I'm running about 14% LTFT. No CEL (SES) light. But want it to run as designed. I recently checked the Fuel rail pressure and it was running low, about 58 psi with key on and ~52 while idling. This, after replacing the fuel pressure regulator during a valve job. I tested the fuel pump pressure at the fuel filter directly into a fuel gauge( No Regulator). It is running about 64 PSI, Lower than spec. So I have bought a Delphi pump and am in the process of dropping the tank.


I have drained the tank, removed the 3 screws a for the filler, removed the tank shield and removed the tank straps. what is the best way to reach the filler neck ground strap screw? It is not obvious.


I have the 1999 Factory Service Manual and there is no differentiation between the 2dr and 4dr. It shows there are 2 rollover check valves. From what I can tell, the 2dr has no such device. Does the 2000 model not have them or is it a 2dr vs 4dr issues


I've searched for the last year+ posts and not found answers to my quesstions. So, what is the best process to a) drop the tank b) disconnect the filler tubes, c) disconnect the pump hoses d) access the hose clamps on the filler neck and vent lines, e) what will I find for the 3 hoses on the fuel pump fittings, spring clips or the GM fuel line fittings? f) etc?


I'll be back at it tomorrow morning. Any help or tips before then would be appreciated.

 

Fuel pressure readings are all taken with the engine off. At the service port, key ON, engine OFF, fuel pump running, pressure must be 60-66psi. It must remain above 55psi for 10 minutes after the pump shuts off. These readings give you the LOWER of regulated pressure or maximum pump output pressure. For example, if max output is 40psi, regulated pressure will be no higher than 40psi. Using that reading alone, could lead to a misdiagnosis of a faulty fuel pressure regulator. To diagnose the fuel delivery system, max pump output pressure must be tested as well. This is most easily done at the fuel filter outlet. An adapter is necessary between the filter and the pressure tester. All fuel pressure and flow must end at the tester, with no fuel allowed to the engine. Key ON, engine OFF, pump running, pressure must be 73-108psi. It must remain above 55psi for at least 10 minutes after the pump shuts off.

Tank removal, (2 door). There is a roll over valve in the filler neck where it connects to the rubber line. That connection must be disconnected to remove the tank, the 3 screws by the filler cap do not need to be removed.

 

There isn't any really easy way to do it. you just need to reach up in there to get to it. Not a fun job at all but can be done with some patience. The fuel lines are the biggest bugger to get to. The tank can only;y be lowered so much before you need to disconnect the lines
Mine didn't need any special tools to get them apart but i heard some years do. mine is an 02. They just had little clips that you squeeze together to release the line fitting. Be careful. If you drop the tank to far or to fast you can snap the lines and or fittings on the sending unit.

 

Thanks for the tips. I got to it this morning. Got the fuel fittings out and had a real tough time getting the fill and vent hoses off the tank. 14 years of being in one place tends to stick a bit. At the fuel pump, 2 of the 3 fuel lines were similar to the fuel filter fitting push fitting. The 3rd fitting was a different kind of squeeze-to-release. Once everything was disconnected, the rest was easy.


The new Delphi pump is a different design from the original AC pump. The original has "AC" molded into it. The new one did not. (it was Delphi) There is no external filter sock, it is internal, an added jet pump. The level sender was a better design with brass pivot and an bifurcated contacts for both contacts, And a new design for the power connector (requires cutting the old one and splicing the new). It even came with a new pressure sender.


Putting it together was another thing. Had a difficult time getting everything lined up. Lift, tilt, yaw, redo over, and over, and over again. I was doing it with no helper. But it finally all lined up and went together.


All the ref to fuel pressure that I gave earlier, was background info. I wasn't looking for help there. I had researched all that before this decision. Cap'n, your info on this site is great. My earlier reading of 64 PSI was while deadheaded at the fuel filter. This is the pump capability, not the regulated pressure. After the install, I had 98 PSI , This, with about 1/2 inch of residual fuel in the tank. wow! I did not do a bleed- down on the pump. I trust Delphi. I have yet to measure the system pressure with the regulator in place. I just got things together and started the engine when my Wife pulled in the drive looking for her spot in the garage. Maybe tomorrow.

 

Thanks, I try to help

A few years ago, AC Delco/Delphi redesigned a bit, performance seems to be about equal to the earlier design. The new connector has been around for several years, and it needs to be soldered to the original vehicle harness, (crimp connectors have no place on a vehicle).

64psi deadhead is a definite fail! At the service port, the results would indicate there are no problems with the fuel delivery system. That's the importance of checking max pump output too. The reason for checking leakdown at the pump, is to make sure that it can hold sufficient pressure. It will prevent a wild goose chase when trying to determine if leakdown problems are in the plenum or in the tank, or both. Just like 64psi at the service port was no guarantee that the pump was good; The same holds true with the pump. Just because the pump is new, and max output is within spec, it's no guarantee that leakdown is within spec