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Starter Relay Issue---1986 F150 300 V6

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Old 04-24-2017, 08:32 AM
stpaulf150
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Starter Relay Issue---1986 F150 300 V6

Hey everyone, I've been having a starter solenoid issue on my 86 F150 300 V6 for the past few weeks. Every 2-3 starts, the solenoid will get stuck in the closed position and the starter won't kick off when I start the truck. I have replaced the solenoid, the starter, all battery cables, and have checked that all connections and grounds are free of rust and corrosion. Still happens, especially when hot. Where else should I be looking? Is a surge of power making the solenoid stick? Ignition switch? Thanks for your help, this is driving me nuts.
 
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Old 04-24-2017, 09:23 AM
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First, welcome to FTE!

High current is what usually welds a solenoid's contacts shut. A tight engine can cause high current to the starter, or advanced timing can as well. And, low battery voltage can cause higher than normal current.

So, is the engine new? (By the way, are you sure it is a 300 V6? The 300 is an I6)
 
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Old 04-24-2017, 09:28 AM
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Hey Gary, thanks for the welcome! Excited to be here with a gang much more experienced than I am.

You're right. The engine is the I6, not V6.

I checked the battery voltage and it's reading fine, although I do know that the current battery (replaced by previous owner) is technically too small for the truck. It's basically a Honda Civic battery, which has worked fine up to this point. Could that lead to this happening?

What's a tight engine refer to?

Thanks again, I really appreciate the help troubleshooting this. I bought this truck basically so that I could learn how to fix it, and I'm really enjoying the process.
 
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Old 04-24-2017, 10:10 AM
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I wouldn't have thought a smaller battery would cause that problem, but maybe. However, if you are going to replace it now would be the time.

What brand solenoids are you using? It is possible to get bad ones, and some have gotten multiple bad ones. Or maybe weak ones. The Motorcraft ones, even from a salvage, are preferred. Or, NAPA ones are said to be better.

A tight engine refers to one with tighter-than-normal clearances internally, like main and rod bearings. When warm the clearances are reduced, and that makes the engine hard to turn over, which pulls a lot of current through the solenoid. Tight engines have usually recently been rebuilt and the clearances tend to get larger with use.
 
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Old 04-24-2017, 10:11 AM
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I wouldn't have thought a smaller battery would cause that problem, but maybe. However, if you are going to replace it now would be the time.

What brand solenoids are you using? It is possible to get bad ones, and some have gotten multiple bad ones. Or maybe weak ones. The Motorcraft ones, even from a salvage, are preferred. Or, NAPA ones are said to be better.

A tight engine refers to one with tighter-than-normal clearances internally, like main and rod bearings. When warm the clearances are reduced, and that makes the engine hard to turn over, which pulls a lot of current through the solenoid. Tight engines have usually recently been rebuilt and the clearances tend to get larger with use.
 
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Old 04-24-2017, 10:20 AM
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stpaulf150, welcome to the forum!

As Gary said, it is not at all uncommon for the "cheapo" new relays to fail, sometimes on the first try. If you decide to go with Napa, be sure to tell them you want the "real" NAPA [normally Echelin] part. In order to better compete with all the other "box" stores, Napa has an inexpensive line as well as their better stuff.

If you have a friend who has a Ford truck, van or passenger car of the same era, ask if you can swap the part and see if that fixes your problem. If it does, plan to pay ~$35 for the Motorcraft of Napa part. Stay away from the $15.00 ones.
 
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Old 04-24-2017, 12:29 PM
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You might find this long-winded thread to be of some interest. The original poster had a similar situation as you. The eventual fix was to get a genuine MotorCraft relay:


https://www.ford-trucks.com/forums/1...solenoids.html
 
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Old 04-25-2017, 07:28 PM
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When it happens again pull off the small wire from the solenoid.
If it stops then the IGN switch is sticking and needs to be looked at.
May not hurt to check into it anyway. Pull the switch and clean it as it must need cleaning after all the years and adjust it.
Dave ----
 
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Old 04-26-2017, 06:27 PM
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Another option is to use a PMGR starter and rewire slightly to significantly reduce the load on the starter relay, aka "solenoid". See here: PMGR Starter Wiring - ???Gary's Garagemahal
 
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Old 04-29-2017, 03:33 PM
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Thanks for all the ideas everyone---

The current solenoid is a cheapo from O'Reilly's, so I'm ordering a Motorcraft solenoid from Summit racing to see if that can solve it. I'll keep ya'll posted.

Interestingly, I read elsewhere that someone used an Accel heavy duty motorcycle solenoid that fixed a similar issue. Anyone heard of this before?
 
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