I have an 86 F150 with a fuel injected 302. 20,000 miles and I don't know if that's 120,000 or 220,000 since the odometer doesn't go that high. Maybe back then they didn't think 100,000 was achievable. Anyway, looking at the high pressure external fuel pump that's mounted on the frame, it doesn't look like its ever been replaced judging from the amount of rust on the mounting bolts. First question is should I replace it now or wait until it fails? My only reservation is that with the quality of parts I may get one worse than what I have. I also want to know if the low pressure pump in the tank were to fail, would the external pump still be able to draw gas? If not I should probably replace both at the same time. It's not a matter of money or time to do it, I'm more concerned about creating another problem. My reason being is that I have access where I work to aftermarket parts which I can get at cost. When I first bought this truck I decided to replace the ignition module which is on the distributor (EEC IV ) as a precaution. Truck ran like crap and I wound up putting the OEM one back on. I see a lot of feedback about the modules not working and complaints that even the OEM Motorcraft ones look to be aftermarket. I've always been hellbent on changing stuff before it fails but nowadays I wonder if it"s worth it.

 

Your fears are well founded, new doesn't necessarily mean good. I just replaced the in tank pump on my little ranger pickup. Like yours, I have a in tank pump and then an external pump. I left my external pump, it looks original also. I have heard rumors this pump lasts a lot longer than the in tank pump.

Will the external pump pull through a dead in tank pump? I don't know, I sort of doubt it though. I was having problems which ended up being something else, and went ahead and changed the in tank pump which was working all the time. My fuel gauge was dead though, and changing the tank assembly did fix that.

Just remember, if you are stuck somewhere and think it might be the pump, hit on the bottom of the tank or rap on the frame pump, that usually gets them going enough to get you home so you can fix it.