Need help....Machine is stalling.

**Tony_R** · 07-20-2009, 02:59 PM

Its a Hydramaster 4.8 CDS.......It sounds kinda like its straining and then stalls...It only seems to do it after the first job of the day.....It dosnt shut off, it just drags down......If I un-cork one of the intakes, it comes up to speed and is fine.....Just does it under a load and after the machine gets really warm...

Any advice would be great...

**Chris Sheldon** · 07-20-2009, 03:14 PM

How does the drive belt look? Any slippage? Any noise from the clutch?

I had a CDS last year that was doing the same thing and it was actually the catalytic converter on the van that need replacement. Customer had it replaced and the CDS ran like a champ.

The van engine seemed to be runing fine, but when I put a tach on the engine I saw that the RPM was flucuating. Also, the Check Engine light was on.

Could be a number of things, but check the basics first. I don't see many CDS's in the shop so maybe Ara will have some better insight.

**Ara Klujian** · 07-20-2009, 03:59 PM

Sounds like it could be a number of things happening like Chris said. Alot of times I notice that the vacuum line is damaged that goes from the intake manifold to the foot control. If there is a leak in that line you will loose RPM. Also check the obvious gas filter and distributor cap and rotor spark Plugs, etc...

**Batista230** · 07-20-2009, 05:14 PM

check the relise valve on the waste tank if its stuck and you put a load on the blower the machine will stall

**Tony_R** · 07-20-2009, 06:48 PM

Thanks for the ideas......That gives me a few thing to check...

This is hard because I cant duplicate the problem without being out on the job.......It will work fine for hours on a long job and then start acting up only five minutes into the next job.....Weird??

Also, im pretty sure ( not positive) the van was holding a steady rpm while the blower/machine would bogg down and stall.....Wouldnt that mean either the main drive clutch or belt was the problem......since the blower is direct driven off the drive shaft??......I dont think it would be the clutch because it would slow way down and then pick up speed again instead of disengage all together....

Its impossible for the blower to bog unless the main clutch disengages or engine belt slips, right?????

**Chris Sheldon** · 07-20-2009, 07:50 PM

It is odd that it only happens once the unit is at operating temperature.

As Batista suggested you may want to check your vac relief to see if it needs adjustment.

You may also try flushing out the blower and cleaning the lobes; MAYBE there is a coat of rust/corrosion/debris built up. You may also have a restriction in your silencer; I have seen them rust from the inside and clog up with rust and silencer media.

Don't trust your ears when listening to the van engine, it may seem to be running smooth, but is it maintaing the proper RPM?

If you can recreate the problem, try disconnecting the silencer from the blower, if it starts running fine, you know that there is a restriction in the blower exhaust somewhere.....just wear hearing protection!!!!!

Just a few more things to consider. The basic thing is to rule out the CDS as the problem, then you can start looking at the van.

**Tony_R** · 07-20-2009, 07:58 PM

Thanks again.....Where is the relief valve located???

**Chris Sheldon** · 07-20-2009, 08:04 PM

Should be on the waste tank.

**Batista230** · 07-24-2009, 02:43 PM

Originally Posted by Chris Sheldon

Should be on the waste tank.

Should be on the waste tank lid
Put plenty of grease on it on both sides and you should be able to push it up and down with a bit of hand pressure

**darylbrown** · 08-13-2009, 05:57 PM

I run 3 CDS 4.8's and 4 other HydraMasters but I don't work on them. However I do often learn what the problem is from my mechanic after the fact. I have had this same thing happen to one of our units and Chris Sheldon hit it right on the head. It is the blower lobes that are causing this. They have build up on them usually caused when the waste tank switch fails and the machine blows waste water past or the machine foams up from Ole Mrs Smiths homemade shampoo mixture she swear by. LOL Trying pouring your acid rinse straight in the blower and rotating the lobes slowly and this should fix your problem.

**Chris Sheldon** · 08-13-2009, 07:19 PM

Tony, did you ever figure out the problem?????????

**Richard Baldwin** · 08-13-2009, 09:01 PM

Im agreeing with the vacuum release valve idea, oil it up or something.

**Ara Klujian** · 08-14-2009, 01:18 AM

Originally Posted by Chris Sheldon

Tony, did you ever figure out the problem?????????

Yeah, I like it when people report back and say what it was. Its almost like an unsolved mystery if not.

**Kenny Wright** · 08-14-2009, 02:11 AM

Guys, I've started having this same problem with my 1994 CDS just as described by Tony. I'll start by checking the vacuum release valve. Is it the screw/spring adjustment on the back of my waste tank that adjusts the Hg under load?

If not, what does it look like?

**Ara Klujian** · 08-14-2009, 03:23 AM

Please dont play with your relief valve. You really need to read your gauge before you make any kind of adjustments. Compare your readings with factory specs. If the readings do not match under full load and other factors like rpm etc have been ruled out then do it. Plug your vacuum inlets at high rpm with a tennis ball or something and read the guage. And yes Kenny, the spring on your tank is the relief valve.

**Kenny Wright** · 08-15-2009, 03:34 PM

Thanks for the help, ARA. I bought the CDS used and do not have a manual. I have learned a lot through repairing it and also asking question while the Interlink mechanic works on it, but there are still important things I should know and don't.

I do keep an eye on the lift and rpm gauges and know how to make adjustments when necessary. Now, I have to make a confession. While oiling the relief valve, I found out that the last section of the waste tank top does come off - I had tried in the past, but it was stuck pretty tight and I though it was permanently attached. I'm pretty regular about cleaning all filters. Let's just say the one I found inside the waste tank was ready to be serviced.

Anyway, problem solved.

**Batista230** · 08-15-2009, 08:33 PM

Originally Posted by Ara Klujian

Yeah, I like it when people report back and say what it was. Its almost like an unsolved mystery if not.

It give you that seance of achievement that we all have helped someone

Originally Posted by darylbrown

It is the blower lobes that are causing this. They have build up on them usually caused when the waste tank switch fails and the machine blows waste water past or the machine foams up from Ole Mrs Smiths homemade shampoo mixture she swear by. LOL Trying pouring your acid rinse straight in the blower and rotating the lobes slowly and this should fix your problem.

If this is the case that can cause machine staling then you should see water and ****e coming out of your exhaust

Originally Posted by Kenny Wright

Now, I have to make a confession. While oiling the relief valve, I found out that the last section of the waste tank top does come off - I had tried in the past, but it was stuck pretty tight and I though it was permanently attached. I'm pretty regular about cleaning all filters. Let's just say the one I found inside the waste tank was ready to be serviced.

Anyway, problem solved.

AJ is right they are calibrated to a certain load and unless you know what you are doing don't adjust the nuts on the spring
its supposed to be stuck on pretty tight and needs a lot of hand pressure to push it down but you should be able to do it