For starters the truck is an 87 f150 302 auto 4x4. I was driving a few days ago and The truck started running rough, mainly at idle but would kinda sputtered when letting off the gas. Seemed to run fine when getting on it. I got home to try and diagnose the problem had it idling in the driveway and it would bog down to about 400 rpm and then back up to 850ish consecutively and after messing with the throttle it stalled. I cranked it over for about 5 seconds and it locked. Pulled al the plugs out and piston on driver side closest to cab was dumping fuel out when cranking it over, put all plugs back in and fuel relay back in it cranked for 5-7 seconds and locked again, obviously the objectors is leaking but it seems like a rediculous amount of fuel for only cranking it over a few seconds.

 

Does that seem normal for a leaking fuel injector, or possibly fuel pressure regulator to blame?

 

Unplug the injector on the cylinder that's leakin fuel. Then crank it. That will tell you if the PLC output is stuck on or shorted to ground (injectors are sink logic) somewhere, or if the injector is stuck open mechanically.

That seems like an awful lot of fuel though. I don't think it would be a fuel pressure issue cause then ALL the cylinders would be doing it.

 

I will try that when I get home, but if that injector is stuck open for whatever reason and the fpr is sending too much fuel it would all dump out of the open injector right? Because it is a lot of fuel and its only in that one cylinder.

 

Yeah, if the injector is stuck open it'll dump fuel regardless of pressure. Get the injector unstuck/replaced first, then worry bout fuel pressure.

I doubt your fuel is overpressure though.

 

Pulled the connector on that injector, still dumping alot of fuel when cranking it. So im going to see if i can borrow an injector from someone and see if that fixes my problem. Thank you for your help.

 

I am sure you already did this, but please make sure you are unplugging the power supply to the coil when you are cranking. If not that will make a nice toasty fire real quick.
Just unplug the vacuum hose from the regulator, and you will know if it the regulator, or the injector. Fuel squirts or runs out when you cycle the key. Then it's bad