I've been doing a lot of experimenting with my fuel delivery system. In car tests with gauge showed that pressure dropped to around 40-42 PSI at WOT in the 4500-5500 PRM range, regardless of regulator setting. What good is an adjustable regulator if my delivery system can't keep up at speed- right?

The mods listed below brought my system up so that it now holds 50 PSI at full throttle and RPM. Max pressure (return line pinched) went from 60 to 70 PSI. Now I suppose I could have just upgraded the pump- and possible may still- but I learned a few things that are prerequisite and I thought I'd pass along.

1) I cut a hole 6" x 11" directly above the sending unit. I snipped the return and emission hard lines and used a tubing cutter to do the pressure line. It's the 3/8" line on the passengers side. Once I got the sending unit out I was able to cut/trim the other lines. I used a brass compression connector to re-connect the pressure line and HP rubber fuel line for the other 3. I made a 8" x 13" aluminum plate to cover the hole. Now this isn't a necessairy step but it sure made this process a heck of a lot easier. (have you looked at what all is involved in dropping the tank?) Fittings, hose and clamps were $10. Note: make sure the lines are deburred before reassembly. The tubing cutter tends to reduce the ID of the line so file/de-burr them as necessary.

2) After I pulled the pump/sending unit assembly, I noticed the strainer "sock" on the pump inlet was so dark I could hardly see through it. It crumbled into pieces when I started messing with it. I replaced it with an auto store part for 10 bucks.

3) There is an accumulator connector where the pump attaches to the sending unit's metal line. It is plastic and metal and has red silicone o-ring type seals inside. I replaced this with a piece of 5/16" HP fuel line. $1.

4) I added a relay with heavier wire going to the fuel pump. Take the stock fuel pump wire and run it to the relay for the "on" signal. Connect power to the relay from a good, hot source. I have stereo amps in the back so I ran it to the amp's power block. Run a heavy wire from the relay to the pump wire right at the tank. Note: I did this first and it didn't make much of a differance until the above mods. Then it made about a 5 PSI differance. About $10.

5) Replace fuel filter/make sure there are no leaks, kinks in the lines etc. $5.

I giving all this to you as a complete plan. I tried all these in a logical order starting with the fuel filter, hot wire etc before pulling the pump. Each one had a small effect but together they brought the system to the point where the pressure holds to the regulator setting- with the original 19 year old pump! As I stated, I may still replace the pump with a higher capacity one but I recommend all the mods regardless.

 

More information. I observed something peculiar today. It was 28' F this morning and I noticed that the fuel pressure gage fluctulated wildly at 1/2 throttle or more until the RPM's got into the 4000+ range. I attributed it to the cold and the removal of the accumulator in the tank. I think it's there to even out the pulses from the pump. My opinion is that with everything so cold I am getting spikes in the fuel pressure. Not sure what all this means but I'll check it after it warms up a bit and see what happens.

 

Yet another hack job......

 

What do you mean?

BTW I checked pressure after everything warmed up and I'm still getting some fluctuation. Could the pressure spikes I'm seeing have anything to do with the Holley regulator?

Planning to install a Walbro 255 HP pump. Maybe the Karban regulator. Let you know what I find.

 

You cut a hole in the floor board=hack job. It's not that hard to pull the tank.

 

have you ever done 1?

especially without a lift?

i've done 1 in my life at work on a lift and it was a royal p.i.t.a. the tank had to be pulled at an angle to get the filler neck out (tilted backwords and downwards if i remember correctly). torque arm disconnected lca's, disconnected, straps disconnected, wiring harness disconnected, exhaust disconnected, heat sheilds i'm sure even more that i've forgotten.

sure no big deal if you have a lift but, u need a lot of space to drop that tank to do it in a driveway, i'm sure its been done but, it's still a royal p.i.t.a. I know with my puny jackstands it would be truly impossible unless i was to fully remove the rearend which would mean reinstalling the springs shocks n all that good stuff.

anyways nice reading interesting knowing that the stock powersource is truly that inadequate. I always saw the aftermarket wiring setups for bigger pumps and just figured it was pretty much bs glad i was wrong.

personally i doubt i'll ever cut a hole in mine either but, if done correctly it's far from a hack job.

 

Actually he cut a hole in the upper portion of the rear cargo area. I've done it myself on thirdgen race cars. Because. Well they were $500 cars that probably would have gone to the junkyward if they were not 'saved' and used as 1/4 mi cars.

Of course when I did it, we made little doors and sealed them for access, kind of like how the asian car companies do theirs from the factory.

-- Joe