can my AMF be causing my truck not to start. Its 3.0 V6. it will crank and run if hook FP to battery. My B+ is hot only sometimes?

 

Starting is not controlled by the AFM:
- http://www.4crawler.com/4x4/CheapTri...shtml#FuelPump

But after you move the key from START to ON, then the AFM takes over:
- http://www.4crawler.com/4x4/CheapTricks/AFM/index.shtml

 

One possible cause, which "fixed" my slow start probelm, was that the connector was not making full contact to the AFM. The fuel pump only engages on start crank (1991 3.0). this would explain way if Pb is jumped your truck will start. It is a goofy illogical sytem.

 

Actually, some logic behind the system. Fuel pump on while starter is cranking is obvious, engine would not start otherwise. Having the AFM fP contact keep the pump running while the engine is running is a safety feature. How so? Engine runs out of gas and stops, fuel pump shuts off and prevents damage to it (cooled/lubricated by fuel) and if the vehicle is in a accident and the engine stops, fuel pump (and flow) is stopped to prevent fuel gushing out of a potentially ruptured fuel line.