Quantcast Deceleration  Throttle  Modulator  System  -  1973  California and 1974 thru 1980 Federal Vehicles Over 6000 Lbs.  GVW

Order this information in Print

Order this information on CD-ROM

Download in PDF Format

     

Click here to make tpub.com your Home Page

Page Title: Deceleration Throttle Modulator System - 1973 California and 1974 thru 1980 Federal Vehicles Over 6000 Lbs. GVW
Back | Up | Next

Click here for a printable version

Google


Web
www.tpub.com

Home


   
Information Categories
.... Administration
Advancement
Aerographer
Automotive
Aviation
Combat
Construction
Diving
Draftsman
Engineering
Electronics
Food and Cooking
Math
Medical
Music
Nuclear Fundamentals
Photography
Religion
USMC
   
Products
  Educational CD-ROM's
Printed Manuals
Downloadable Books
   

 

Share on Google+Share on FacebookShare on LinkedInShare on TwitterShare on DiggShare on Stumble Upon
Back
Choke System
Up
TM-5-4210-230-14P-1 Aerial Ladder Fire Fighting Truck Manual
Next
Secondary Throttle Operation
TRUCK GROUP SERVICE MANUAL TM 5-4210-230-14&P-1 GENERAL Figure 17  Throttle Modulator Diagram 1.  To Speedometer 3.  Spinner Valve Speed Sensor 2.  Bleed Line Open to 4.  To Transmission Vacuum Source Below 5.  To Vacuum Source Cutoff Speed 6.  Throttle Lever 7.  Throttle Modulator Bleed Line Closed To 8.  To Air Cleaner Vacuum Source Above 9.  Bleed Line Cutoff Speed The   throttle   plate   is   held   in   a   partially   open   position during  vehicle  deceleration  to  aid  combustion  and  provide  an acceptable exhaust emission level. When  the  vehicle  decelerates  to  the  cutoff  speed,  the vacuum bleed line is opened by the speed sensor, causing the modulator  to  retract  and  allow  the  throttle  lever  to  close  the throttle plate to curb idle position. The  speed  sensor  and  throttle  modulator  are  serviced only as complete replacement units. Deceleration  Throttle  Modulator  System  -  1973  California and 1974 thru 1980 Federal Vehicles Over 6000 Lbs.  GVW The     deceleration     throttle     modulator     system     (DTM) consists basically of a vacuum operated throttle modulator unit on  the  carburetor,  a  solenoid  vacuum  valve  and  engine  speed sensor unit (Fig. 18). Normally   an   engine   will   emit   relatively   high   levels   of unburned   hydrocarbons   during   "closed   throttle"   deceleration. This is because the intake of air/fuel mixture is not sufficient to support     complete     combustion     and     the     engine     "misfires" resulting  in  fuel  being  passed  through  the  engine  unburned. The   deceleration   throttle   modulator   system   overcomes   this condition by maintaining a slightly greater throttle opening (high idle)   during   initial   deceleration   which   permits   intake   of   just enough  additional  air/fuel  mixture  to  promote  combustion  and eliminate misfire. The   engine   speed   sensor   is   calibrated   to   activate   or deactivate   (extend   or   retract)   the   throttle   modulator   unit   at approximately 1850 RPM engine speed. Above  1850  RPM  engine  speed,  the  solenoid  vacuum valve   is   activated   (held   open)   by   electrical   current   from   the engine speed sensor unit.  This permits manifold vacuum to act upon the diaphragm of the throttle modulator unit extending the modulator unit to the high idle position. Upon deceleration, the returning     carburetor     throttle     lever     contacts     the     extended modulator, thus holding the throttle in high idle position. When  engine  speed  drops  below  1850  RPM,  the  speed sensor unit deactivates the solenoid vacuum valve allowing the valve to close and bleed the vacuum from the throttle modulator diaphragm  spring  to  retract  the  modulator  unit  and  allow  the throttle lever to return to normal curb idle position. For  deceleration  throttle  modulator  service  instructions, see CGES-215 Emission Control Systems. CGES-125-T  Page 11 PRINTED IN UNITED STATES OF AMERICA

Privacy Statement - Press Release - Copyright Information. - Contact Us - Support Integrated Publishing

Integrated Publishing, Inc.
6230 Stone Rd, Unit Q Port Richey, FL 34668

Phone For Parts Inquiries: (727) 493-0744
Google +