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Discussion Starter #1
Ok I got an 86 full size bronco with a 302 efi automatic. I have been fixing electrical issues left and right like the alt wasn't charging wasn't starting finally got all that squared away but I still am having issues when I need to start truck when it is hot. This thing is all stock. Changed the starting selinoid battery cables and grounds. When the truck is hot it act as if the battery is dead when ya try and start. It will crank barley. Now I checked voltage at battery 12.5 volts before starting but on the starting silenoid where the where goes to the starter motor it drops down to about 6-8 volts. Because of this I made mere grounds and still have same issue. My grounds go from battery to where the jack gets mounted another from the battery to the smog pump bracket and another from the intake manifold to another hole where the jack gets mounted to. Using high quality 4 gauge wire for grounds and battery cables. The one thing I really noticed was that the wire going to starter and the positive battery cable gets really hot. If I wait about an hour or so truck starts with no issues. All metal has been sanded down to bare metal for all grounds. Please help.
 

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Have you checked the timing? Usually if it is hard to start when the motor is hot it is from the timing being off.

If you continually, not knowing if you do, try to crank a hard starting motor over the battery cable will get very hot.
 

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its the starter, when the starter itself is hot, it is the problem.

dont believe me run it for awhile, try starting it if it drags/cranks slow. take your hose and water it down then try it. THE STARTER, DONT WATER THE BLOCK.
 

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Discussion Starter #4
Ok thanks. Lol its really funny cuz I was just tellin my wife that I gotta check the timing. Thanks guys.
 

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yo,

That voltage drop is an issue for sure;

Dead Cell; "... Sometimes, a battery will have just one cell go bad or short out. When this happens, the battery will seem fully charged, but fail to start the car, or it may start the car right after charging, but then fail to start the car an hour or more later. If this happens measure the S.G. in each cell. If one cell has a lower S.G. than the rest by a significant amount, replace the battery - there is no way to fix this problem. This condition most often happens to batteries subjected to lots of vibration, and sometimes to new and almost new batteries that have a bad cell from the factory..."
Source: by Gordon via miesk5 at FSB
Voltage; "...a normal battery that is fully charged produces 12.6 volts, not just 12.0 V. (Remember, when measuring battery voltage, everything in the car should be off, or the battery should be disconnected. Voltage measurements are always "no load" measurements unless the battery is being tested for it's performance under load)..."
Source: by Gordon via miesk5 at FSB


could be due to a battery internal short

and;
Starter Relay Ground Wire Addition & Location Video in an 86
Source: by my Brother-In-Grease & Cables, JKossarides ("The Bronco", Jean) at http://www.supermotors.net/registry/media/782810


G701 Behind IP near RH side of radio; G801 On LH inner fender behind headlights; G802 On RH inner fender behind headlights; G903 At LH side of rear crossmember; G909 at lower LH cowl access hole; G1003 On LH side of frame behind front crossmember; G1006 Rear LH side of frame at rear crossmember; G1303 at LH radiator support Locations in an 86 (see #5)
Source: by Seabronc (Fred W (Rosie) at Ford Bronco Zone Forums



Cable Replacement in an 86
Source: by Ryan M (Fireguy50) at FSB
 

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mine does this too, i think it is because of some aftermarket headers i have that get hotter in the surrounding area than the stock manifolds did, and i think theyre closer to the starter too. they heat the starter up and when its hot it wont crank easily (ive never had it not start because of this, just very difficult). you could put a heat shield around the starter or the exhaust.

also, it doesnt help how small the stock battery wires are.
 

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I'm gonna go with starter. U checked the cables and everything and it fires up fine cold right? That's when the motor would have the most resistance compared to a hot motor...

Let us know what u figure out!
 

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Discussion Starter #8
If it was a dead cell why would my battery measure 12.5 volts also I have done load test on the battery with a toaster oven load tester also have tried a different battery and does the same. Was talking to the wife and was told here brother in law had the dizzy out so imma check the timing. Also tried housing down the starter and still didn't work. Imma measure voltage at post to starter during cold start as well
 

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ok heres another quick test, if you dont have a timing light right off. once its hot and dont want to start, pull the spout connector and see if it fires up easier. (ya know its timing then)
 

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I'm with Miesk on this one. I was always told that if your battery drops below 10V while cranking (load test), your battery needs to be replaced very soon. When you crank and voltage drops to 6 VDC--AMPS goes up. Amps=heat. Heat is the biggest enemy of electrical components. Your starter could be bad, due to your battery giving it low voltage/high amperage. IMO.
 

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Since you replaced battery cables and the fender mounted "starter relay" you have voltage on the (S) right side thru that cable down to the starter motor because it's cranking over so I'm going with the starter motor, seems like it has a lot of resistance, a sign it's on the way out BUT do the voltage drop test and then,

A. ground your NEG battery cable to a clean spot of the frame, oddly on my 86 there existing holes in the frame in that area you can use for a home made keeper, bare the cable to the core placing it right on to the frame to help with overall continuity AND check my video on grounding your starter relay at www.supermotors.net/17406 - Starter Relay Ground - dtd Feb 26,2010

B. Put at least an 850CCA battery on your wish list, I got mine at Costco for $81.00 out the door and the BKO thanks me everyday.

Definately check the timing is at 10 degrees BTDC using the spOUT and timing light AND test the alternator as well...


Good Luck ~ :thumbup
 

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Discussion Starter #12
Ok well did a cold start test. Used my multi meter measured batter voltage 12.5 at battery it self and starter relay. Did a start test grounded my meter to battery and measured voltage at relay going down to starter 6-8 volts starts with no issues every time so because I don't have a light I put the truck on tdc starts all the time now just runs like crap and no power goin to my boys shop to use his timing light to fine tune but I think the problem is gone. Have their been any types of issues with heat soak on the starter on these types of trucks like I said truck is all stock so I couldn't see heat soak being an issue. Starter is new and had my alt tested at advanced and tested good.
 

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Almost sounds like the solenoid is bad; just because it's "new" doesn't mean it is good. If you remove the cable going to the starter, and crank it, what voltage is going to the post? If it's 6-8 volts, you need a new solenoid.
 

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I'm with Miesk5 and the others who said... bad battery.

If it is dropping to 6-8 volts while cranking, it is on it's last leg, and you are just putting off getting stranded.
Look at the chart below... 12.5 volts is only aproximately 80% charge.


Using a digital voltmeter, simply check across the battery terminals.
You should get 12.66 volts.
Next turn your headlights on for ten seconds and check again.
This dissapates any "surface charge"
It should still be in good shape.

Battery Charge Table
12.6V or higher: 100% charge
12.4V - 12.6V: 75-100%
12.2V - 12.4V: 50-75%
12.0V - 12.2V: 25-50%
11.7V - 12.0V: 0-25%
11.7V or less: 0% (and probably not capable of being recharged)
 

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I'm with Miesk5 and the others who said... bad battery.

If it is dropping to 6-8 volts while cranking, it is on it's last leg, and you are just putting off getting stranded.
Look at the chart below... 12.5 volts is only aproximately 80% charge.


Using a digital voltmeter, simply check across the battery terminals.
You should get 12.66 volts.
Next turn your headlights on for ten seconds and check again.
This dissapates any "surface charge"
It should still be in good shape.

Battery Charge Table
12.6V or higher: 100% charge
12.4V - 12.6V: 75-100%
12.2V - 12.4V: 50-75%
12.0V - 12.2V: 25-50%
11.7V - 12.0V: 0-25%
11.7V or less: 0% (and probably not capable of being recharged)
He already said he had the battery load tested. I still say solenoid or starter.
 

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If there were no voltage going thru the (S) right side of the "starter relay" thru that cable going down to the stater motor the BKO wouldn't crank over or start but you'd get the "click".....thinking battery or relay.....?

One important issue with starter relays is to make sure ALL cables and wires that converge onto it are clean, especially wires with "loops" because they're really brass and corrode easily building up resistance, make sure the relay studs are free of corrosion and battery cable ends are not CRACKED causing arcing adding to starting problems.....been there on that one.....where a quick visual insepction can detect issues.

I agree that you need a mimimum of 8 volts from the battery to RUN, START and operate normally otherwise at 6 volts there's just barely enough juice to start but once running the battery will fail because it can't charge any higher to sustain the demand.

Any results from the SM voltage drop test....?

Good Luck ~ :thumbup
 

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He already said he had the battery load tested. I still say solenoid or starter.
You might be right! I'm not saying that it can't be the fender mounted starter relay, nor am I saying that it can't be the starter.

I can say, that I don't know what a toaster oven load tester is, nor do I know exactly what the results of his testing was.

I can also say that a battery that is only reading 12.5 volts without a load is NOT a HEALTHY battery. Full charge should be 12.66 volts, or more.

I estimate that 12.5 volts at full charge is really only about 80% of a healthy battery. He tells us that he gets 6-8 volts when cranking at the starter, perhaps he should check his voltage at the battery while cranking and see if it drops to the same 6-8 volts. If it does, that would take the solinoid out of the equation.
 

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I just re-read the whole thread, and would like to add that it is also quite possible that the starter is on it's last leg. I thought that he had replaced the starter, but upon re-reading I see that he hadn't.

Often as a starter gets older, it builds resistance and draws more current for it to crank the engine. The relatively high amperage traveling through the cables causes them to get hot. As the starter heats up, it creates even more resistance, and the battery may not be able to over-come the added resistance. It is quite possible that he has two problems going on at the same time. A weak starter that requires a strong battery, and a weak battery.

Two years ago I replaced my battery, and last year the starter. I was amazed at the fact that the starter must have been on its way out for a number of years, because the new one cranked the engine at a much higher rate of speed. Prior to swapping out the starter, I noted that the old starter cranked the engine slower than my other cars' starters cranked them. I flexed my muscles and imagined that my old 302 was a high compression engine.

Well... my new starter and strong battery just whip that engine into cranking and I smile, in that it starts first time, every time, just like a new truck! :) Now my rusted exhaust is getting a little noisey, and I flex my muscles and make believe that it has a larger engine in it. :yikes: :)
 
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