Slow engine cranking

[Rikadoo]

Hey i have read old posts, an actually found similar posts, however the results were so tremendous i thought bringing this to the group was warranted. 
Customer brought there 2005 coach with a Cat engine to us to address severel issues, one of them being seems slow when cranking, they had been elsewhere where they were sold 2 new batteries. The result was the same, two fully charged batteries yielded what appeared to either be a starter or engine issue as it would engauge then struggle to crank over, but it would always start, so i had suspected possable Voltage drops mainly due to the visual cues i was seeing, after just one VD check of 4 volts accross the battery switch, i made the decision to clean all the connections, and replace the battery switch. The tool that helps with this the most is a angle drill with a small abrasive pad, disconnecting the batterys i started with them, to the frame where they had two different attaching points, on to the starter, cleaned both the ground and the positive connections, i replaced all the lock washers on every connection, and applied electrical grease on every spot as i was reassembling. As for the battery switch of course we recieved the wrong parts (my fault) so till we get the replacement part i reassembled it in case we had to move it. So rechecking for voltage drop at the same spot went from 4 volts to 1, however the results with that are amazing, the difference in the cranking performance are day an night, dont get me wrong it is nowhere near that of a gear reduction style starter, but it is all of what these old style starters could do in there prime. To be sure im positve that due to the extreamly low cranking amps that caused this starter to slow down may have accelerated the wear on the brushes and may be a problem down the road. But just knowing how with age and the derogation of connections that electrical performance can be effected. I bet with after preparing to do the job i had MAYBE 1 hour in removing an cleaning all the high amp connections. Also as you see the solinoid at the starter, when i was bidding the job i said i “would not” be removing the reverse torx bolt for fear it would snap, so you can tell that too has its issues, but for the damage that im sure the starter has endured had i not recieved the results i was aiming for the next step would have been to replace the entire starter, which i will still propose to the customer. For the battery switch i remained with the mfg. Cole Hersee which is still available on line, that in my haste of finding the proper wire configuration i failed to note the post size, i needed 1/2 inch an bought 3/8🤦‍♂️ “i was sooo close😂” 

[jacwjames]

Wow, lots of rust, no wonder there are voltage problems.  Wonder where the coach has spend most of it's life?

Keep us posted, always interesting to see how different problems are solved.

[TomV48]

Ditto.   Good luck

[Frank McElroy]

12 hours ago, Rikadoo said:

Hey i have read old posts, an actually found similar posts, however the results were so tremendous i thought bringing this to the group was warranted. 
Customer brought there 2005 coach with a Cat engine to us to address severel issues, one of them being seems slow when cranking, they had been elsewhere where they were sold 2 new batteries. The result was the same, two fully charged batteries yielded what appeared to either be a starter or engine issue as it would engauge then struggle to crank over, but it would always start, so i had suspected possable Voltage drops mainly due to the visual cues i was seeing, after just one VD check of 4 volts accross the battery switch, i made the decision to clean all the connections, and replace the battery switch. The tool that helps with this the most is a angle drill with a small abrasive pad, disconnecting the batterys i started with them, to the frame where they had two different attaching points, on to the starter, cleaned both the ground and the positive connections, i replaced all the lock washers on every connection, and applied electrical grease on every spot as i was reassembling. As for the battery switch of course we recieved the wrong parts (my fault) so till we get the replacement part i reassembled it in case we had to move it. So rechecking for voltage drop at the same spot went from 4 volts to 1, however the results with that are amazing, the difference in the cranking performance are day an night, dont get me wrong it is nowhere near that of a gear reduction style starter, but it is all of what these old style starters could do in there prime. To be sure im positve that due to the extreamly low cranking amps that caused this starter to slow down may have accelerated the wear on the brushes and may be a problem down the road. But just knowing how with age and the derogation of connections that electrical performance can be effected. I bet with after preparing to do the job i had MAYBE 1 hour in removing an cleaning all the high amp connections. Also as you see the solinoid at the starter, when i was bidding the job i said i “would not” be removing the reverse torx bolt for fear it would snap, so you can tell that too has its issues, but for the damage that im sure the starter has endured had i not recieved the results i was aiming for the next step would have been to replace the entire starter, which i will still propose to the customer. For the battery switch i remained with the mfg. Cole Hersee which is still available on line, that in my haste of finding the proper wire configuration i failed to note the post size, i needed 1/2 inch an bought 3/8🤦‍♂️ “i was sooo close😂” 

Good job.  Checking for voltage drop is something that should be top on the trouble shooting priority list vs just assuming weak batteries or a bad starter.  Years ago, I ran across a similar slow crank condition only to fund a corroded ground cable on the engine block causing the engine block to be at about 3 volts vs ground.  So, the slow cranking starter was only seeing about 9 volts.