Engine cutting out
Discussion
My computer illiterate friend has a 1992 4.3L Griffith.
Last year it started a fault where the engine would cut out after running initially for 3/4 of an hour. It would then restart after a short period.
The time before cutting gradually shortened so that now it runs for no more than 6 seconds before stopping but will immediately restart. I'm therefore discounting any possibility of it being heat related.
It sounds for all the world like it's not getting the fuel flow rate that it requires. I have access to the Heath TVR manual which says that pressure regulation is mechanical. Yet, when you go to first position with the key, the pump runs for a short time and then cuts out as if there is an electrical pressure switch - is this usual?
The ignition module is new. The dizzy trigger is a second-hand replacement. Coil is new.
I've cleaned and tested the idle stepper motor.
Further suggestions greatly appreciated as each week I have only a short time to look at the car in a cold and badly lit shed!
Last year it started a fault where the engine would cut out after running initially for 3/4 of an hour. It would then restart after a short period.
The time before cutting gradually shortened so that now it runs for no more than 6 seconds before stopping but will immediately restart. I'm therefore discounting any possibility of it being heat related.
It sounds for all the world like it's not getting the fuel flow rate that it requires. I have access to the Heath TVR manual which says that pressure regulation is mechanical. Yet, when you go to first position with the key, the pump runs for a short time and then cuts out as if there is an electrical pressure switch - is this usual?
The ignition module is new. The dizzy trigger is a second-hand replacement. Coil is new.
I've cleaned and tested the idle stepper motor.
Further suggestions greatly appreciated as each week I have only a short time to look at the car in a cold and badly lit shed!
Yes the pump going silent after a couple of seconds is normal. When it cuts out does it cough and splutter a bit as though fuel is running out or is it an instant cut out. I am just thinking is it running for 6 seconds from the initial pressurisation and then when that pressure has gone there is no more fuel and it stops. When it does cut out you could see if the system is still pressurised by disconnecting the fuel line and seeing if there is presure.
If there is pressure and it stops, it looks like ecu related, assuming you are sure it is the fuel side. try disconnecting the ecu, clean contacts and try again.
If there is pressure and it stops, it looks like ecu related, assuming you are sure it is the fuel side. try disconnecting the ecu, clean contacts and try again.
The ECU ignores the AFM output for the first few seconds of starting and provides a fixed amount of fuel, then once the engines running it trims the fuel to suit the AFM airflow output. If the airflow reading is too low due to an airleak or faulty AFM the engine will die. It will however run at higher RPM if its an air leak- it just wont idle. Try and run it with the AFM disconnected and see if it keeps running. It will be rough however. If it is fuel pressure, then you have a massive restriction somewhere if the engine wont even idle.
blitzracing said:
The ECU ignores the AFM output for the first few seconds of starting and provides a fixed amount of fuel, then once the engines running it trims the fuel to suit the AFM airflow output. If the airflow reading is too low due to an airleak or faulty AFM the engine will die. It will however run at higher RPM if its an air leak- it just wont idle. Try and run it with the AFM disconnected and see if it keeps running. It will be rough however. If it is fuel pressure, then you have a massive restriction somewhere if the engine wont even idle.
Well, what d'ya know?! Disconnected the AFM and sure enough she continues to run, albeit rough as hell! So I reckon we can definately say it's the AFM unless anyone wants to throw a spanner in the works and claim that it could still be the ECU?
phil0185 said:
blitzracing said:
The ECU ignores the AFM output for the first few seconds of starting and provides a fixed amount of fuel, then once the engines running it trims the fuel to suit the AFM airflow output. If the airflow reading is too low due to an airleak or faulty AFM the engine will die. It will however run at higher RPM if its an air leak- it just wont idle. Try and run it with the AFM disconnected and see if it keeps running. It will be rough however. If it is fuel pressure, then you have a massive restriction somewhere if the engine wont even idle.
Well, what d'ya know?! Disconnected the AFM and sure enough she continues to run, albeit rough as hell! So I reckon we can definately say it's the AFM unless anyone wants to throw a spanner in the works and claim that it could still be the ECU?
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