I had this problem on my '97. Would crank, the fuel would prime, but it wouldn't start unless I used starting fluid. My problem was the pressure regulator. Easy fix but be careful it's seated properly and tight! Mine wasn't and well .... Just make sure!

 

* UPDATE II * Alright, retested everything one more time just to make sure, the hose on the tester had getting pinched, guage wasnt reading right, here are the new results. Key On: 61psi while priming then 55 psi and slowly falls, Trying to Start, 61psi, Running on Startinf Fluid, steady at 55psi until motor dies. So with these results seems my fuel pump is running ok, so this leaves me with the fuel pressure regualtor and the injection system right?

 

Newer vehicles require quite a bit of knowledge and experience to be able to properly diagnose without just throwing parts. If you have specific questions that you need answered, please feel free to ask them and we can work through the "babble" to get you a better understanding of what is going on and what is required to properly diagnose the issue(s).

Now, the pressure rises to 61psi on key-on, then 55psi (assuming this is directly after the pump shuts off), then slowly falls, this would indicated that the pump is working properly, however, there is a leak in the system. Possibilities for leaks are the FPR, injector o-rings (rare), injectors themselves (not so common, but not rare), fuel lines themselves (easy to check), or the check valve in the fuel pump itself (check by bleeding the pressure down to 10psi and observe as indicated in the fuel pressure diagnosis thread).

 

Ok, I had to giive the gauge back for now, and yes the drop of 61psi to 55psi is when the pump starts humming. And as far as leaks , I dont see of smell gas any where it shouldnt be. And as far as leaks should I be looking at supply and return lines too? And the next step I guess is to take the upper plenum off and look for any visible leaks? I am mechanically inclined, I race and work on cars all the time, just that the whole newer fuel systems can be complicated, and I dont always have the right tools for certain a job. But if you can steer me in the right direction its greatley appreciated.

 

The most likely cause of the leak down in the fuel system after the pump shuts off is the FPR. You will need to get the top end of the motor opened up (upper plenum removed) and then reinstall the fuel lines. Do not try to short cut it by just bending the lines out of the way. As quite a few other people have found out, it becomes a royal pain to get the lines back on after they have been tweaked! And often will result in cut o-rings where the lines go into the spider. Once the lines are back in place with the upper plenum off, you can re-pressurize the fuel system and look for leaks around the spider. It may be necessary to have a mechanics mirror to look around the back of the spider for wet spots and/or dripping fuel.

 

Ok, did as you said, that plenum is fun to get off, hooked back up and pressurized the system, did not detect any leaks around any of the "spider legs" and none on the spider itself, so am I best of to replace the FPR, I dont think theres any way to tell if its bad just by looking at it right?

 

The older CPI FPRs typically leaked into the intake. You could try disconnecting the return line (smaller of the two) at the back of the engine and putting a cup of some sort under it. Pressurizing the system and then watching the discharge after the pump has shut off. Be aware that a lot of fuel may come out initially if the pump runs for the prescribed 5 seconds.

 

Is there any way to tell if the injection system itself is working, also are there any advantages of replaceing the spider with the new multi-port injection system?

 

With an appropriate scan tool (tech2 or equivalent), you can run an injector cycle test which would enable you to turn on each injector independently and inspect the flow and pattern from the poppet nozzles.

About the MFI spider, the benefit is in not having the problematic poppet nozzles, but if the truck was running well with decent fuel mileage prior to the problem, I doubt that the poppet nozzles were being a problem.

 

So since I dont have a scan tool, whats my best shot in the dark, prior to this problem vehicle ran good, had good gas mileage, almsot 19 city and 23 hwy, only thing I did notice is that the week prior to this it seemed to be a little slugish at some points, so should I through in a FPR and try that or??