Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!

Ford F-Series Fuel Pump/Fuel System



  • have same problem with my 4.9 can you tell me what and where is the IIC box is
  • There is a relay under the hood on the driverside finder just aft of the air filter box. It is in the group of relays all in a line there. Locate it and disconnect it. If the fuel pump shuts off you know the problem is the relay.
  • Truck was running fine, parked it for a few days and now it just cranks. Pulled a plug no apparent gas. replaced the fuel filter. Replaced the fuel relay. I can still hear the fuel pump doesnt cut off in either tank. Please help.
  • Turning on the ignition the pump should only run for about three (3) seconds. If it keeps running then the relay is bad or there is a jumper wire on the fuel lead of the analyzer plug to ground. If this is the case, remove the jumper wire to ground. This should only be installed if the system (pump) is being checked.
    I don't want to sound silly or stupid or make you feel like that but is there fuel in the tank? Strange things can happen, like someone steeling the gas...
  • Plenty of gas in both tanks. Where is the analyzer plug, not familiar with that.
  • Analizer plug or diagnostic plug is located on the driver side fender well next to all the other relays. I believe it is the most inside one (toward engine) near the air box. It is just clipped to the row of relays. Odd shape, with 6 slots (flat blade) in it. If there is no ground jumper wire going to it then it is not the culprit. If that wire is shorted somewhere in the system though it will make the pump run continuisly with the ignition switch in the run position but the engine not running. It would probably be wise to pick up a "Chilton or Hanes Manual" for the truck. they are available at most parts houses for around $20.00...
    I am not certain but I think the fuel pump wire (s) are green with a pink tracer, but it is best to check the book to be sure of this.
    The only time the pump should run continuisly is when the engine is "running". But even if the pump is running continuisly the engine should start. Makes me think of the relay may be at fault.
  • I got the truck started using starter fluid. Now it idles 'okay', but if you step on the gas the engine bogs down. I can ease the rpm's up.
  • Been having troubles myself that seem to match those listed here exactly. With the two tanks, it used to be that only one tank acted up, choking every now and then and bogging down until it eventually died off entirely. Swapping to the reserve tank seemed to work just fine though, so I didn't worry about it. Now the reserve has started to do it as well, and both whereas the first tank used to do it only sparingly, since the reserve started it both tanks are doing it constantly now. When I turn the key and prime the pumps, they stay on constantly, just as described in the posts above. It'll run fine sometimes for a minute or two, then it'll begin bogging down if I use too much pedal. Then it eventually gets to where it can't even start. I took it to the shop, had them look through the whole fuel system. Everything checks out fine, even the Fuel Inertia Switch. The only thing they mentioned was that my PCM is heavily water-damaged and that they couldn't be sure if replacing it would solve the problem.

    My question is, could the PCM cause this? If it's unlikely, then where do I need to be looking? I know there was talk of a ground jumper, someone even mentioned it might be some kind of ignition control module or such. I don't know where any of these are located in the truck, and I'm running out of time before I'm out of the Army, and technically out of a job and home. I HAVE to get this truck running again, please help.
  • If your fuel pump relay is good. I have no explaination why the pump would run continually while the engine is not running. As far as starting on Starter Fluid (either) then ideling ok, It sounds to me like the pumps (both)are shot (worn out). Did you run a pressure check on the pumps? Maybe you need to hook a test gage to the schreader valve in the fuel line behind the engine and start the engine (even if you have to use starting fluid, which I don't like at all), once the engine starts and idles, keep an eye on the pressure gage. It should have a minimum of 40 psi and should probably be more like 60 to 70 psi. If this pressure is low (below 40), I suggest replacing the fuel pumps. Other than this, I have no idea what could make what you describe happen.
  • I tested the pressure and it showed fine (58 psi w/o the truck running 53-55 running). Now the problem has become intermittent, I will get a check engine light and it will barely run. The light kicks off and it runs great for a short time then the light comes on and it's back to not drivable. Thought for a while it might be the pressure regulator but I can't imagine that being intermittent or seeing the good numbers noted above. Would the regulator have a check engine light?
  • Yes your numbers look great. Which makes me think that it is probably a bad wire or connection somewhere. Next time you start it, just leave it running and start moving or shaking the wires under the hood. If you find something that makes it run different, strip the harness and check for a bad wire. Intermittent problems are always the hardest to find. It would be great if you had an Engine analyzer to check it. If you lived just down the road I would lend you mine but it just isn't the case here I guess. So, maybe you know someone who does have one? At least that might tell you where your problem is...
  • Mike,

    I went out and got an analyzer. The problem just gets stranger. I did the key on engine off test and it made my engine light turn off it tested okay. The only stored code was a engine control assembly problem (thats what the book from the analyzer called it) when I looked it up on the internet it said a power interrupt. Code 512. If I run it without the analyzer the light comes back on and it run horrible. I did the engine running test and got a all okay code 111 once and 225 (knock sensor signal not detected. Even before the cel come on it runs rough without the analyzer. With it it runs great. I'm at my wits end. any help would be greatly appreciated.
  • This is truly dazzling. But it sound like a bad connection in the wiring harness. Did you do the wiggle test? With the engine running move around the engine compartment wiggling the wiring harness ( actually bending it when ever possible), anywhere you can get hold of it, then check the analyzer again to see if anything new has come up. Also while doing this wiggle test, listen for changes while the engine is running. I am going to investigate this a little further as I have time. I will leave your e-mail active on my computer while doing so and making sure I haven't forgotten. Anyway, when I find something I will write again. and if you find something PLEASE let me know. Thank you.
  • Also, what kind of anylizer did you purchase?
  • he 512 code is the engine "Keep Alive Memory" which tells me that the computer is at fault. It would seem that it has no Open Loop Capability.
    When ever you replace a part or make a repair, you are supposed to disconnect the battery. Removing the negative battery post makes it safer to work on the engine AND tells the computer it needs to look for new parts or corrections to the control system etc.
    Disconnect the battery, leave it disconnected for at least 10 minutes. Then replace the battery lead. Start the engine and take it for a drive. It WILL RUN ROUGH for a bit. You need to run it continually at a constant speed of 55 MPH for around 10 miles so a highway is always best. Keep the speed as constant as possible while the computer checks the engine and controls positions and situation. Hopefully this will create a keep alive memory for your computer. Code 512 is the knock sensor which I believe is located on the passengers side of the vehicle block. Check the connector and wire from it into the harness.
    code 111 is the ok code for the system. The analyzer is probably replacing the vehicle computer while getting this code and after disconnecting the analyzer it tries to go back to Keep Alive Memory because the problem hasn't been corrected but can't because it hasn't got a memory. Maybe a new computer is in order. Please let me know what you find.
  • Mike,
    I appreciate your time and help. The analyzer I bought is an Actron code scanner.
  • Mike,
    I took out the computer and see no signs of heat or burning which I have seen on other forums being the common problem. Do you know of anyone that can test the computer so I am not spending the $ on something I don't need.
  • I am sorry, I sure don't know who might be able to test it. Maybe a smog certification outfit...Not sure. Seems like everything I have heard is people saying to replace never anything about checking it. I suspect the one in my truck is also the wrong computer so somewhere down the road I am looking at purchasing a new one as well. If you find someone who does, will you please let me know?Good Luck.
  • I have 1992 V8 XLT with 2 gas tanks. The truck runs great, until today. I drove it home from class last night about 15 miles and parked it around 9pm. I got up this morning and it won't start. Just turns over. I can start it spraying starting fluid in the intake, but dies if I stop spraying it. I'll list what I have tried, but it has me stumped.

    My fuel rail has no pressure at all. I can't hear either of the fuel pumps kick on, no matter which tank I select.

    I checked the selector switch, it is working. I triple checked to make sure I have gas in both tanks.

    I checked the inertia switch, it wasn't tripped. But I tripped it and reset it anyway.

    I replaced the fuel pump relay in the distribution box under the hood.

    I checked all fuses in the distribution box, and in the cabin under the dash. None were blown.

    I tried unplugging the Map sensor.

    I tried disconnecting the battery for 3 hours straight.

    I checked for broken wires, but I can't find any, unless they are hidden else where...

    One other bit of information that may or may not help. I live a block from the ocean which can be a very corrosive environment.

    I am stumped. Does anyone have any suggestions that I haven't tried? Similar experiences? Any advice would be GREATLY appreciated. Thanks for your time.
  • Update, I'm pretty sure its the EEC, I used a wire to jump it and get a CEL code and it failed the test. 15 flashed. Plus I took the kick panel off and it looks pretty rusty. 100 bucks for a new one tomorrow. Wish me luck.
  • Check the fuel Filter. It should be located in the frame rail on the drivers side.
  • Mike,

    I did every test at home that I could do and still couldn't prove it was the PCM. I finally took it to a Ford dealership and for a $200 fee found out the PCM had a short in it. So now on the hunt for a new computer. Autozone has one for $297 but I will look around for a deal. I'll let you know what I find.
  • It pleases me that you have found the problem, although it has taken a lot of searching and replacing parts. I appreciate you letting me know. I know there are re built units out there as well but don't know how much stock you can put in them. So, apparently, putting your analyzer onto the truck puts the engine into the open loop causing it to run smoothly???Strange, anyway, I'm glad for you. I am still fighting mine getting it smogged here in Cali, my analyzer says it's no. 6 cylinder when I run a cylinder balance test on it. So I guess it could be the injector or compression who knows till I test for all.
    Thank you and keep me informed as to the new computer and how it runs after installation.
  • I was wondering if you had any luck with a new EEC? I am having a similar problem with my 1991 F150 6cyl 4.9l and I am thinking about getting another EEC.
  • It actually turned out to be the fuel selector switch. Even though I was getting power to it and I was getting a reading on my multi-meter and also at the inertia swtich, it wasn't sending signal to the pumps. Forget the multi-meter and use a test light at the switch, and running power to the pumps by carefully splicing the wires near the back tanks. Also, it helps to have someone who can switch the ignition on and off for you. You can do all this without dropping the gas tanks too. Good luck
  • 1990 ford f150 6 cylinder, bought this truck 2 months ago, would not start , was not getting fuel to spark plugs, spray gas or eather in throttle body would run till it was gone, put new fuel pump, fuel regulator, and just put in new fuel injectors, still not getting fuel to spark plugs, put nodes on wiring to check power to fuel injectors, nodes blink real fast, so i am getting power to the injectors, this truck has duel tanks, it was running off of the back tank only, if you push the selector switch from back to front tanks,you can hear the pump run, i took out the front tank, and left it out because it had water dirt build up and the fuel pump was no good, since i put in this new stuff i have not check the fuel pressure, bot it is getting fuel to the relief valve on the fuel rail, if anyone can help me i would really be thankful,
  • mike9408mike9408 Posts: 74
    edited December 2011
    The fuel pump should run for a few seconds after turning on the ignition switch. You should be able to hear it run during this time...Have someone turn the ignition switch on while you listen at the tank...If you cannot hear the pump run I would check the fuel pump relay. It should be located on the drivers side inside fender well just behind the air filter box. Also, check the inertia switch on the inside of the cab next to the steering column where it goes through the firewall, reset it if necessary.
  • mike, fuel pump runs, it runs about 3- 5 seconds, iam getting fuel up to the fuel rail, my fuel injecters are not spraying, does fuel pressure open the injectors or does the computer do it when start up, thank you
  • I have a 92 with a 302 duel fuel tanks...The truck starts up and drives great on a cold start up, after driving for appox. 15 min. if i shut the truck off it won't start back up..just turns over..if I wait for about a half and will start back up..but runs rough. i have replaced fuel filter,pressure regulator. Also, When I do try to start it when hot..if I hold the pedal to the floor it tries to start but usually for a second and then stalls. I only use the front tank..the back never worked...but I can hear both pumps kick in when I turn the key. Just looking for some help..thanks
  • do this, next time it does it. pull one of your spark plugs off and see if you are getting any gas in your cylinder,if not it might be your sock on your fuel pump, or your fuel pump might be getting hot and not pumping enough
Sign In or Register to comment.