ford f250 battery question

R&W

Member
i have a ford 2000 ford f250 that cranks kinda slow. it has one 850 cca battery that is about a year old and load tested fine. the other battery is a 750 cca that also load tested fine that is about a year old or a little over. if i turn the key on to cycle the glow plugs then try to cranks it cranks slow, then if i let off for a second and try it agian it cranks a little faster but is still slow but it does start. ive had the starter tested and it was fine. iver cleaned all connections. could it just be because its a 750 cca battery? could i replace just the 750 cca one?
 
I would look at the starter. My f350 did
that and I changed the starter and it
started great. My curiosity got the
better of me and I pulled it apart and
the bushings in the end cap were shot
and dragging.
 
With a dual-battery system, any time you don't change out both at once with identical batteries, you are asking for weird problems.

That being said, I'm gonna guess one of the batteries isn't actually very good/contributing much cranking power or there's a poor connection between the heavy battery cable itself and one of the terminals soldered or crimped to it. (ASSUMING you have the connections at the battery "clean, brite, and TIGHT".)

ONE test... disconnect one battery (be safe, wear eye and face protection), carefully tape up or otherwise insulate the (+) cable, and try cranking it. Repeat with the other battery.

Does each individual battery try nearly equally to crank the engine, or does one not do much?

Trying that will HOPEFULLY narrow the problem down to one side or the other.
 
Hello Ramp;W,
I think a starter draw test is what you need to do. Sounds like it is
drawing lots of amps! One thing you can do. After cranking the engine
when it does not start, feel all the cables connections.
A hot one is the problem one. Tap the connection lightly first,
with your fingers, you may find a real hot one!

Guido.
 
(quoted from post at 04:16:05 01/20/16) i have a ford 2000 ford f250 that cranks kinda slow. it has one 850 cca battery that is about a year old and load tested fine. the other battery is a 750 cca that also load tested fine that is about a year old or a little over. if i turn the key on to cycle the glow plugs then try to cranks it cranks slow, then if i let off for a second and try it agian it cranks a little faster but is still slow but it does start. ive had the starter tested and it was fine. iver cleaned all connections. could it just be because its a 750 cca battery? could i replace just the 750 cca one?

It takes a right good load tester to load test bats with that much energy... Can you give more detail on the load test and tester used... I have never thought about what bob suggested cranking with one battery but that would be a good load test. Record the voltage readings while performing that test...
 
Always change all batteries in multi battery setups
when there are battery issues. 99% of problems will
disappear.
 
Drop by your local battery store and ask for a load test. I bought the one they sell at harbor freight and for a bit more than $20.oo it is one very handy tool. Your way works too but the meter really narrows things down quickly. Also you can lite your cigarette on the glowing coils.
 

I spec it does OK on a little bitty battery... It won't pass the mustard on most all automotive bats unless its deader than a door nail...
 
I have owned Ford diesel trucks since 1990, doesnt make me an expert, just experienced, LOL
When everything is up to snuff electrically a 7.3 with the correct wt oil will whip over fast as long as it is above 10 degrees or so.

A few things come to mind. As others had said it is almost always false economy to replace those batteries one at a time. Some of the smarter people here can probably explain why but it just plain doesnt work out well to have different age and type batteries. You also want the highest amp batteries that fit in the trays as there is a tremendous draw on them when starting, what few people know is those glow plugs dont go off when the light goes off, they are still on while you are cranking and for up to a minute after it starts.

If the factory post ends have been replaced with clamp on junk that is likely at least part of your problem. The positive cable that runs across the core support is real expensive and often jury rigged and often the problem. Checking for areas of high resistance is as easy as cranking for 5 seconds then quickly touching battery posts and other connections. Warm or hot are bad connections that need repair.

If you had the starter tested off the truck all they know is it turns when the power is applied, tells you nothing about how it acts under load. As the other posters said you need to run an amp draw test on the vehicle. The starters will slow down and draw lots of amps. Auto Store starters are decent if you avoid the cheapest ones and rebuilds.
 
Back in the 1980's Dad had an olds diesel car. IIRC it would fire right up when cold but hard to start hot. This was very odd so that must of been which way it acted. We eventually noticed it cranked sort of slow. Took the starter off and took it apart and one of the brush holders was cracked and that brush wasn't working or was partially working ?
So if I pulled a starter to have it tested I darn sure would of pulled it apart for an inspection and freshening up.
 
I have one of those cheap testers too. It is OK on the lawn mower and smaller batteries, but not on diesel starting. Get a good carbon pile tester for those. Using one battery at a time, read the voltage while cranking. Then use the tester to bring the voltage down to the same reading & note the amps.
 
What are factory specs for the batteries?

When I was a Ford Service Manager around 1990, a farmer had his F250 in for something or other. We noticed the starter seemed a bit slow. We tested the batteries and they weren't quite up to par.

I quoted him a price on two new Ford Motorcraft batteries and he declined, saying he could get batteries cheaper somewhere else. Two months later, we sold him a pair of new Motorcraft batteries AND a new $360 starter.
 
Guido stole my reply.

It's a quick free test. And you'll find out real quick if you've got a bad connection. Feel the cables themselves too - all around as much as you can.

Doesn't prove everything's good if you don't find a hot spot, but it'll flag a problem if you do.
 
Had a 2000 Ford 7.3 and experienced same problem one time. As other have said you need to change both batteries at the same time and should be or equal cranking power. The weaker battery will draw from the stronger and make it weaker.
 
Hello JRSutton,

Sorry, I did not know you were playing. This long distance guessing games are fun! That is why you are playing?

Guido.
 
Hello jeffcat,

Surely you jest! Bob's method will work better then your tester. I would think your tester has a capacity of 100 Amps? Would not load test those batteries with hundreds of amp capacity

Guido.
 
If the load tests were done recently, tested at the right amperage and voltage and passed then look elsewhere. Typical industry standard for lead acid batteries is to test at 1/2 CCA and monitor voltage. Batteries must be fully charged prior to a load test. They are either acceptable or not. When the truck has known good fully charged batteries further testing can be done. You posted you have cleaned all connections and the vehicle cranks slow. The next step would be voltage drop tests. If it cranks slow you are either losing voltage or increasing amperage draw. Voltage drop tests need to be done on a loaded circuit (cranking). Test the voltage at the battery terminals before cranking after it sits overnight. A fully charged battery will have either 12.6 or 12.7 at the battery at room temp.
 
Hello ASEguy

That is a novel idea! Battery voltage and temperature ALL in the same sentence!

Guido.
 

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