Symptoms: Truck will not start on battery power, and struggles to even run lights. Battery installed 8/2014, tests 12.4V static, not load tested yet.
Truck has had intermittant no-start issue that has gradually gotten worse. As of yesterday, will NOT start on battery. WILL always start when push-started (so far). While running, will stumble at idle with lights on, and voltage meter shows spikes when turn signal on.
Initial Conclusion: The battery (via loose connection or ???) is somehow being isolated from the system. The truck is running on alternator alone.
Where I’m going next: Take battery to parts store and load test. Try to jump straight to starter if batt checks good. Sit down with Haynes and reverse-engineer the charging/starting system and check for flow interruptions.
Any good ideas out there? A hint in the right direction? All help appreciated!
There is a wire that ties between the positive side of the battery and the power panel under the hood. Verify voltage is good to the main fuse and other fuses in the panel while you have a good load on the battery, like the headlights and blower. If power is okay there then you need to check power between that panel and the ignition switch and the dash fuse panel. It’s a step by step process.
To see if the alternator is working okay you will need to get the engine running and check the voltage at the main output terminal while the engine is running around 1,500 RPM. You should have between 13.5 and 14.8 volts on the main terminal. You should also have very close to the same voltage across the battery if the wiring is okay between the two points. You could measure the voltage drop between the main terminal of the alternator and the positive battery post with a good load on the charging system. You should see less than 0.3 volts of drop if the wire connection is good.
There is a safety switch used between the ignition switch and the starter solenoid. If just the starter is having trouble you need to make sure power is passing through the switch and on to the starter solenoid lead which provides power to run the solenoid, which then connects the main battery lead to the starter motor to get it running.
With a vehicle this old, I’d expect that the battery cables are corroded so bad that the current cannot flow as it should.
Battery connections are the first place to begin when you have a “No Crank” situation. Even
if you have a new battery, if the connections are loose, dirty or corroded, you will not be
allowing the full flow of current to pass thru the connections. The connection may be
enough to turn on the lights, but not enough for the huge flow that is needed to operate the
starter. This is where many people say that they know the battery is good….”because the
lights come on”. This is no more a battery test than licking a 9volt battery. It only tells you that there is electricity…not how many volts or the amperage that flows from the battery.
Jump starting may have wiggled the terminal just enough to allow the current to pass and start the engine, but tomorrow you have the same problem.
First remove the cables from the battery and use a wire brush to remove any corrosion and dirt from the battery posts and the cable terminals. There is a tool with a round wire brush for this purpose, found at any auto parts store for less than $10 http://shop.advanceautoparts.com/p/kd-tools-terminal-battery-brush-kdt201/25980576-P?searchTerm=terminal+brush.
Before connecting the cables, apply a coating of di-electric grease to the battery posts this will keep oxygen away from the connection so that it will not corrode as fast.
It is just as important that the other end of the cables also have a clean connection. Remove the positive cable from the battery again so that you do not short anything out. Follow both cables to their far ends, remove this connection and wire brush the connection and the cable terminal clean and retighten these connections.
If there was work done recently, there may have been an “engine to body” ground that was not installed following the work. These grounds normally run from the rear of the engine to the firewall and are uninsulated and most are a braided wire. If any of these are found unattached…reattach them.
Remember….this is not a “Sherman Tank” don’t over tighten the connections.
Tight…tight………………too tight…broke!!!
When you say it won't start, do you mean it won't crank? Or it cranks ok, but doesn't catch and run?
I mean, with a battery that checks good...it can't even light the headlights properly, let alone crank. Before it got "this bad," it would do the "crazy solenoid clicking" thing, and eventually start. Now, nothing. The (dimly) lit dash lights go blank when the key's turned, and the clock occasionally resets to 12:00. It HAS reliably push-started, though.
Even if I allow that the AAP battery load test might be suspect…NO WAY is the battery that gone, at 12.4V static. Obv. dark now; in the morning I’m going to hot-wire to underhood solenoid (and negative to block) and see how it goes. If it works, I’ll take negative off the block to see where the restriction is.
OK, forget the starting issue, just find out why the lights are so dim. that should be easy with your voltmeter. It’s probably a bad connection to the battery, either the + side or the ground side. Check the voltage between the battery – and a good ground for a good first check.
All the symptoms that you describe lead right back to bad battery cables. They could look good at the terminals, but under the insulation they are so corroded that enough current cannot pass.
One fairly common problem that happens is internal wire corrosion at the battery clamps due to battery acid leaching into the connection. One easy test method for this kind of problem is to use the meter to look for voltage drop across the main power connections coming from the battery while the lights are turned on to create a load on the circuit.
Negative terminal removed. Testes with multi-meter at very low ohmage (couple dozen). Moderate amount of corrosion between terminal and wire–replacing anyway.
Positive terminal removed. Tests same as above.
Underhood starter solenoid removed. Tests ok (“thunk” and continuity between main terminals when voltage passed through it.)
Starter removed and tests ok (spins rapidly when current applied.)
Car COMPLETELY DEAD now when trying to start (no lights, dashboard stuff, etc).
Hotwiring across starter solenoid does nothing. Grounding to Al intake manifold, too.
Battery volts remain 12.4V.
I’m beyond my depth now–looks like something to do with the brain box? If it were a bad igniton switch, jumping across the solenoid would fix it, right? I’m also hamstrung by the fact Haynes does not include battery/starter wiring on the schematic–I guess it’s just assumed you know how all that ties in to sensors, injectors, etc.
Negative terminal removed. Teste[d] with multi-meter at very low ohmage (couple dozen).
IF you mean, say, 24 ohms from removed negative terminal to truck body, that’s way too much. It should be a few thousandths of an ohm (0.004 ohm will drop 12 volts to 10 volts at the starter with 480 amps starting current.
The real problem seemed to be your battery cables. As stated by others, there should be basically no resistance in those heavy duty wires. I doubt there was a problem with the solenoid but the contacts do wear out. When that happens you will hear a good thunk sound as the solenoid activates but power doesn’t get switched to the starter motor due to the worn out contacts, so you get no action. A bad solenoid wouldn’t cause the other power problems you stated you had but bad battery cables or connections sure would.
As I explained in my previous post you should check things while the wires are connected and look for a voltage drop while there is a good load on the circuit. When you find the bad connection you will see the voltage across it due to the resistance and current draw through it. Ohm’s Law is a good thing to study and learn about how it works.
If you are using a digital multimeter, did you happen to see a small m in front of the ohms symbol? Looks like this mΩ? Thats milliohms. A milliohm is a thousandth of an ohm.
I don’t understand how replacing the starter solenoid would affect the headlights. But who cares? Mystery solved. Glad you got your F150 back on the road.
Note to OP: It’s more difficult than a person would think when diagnosing starting circuit problems. The reason is that the starter motor – b/c it has to turn the engine and overcome the piston compression – it draws a lot of current, 100 amps or more. There’s few if any appliances in your house – even most electric water heaters – that draw that much current. It takes very thick wiring and tight, close to perfect connections for the entire circuit loop for the starter motor to work at all.
So when diagnosing problems with the starting circuit, common techniques like test lights aren’t of much use. You need a way to measure electrical resistance accurately down to a few thousandths of an ohm. 1/1000 of an ohm will produce a voltage drop of 1/10 of a volt at 100 amps. And you can only get away with maybe 2 volts of voltage drop before the starter motor will begin to complain.
(Oh, and replaced pos. terminal too. Now, it starts quicker than ever!)
I’ll bet that was your problem all along, despite your ohms testing.
Anyone here a fan of Star Trek Next Generation? As the Borg say, “Resistance is Futile.”
Checking wires for resistance is pretty useless. Go buy a new starter cable for your truck, strip all the insulation off of it so it’s just a bunch of bare wire. Take one single strand of that cable out and test the resistance. It will be about 0. Now install just that single strand between the battery and starter and try to start the engine. Will it work? Of course not. A poor or corroded cable or connection works the same way. It will ohm check good for the small load the meter puts on the circuit, but not for real-life conditions.
Testing for a problem like yours needs to be done dynamically, testing for voltage through various parts of the system while the circuit is electrically loaded. I’ll bet that if you had an assistant hold the key in “start” position while you poked the positive cable in several spots you would have found where you were dropping voltage.