I've been working on this truck for weeks now. Turns over great but no start. Sometimes it'll kind of hit on the first try but never really fire up. I'm going down the rabbit hole of the circuit opening relay / efi relay / jumper under the hood. I replaced the fuel pump in the beginning when I first bought the truck thinking that was the problem. The guy I bought it from was driving it and then starting experiencing the efi fuse blowing and the truck cutting off every so often until it just wouldn't crank back up again. I have checked that it is getting spark from the coil. I've used different COR amd efi relays from a parts truck. As I have dove off into this truck and turning it over several times, why would fuel be leaking back out of the rubber line leaving the fuel regulator and meets the hard line that goes to the tank? Doesn't that bleed off fuel from the intake to the tank?
Any help would be greatly appreciated

 

Just to be sure, you mean the rubber line going from the fuel pressure regulator to the hardline that runs back to the tank? The fuel pressure regulator at the rear end of fuel rail? When you crank the truck over, do you get fuel flowing in that line? You should, while you're cranking. OR when you put the jumper in, and turn the key to run. That's the return line for the fuel not used by the injectors. It should NOT be leaking out of the join, however! Shouldn't have fuel leaking anywhere, honestly. Or do you mean the vacuum line on the top of the regulator? If there's fuel leaking out of that, you need to replace the fuel pressure regulator.

Are you sure the COR you put in was good? Have you tried putting the jumper between Fp and B+, and then cranking it to see if it would run that way? Do NOT drive it like that, but it's a good test. If it won't run with the jumper in, either the fuel pump is bad, or the filter is clogged. When was the filter last changed? Is it allowing good flow through it? Are the fuel lines coming right out of the tank cracked or clogged?

Have you checked the MAF to make sure the switch in it for the COR is functioning properly? Have you checked the big hose for any leaks, cracks, etc? Have you checked for any vacuum leaks? That all the vacuum lines are routed correctly, and on tight?

Are you getting any codes? If so, what?

Ok, My brain is getting cramps, so I'll stop there...
Pat☺

 

Yes, the rubber line that meets the hard line at the firewall. After cranking and cranking with no start fuel will seep from where those two lines meet. If I pull the rubber line off, fuel spews out of the hard line.
I'm not positive the COR I tried was good but thought it was less likely 2 would be bad. I have used the jumper under the hood on the driver's side but still with no crank.
I haven't disconnected any fuel line while cranking to see it pumping but I've just cracked the line at the cold start injector after cranking several times and get fuel under pressure from there.

 

I am far from a super duper mechanic, but it seems to me that if you have fuel under pressure, and spark, you've narrowed it down. Injectors? Injector wiring, IE: the wires going to the injector's ground point, which is a 4- into-1 ring terminal bolted down on one f the bolts on the supports that help hold up the intake manifold. Also, there are the wires coming from the ECU.
Finally, the ECU it's self.

And just to be sure, you have spark going from the distributor to the spark plugs, and that the the plugs are good? Is the head's ground in good shape? It's a wire from the rear bolt holding on the hoisting hook on to the firewall right behind the head. Very important, as without it, the spark from each plug will be very very weak, IE: not strong enough to fire the cylinder.

Hope something in my rambling is some small halp...
Pat☺

 

I sure do appreciate your insight. It helps just having someone else throw out suggestions that I may have over looked. Yes, spark is good from coil to distributor to the plugs. The plugs and plug wires are brand new and are in correct firing order. I can see a few grounds that look good but I'm gonna check the specific ones you mentioned.