|
If fuel supply is the issue, it will show up as decreased fuel pressure which can be measured. The mechanical MFI pump likes 15 psi and will become unhappy much below that and the engine will run poorly. (I had the exact same problem as mar2mar, resulting in severe engine stumbling. The valve he mentions is a check valve that keeps fuel pressure at 15 psi. When it fails or the spring becomes weak over time, fuel pressure drops. As mentioned above, a failing fuel pump will also cause low fuel pressure.)
Another possibility since your case seems to be warmup dependent is that the warmup circuit on your mechanical pump is stuck. If you are getting an enriched mixture all the time, the engine could run poorly when warm. Check the small hose that goes from the heat exchanger to the pump - it delivers warm air to the pump. If that has fallen off or ruptured, the pump will think the engine is cold all the time and stay rich.
|