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Discussion Starter · #1 ·
Hello Fellow FB Nation Members,

So this TA I purchased in 2020 has had a brutally frustrating issue with the fuel pressure dropping within 3 seconds to 0.

Car is a 1995 Trans Am WS6 with Golen built 383 LT1 with a P1SC ProCharger etc.....

What I've done leading up to the successful repair:
1. Replaced failed Walbro 255 primary pump and secondary 255 pump (Racetronix dual)
2. Replaced fuel filter at the same time as pumps
3. Injectors Ohm properly and spray pattern tested
4. Replaced adjustable FPR (looks like a conversion kit to a stock unit?) to a new stock FPR, idling around 900RPM with AFPR idling at 40 and now idling at 38-39psi (within GM spec) on the stocker

I could not figure out what was causing the fluctuations with fuel pressure. When I drove it I noticed the pressure would drop under 38lbs, which it shouldn't do but under accel it would rise over 40 normally. Pumps are brand new (not sure I trust Walbro any longer) so I thought maybe the primary pump's check ball was shot (75 miles on them since last August) but unsure. Idle would drop to 500 coming to stops and eventually rise back to 900. Getting off of a freeway and braking, the car would lose power and backfire over 2K RPM. 15 mins later it would start and go. Everything seemed fuel related to me.

The Repair....(so others can avoid what I had to map out):

I researched and researched some more and found the one-way fuel check valve theory in a non-4th gen video.

1. I bought Evil Energy 3/8 check valve off of Amazon and the strengthened 3/8 fuel hose and clamps packaged together
1a. The feed line is plastic to the fuel filter inlet and 3/8 steel to plastic again before it's routed to under the rocker panels
2. I purchased a Doorman mini/midget steel cutter to cut the 3/8 line (trust me, you'll want this
3. Jack up your Bird before the driver rear wheel and place a jack stand under the axel OR if your chassis has the giant sway bar like mine, I use that as a jack stand point
3a. Jack up the chassis just after the driver front wheel and leave it there (ensure car is secure)
4. Release fuel pressure and open the fuel filler cap, hang it gas door
5. Slide under the car AND CAREFULLY loosen and remove WRENCH-side of the steel line at the fuel filter
5b. Ensure you allow all the fuel out under pressure before proceeding to Step 6, keep a drain pan handy to catch the fuel out of the line and ensure you save the grommet from the steel line that screws back into the filter
6. I'll save you the guess work: from the mandrel bent 90* turn on the steel line off the fuel filter, use your fuel line cutter TWO inches AFTER the 90* factory bend, this gives you 2" for worm clamps to tighten up the fuel hose you'll add. Remove the fuel filter bracket so the feed line can move freely
7. Move the cutter 4" over towards the drive shaft and make the final cut.
8. Take the 3/8 fuel hose and cut a 5" piece. Use the worm clamps to tighten the 3/8 hose to the 3/8 fuel check valve. Cut an even piece of rubber from your 5" line WHEN you're under the car for accuracy to join lines
9. Use anti-seize on the threads of the feed line you previously removed and place the o-ring back onto the feed line (don't forget this!." Leave the fuel line a bit loose (don't fully tighten) so you can mock up the new install AND ENSURE the arrow on the check valve is pointing upstream/toward the engine
10. Loosely tighten the worm clamps on the feed line closest to the fuel filter
10a. Now take the other piece of rubber fuel hose and affix it to the other end of the fuel line. Force the fuel line at least 2" onto the line and now join the rubber to the other end of the check valve (use WD40 to lube the lines)
11. Ensure the mock up is safe and tighten the fuel filter nut and then tighten all the worm clamps. Reinstall the fuel filter bracket to provide stability

That's it....Now check your fuel pressure at either the in-car guage or at the Schrader valve. Ensure no leaks are present while the system is primed, if so, check your clamps.

With mine, I've never seen the car hold steady fuel pressure, ever. The check valve does its job well and held perfect pressure for some time.

Be very careful doing this, measure twice, cut once and follow the steps to resolving the lost fuel pressure. Sometimes there's no explanation and the check balls in the pump is a stupid idea but also I think Walbro quality slid years ago but that's my opinion.

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