ROL AIR 120 PSI SUDDEN STOP

8 years 9 months ago #1439 by gigamile
ROL AIR 120 PSI SUDDEN STOP was created by gigamile
Hi I have a ROL-AIR 6590hk18, been sitting in the shop for a couple years now, I replaced the engine, oils, filters, and unloader valve with new. I run it for a bit at idle with the drains open, just to get it worked in, then closed the drain valves and set rpms 1900 - 2800 rpms. it worked fine for about 20 minutes. then it just stopped suddenly at 120 psi, blowing air out the vent tube on the pump, after draining all air it will start/run fine at 120 psi it stops and blows air out vent. the pilot valve is (preset) operating at 115 on - 130 off. air does not seem to come out the vent till it locks up. It is acting like pressure is balanced above and below the pistons. I am wondering if it could be a check valve or piston blow by, or something else. Any help would be appreciated, any idea's as to what the cause could be. thankz David
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8 years 9 months ago #1440 by MTR-Admin
Replied by MTR-Admin on topic ROL AIR 120 PSI SUDDEN STOP
Thanks for the post David,

There is a chance it's the Check Valve (#7 in the schematic diagram) but it's unlikely; you can take the Check Valve out and clean it if it looks like there is debris or rust build-up and reinstall it.

My money is on the pump...you mentioned it's blowing out of the "vent tube"; you're referring to the Oil Breather, part# 36507050CH, correct?

If this is the case, then the Valve or Rings are probably worn and need to be replaced. The Reed Valves may be either damaged or not closing completely during the end of the compression stroke, which would allow positive pressure to build up in the Cylinder.

The Rings may also be worn, or the gaps are aligned which will allow air to reach the crankcase.

I would pull off the Head and see what you can find, but it would be a good idea to start with a Valve Kit, and possibly Rings as well.

- MTR

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8 years 9 months ago #1441 by gigamile
Replied by gigamile on topic ROL AIR 120 PSI SUDDEN STOP
ThankZ I will certainly check the valve, I just can't figure how so much pressure could build below the pistons, tomorrow I want to do another test run and see how fast the pressure builds and blows out the vent. yup the air is pouring out the Oil Breather, part# 36507050CH. Even if the check valve is stopping the pump, the air coming out the breather is quite unacceptable. I will check the area's you mentioned. This is my first model HK18, I got HK28's and HK30's, and have never had pressure in the oil sump like this.

thanks again, Dave

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8 years 9 months ago #1442 by MTR-Admin
Replied by MTR-Admin on topic ROL AIR 120 PSI SUDDEN STOP
Dave,

Also take a look at the mesh unloader port on the Pilot Valve, it could very well be clogged; if this is the case and the pilot valve can't "unload" the air through the unloader port, you will certainly get back pressure that will cause the unit to stall.

I would simply remove the mesh screen and clean it up and clean the pilot valve where the mesh screen sits, most likely it's clogged up pretty badly.

- MTR

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8 years 9 months ago #1443 by gigamile
Replied by gigamile on topic ROL AIR 120 PSI SUDDEN STOP
I got the unit going today, the check valve was junk, completely stuck open. I replaced it, the pump run good, the sump pressure while operation returned to minimal. although since i used a used engine with low compression i ended up setting idle rpms to 2200 rpms in order to avoid stall during transfer to high rpms. also changed alot of oils today. But it turned out ok. will run this unit untill engine wears out I have a 6.5 HOn black model for replacement later on. ThankZ for all the help. Will be checking in periodically. ThankZ again. Dave.

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8 years 9 months ago #1445 by MTR-Admin
Replied by MTR-Admin on topic ROL AIR 120 PSI SUDDEN STOP
That's great to hear Dave, glad it's working for you now!

The unit idling a bit faster than typical shouldn't hurt it, you can another Honda on standby anyway so you should be okay.
Typically when this happens it's either the Unloader is clogged or the Check Valve.

Thanks again for posting and we'll be here when and if you run into more unexpected problems.

- MTR

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