possible fuel injection problems

I am new to this particular group but I need some info. My father-in-law has a 1990 F150 with the 4.9 straight 6 that abruptly quit on him one day. Here is what I know: He replaced the fuel pump, it measures over 40 psi on the fuel rail which is more than enough. It is getting good fire through the distributor and to each spark plug. That leaves 2 possiblilites as far as I know but perhaps someone can throw me some advice. I am leaning towards the suspicion that all 6 fuel injectors aren't getting whatever voltage they need. (I don't have a meter with a movement to look for short pulses, only a digital multimeter...) The common denominator would be the EECM (computor). I am thinking that either the computor is shot or it's got power issues. I see on the diagram that there is a fusable link going to p1. I assume this is juice to the computer. Does anyone know where that fusible link is??? Other possibility: I didn't see a mass air flow sensor anywhere so I assume it's a speed density setup with the sensor on the engine for the cam. Is this the case and if so, could that sensor going out keep it from cranking? We put a healthy shot of ether through the air filter housing and got it to crank momentarily, but on it's own it acts like there is no gas. That is why I am leaning towards the injectors where the common element is the computer since we have such good pressure at the fuel rail. Any advice, insight, etc... would greatly be appreciated by myself and my father-in-law.

I really don't know what it is, but if you call the garage or maybe the parts store they might be able to help you, also all-car will diagnois the truck for free when you get it going. Good luck