Hello im new to all this but I was seeing if someone could help im left scratching my head on this one. Ok so I have a 1995 gmc jimmy with the 4.3 vortec when I first got the rig it idled real ruff and loaded up but would clear out once you opened it up but I ran it like that because its my woods ride and didn't really care so I decided to give the ol girl a tune up and put new filter plugs wires cap and rotor button and new oil thinking that would clear her up but didn't do anything still same ol ruff idle so I kept riding her like and one day it started missing real bad around 3k so I got it home and pulled the plugs to find the left side plugs were black from running ritch but the ride side were a nice golden brown like they were spost to be so I put them back and the thing has not hit once every since then I have replaced the coil the tps sensor the map sensor the coolant temp sensor and still nothing wont hit a lick it has fire and did a compression check and all cylinders have right around 120psi and wont hit off starting fluid so I took the upper plenum off to find that the fuel pressure regulator was bad and washing out the lower intake so I replaced that and still nothing wont hit at all. So I could use all the help I can get

 

1995 had 3 different possibilities of 4.3L engines. Does your engine look like this?

 

Yeah thats her

 

Sounds like a fuel leak in the plenum. To make sure this is the problem, you need to check fuel pressure and leakdown using a fuel pressure tester connected to the service port next to the distributor. When you initially turn the ignition to the RUN position, the fuel pump will be activated for ~2 seconds, and then shut off. Fuel pressure needs to be checked during this 2 second time frame while the pump is running. Key ON, engine OFF, fuel pump running, pressure needs to be 55psi to 61psi, and it must remain above 50psi for at least 10 minutes after the pump shuts off.

Rule of thumb on this engine is if the driver side is fuel washed, the lines inside the plenum are leaking. They're made of a plastic material and over time they dry rot, crack, and sprout leaks. They connect the steel pressure and return lines at the rear of the plenum, to the injector assembly. The service port is part of the pressure line. Dorman part #55163 and cost is around $50



If the passenger side is fuel washed, the fuel pressure regulator is leaking. If there are any leaks inside the plenum, it will cause a rich condition and symptoms like you're experiencing, (flooding, fouled plugs, runs rough, etc). The excess fuel drains into the crankcase and it will dilute the oil. If you wait too long before repairing the leak, it will destroy the rod, main, and camshaft bearings. After the leaks are taken care of, change the engine oil & filter. Post the results of the pressure and leakdown tests.

 

Yeah the fuel pressure regulator was leaking so I replaced that and I have done a fuel pressure test and im sure its not getting what it spost to its only getting like 50 psi at prime and leaks off pretty fast and I made sure the lines your talking about there were not leaking when I done the pressure test so im sure it is the fuel pump but right now im just trying to get it to hit then will tackle that after I get her to run for a min or ether. It should still hit on ether if the pump is bad correct?

 

Not recommended to use ether, too dangerous and can cause serious damage to the engine, and you. Best to use carb cleaner as it is less volatile. Provided the plugs are not fouled out, it should start though.

In your first post, you mentioned the plugs on the driver side were fouled. That would indicate that the fuel lines are leaking, not necessarily the regulator, although the regulator could also be leaking.

These engines need fuel pressure, and leakdown, to be within specs, in order to start and run right. Leaks from the fuel lines in the plenum are not always visible during a pressure test. Best to do a pressure and leakdown test at the pump, and at the service port. Checking at the pump requires a little "creative plumbing" to modify the tester so no pressure of flow goes to the injector assembly, and especially the regulator. The pump should build ~100psi and if the regulator is exposed to ~75psi or more, it will rupture the diaphragm, (you can't just kink off the return line when testing).