I have an '88 Dakota, 230K miles, with the following problem:
For the last month or so, the truck has been hard to start--had to crank once, wait 10 seconds or so, then crank again. Gradually, this problem increased to the point where it would stumble at WOT, then even at 3/4 throttle or so.
Thinking it was the fuel pump, I replaced it, along with the filter. Problem remains; in fact, it seems even worse, to the point where the truck only idles (can't put any load on it, or it stumbles).
So, at this point I suspect the fuel pressure regulator. However, I don't want to buy it unnecessarily. Given that a
F.P.R. is designed to send a part of the pump output back, would pinching off part/all of the return line be a valid diagnostic test?
Anything else that comes to mind?