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[Datsun 1200 encyclopedia]

Fuel Shut-Off System

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Category: Fuel System

The Fuel Shut-Off System was introduced in some 1980 B310 USA models. It leverages the anti-diesel valve to stop the fuel flow during periods of deceleration. This is similar to what EFI systems do. It is only active at higher speeds, namely above 40mph.

1980: All California models  
1980: FED A15.MT
1981 CAL, FED, FED.MPG and CAN.MPG models. 
  Canada models did not use fuel-shut off except for 
  MPG (FU Engine) models.

For safety and good performance, the FSOS does not work unless the engine is decelerating.

  • Only works when decelerating (vacuum is high AND speed above 40mph)
  • Does not work in neutral, so engine will not stop due to lack of fuel
  • Does not work when clutch is engaged (so you can blip the throttle)

Components are:

This would be an interesting system to retrofit to older models for increased fuel economy.

Fuel Shut-Off System replaces Throttle Opener.

  • Hitach DCH306-67
  • Dual-mode spark advance (intake vacuum works at idle, improving fuel economy)
  • Double-lead anti-diesel valve
  • 16767-H7280 UNIT-ENGINE REVOLUTION A14 FED(KFU) B310 [Engine Rev Switch, 1000-1150 RPM)
  • 16024-H7281 THROTTLE SWITCH ASSY A14 FED(KFU) B310 [Throttle Valve Switch]
  • 32130-H9011/32130-H9010 EXTENSION ASSY-REAR [unique, but others may work]
  • 32006-K2401 SWITCH COMP-NEUTRAL COUPE 5-SPEED(CAL),FED KFU [Neutral Detecting Switch] replaced 32130-H9705 32006-K2400
  • 10mph switch in speedometer

Coasting Cut-off

Nissan intoduced a similar system for 1968 USA Datsun Pickup model 520-TU. Call "coasting cut-off", it's main purpose was to reduce unburned hydrocarbons on decelleration. It is described in Nissan "Service Bulletin Vol. 79"

* Datsun 520-TU from 1967 October (1968 model years + 1968-1969 521 with J13)
16010-20610 Hitachi carburetor DCA306-4
* with magnetic valve and accelerator switch
16010-B0412 Hitachi DCA306-4A
16010-B0412 Hitachi DCA306-4BK (ISO)
16328-20600 Vacuum Switch (VS37-1)

"FUEL CUT OFF this vehicle is equipped with a fuel cut off to maintain emissions"
1969 Datsun 521 LTU J13-equipped pictured
Vacuum Switch is just below the gold sticker

The carburetor contains "Solenoid Valve (24D)" and a bolt-on micro-switch "Throttle Switch" and bracket. The solenoid looks like an Anti-diesel Valve, but will be on a non-BCDD, non-auto choke carburetor.

DCA306-4A_bx.jpg J15_carb-c.jpg

Fuel-cut Valve
[need photo] is in same location as later Anti-diesel Valve

Not to be confused with "Coasting Air Solenoid Valve" (triangle base on Hitachi DAF328)

Not to be confused with Anti-diesel (Fuel-Cut) Valve (Hitachi DCH340):

Not to be confused with a Boost Controlled Deceleration Device (BCDD) Valve:
DCH340-1dx.jpg DCH340-1ax.jpg
BCDD starting June 1971 for Datsun 510 USA (same time as auto choke)

Or B.C.D.D. with vacuum control valve

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