Last month I replaced the lower intake truck ran fine. 30 days later no start situation no CEL was on, I check for codes with scanner I get P0340 and the random cylinder misfire code cant remember number.

I inspect the cam sensor harness and area looks fine so I replace the sensor same deal No start.

I checked for spark I have spark at all plugs

I check fuel pressure it pops to 60+ but after a min. or so it goes to 40 and falls slowly, Im guessing FPR is leaking but, might I add, I changed the fuel pump 2 years ago 250.00 auto zone model I know I read somewhere I should have gone with AC Delco with it but I didnt know.

Can I assume I have to pull the plenum

Can I use propane just to see if it will start. I saw where you can pull a sensor to insert a propane torch.
I used a short shot of starting fluid in the throttle body with no results

All I have is some dieseling and backfire from the Throttle body after a 3 second crank

 

P0300 is usually caused by a secondary ignition fault, (plugs, wires, distributor cap, rotor, ignition coil). These engines are pretty fussy when it comes to these parts, especially plugs, cap & rotor, they really need to be AC Delco. If you did not check/adjust camshaft retard after the distributor was reinstalled: P0300 can set if it's not within specs. It must be done with a capable scan tool. If the distributor was installed one or more teeth off, P1345 would set, so you're good there.

Fuel pressure should be 60psi to 66psi with the key ON, engine OFF, fuel pump running. Pressure must remain above 55psi for at least 10 minutes after the pump shuts off. If it fails either part of this test, you can't "assume" anything without further testing. To determine where the leak is, check maximum fuel pump output pressure and leakdown at the fuel filter. All pressure must end at the tester during this test, so you'll need to perform some "creative plumbing" to your pressure tester. Pressure must be 73psi to 108psi and must remain above 55psi for at least 10 minutes after the pump shuts off. If it fails either part of this test, the problem is in the tank. If it passes both of these tests, the leak is in the plenum.

The backfiring from the throttle body, does it happen just as you stop cranking the starter, or while the starter is still cranking the engine?

 

YES, I back fire after a 4 to6 second crank through the throttle body the it might diesel for a second, I can smell fuel in the throttle body.During the crank seems like it has no fuel. Thanks Hook

 

Hook any pics of the "creative plumbing" fixture you speak of? I cant picture what I need maybe cutting the end off of an old filter to start?

 

Good info, thanks, that helps a lot!

Make sure you have continuous battery voltage on the pink wires at the ignition module and ignition coil when the ignition switch is in the CRANK and RUN positions.

As for the "creative plumbing", this is a tool that I made a while back for 97 & newer CSFI systems. All of these parts are available at an auto parts store and a good plumbing/hardware store, (Lowes, Home Depot etc). It connects inline at the fuel filter in seconds. It will check regulated pressure and leakdown, fuel pump maximum output pressure & leakdown, and will also determine if leakdown is in the tank or in the plenum. It will not identify an internal leak in the fuel pressure regulator, that requires an additional shut off tool.

 

Is that just a normal air gauge or a special gauge fuel proof type?? Thanks

 

It's just a cheapie guage, I think $5 at Harbor Freight. When I bought it, I figured if it takes a crap, no biggie, it was just an experiment. Damn thing has been working fine for a few years, using it almost daily. I've got several testers and that gauge is fairly accurate, go figure coming from Harbor Freight, maybe I just got lucky. Grainger has some nice gauges, but expensive.

Edit: Seems like it was a total of $45?? The female quick connect fitting is spring loaded and that was the most expensive thing, http://shop.advanceautoparts.com/web...line+connector

 

OK decided to make the gauge but I'm confused, my truck has a threaded end and a quick connect on the other

Coming from the tank its threads is that normal?

 

Here is what I mean

 

To connect the tester, disconnect the quick connect fitting from the filter, connect the female quick connect fitting on the tester to the fuel filter, connect the male tube to the female quick connect fitting that you removed from the filter.