1996 Ford E-Series Van Fuel pump relay (in power distributi

A few months ago my E-350 van failed to start and my uncertified mechanic diagnosed my problem as a bad fuel pump, which was replaced at a cost of $750. Several times since the replacement (with a new Ford fuel pump) the engine has again failed to start. I studied the manual and found the location of the fuel pump relay and replaced the relay with a new one. With the new relay, the engine started immediately, but the failure to start has recurred again, after a few weeks--and again was resolved for now, with my again installing a new fule pump relay.

I had a similar problem in 2005, wherein I stopped in Cecil, GA. To gas up, and when I tried to leave, the engine would turn over, but not start. So, I had it towed to Cook County Ford, near Cecil, GA. And the fuel pump was replaced--and the problem had not recurred until a few months ago, when it was again replaced, as mentioned above. In 2005, the Ford mechanic said that fuel pump failure for these E-350 vans is a common problem.

So, now I have a vehicle that I cannot trust, and am seeking advice from a certified auto mechanic.

Any assistance/advice that you can provide on the basis of your experience/expertise, will be greatly appreciated. Bob Manley