Possible D2 Governor Problem

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Possible D2 Governor Problem

March 18, 2016, 06:43:03 pm

Noticed yesterday my air pressure stayed at 120psi almost the whole trip (105 miles). Usually it cycles down to 90psi then builds to 120psi. Remembered that I did notice that the air dryer was popping off more often than usual before we took off. Figured it had to be the D2 governor and picked one up at NAPA. It was a reman part number 275491RX.

Install was fairly easy 2 hoses and 2 bolts. After install pressure was way high. It hit 130psi and I shut the engine down to keep it from going higher. Air dryer never popped off. Removed and checked all fittings and resealed J37 adaptors and reinstalled. Same thing.

Maybe defective D2 out of the box?

Removed the new D2 and installed the old. It worked the same as before. Would build pressure to 120psi then the air dryer would pop off. If I tapped the brake pedal the pressure would drop to 105-110 then immediately start building back to 120psi and the air dryer would pop off. Normally the psi would have to drop to 90 before it would start building pressure again.

Air dryer was serviced about 3 years ago. Not seeing any water or power out the air drains. Anyone have any ideas?

see ya
ken

Re: Possible D2 Governor Problem

Reply #1 – March 18, 2016, 06:54:59 pm

Ken, I seem to remember that some D2 s are set at different p[ressures to what we normally see and maybe?? it just needed setting. with the screw in end. I am sure Brett etc will check in on it soon.
I took an old one of mine apart and noticed that it was wearing on one side only (valve/shuttle inside) and thought that was why mine was "hanging up" sometimes. I put new seal and greased it up as a spare.
JohnH

Re: Possible D2 Governor Problem

Reply #2 – March 18, 2016, 07:00:30 pm

@John,

Doh! Left out that I did try the new D2 with the adjustment as far out as I dared. Now that I think about it is it possible to lower the cutout pressure that you turn the adjuster in instead of out??

see ya
ken

Re: Possible D2 Governor Problem

Reply #3 – March 18, 2016, 07:10:15 pm

Ken, to lower the pressure turn screw CLOCKWISE
Raise the pressure COUNTER-CLOCKWISE
Each turn is about 4lbs change.
JohnH

Re: Possible D2 Governor Problem

Reply #4 – March 18, 2016, 07:13:44 pm

@John,

Given an either/or choice I'll 90% of the time pick the wrong one.

I'll try installing the new D2 tomorrow and try a clockwise adjustment.

see ya
ken

Re: Possible D2 Governor Problem

Reply #5 – March 18, 2016, 07:14:23 pm

I have been getting the reman d-2's that go to 130 before cutting off. This is on my crane and the last three have all done the same. I haven't bothered to reset them as it is not a big issue for me to have 10 more psi. They do drop to 90 psi before recycling though. Not knowing how the Foretravel signal goes to the governor, is there a chance the signal comes from the air drier and it is the problem? Mine come from the front air tank on the crane.

Re: Possible D2 Governor Problem

Reply #6 – March 18, 2016, 07:31:43 pm

I purposely set my new D2 to unload at 130psi. Hasn't caused any problems. Your air system can go up to 150psi before the safety valve on the wet tank opens - don't ask me how I know this.

BENDIX D-2 GOVERNOR MANUAL Pdf Download.

Re: Possible D2 Governor Problem

Reply #7 – March 18, 2016, 07:37:25 pm

@craneman,

Good info. I am hesitant to bump up the pressure on my 200,000 mile 24 year old compressor though!

I think the cutoff pressure on mine comes from the wet tank.

see ya
ken

Re: Possible D2 Governor Problem

Reply #8 – March 18, 2016, 07:45:38 pm

@Chuck,

Thanks. The manual does say clock-wise to decrease pressure. I'll post an update on how it goes tomorrow. I'm getting pretty good at R & R on the governor.

Chuck when you set your governor to 130 does the cut-in pressure go up to 100 or does it stay at 90?

see ya
ken

Re: Possible D2 Governor Problem

Reply #9 – March 18, 2016, 07:53:57 pm

I had mine replaced with a 105 cut in. Trucks go down to 80 and my old one went to 90. You can adjust the top pressure and 105 is not an issue really.

Re: Possible D2 Governor Problem

Reply #10 – March 18, 2016, 08:09:26 pm

Quote from: kenhat – March 18, 2016, 07:37:25 pm

@craneman,

Good info. I am hesitant to bump up the pressure on my 200,000 mile 24 year old compressor though!

I think the cutoff pressure on mine comes from the wet tank.

My crane is a 1981 International with 600,000 miles no leaks.
see ya
ken

Re: Possible D2 Governor Problem

Reply #11 – March 18, 2016, 09:24:48 pm

Quote from: kenhat – March 18, 2016, 07:45:38 pm

@Chuck,
Chuck when you set your governor to 130 does the cut-in pressure go up to 100 or does it stay at 90?

Supposedly, the range between "cut-in" and "cut-out" is fixed at 20 psi. So if mine cuts out at 130psi (which it does), it should cut in at 110psi. Actually, on my dash gauges, it seems to cut in around 105, but hard to tell exactly where it occurs. I was mainly trying to get it where operating pressure would never go below 100psi, so I could air up my tires to 100 without so much hassle. Achieved that objective, so I'm happy.

Re: Possible D2 Governor Problem

Reply #12 – March 18, 2016, 11:53:04 pm

I believe it is false economy to use Chinese re-mans for D2 governors when new ones are so few dollars more.

Re: Possible D2 Governor Problem

Reply #13 – March 19, 2016, 12:46:21 am

Quote from: kenhat – March 18, 2016, 07:45:38 pm

@Chuck,

Thanks. The manual does say clock-wise to decrease pressure. I'll post an update on how it goes tomorrow. I'm getting pretty good at R & R on the governor.

Chuck when you set your governor to 130 does the cut-in pressure go up to 100 or does it stay at 90?

see ya
ken

I believe it is still cutting in at 90, I will check it in the morning.

Re: Possible D2 Governor Problem

Reply #14 – March 19, 2016, 01:42:53 am

When I re-built my air dryer I replaced the D-2.
I set it to a 130# cutoff.
Brakes work a bit better and filling the tires with the engine compressor works better.
No issues.

Re: Possible D2 Governor Problem

Reply #15 – March 19, 2016, 04:56:54 am

Ken, since I purchased my coach in Jan 2014 it has always cutoff at 130.

Greg

Re: Possible D2 Governor Problem

Reply #16 – March 19, 2016, 08:31:17 am

Quote from: amos.harrison – March 18, 2016, 11:53:04 pm

I believe it is false economy to use Chinese re-mans for D2 governors when new ones are so few dollars more.

The remanufactured ones I buy at Franklin Truck Parts come in Bendix packaging. Have not noticed any performance difference other than the cut out pressures are higher. In doing a Google search there was a reference to a truck manufacturer having a un-adjustable governor set at 130

Re: Possible D2 Governor Problem

Reply #17 – March 19, 2016, 10:23:47 am

Quote from: kenhat – March 18, 2016, 07:45:38 pm

@Chuck,

Thanks. The manual does say clock-wise to decrease pressure. I'll post an update on how it goes tomorrow. I'm getting pretty good at R & R on the governor.

Chuck when you set your governor to 130 does the cut-in pressure go up to 100 or does it stay at 90?

see ya
ken

Update it cuts out at 130 back in at 100

Re: Possible D2 Governor Problem

Reply #18 – March 19, 2016, 04:25:50 pm

Put the new D2 back in and adjusted clockwise (thanks Mr. Haygarth!). Cut-out at 115 psi. Not bad for just eyeballing it. Adjusted it to 130 since that's what all the cool kids are doing.

Builds pressure and cuts out just like it's supposed to but I still have my original problem of building pressure before it drops "20psi".

Going down a bumpy road I see the pressure go down about 5 to 10 psi. Then it starts building back up to 130 psi. Looks like for some reason it's not cycling correctly. It should not start building pressure again until it hits at least 110psi. Same story if I tap the brakes when stopped. Drops 10 or so psi and starts building pressure again.

So I build pressure and the air dryer cuts-out. At this point there should be a cut-out valve on the compressor. Is the cut-out valve the governor? Both my old and new D2s are giving me the same symptoms. Seems unlikely they would both have the same defect.

It doesn't seem to affect the operation of the coach but my concern is that I'm overworking my compressor & very slightly hurting my MPG.

Anyone have any ideas on this?

Pics just because... And yes my entire engine compartment needs a good cleaning. It's on the list.

see ya
ken

Re: Possible D2 Governor Problem

Reply #19 – March 19, 2016, 04:54:32 pm

The air line to the governor is a signal for how much pressure is in the system. The pressure overcomes the spring you adjust in the governor and supplies air to the unloader valves in the compressor to keep it from building more air. Given that the compressor is always turning whether or not it is building air you will not notice any mpg difference. It is possibly that the unloaders may be a little weak.

Re: Possible D2 Governor Problem

Reply #20 – March 19, 2016, 04:58:48 pm

Ken,

On our coach, the D2 gets its pressure signal off the wet tank. Assuming yours is the same... Your dash pressure gauges are reading the pressure in the front and rear tanks, which are isolated from the wet tank by check valves. SO, it is possible for the pressure in the wet tank to drop to the D2 "cut-in" pressure, without you seeing a corresponding drop in the front and rear tanks. This would require a "leak" or malfunction in some component that is tied directly to the wet tank. On our coach, that would be either the remote drain valve line, or the air hose connection (that is used to fill your tires), or the line to the D2, or the air dryer. There are 2 lines coming off the wet tank going to the dryer: a 3/8 nylon tube and a 5/8" braided hose. The 5/8" hose is protected with a check valve at the wet tank. If the check valve leaks, it is possible to lose air pressure going backwards through the dryer.

Any chance you are losing excessive air pressure through one of those paths?

Might also look at the high pressure safety relief valve (on wet tank) to be sure it is not stuck partly open and leaking.

PS: You did replace the dust cap on the D2, did you not?

Re: Possible D2 Governor Problem

Reply #21 – March 19, 2016, 10:52:49 pm

@Chuck,

I like that line of reasoning. I will have to do some testing to see if that is the case.

And yes I did put the dust cap back on.

I'm in Dallas for a week so will work on it as I can.

see ya
ken

Re: Possible D2 Governor Problem

Reply #22 – March 19, 2016, 10:58:20 pm

Don't be afraid to check the signal line to the gauge and even the back of the gauge for the air leak. I had one with a bunch of time in it before we found it.

Re: Possible D2 Governor Problem

Reply #23 – March 21, 2016, 06:02:58 pm

Quote from: kenhat – March 18, 2016, 07:45:38 pm

@Chuck,

Thanks. The manual does say clock-wise to decrease pressure. I'll post an update on how it goes tomorrow. I'm getting pretty good at R & R on the governor.

Chuck when you set your governor to 130 does the cut-in pressure go up to 100 or does it stay at 90?

see ya
ken

Ken,

Before I reset mine (OEM) under the advice of Gary Bouland and Caflashbob, it was cutting in at 90 and cutting out at 110. Reset to 130 cut-out and now cut-in is at 110. I checked it on fast idle a few times to make sure. Now I have better brakes and more air for the system to work with.

Since both D2 governors had the same result it might be that the unloader mechanism on the compressor needs servicing. It works with the governor and if the if the lines aren't leaking there might be a problem with dirty valves or weak springs. Just my guess. Compressor, Governor, and Unloader Assembly

Jerry

Re: Possible D2 Governor Problem

Reply #24 – March 21, 2016, 07:39:24 pm

just how quickly does the pressure drop from 130 to 110? is this even when stationary?

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