Home » Public Forums » GMCnet » Another reason for a back-up brake pump
| Another reason for a back-up brake pump [message #364206] |
Sun, 23 May 2021 09:17  |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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Well, we went to out first rally since Manfield. There was an interesting situation when the coach was almost there.
When checking in, I stopped at the little building and talked to the nice lady and pulled away. There was quite a rise and just before the crest, the engine sputtered and died. From the sound of it, it was vapor lock. I tried to get our old dog off the engine hatch because I have cured this before (years ago) by getting the carburetor cooled off fast.
Problem: The old dog did not want to move. It took me much longer than I like to get the hatch open. When I finally did, the carburetor was dry almost totally dry. The accelerator pumps didn't do much. I had no simple way available to get fuel from the system and pour it into the carburetor.
I should also mention that the Chaumière was full of year old winter gas.
Needless to say, I had time to think. As I sat in the sun, and calculated the time to local sunset, it also occurred to me that we where head up by a lot and in the sun. If I could roll the coach back down the slope and through the gate, we could be A: Out of the Sun and B: Much closer to level. This was a maneuver with some risk. I knew I could back the her on the mirrors, and the added vacuum pump should give me brakes enough to control the situation.
BUT, I had installed the that vacuum pump years ago and never had an occasion to really test it. My parking brake does sort of work, but I didn't want to try that here in the case that it did not release.
So, I turned on the ignition and cycled the brakes to hear (just barely - me not the pump) the little pump run and the brakes felt good. I got my mental picture of the situation well defined and held the brake while I popped the transmission out of Park.
The backward roll was completely controllable to hold the speed down, I was on and off the brake and the pump was there for me.
We settled into a shady place and I pulled a bottle of water out of the reefer and listened to music for about 15 minutes give or take.
When I thought I had a good chance, I engaged the battery boost (on a 73, this is not a momentary) and started cranking. It took about 15 seconds for the first fire and then they kept on coming and she was soon at a stable idle. So, I started back up the hill and this time I had no problem making it to the campsite.
I do actually have a boost pump. I acquired it years ago and it is still under the dinette seat where it is safe. Maybe I will bump that priority a little and try to burn off the year old winter fuel.....
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: Another reason for a back-up brake pump [message #364209 is a reply to message #364206] |
Sun, 23 May 2021 11:11  |
rjw
Messages: 697
Registered: September 2005
Karma: 4
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Senior Member |
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Matt Colie wrote on Sun, 23 May 2021 10:17
BUT, I had installed the that vacuum pump years ago and never had an occasion to really test it. My parking brake does sort of work, but I didn't want to try that here in the case that it did not release.
So, I turned on the ignition and cycled the brakes to hear (just barely - me not the pump) the little pump run and the brakes felt good. I got my mental picture of the situation well defined and held the brake while I popped the transmission out of Park.
The backward roll was completely controllable to hold the speed down, I was on and off the brake and the pump was there for me.
Matt,
Sorry to hear about your fun at the gate the other day. I had similar problems (not related to vapor lock, but an ignition problem that I ultimately solved) on a trip to Reno a few years ago. I had previously installed a vacuum system put together by Dave Lenzi. As a result I had no worries about not being able to stop in the mountains or any other place and there were about half a dozen times she quit. I previously had the JC-4 pump that's been recommended by various GMC people until I did a little test.
http://gmc.mybirdfeeder.net/GMCforum/index.php?t=msg&th=39705&start=0
I'm curious as to the pump you have?
Richard
76 Palm Beach
SE Michigan
www.PalmBeachGMC.com
Roller Cam 455, TBI+EBL, 3.42 FD, 4 Bag, Macerator, Lenzi (brakes, vacuum system, front end stuff), Manny Tranny, vacuum step, Tankless + OEM water heaters.
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| Re: Another reason for a back-up brake pump [message #364210 is a reply to message #364206] |
Sun, 23 May 2021 11:15 |
Tom Katzenberger
Messages: 399
Registered: June 2019
Location: Kingsville, MD
Karma: 4
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Senior Member |
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Matt,
Thank you for sharing. I have the fuel boost pump switch on the left side dash cover below the steering column. On this new rebuild, I will put it back there for the reason you described.
I also have the vacuum back up pump, but will check it periodically. I am wondering if I should include a dash vacuum guage for the back up vacuum pump?
You guys sharing all these experiences is very helpful and for that and more I thank you.
I am glad all worked out well.
Safe travels and thanks again,
Tom K.
Tom & Oki Katzenberger,
Kingsville, Maryland,
1977 23' Birchaven, 455 C.I.D., Micro Level, Howell EBL-EFI Spark Control, Macerator, York Air Compressor, 6 Wheel Disc, Quadra Bag, Onan W/Bovee Ignition
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| Re: Another reason for a back-up brake pump [message #364218 is a reply to message #364209] |
Sun, 23 May 2021 18:49 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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Richard,
I do not recall which pump it is, but it is not the JC-4 and it is not the pump that Ford bought from Bosch for their electric cars. Even with the coach just outside my window, it is rain hard enough to make me wait before I go out there, but I will get back to you.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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