Diesel cranking issue

[GlenB]

My Cat normally starts right up. Last two times it almost sounded like low battery. 2005 expedition fleetwood 300 Cat. The main batteries show 13.60 and the Aux batteries show 13.58. These are readings from my elect control panel. Any ideas on what to check. RV is either plugged into 30 Amp at home and right now 50 Amp at campground. Cranking batteries 4 yrs old I think...tks for help GlenB

[twinboat]

Have someone watch the battery voltage while cranking.

A good reading at rest doesn't mean the batteries still have the CCA the engine needs.

If they drop down to 10 volts or less, get them tested.

[RKins]

Check the water in them. Should check it regularly (set a reminder on your calendar for monthly).

[mymyst]

Only way to know if it's the batts is pull them and have them load tested. I just replaced 2 large crank batts at beginning of third year since new. Weak batts can also wreak havoc with the ECM box on the transmission as well. I intially thought I was having a tranny issue, but learned it was just weak batteries even when the volts looked normal at rest.

[Skip426]

Your current voltage reading indicates you're plugged in and the on board charging system is charging both banks of batteries .

Your chassis batteries , at rest , if in great condition would show 12.6 volts approx.

Disconnect from shore power then use the panel read out , then crank the engine and check the read out again.

As mentioned by other members , removing the batteries for load testing IS the final call on battery condition.

[Maik]

I had this problem before with my engine not cranking properly with fully charged battery. The problem was in the battery terminal connections. I cleaned them and it started just great. It can also be on your starter connections.
Hope this helps and you find the problem.

[Jean n Steve]

I've seen poor battery connections affect slide travel, too. You might try moving them (if you have them) after disconnecting from any external power.

[TQ60]

Before doing anything get a helper and voltmeter and check things.

First place voltmeter on POSTS of battery and have helper crank it.

No need to start as you are just checking starter starting voltage drop.

Next is what few folks do...

Place one probe of meter on post of battery and other on the terminal on same post and have helper crank again.

ANY voltage reading here indicates interface is not optimum.

Do same on all posts.

Do this before any other work so you know the condition before starting and can measure improvement after repair.

Note...remember this process for trouble shooting any intermittent things as same is done across connectors or plugs

[Ivylog]

Try cranking while holding the boost switch down. Spins faster?

[smp005]

Just had our chassis batteries replaced 3 days ago - what a difference! Our C7 "turned" over before - now it "spins" over!! Huge difference! Ours were completely dead this spring but last summer we had the same issue as you - slow to crank over and I was constantly hitting the boost switch. Should have replaced them in August...

Worth every penny of the $250.00 and per the FL dealer the ones that were in it were not the proper spec (CCA) and that alone can cause issues with the ECM and starting...

[GlenB]

Thanks to all who sent help....I replaced the Alliance Cranking Batteries today and all is well. I thought I had replaced them 3 or 4 years ago but when I looked in my service tickets I found the batteries had been in use for over 5 years. In Mississippi that is about as good as it gets with heat issues etc....Glenb

[Skip426]

Originally Posted by GlenB

I found the batteries had been in use for over 5 years. In Mississippi that is about as good as it gets with heat issues etc....Glenb

Yes; people tend to forget that temps over 80 are as hard on batteries as those below zero.