CDS 4.8 isn't running at correct rpm

Bryce C · 2025-06-12T17:17:02-0400

My Hydramaster CDS 4.8 starts at around 1100 rpm on the high setting, and slowly loses rpm and drops to around 600 rpm Weak vacuum, water pump has weak pressure, and my local truckmount service people say they won't work on it. The don't service anything on the engine side of pto setups.

It is a 2013 and doesn't have the adjustable vacuum pods like I read some older models have. There is an electrical pod under the dash but I don't know if anything is adjustable on it. The local truckmount service folks checked for vacuum leaks in the lines that may affect this and didn't find any. They think it is electrical.

I'm waiting to hear back from a friend who is a Hydramaster tech I met at MF this year. For now, do any folks with experience with these CDS systems have any thoughts?

Bryce C · 2025-06-12T17:19:12-0400

Based on what they saw, the local truckmount service folks think the tm will be in great shape once this engine rpm issue gets resolved... The van is a 2500 Express

I set out to buy this thing in April, couldn't pick it up until May because they rebuilt the van engine, and here I am in June and I still haven't cleaned with this thing once

Bryce C · 2025-06-12T17:41:27-0400

Well, looks like the previous owner just spliced in the electrical rather than getting the proper harness. My friend at Hydramaster just helped me realize that. He's ordering me the right harness and will talk me through installing it when it comes in. Things are looking up. Maybe..!

Dwain Ray · 2025-06-12T22:28:38-0400

Bryce C said:
Well, looks like the previous owner just spliced in the electrical rather than getting the proper harness. My friend at Hydramaster just helped me realize that. He's ordering me the right harness and will talk me through installing it when it comes in. Things are looking up. Maybe..! View attachment 131308 View attachment 131307

Heres the installation/ operation/ troubleshooting for that throttle controller hope it helps. I had to screen shot it. I have it as a pdf file and i don't know how to send it if you have any questions i built my machine from scratch and used this same throttle controller and im familiar with it