1. Welcome to PlowSite. Notice a fresh look and new features? It’s now easier to share photos and videos, find popular topics fast, and enjoy expanded user profiles. If you have any questions, click HELP at the top or bottom of any page, or send an email to help@plowsite.com. We welcome your feedback.

    Dismiss Notice

89 F250 electrical gremlin

Discussion in 'Ford Trucks' started by Wilnip, Jan 11, 2013.

  1. Wilnip

    Wilnip Senior Member
    Messages: 583

    Truck idles fine, but when you start driving, it's like someone is turning the ignition off and on. Also, gauges not reading properly. Volt meter says 8-10v but have 14.2 at the battery. May be 2 different issues. Anyone have any ideas?
     
  2. Plowtoy

    Plowtoy Senior Member
    Messages: 929

    Check your ign switch. I had a ranger once that if you hit just a little bump in the road, the key would turn off and back on while driving down the road, I stopped replacing the muffler after about the 3rd one. I did get used to hanging the key ring over the top part of the cylinder and that seemed to help but it really just needed a new cylinder. I think thats pretty common in those older fords.
     
  3. tjctransport

    tjctransport PlowSite.com Addict
    Messages: 1,390

    these early trucks had a problem with the ignition switch separating. the plastic part separates from he aluminum part and you loose contact.
    easy fix by changing the switch.

    as for the volt meter, it is a sticking gauge. all my 88 to 91 trucks did it.
    you can either bop the top of the dash once running, or change the gauge.
     
  4. Brian Young

    Brian Young PlowSite Veteran
    Messages: 3,382

    Like the others said, sounds like an ignition switch, pretty easy fix. Let us know how it turns out.
     
  5. Wilnip

    Wilnip Senior Member
    Messages: 583

    We replaced the coil today, not it. I thought of the ign switch but turning the key doesn't make a difference when it acts up. I will dive into that in the morning and see if it's the issue.
     
  6. LEVE

    LEVE Member
    Messages: 79

    IIRC, that has an ignition module on it. The module can become intermittent, When this happens it kills all spark and the engine dies, just like turning off the ignition key. Take a look to see if the dialectic grease between the module and the heatsink is dried up. If it is, you may get by with new grease. Otherwise, a new module. It could be overheating, dying and then self-healing after it kills the engine. If this is the case, that self-healing mode won't last too long.
     
  7. MickiRig1

    MickiRig1 PlowSite Veteran
    Messages: 3,617

    Does it have duel gas tanks? My tank switcher went bad and it drove me nuts! You loose fuel pressure then it decides to work.. If you go the ignition module route get the heavy duty one. Have them test it before you walk out. I have got 2 bad ones right out of the box. Another failed within 5 minutes of starting the truck. The part stores have the tool to remove it. You have to have it to get it out. Check all your ground wires, clean and protect with dielectric grease. Coils are another thing i have replaced a few times. Check it's connections. If the spark plug wires are old. I would replace them too. Distributer caps seem to last 2 years. I write the date right on the cap with a marker.
     
    Last edited: Jan 13, 2013
  8. Wilnip

    Wilnip Senior Member
    Messages: 583

    Here's what happened so far. I ruled out ign switch by unplugging the wiring harness and using jumper wires to start and road test, not the problem.
    I checked the ign module, which was cracked so we thought that was the problem. Put new on on and no spark. So I figured the pick up coil was damaged in the process. So this morning I read MickiRigs post and had my guy remove and have parts store test module, which was defective. Put on 2nd new module and it fired up. Test drove to have the same problem. My employee did find that the ground coming from module and computer has voltage. No idea why. That may explain why the trucks volt meter drops and oil pressure and water temp gauges go crazy when driving. Any other ideas before I send give up on this otherwise decent truck? And thanks for all the suggestions so far.
     
  9. MickiRig1

    MickiRig1 PlowSite Veteran
    Messages: 3,617

    Have you cleaned and protected with Dielectric grease ALL your ground wires under the hood? Look at the wire harness real good. It may be too close to exhaust manifold. Could be rubbing somewhere. It sounds like a wire issue. Fuel pressure is good and pressure regulator works? That should have the two pump system. The pumps must have the correct voltage to work right. The high pressure pump is on frame rail and gets all kinds of weather abuse. My pump holder rusted out on my 89. Have you looked at your rotor and cap? How far from Akron are you? I have a new set of spark plug wires for a 5.8
     
  10. Wilnip

    Wilnip Senior Member
    Messages: 583

    Cap and Rotor are ok. We added a body to frame ground, and checked a bunch of other grounds. Some were not so good. I took it to the local shop today to let a fresh set of eyes look at it. I also told them to test the fuel pressure. I believe its electrical because when you turn on lights and blower motor, the volt meter drops to 9V, the temp gauge pegs hot, and the cutting out gets much worse. But you still have 14.2V at the battery so the alt is charging. When you do not have an electrical load on, it runs much better, but not perfect. Gotta be a short, but cant find it. This all started when the starter went bad and the solenoid fried. Since then we replaced the starter, solenoid, coil, ignition module.
    I'm about 3 hours from Akron.
     
  11. MickiRig1

    MickiRig1 PlowSite Veteran
    Messages: 3,617

    I tend to think it is in the run circuit of the ignition. Your not getting enough amps supplied to that circuit. My repair manual is somewhere in my garage. I can't remember which color the large wire is. By turning on a load that uses amps, you are dropping the voltage. The computer needs like 8 - 9 volts to operate. You said it started after you changed the solenoid and starter? Look real close at the connections and wire conditions. Of the wires connected to the post on solenoid. That is where the whole truck draws power from battery and alternator. The headlights should be on the always hot circuit, it supplies power to ignition switch, lights and stereo.
     
  12. Wilnip

    Wilnip Senior Member
    Messages: 583

    I checked the wires and solenoid several times. Even bolted all the wires on the hot side together and eliminated the solenoid just incase the solenoid was shorted out. That didn't help either. I agree with the ignition being robbed of voltage. That's exactly how it acts. But why? Ugh. Thanks for all the tips MickiRig.
     
  13. MickiRig1

    MickiRig1 PlowSite Veteran
    Messages: 3,617

    I laid awake last night thinking of what it could be. Problems like this just makes me think over and over what could it be? I am a trouble shooter at heart.
    When it does it, try lifting wire harness and moving it. You may find problem. I hope.
    A buddy of mine with a 93 - 5.8 had the same problem. I will call him tomorrow and see what they found.
     
  14. tjctransport

    tjctransport PlowSite.com Addict
    Messages: 1,390

    these trucks have the fuel pump and ECM relays on the driver side front fender. the connections to the relays are exposed, and prone to corrosion/failure.
    i had 3 that had an ECM failure and would not send power to the fuel pump. the only way to keep them running was to bypass the fuel pump relay power feed with a wire direct from the battery, triggered with a wire off the ECM relay. the only problem with doing it this way is that you also bypass the fuel pump inertia switch. so if the truck is in an accident, the fuel pump will run until the key is turned off
     
  15. MickiRig1

    MickiRig1 PlowSite Veteran
    Messages: 3,617

    Might think about getting one of the volt gages that plug into the cigarette lighter socket. So you can tell if the voltage really does drop.Make a setup with your VOM to test the voltage. The fuel pumps and computer need to have the correct voltage to operate. Something has to be limiting your amp flow to the working circuits. It could be your fuel pump relay or it could be a load / voltage drop issue. I HAVE NEVER seen the stock voltage gages fail or be the problem. Ford pays a lot to have them right.
     
  16. White Gardens

    White Gardens 2000 Club Member
    Messages: 2,665

    Didn't these trucks have an external voltage regulator on the passenger fender?

    Could that be the culprit also?



    .......................
     
  17. MickiRig1

    MickiRig1 PlowSite Veteran
    Messages: 3,617

    They are internal.
     
  18. White Gardens

    White Gardens 2000 Club Member
    Messages: 2,665

    When was the chang-over year? I know in 87 they were external.



    .............
     
  19. Wilnip

    Wilnip Senior Member
    Messages: 583

    That's a good point but I tested it this way. When the truck is in the shop, I turned on blower and lights. The volt meter drops to 9 or so. I put a meter on the battery and its at 14.2. So I don't believe that it. We changed the plug on the alternator since I know that it causes a lot of problems. It didn't help. On the bright side, I bought a 94 F350 with a Fisher plow on eBay yesterday. It will be delivered Wednesday. It will be my salt truck next year and will pick up the slack of the 89 for now.
     
  20. MickiRig1

    MickiRig1 PlowSite Veteran
    Messages: 3,617

    Don't give up on the 89 yet. I still think it's a connection or feed problem. If you have 14.5 at the battery, it's charging. The voltage / amp flow to the truck is the problem!