SU HIF44 carburetors with FASD

Later models are fitted with a twin SU HIF 44 carburetors. The basic principles of these SU’s are identical, only the float chamber of the HIF series is below the main jet instead of on the side.

The SU HIF44 carburetors are equipped with a separate cold start device (choke). The unit is an independent working device that operates on the coolant temperature and the throttle position. It is better known as FASD, or Fully Automatic Starting Device.

From 1985 onwards the six cylinder engines are fitted with an electronically controlled fuel management system, and consist of a stepper motor controlled carburetor, the HIF44E (electronic) operated by an ECU, that measures the ambient temperature and coolant temperature.

The FASD is not repairable; there no service parts available for the unit, however you can adjust the unit. This is a test to see if the FASD unit is working.
Before you try this ensure that the carburetor is working correctly and check all components as described in the HS 6 section.

1) Remove the air filter unit from the carburetor.

2) Run the engine for 5 minutes, until normal temperature has reached. Check that the FASD inlet port is not admitting any air, if it does the FASD is faulty.

3) It is possible that the FASD module, located behind the minor instruments is fault. In such a case the engine will start well from cold and will run well when hot, but shows symptoms of excessive richness. Check that there is a 12-volt across the cables supplying the delay valve between the carburetor and the FASD.

4) If starting the engine and initial running are satisfactory but the FASD seems to stay on to long, check that when the engine is hot, coolant is circulating past the FASD unit. If an early pattern inlet manifold is used, the coolant feed can be blocked. Change this to a later series.

5) Reluctance to start and run when cold may be due to fuel starvation. Remove the FASD and check that the non-return valve ball is not dislodged.

If all seems to be in working condition but the engine is still not running correctly an adjustment of the FASD may be attempted. Adjusting is needed when too much or a to long period the air is flown to the FASD unit. For this test a piece of paper or cardboard disk with a hole in the center may suffice is needed, and a way to measure the temperature of the coolant of the FASD water jacket.
Temperature sensitive labels are available and can be used. But if the water temperature can be measured with any other device, like an electronic sensor it can be used as well.

1) Remove the air cleaner adapter from the carburetors.

2) With the engine cold, remove the rubber plug from the end of the adjustment tube. Adjustments are done with an Allen key into this tube.

3) Use the temperature sensitive labels by sticking them on the waterway close by the FASD module.

4) Start the engine and allow it to idle. If the engine will not start turn the Allen key 2 full turns clockwise and try again.

5) With the engine idling place the airflow detector over the FASD air intake so that the passage of air holds it in place.

6) As soon as the water jacket temperature reaches 65 degrees C turn the Allen key clockwise until the FASD stops taking air. The indicator will fall of; all of this must be done within 30 seconds of the desired temperature being reached. If not, the engine should cool for at least one hour before the test can be done again.

7) When the FASD is working properly you can remove the Allen key, refit the air cleaner adapter.

No provision is made for overhaul; renewal would be the only solution. The delay valve however can be replaced separately.