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Fuel pump replacement and now truck won’t start


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I’ve got a ‘94 Sonoma 2X4 4.3L that was having issues with rough idle when cold. Had a code 45. Changed the bad O2 sensor, cleaned TB, nothing. Replaced fuel filter and it had dirty fuel backwashing out. Fuel pump was crazy loud and noisy always once key was in start or running. Truck had no issues starting or running. Just rough idle even cold. Dropped fuel tank and replaced with complete fuel pump assembly. Hooked everything back up but truck will not start. You can hear the pump engage when key placed in start. Removed fuel line for discharge side of filter and confirmed fuel flow. I’m at a loss for a running truck won’t start back up after a fuel pump replacement when it clearly has power and fuel flow. Fuel gauge reading just fine too. Any ideas?

 

 

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I was going to grab a fuel pressure gage kit to start testing the system. I assume the regulator is under the plastic cover on top of engine?


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  • 2 weeks later...

I figured it out. Summit sent me the wrong fuel pump. Apparently there are two from Spectrum for my truck. One for TBI (25psi) and another for CFI (125psi). When I bought it they only offered one option. What a tremendous waste of my time and money. Sending the wrong one back, too bad for them that it’s used. Already ordered the right one. Now that I’ve taken apart the FI system I’m going to just replace the regulator, seals/gaskets, and main supply/return lines. The individual injectors and tubing seem fine. Jetted them with carb cleaner and then compressed air. No leaks and nice flow. Either way, another week of waiting for the parts to come due to the holiday. I’ll post back when I’ve got it done and fingers crossed works perfectly.


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  • 2 weeks later...

I need your help. I refurbished the fuel injectors solenoid, diaphragm, and fuel inlet lines. Popped the top cover back on and now I’m left with this one tiny hard plastic vacuum hose and no idea where it goes. Vacuum diagrams are useless. What I need is a photo of where it goes. In the process of trying to find its home I detached the purge valve and now have no idea where it goes back. The valve has a long hose with connector at end and a short hose with l-shaped connector. I can only see the one line behind the drivers side valve cover. I know I pulled it off there but have no idea where the other end goes. I feel like an idiot but the lack of decent diagrams or photos doesn’t help either. The YouTube videos are garbage because they all have no details and either taken at night or with insufficient light. Here’s a photo of the completed fuel injection job and one of this crazy vacuum line I can’t figure out. a86a7667b9ab11cbc534d6e17211744e.jpg93a6cb7985325bf308395cf378f50668.jpg


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I think it might be the line that goes to the Evap Can Purge Control Valve. There is a unused port on the valve but there's nothing to plug the line into. I don't have rubber connectors laying around so not sure if it's the right place and I just need to get a connector or this hose goes someplace else. Very confusing because the vacuum diagrams for my truck with Z code don't even show what I have. If I look at the W code, it sort of makes sense. It shows a port coming off the rear passenger side of the upper intake. From there the hose t's off. One goes to HVAC which I assume is the vacuum ball mounted under the hood. The other shows going to this control valve. I even bought the complete set of shop manuals and they are a complete waste. This is where YouTube and photos come in handy. I've yet to find one so if anyone could please pipe in and help out, I'd greatly appreciate it. In the meantime I've installed the correct fuel pump assembly and tried to start the truck. It started right up for a few seconds, probably just burning off the raw fuel injector cleaner I used to clean up the lower intake and injector holes. Then it died and so did the battery. Charging it slowly overnight in hopes I can make another run at it today.

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Now I’m SOL. No fuel pressure and won’t crank. Keeps get worse. I’m guessing I put the pressure regulator on wrong or screwed up the spider assembly. No idea on the cranking issue. New starter and cables. Fully charged battery. Turns over a couple times then dies.


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