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Dieseljunky2
Dieseljunky2, Ford Mechanic
Category: Ford
Satisfied Customers: 3946
Experience:  ASE Certified, Ford Certified, Cummins Certified, & 20+ years in field experience
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Ford F150 Pickup starter solenoid

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I have a 1986 ford f150 w/Fuel Injection. It wouldn't start. I've replaced the starter, alternator, solenoid(twice), ignition switch(twice) and all GND and POS batt cables. I got the truck to start after replacing the cables, however when I turned the truck off and took the keys out starter continued to turn. Removed the ground from the batt and removed starter cable from solenoid. Re-connected batt GND and used tst-light to verify solenoid is stuck closed (it is). Also, tested voltage to the 's' terminal wire. Low voltage is constantly applied to this 's' wire with the key in RUN position(I think this is odd). 'S' wire recieves normal START voltage with ignition switch in START position. My concern is the 's' terminal being fed a constant low voltage with the ign-switch in the RUN position. Since I have replaced the Ign-switch (on top of steering column, behind dash) twice, I do not believe it to be faulty. Any help is greatly appreciated.

Dieseljunky2 :

Hello, is this a manual transmission truck?

Customer:

No. It is automatic. ?

Customer:

VIN: 1FTDF15N6GKB63454

Dieseljunky2 :

On your neutral safety switch, there are 2 red with light blue stripe wires. Disconnect the neutral safety switch connector and see if either of those have the low power voltage you are referring to. Let me know. Thanks

Customer:

Assuming the NSS is attached at the actuator arm underneath the truck, I guess I'll have to get back to you. I'm indoors, beer in-hand, watching the Rangers. I shan't crawl back under that truck until after Easter services tomorrow.

Dieseljunky2 :

That's fine, I should be back on tomorrow around this time or a little earlier. I will get back with you when I see your response. Thanks

Customer:

Agreed. Happy Easter!

Dieseljunky2 :

Happy bunny day to you as well.

Customer:

Okay. after having crawled under the cab at the driver's side, it appears this F150 is equiped with the AOD transmission, where the NSS is located indide the transmission. I did however locate a small cylinder (looks similar to an oil pressure switch) mounted at the top just above the shift lever assy into which run 4 wires. I was NOT able to separate the wire bundle at the plug, as it is stuck together beyond my abilities without having the truck on a lift. However I did manage to poke the tst light into each described wire. Two of these 4 wires match your description as red w/blue stripe. I tested these wires w/tst light as an assistant articulated the IGN-switch. Each wire tested exactly as the starter solenoid 's'-terminal wire. Each wire exibited constant low-voltage feed with the IGN-switch in the IGN-ON position, and exhibited full/normal voltage with the IGN-switch in the IGN-START position. If it is imparative that the plug be separated to run this test I shall again try to do so, hoping to not break it or pull the wires out of it.

Dieseljunky2 :

Disconnect the ignition module connector on the distributor and see if the voltage goes away. The ignition module has a wire going to it from the starter switch wire to turn it on when the starter is engaged. It may be that the module is shorted internally and feeding voltage back into the wire. Let me know what you find. Thanks

Customer:

Conditions; distributor Ign-module UNPLUGED, batt hot, starter supply disconnected from solenoid;; tst-light RESULTS: (1) starter solenoid 's' terminal exhibits same (low-voltage w/IGN-RUN, normal voltage w/IGN-START; (2) AOD transmission NSS loop exhibits same (low voltage w/IGN-RUN, mormal voltage w/IGN-START. Please advise nxt step(s). I'll be up for a couple hours, but dusk has fallen here, therefor my trusty halogen lamp must suffice.

Customer:

....additionally, there are 3 wires that connect directly to the HOT side of the starter solenoid, each with a fuse-link (I assume to suply power to accessories/lights/e-falshers, etc.). 1 BLACK, 1 RED, and 1 BLUE. The BLACK wire isolated supplies power to the 's' when IGN-START condition is met, but is dead/open when IGN-RUN condition is met. Adding the BLUE wire makes no difference with IGN-RUN or IGN-START. Adding the RED wire creates the low-voltage feed with the IGN-RUN condion.

Dieseljunky2 :

The only thing left in the system component wise is the ignition switch. You stated that you replaced the ignition switch already. Just to cover all the bases, remove fuse #5 in the fuse box in the dash and see if the power goes away.

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Customer:

Gimme about 10 minutes and I'll hollar back.

Dieseljunky2 :

ok

Customer:

True, the only HORIZONTAL fuse in the block, a blue 15A. Pulled the fuse out and re-conducted test (Ign module UNPLUGGED, batt hot, starter feed disconnected at solenoid:: Same results, no change to tested 's' terminal wire (ING-RUN=low voltage feed, IGN-START=normal voltage feed. The installed switch is a warranteed item respective to the first new one purchased (Auto Zone). If the remaining option is only the ign-switch, I wonder if an OEM purchase is in order, rather than playing roulette with third-party vendor-items, built/assembled under contractor guidlines. Determinations, thoughts???

Dieseljunky2 :

Does the voltage go away completely when the switch is turned off?

Customer:

yes, completely.

Dieseljunky2 :

Well. there is one more test that should be performed. That would be to remove the red/blue wire from the connector at the ignition switch, then turn the switch on and see if you have the voltage. If the voltage is gone, then the switch is the problem. If the voltage is still there, then you have two wires rubbed together and are getting a cross short from an ignition powered wire somewhere in the system. Can you remove that wire from the connector and then retest for power?

Customer:

If you mean actually removing the wire alone from the switch plug assy, leaving the plug in-tact with the switch, I fear I'll not be able to comply immediately. But, if you mean to remove the switch plug from the switch and runt the test again, testing the blue/red wire within the plug, that I can accomplish, albeit it'll be a few more than 10 minutes.

Dieseljunky2 :

I mean to remove only the red/blue wire and leave the rest of the wires hooked up. That way you can turn the switch back on to check for power. If you want to finish tomorrow, that's fine. Just reply back when you have checked. I am on most afternoons and evenings. Thanks

Customer:

How do I remove the wire from the plug/connector?

Dieseljunky2 :

After you take off the connector from the switch. Look at the side that goes into the switch. There should be either a red or gray insert in the center of the connector face. This pops out first. Then locate the wire in the connector . Looking at the wire on the conntor face, look insidethe hole where the wire terminal goes in. One side should have a very small tab sticking out and catching on a lip in the connector. You can depress that tab with a paper clip wire. Then the terminal should slide out.

Customer:

Wire extracted, switch in tact, all else as before:: isolated red/blue wire tested - switch articlated to IGN-RUN position, constant voltage feed, IGN-START position=constant voltage feed.

Customer:

.....or was it the 's' terminal wire to be tested???

Customer:

I may be getting the roof torn off the house in a minute....tornadoes and hail.

Dieseljunky2 :

The wire itself was to be tested. If the wire has power still, then to make certain, disconnect the neutral switch connector. It is now the only way to finish testing. If the wire still has power, you have a short. If it does not, then replace the neutral switch. Let me know tomorrow after the storm. Thanks

Customer:

will do. Thanks for your diagnostics this far.

Dieseljunky2 :

No problem

Customer:

I am so sorry; I forgot that today was Bible Study (weekends fly by too quickly), and I have been out all evening until now. I will be home shortly after 1800CDT tomorrow and will directly attempt to conduct the transmission NSS disconnect test and return hereafter to document the results. I shall write again tomorrow.

Dieseljunky2 :

ok

Customer:

Alright, hereit is:: Starter disconnected at solenoid; batt hot, IGN-module unplugged from distributor, IGN-switch connected to plug w/red/blue wire removed from connector, AOD transmission NSS disconnected at plug:: IGN-RUN == (1) 's' terminal wire exhibits NO VOLTAGE; (2) red/blue wire pulled from IGN-switch exhibits NORMAL VOLTAGE, (3) disconnected NSS plug - 1st red/blue wire exhibits NORMAL VOLTAGE, 2nd red/blue wire exhibits NO VOLTAGE. So, the only two wires exhibiting voltage with the IGN-RUN condition are the disconnected red/blue @ the IGN-switch and 1 of 2 red/blue wires @ incomming NSS plug. And so, what say ye?

Dieseljunky2 :

The red/blue wire is shorted to power between the ignition switch and the trans switch. Most likely in the harness going down to the trans sensor. At this point, it will just be a visual inspection of the harness to look for broken insulation or two wires melted together.

Customer:

I was soooo hoping it was the neutral safety switch. Thank you so very much for striving with me to this point. I greatly appreciate your tenacity and expertise. I hope your continued work in this capacity is fruitful.


 


Cheers!

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