Slow Crank

Ford 901 cranks normally for about two seconds then slows way down. I tried replacing the starter with another that works well, same problem. I took the starter to the shop that rebuilt it four years ago. It checks out. I took the battery to the store where I bought it ten months ago. It checked out excellent. I checked all connections with my digital meter. Virtually no resistance measured anywhere. The only thing that doesn't check good is that while cranking, the voltage drops to 8.5 to 9.0 volts. I ran the tractor for 3-4 hours three weeks ago, then pulled it into the shop for service. Two days later it presented this problem. Any ideas?

Is the ground corroded or something?

I have had batteries that tested good before and worth a darn.
Sound like as soon as you give it a crank or two and build
compression the battery isn't strong enough to spin it. If your
sure all connections are good I would try a different battery
and see what happens. Simple and cheap test if you have a
different one out of something you know is good.

I have had batteries that I knew were no good and the auto parts store said they tested good. And I had the same type of tester that they said was good and in mine it had a wire burnt off, think the stores were the same way.

Hydraulic pump loaded?

Hydraulic or transmission load during cranking? Had a Case 680 that would almost start, then slow cranking while still had black smoke at exhaust. Owner found some hydraulic levers in detent after the grandkids were playing on it. With levers back in neutral started just fine..

(quoted from post at 16:38:08 05/26/17) Ford 901 cranks normally for about two seconds then slows way down. I tried replacing the starter with another that works well, same problem. I took the starter to the shop that rebuilt it four years ago. It checks out. I took the battery to the store where I bought it ten months ago. It checked out excellent. I checked all connections with my digital meter. Virtually no resistance measured anywhere. The only thing that doesn't check good is that while cranking, the voltage drops to 8.5 to 9.0 volts. I ran the tractor for 3-4 hours three weeks ago, then pulled it into the shop for service. Two days later it presented this problem. Any ideas?

Click to expand...

What method did the store use to check the battery?A honest load test? what?

(quoted from post at 17:42:14 05/26/17)

(quoted from post at 16:38:08 05/26/17) Ford 901 cranks normally for about two seconds then slows way down. I tried replacing the starter with another that works well, same problem. I took the starter to the shop that rebuilt it four years ago. It checks out. I took the battery to the store where I bought it ten months ago. It checked out excellent. I checked all connections with my digital meter. Virtually no resistance measured anywhere. The only thing that doesn't check good is that while cranking, the voltage drops to 8.5 to 9.0 volts. I ran the tractor for 3-4 hours three weeks ago, then pulled it into the shop for service. Two days later it presented this problem. Any ideas?

Click to expand...

What method did the store use to check the battery?A honest load test? what?

Click to expand...

They used both the latest computer tester and the old style heater load tester.

(quoted from post at 16:49:12 05/26/17) Is the ground corroded or something?

Click to expand...

Resistance is measuring zero from ground terminal to engine block.

I went down and checked the remote valve. It is in neutral and the lift is all the way up. I will try swapping the battery out tomorrow.

Another vote for swapping out the batteries. I just ran into this on my John Deere, just about drove
me nuts figuring it out. I used a carbon pile tester and it tested fine, until I left it loaded for
about 10 or 15 seconds then the voltage suddenly dropped like a rock. I think it has something to to
do with the connection between the cells. Load it for a little while and you lose the connection and
a couple of cells. Never saw one act that way before.

Is there a good ground running from battery to frame and frame to motor?

Was the old tester capable of loading the bat 500 amps... Are was it one of those hand held HF 100 amp jobs...

Forget the resistance test its of no help do a voltage drop test to find a bad connection... Voltage drop is lost voltage under a load!

https://www.youtube.com/watch?v=YRtqkneyKCI

With little knowledge and little test equipment all we got is your reports and using a voltmeter... Its doable for those that want to learn but not for those that don't.. First make sure you have a fully charged battery Take a few minuets and do a voltage drop test report your results.

Before you get to deep into it all connections good a good battery with a bad starter the voltage will not drop below 9V. You can dead short a good battery across the terminals it will hold voltage above 9V for a short time while its melting all the wires... :shock:

Did you try a different solenoid?

Pull the plugs out, crank, if it slows down it is hydraulic loading issue.

I would check for hot connections after cranking. If any of them get hot it's a bad connection and needs cleaning. I agree with the post of
asking about the 100 amp load tester. If your battery is capable of putting out 400 amps then a 100 amp load tester is not an accurate test
cause it shows the battery as being good. Have you check the fluid level and state of charge on each cell with a hydrometer if it's a battery
that you can add water to???

Since your starter cranks good for a short while that says it's good. The only things that change while cranking are the battery state of
charge and bad connections get hot reducing amperage needed for starter to function properly. Battery that's low on fluid will give the
symptom you're mentioning. All these are the easiest things to check with out removing anything.

As stated in the original post all connections have been checked and cleaned. connections that were heating up were cleaned or replaced until heat is negligible. Battery to block ground shows zero ohms. Starter frame to engine shows 2 MA. pos battery post to NEW solenoid shows zero. Sol. to starter terminal shows 2 MA. Voltage drops to 8.9-9.2. Battery is rated at 730 CCA tests at 811. and 12,79 Volts. I will be trying a different battery this AM.

A short quick test.

One other thang to take into consideration is how the voltage jumps back to a fully charged state of 12.6

A short load test are just hitting the starter for 5 seconds dose the voltage go back to the recorded voltage before this test. If not you have a weak battery.

We don't get questions when the starting/charging system is working as it should. When you resolve the issue with a volt meter test it and report you findings. Test every vehicle you have write it down this is the known good facts to base your test on when its working good. Tractor, car are lawn mower with a year old battery your test should test the same.

When you take your bat back for a test watch and ask does he load the bat to haft its rated CCA for 15 sec. Did the battery voltage fall below 9.6V. His fancy tester can not do'dat in reality only in theory but his carbon pile tester should be able to are its not up to snuff for the job and only eye candy.

Its been reported HP has a 500 amp carbon pile tester for $50 that's a deal and the tool needed to preform a true load test.

Hydrometer testes are useless if the voltage is 12.6 after a short load test no need to use a hydrometer if its 11.6 after a short load test no need to use a hydrometer. I see no need for it other than to waist my time proving what I already know.

Another neat test is to remove the positive cable at the starter clamp that lead to the positive lead of a carbon pile tester and clamp the negative lead to the starter housing body. Load the system to 200 amps and record the voltage at the battery. If is normal the battery and connections are good. Normal would be 10.5V are higher for a healthy system depending on the CCA of the battery. With a healthy 750 CCA battery I would not expect it to drop below 11.5V...

Checking the resistance on a static system is almost pointless. You need to measure voltage drop when the system is
dynamic, ie cranking.