Okay fellas, I have an '88 Trans Am, 305 TBI. I just installed a Walbro HP fuel pump today, figuring that the TBI's pressure regulator (which I've made adjustable, BTW) will bring the pressure down enough to be usable. Well, to make a short story long - I get no fuel from the injectors. I can hear the pump running, my fuel gauge pegs (0-15psi) and the engine just cranks and cranks - no gas. When I stop cranking, it takes several seconds for the gauge to register the pressure before it drops to zero; I figure it's pretty damn high causing the injectors to lock up. Concur?

So my next thought is to run another pressure regulator inline. I figure I would do the following: (1) Install a Mallory 3 port return style regulator in the rubber supply line, (2) "T" the return into my fuel return line at the point where the line is the high pressure rubber, (3) run this regulator at about 24psi - drop it to about 14 at the TBI using the stock FPR.

Do I have to change out the rubber lines to TPI "quality" lines to handle that pressure? Or will those lines handle that pressure? (Hopefully they are the same lines between TPI and TBI)

What do you guys think?

Before you ask, I went to this setup in preparation for a dual TBI rig on my 383, which will eventually have twin turbos on it as well. My fuel pump died on me Friday, so I figured now was as good a time as any , especially since I only wanted to do this swap once.

Steve

 

Steve,

I'll agree. Once you've replaced a fuel pump, you probably aren't going to be looking forward to repeating the task.

I'll also agre that your lack of fuel may be due to excessive pressure. You really need to get the line pressure down to the 15 PSIG range. I'm surprized that the regulator can't handle the overflow. Are you certain that the regulator was assembled correctly? I've modified a TBI regulator to be adjustable as well, and they aren't as straightforward as the TPI style.

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Later,
Vader
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"Make Me Bad"
Adobe Acrobat Reader 4.0

 

Thanks for the reply Vader; you're right, I'm not up for doing that swap again. Only took about six hours which included removing the rear end and swapping the brakes and stuff to a 3.73 rear, Spohn relocation brackets, Spohn LCA's and Spohn panhard bar. Wasn't too hard, just time consuming.

Do you think my idea about the Mallory regulator will work? It's adjustable from 3-50 psi, which should be workable. I know the regulator in my TBI is working properly because I adjusted it up from 9 to around 12 and have ran it that way for about six months. You can hear a hissing noise from the TBI when I shut the key off which sounds like fuel pressure bleeding off. That combined with the slow bleed-off of the gauge (to me) points to too much pressure.

Will the Mallory regulator work?
Will those stock hoses handle that pressure?
Am I going to be driving a torch?

Thanks for your help,

Steve

 

Steve,

Getting the fuel pressure back into the normal range for the factory regulator is probably a good idea. I would suspect that the stock FPR is having more trouble with the flow volume than the pressure. Diverting some of that fuel back to the tank before it gets to the FPR in the TBI may help.

It might also be a good idea to inspect the fuel return lines to the tank to make sure there are no pinches, kinks, twists, etc.

------------------
Later,
Vader
------------------
"Make Me Bad"
Adobe Acrobat Reader 4.0