Engine dies when brakes applied - Off-Road Forums & Discussion Groups
Go Back   Off-Road Forums & Discussion Groups > Jeep > Jeep-Short Wheelbase

Jeep-Short Wheelbase All discussion of short wheelbase Jeeps: CJ, TJ, YJ and JK



Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 01-15-2002, 11:53 AM
**DONOTDELETE**
Guest
 
Posts: n/a
Default Engine dies when brakes applied

I've got an 85 CJ-7 with the 258. Thanks to California's emission laws, engine is stock. It came equipped with power brakes.

When I'm driving and apply the brakes, my rpm's drop and the engine will actually stall if I don't do some fancy footwork and actually rev the engine as I'm slowing down. The problem seems to be worse if I brake suddenly as opposed to lightly braking and coasting to a stop. If I'm sitting at a stop and apply the brakes, the RPM's are unaffected.

I've come up with 2 theories? The change in momentum of the vehicle slowing down is somehow altering the gas flow into the carb???

OR

I believe the brake booster somehow utilizes vacuum pressure from the engine. How it works, I don't know. Could there be a problem with the brake booster or vacuum system, that would cause a vacuum leak and therefore cause the engine RPM's to drop???

Anyone that's experienced the same thing or has any advice would be greatly appreciated.


Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2  
Old 01-15-2002, 12:22 PM
Carpal \'Tunnel
 
Join Date: Nov 2000
Location: Manitoba, Canada
Posts: 2,687
Thanks: 0
Thanked 0 Times in 0 Posts
TiminMb is an unknown quantity at this point
Default Re: Engine dies when brakes applied

Both ideas are possible. Start with the brake booster. Does appply the brakes while the vehicle is idling affect idle quality? If there is a defect in teh booster (which runs off vacuum ) it will show up then.

If it'snot the booster, then you carb could have sediment in it or other blockage which needs cleaning out. Read up on the carter carb cleaning idle air screws, or better yet just get ambitious, buy a rebuild kit, tear it down and clean everything thoroughly..

Tim

84 CJ7, 258, HEI, M/C 2100 carb, 5 inch lift, RS9000's, 33x12.5 BFG M/T's, 4.56's and Detroit softlocker, full cage & belts, Xenon flares, Dana 44 rear, GM dual diaphragm brake booster
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote Quick reply to this message
  #3  
Old 01-15-2002, 12:55 PM
Addict
 
Join Date: Jan 2000
Location: Green Bay, WI
Posts: 573
Thanks: 0
Thanked 0 Times in 0 Posts
greencj7 is an unknown quantity at this point
Default Re: Engine dies when brakes applied

Ditto what Tim said, but since you stated that when you're stopped and apply the brakes the RPMs are unaffected, I would check the carb first. Probably a worn needle and seat or sediment. The rebuild kits are pretty inexpensive and the project isn't hard at all. Don't forget a new fuel filter, too.

Ken

Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote Quick reply to this message
  #4  
Old 01-15-2002, 01:08 PM
Way Outta Control
 
Join Date: Sep 1999
Location: The Palouse
Posts: 13,392
Thanks: 0
Thanked 2 Times in 2 Posts
LEVE is on a distinguished road
Default Re: Engine dies when brakes applied

I'd suspect that it's not a vacuum problem... but a problem with the entact emissions stuff and BBD Carb.

When you lift your foot and start braking the Pruge Signal is sent via the comptuer and tells the engine to suck up the fumes building up in the gas tank and route them to the carb to be burned. Over time, and because of circumstances (Like off camber Jeeping, and over-filling the tank) the charcoal emissions canister gets full of gas. So now when you lift you foot and start to break the purge line is not sucking fumes and mixing it with the intake air. The carb's now sucking raw gas from the driver's side emissions canister and flooding the engine.



For a possible cure, and a better desciption see:


Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote Quick reply to this message
  #5  
Old 01-15-2002, 01:13 PM
AllLockedUp's Avatar
I Might Just Know What I'm Talking About
 
Join Date: Jun 2001
Location: Somewhere in Cow Hampshire
Posts: 1,705
Thanks: 0
Thanked 0 Times in 0 Posts
AllLockedUp is an unknown quantity at this point
Default Re: Engine dies when brakes applied

Rather than spend the money on a $65 charcoal canister now, chekc your vacuum lines first. My buddy's Jeep had the same symptoms, it was a bad line.

85 CJ-7 258/T176/D300 Scout D44s F&R with Lock-Rites and 4.56 gears. 4" springs with lift shackles 36" SS TSL Radials Hella Rallye 4000s for guiding small planes into the woods
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote Quick reply to this message
  #6  
Old 01-15-2002, 01:24 PM
surveyboy's Avatar
Addict
 
Join Date: Aug 2001
Location: Riverside, California
Posts: 596
Thanks: 0
Thanked 0 Times in 0 Posts
surveyboy is an unknown quantity at this point
Default Re: Engine dies when brakes applied

Leve, who's page is that? that index has lots and lots of info. I think I've seen parts of that other places, but not sure. Never mind, I found it. thanks for the link
surveyboy

http://www.csupomona.edu/~sdmiller1/jeep.htm
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote Quick reply to this message
  #7  
Old 01-16-2002, 01:45 AM
**DONOTDELETE**
Guest
 
Posts: n/a
Default Re: Engine dies when brakes applied

Thanks guys. You've given me some great ideas. I got tired of always being told every problem was due to my vacuum lines, so I replaced all of them not too long ago, but it's always a possibility so I'll check them over. I never would have suspected the charcoal cannister. That's one of the few parts that hasn't been replaced or repaired in the 16+ years of the Jeeps existence so there's a good chance it's the culprit.

Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote Quick reply to this message
  #8  
Old 01-16-2002, 05:40 PM
**DONOTDELETE**
Guest
 
Posts: n/a
Default Re: Engine dies when brakes applied

What about the carb float? The gas level in the carb bowl could be to high. I'm stock also and running "perfect". I have a new carb and new brake booster. If I apply the brakes the idle will change slightly. If I panic stop and lock up the brakes it sometimes will die. The nature of the beast? I dunno.

Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote Quick reply to this message
  #9  
Old 01-16-2002, 08:40 PM
Drury's Avatar
Old Hand
 
Join Date: Sep 2001
Location: Austin, TX
Posts: 745
Thanks: 0
Thanked 0 Times in 0 Posts
Drury is an unknown quantity at this point
Default Re: Engine dies when brakes applied

Just one other thought and is very unlikely since this sounds like it has been happening for a while. But on my old Commanche, when the alternator would start to die, applying the brakes was just enough draw to stall the engine. I doubt this is your problem, but I thought I would offer it anyway.

78 CJ7 Golden Eagle/TR Ignition/Weberized/2" leafs
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Off-Road Forums & Discussion Groups forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -5. The time now is 04:06 AM.


Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Relevant URLs by vBSEO 3.2.0
Copyright 1994-2009, VerticalScope Inc. // Off Road forums & discussion groups sitemap
side by side | atv | dirtbike | snowmobile | sandsport | competition | land use | Jeep | Toyota | Ford | GM