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Discussion Starter · #1 ·
Okay here we go again the never ending saga with this beast.

My bronco died out on me a few weeks ago and I finally tracked it down to being the fuel relay harness connector was bad. Replaced that and it fired right up. Now having another issue, it runs but misfires badly. It seems to do it less when I remove the spout connector and kick the ecu out of the timing. I know the timing is correct because I just timed it. Plugs/wires/dizzy are all new as well because I replaced all these components when it crapped out the first time and I had no spark. The only symptom now I can tell is that my fuel relay vibrates. Like an electric toothbrush. I haven't owned one of these before but I am thinking that isn't normal. Fuel relay is 3 months old. Any advice is much appreciated.
 

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95 EB Bronco, 5.8L
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Likely electrical, I would check for any bad grounds, corrosion on the connection pins etc. If those are all good and it's still buzzing, try swapping out the relay with a similar part# relay. Have you checked fuel pressure? Replaced fuel filter?
 

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Discussion Starter · #3 ·
Yes sadly I think I am going to have to chase down an electrical issue. Fuel filter/pumps are new. Haven't swapped out the relay. Hate to just throw new parts at it but I suppose it's worth a try. Thank you.
 

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95 EB Bronco, 5.8L
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I'm not sure about the your EFI setup on your 86, but on an old Ranger of mine, there was an identical relay in the control box. You might luck out and if yours is similar, you could try temporarily swapping them without having to buy a new one.
 

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Discussion Starter · #6 ·
Yea I don't think I have any other relays that are compatible. Wouldn't be the worst thing to try I suppose it isn't like it is expensive. I just highly doubt it is the relay as like I say, it is only a few months old. I do know that the inertia switch on the Bronco was bypassed by the previous owner. Think that could be the culprit?
 

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1986 Bronco Eddie Bauer 5.0 mostly stock
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Yea I don't think I have any other relays that are compatible. Wouldn't be the worst thing to try I suppose it isn't like it is expensive. I just highly doubt it is the relay as like I say, it is only a few months old. I do know that the inertia switch on the Bronco was bypassed by the previous owner. Think that could be the culprit?
Buzzing is generally caused by voltage issues, so you may have a bad connector or bad wire or bad ground or a bad relay. As far as the inertia switch, it depends on the quality of the bypass job...if the jumper wire is a corroded flimsy piece of crap then yes, that could be a problem, but if its a good jumper capable of carrying the juice needed then it's probably OK. If i recall correctly, its a pretty good size wire, like a 12 gauge maybe that runs through the switch, so your jumper needs to be that same size.
 

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Discussion Starter · #8 ·
Okay I'll have to look. The harness connector was bad, so I just replaced that so I know that is good. Bad connector was causing a no start. Now the issue is purely the vibrating relay and the misfire. My understanding is that the vibrating is the relay constantly getting and losing voltage? So have to dig through the rats nest I guess 👍. Yay 80's EFI.
 

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1986 Bronco Eddie Bauer 5.0 mostly stock
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If i understand the relay correctly, it takes X amount of power to operate the switch inside, and if it don't get X amount of power then the switch isn't happy and instead of staying open or closed, it buzzes like crazy trying to stay one way or the other.

What shape is your charging system in? Have you put a battery charger on and let it do a good long slow trickle charge? you may have a bad alternator or something like that as well. At the very least, id give the battery a long slow charge to full and see if it still buzzes.

Also, i don't know if there are any fusible links in the fuel circuit, but you may want to check them all anyway. I had a fusible link that had gotten toasty, but never completely burnt up on my XLT, it was still providing power to my accessories but not like it was supposed to, i replaced it and everything perked back up and the link crumbled in my hand.
 

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Discussion Starter · #10 ·
Okay will do. Just charged the battery and alternator is good but I can do voltage tests on them. Another note though in this scenario I find very interesting is that the misfire is almost non existent when I pull the spout plug and kick the ECU out.
 

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1986 Bronco Eddie Bauer 5.0 mostly stock
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So what exactly was wrong with your old fuel relay harness connector? Had it gotten hot and melted or warped the end and it wasn’t making a good connection anymore? Or was it just crusty and dry rotted?

If it had gotten hot and warped then you still may have an underlying electrical issue. Low voltage or bad grounds and cause the wires to get really hot especially at connectors.


Sent from my iPhone using Tapatalk
 

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I have uploaded a photo below. Bottom right the plastic around the terminal looked melted and the connection was loose. Looks like a beige wire. Possible had a brown line through it at one point in time.
With key off, check that terminal for battery voltage. If voltage is present, your issue is the disable link on the passenger fender well going to the starter solenoid… if no power present, turn the key on and check for power. If power present, is it cutting off and on rapidly?
 

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Okay I will check. Thank you! Any photo of what the link is I am looking for? To clarify it should have absolutely no voltage with key off?
For some reason I didn’t get a notification for this thread…

you should have voltage in one leg with the key off, and three legs should be voltage with key on. I’ll get pictures and possibly video shortly.
 
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