Project Samurai – Carburetor & ECM

Many Samurai met their fate not in battle, but the junk yard due to failed emissions testing. The carburetor used was electronically controlled, a precursor to fuel injection. It is a Hitachi DFB306 2-barrel downdraft type carburetor with primary and secondary barrels.

The electronics used includes a secondary vacuum solenoid valve, EGR vacuum solenoid valve, idle up vacuum solenoid valve, float bowl vent solenoid, fuel cut solenoid valve, mixture control solenoid valve, altitude switch, under the hood temperature switch, engine temperature switch, O2 sensor, engine RPM, fifth gear switch and two throttle position switches.

The mixture control solenoid valve which is operated by the electrical signals from the Electronic Control Module (ECM) so as to maintain the optimum air fuel ratio of the primary slow and the primary main systems at all times. This type of carburetor was only used for a limited time period and most mechanics who are not familiar with them try to treat them as a conventional carburetor and have trouble.

The ECM is the brain that controls important functions of the engine. A Samurai can run without it, I have seen one that did, but the secondary, EGR, idle up, vent solenoid will not function and it will run rich with the mixture control valve not working. The ECM has a limp mode that will cause it to run full rich if there is a problem with the O2 sensor or other inputs. The ECM must be checked with the diagnostic feedback test prior to adjusting the carburetor.

In addition to the electronic controls there are numerous vacuum lines, switches and valves to check. A must is the float bowl vent tube nozzle. Vent tube nozzle (Suzuki part 13211-831Z0)

Note: This part is also available from:
http://www.spidertrax.com/s.nl/it.A/id.2138/.f
http://www.lowrangeoffroad.com/index.php/venturi-tube.html
http://www.rocky-road.com/venturi.html

The bible of the Suzuki Samurai is the Field Service Manual. It is available for download at 1986-1988 Suzuki Samurai Factory Service Manual

Most importantly, besure to lube the linkage with AMSOIL Metal Protector and clean out the intake with AMSOIL Power Foam.