to see that it was dry and clean without oxidation or some sign of shorting. It is now clean and dry and coated with a little grease and reassembled. I checked the continuity between the interface connector and the test connector and also the fuel pump relay and they all test sound. I just had time in the dark to put the key in and turn it to the on position but no 2 second hum from the fuel pump. I have checked all of the ground connections that I could find and cleaned them and reassembled them. I found one at each headlight area and one from the block to the firewall plus a strap to the hood and one at the interface connection at the firewall but I cannot say that I have found the one on the inner fender but I will look again tomorrow. The two heavy duty wires (other than the main cable coming from the battery -) duck into the wire harness and then it is hard to see where it would connect to the chassis.
I think that I should have a 2 second reading on my test meter of +12V when I turn on the key to energize the fuel pump solenoid (across the solenoid terminals) and then have it drop out after 2 seconds and loose the grounding from the ECC if it is working correctly. I will try to check that out tomorrow if it isn't raining.
I will continue to study your reply and try to digest your comments so I may have more to report tomorrow. Thank you again for your information.

 

G101 is the one you are looking for:

courtesy of Subford

 

Thank you rla2005 for the help. It has been raining and I haven't had a chance to get back into the truck without getting me and everything else soaked. I will head for checking out the grounding of the system as the first task when I can get back to it. We have had a real soaker for the last day or so.

 

zemus420, I had found the inertia switch earlier but didn't know that it was the inertia switch. It looks like a circuit breaker with a white button on the top. I thought that it was an overload breaker of sorts with a reset button. Probably the reason that I am so ignorant about this truck is that it has been quite a trusty truck for me.

 

The ground for the computer is a black wire with a green stripe and it is hooked to NEG post of the battery and not any part of the truck. It will (should) also have a one wire connector close the the NEG post of the battery.

This is a common problem after washing the engine compartment with died out grease in the computer plug. In other words the computer is bad from a shorted pins in its plug.
The engine runs so you do have power to the computer and a ground for the computer or the injectors would not be firing.

The Computer ground on an 87:



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I had a little time between the rain ending and the Christmas Eve service at church to look at my setup and this is what I found. On this pickup, the negative post of the battery has 2 additional wires molded into the connector besides the main heavy frame mounted cable. They connect to 2 black wires one with a green stripe and the other with what looks like white or something close to it. There was a compression connector attaching the 2 black striped wires to the wires from the post clamp. I unwrapped the tape that was around them and checked the continuity of both wires and they were of sound connection so I re-wrapped them together with new electrical tape to keep them clean.
I had a chance to test the fuel pump relay connector with my meter and found 12.6 V between the fuel pump hot yellow and ground, 12.5 V between the fuel pump hot yellow and the fuel pump black, 12.6 between the fuel pump solenoid red and ground, lastly 10.24V between the fuel pump solenoid red and the fuel pump solenoid T/LG. I put the meter on the 2 solenoid wires with the key in off pos. and read 0, turn the key to on pos. and the voltage pops to 10.24 and stays there. I get the same readings through the test connector also. I then ran out of time and had to scoot. Tomorrow or so I will jumper the fuel pump relay contacts to make the fuel pump run, start the truck and try to read what the T/LG wire does while starting and running. Thank you for your attention, I really don't know what to do after I try the next test or what I will do when I find out the results. I wonder if there is a way to reset the ECM other than disconnect the battery as I have done a few times recently? Thank you all again.

 

Well, I got a lot of good info on this subject a couple years back when my 86 F150 decided the fuel pumps would run intermittently. Link to that discussion.

https://www.ford-trucks.com/forums/1...y-control.html

Now, the 86 is a completely different animal as to the wiring layout, but the real solution is in that there are multiple grounds applied to the ECM and the ground you apply to the fuel pump relay via pin 22 of the ECM is dependent on a good ground at pin 49 of the ECM. You could check for continuity to ground at pin 49 of your ECM connector.

 

Pin #49 is not a ground point or pin to use. Pin #49 is the EGO ground and it does not connect to any ground point.

Computer grounds and 5 Volt supply:


Pin #49:

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a few years ago i ran into the same problem on an 87 F150 5.0 farm truck. ended up being a bad computer not sending power from the EEC relay to the fuel pump relay.
i ended up running a separate relay powered directly from the battery to the fuel pump, that was triggered by a keyed ignition source in the fuse box.
my remedy is still working, but the truck is for farm use only. it is so rotted it would never pass state inspection for on road use.