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CarburetorsCarb discussion and questions. Upgrading your Third Gen's carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.
I just got a 1987 Trans Am, I think it was a TBI that now has a Holley Double Pumper... I just replaced the fuel filter under the car today and tried to use a inline fuel pump.
I barely get fuel thru the second filter I added to check the fuel flow next to the pump (I will remove this one later) but my main question is can I add a inline fuel pump and leave the one in the tank there disconnected or not working? if that is ok does anyone have the model of a pump I should use the one I bought (link above) appears to be weak for that application...
Also the Carburetor has a leak towards the front of the engine not sure if the fuel pressure is high or it needs a rebuilt...
A typical in-line fuel pump is TERRIBLE at "sucking". They produce pressure on the output side easily enough, but don't "suck" through obstructions very well. For that matter, so is a cam-driven mechanical one. Those both rely on a free-flowing, unobstructed flow of fuel to their input.
Which of course is what a non-functional in-tank pump is... an obstruction. Some are worse than others, MUCH worse, but they're all an ... obstruction.
Best to either USE the in-tank pump, in conjunction with a 3-port (in, out, return) regulator; or do away with the in-tank altogether, and THEN use either a block-mounted mech pump like carb setups have had since the Ice Age or a far less reliable electric in-line one.
Incidentally, TBI wasn't introduced in these cars until 88. So your 87 didn't come with that. Had to have been either port EFI if it came with a 6-cyl or TPI, or a carb if it was the LG4 motor.
Tell us the 8th digit of your VIN and we can tell you what it came with. Might help if the exact nature of what you're working with is known.
That **** ain't gonna work well. In fact if you read the instructions that come with those pumps they even tell you to mount them within 18" of the tank as low as possible so the pump is fed by gravity and can push the fuel forward. With the pump in the engine bay, you'll drain the fuel bowl under full throttle and starve the engine for fuel.
Your gonna have to drop the tank at some point no matter what direction you go, because sucking through a broken pump isnt going to work well at all. Replacing the pump and putting a return style regulator on, as suggested is a good idea. I've taken the broken pumps out and modified them to become the pickup with some 3/8" hose.
At this point I don't even know for sure if this car has a fuel pump in the tank, I was looking at the engine block and it has an aluminum blockoff plate for the mechanical fuel pump location... since it has an aftermarket carburetor I do not know if it was a TPI or quadrajet originally.
It was a 305 TPI, F in the 8th digit. Looks like someone installed the regulator Sofa is talking about behind your AC compressor over the valve cover. Sometimes regulating the in-tank EFI pump works OK, but it's finicky and prone to issues. Personally I'd install a carb sending unit and mount the inline pump per the instructions as close as possible to the tank, but I'd rather put in a bit more work to ensure the car is going to run right.
It was a 305 TPI, F in the 8th digit. Looks like someone installed the regulator Sofa is talking about behind your AC compressor over the valve cover. Sometimes regulating the in-tank EFI pump works OK, but it's finicky and prone to issues. Personally I'd install a carb sending unit and mount the inline pump per the instructions as close as possible to the tank, but I'd rather put in a bit more work to ensure the car is going to run right.
Thank you Drew...
I guess I am going to have to drop the tank anyway...
Do you think it is ok to mount the fuel pump next to the fuel filter and run a braided fuel hose to the pickup line in the fuel sender unit?
That's a reasonable plan, as long as it's with the in-tank one gone.
Like Drew says, using the in-tank pump works and is often done, but also often causes trouble. Personally, if I had what you've got, I'd use a block-mounted mechanical one after doing away with the non-functional in-tank. I wouldn't mess with an electric at all.
Since your car was TPI (I thought it would turn out to be, based on where the stock steel line emerges) I'd suggest re-routing the lines somewhat like the factory did, if you can. They came up the driver's side to nearly the front of the trans tunnel, then over across the tunnel and down to the pass side "frame" under the evap housing, then forward to just past the engine mount. Alternatively you could route them around the front; up the driver's side "frame", across underneath the radiator core, then back along the pass side "frame" to near the block-mounted pump. I'd cut them off at a convenient place, flare them, and run either steel line or braided-stainless PTFE around that way. Being EXTREMELY careful to assure that they won't hit curbs in parking lots or otherwise be at risk, of course.
If the carb leaks it probably needs a rebuild. What is its list #?
I have another holley carb from my 79 vette that I replaced with the original rebuilt quadrajet I am going to try to install it tomorrow.. I replaced the fuel pump in the tank since it had the access port already cut under the carpet... I will try to run it for a couple of months to check everything else in the car... if the engine or trans is not good I may go another route.. if everything is ok I will order the Holley EFI system
Hopefully tomorrow I will have the car running... thanks everyone!
The fuel strainer from the old pump was flouting in the tank I was able to remove it, the tank looks good inside, I added 5 gallons of recreational fuel when I got the car... I guess it is ok to run it... Or do you guys think I should empty the tank and start with 100% fresh fuel? not sure how much it had before I added the ethanol free fuel...
I just got a 1987 Trans Am, I think it was a TBI that now has a Holley Double Pumper... I just replaced the fuel filter under the car today and tried to use a inline fuel pump.
I barely get fuel thru the second filter I added to check the fuel flow next to the pump (I will remove this one later) but my main question is can I add a inline fuel pump and leave the one in the tank there disconnected or not working? if that is ok does anyone have the model of a pump I should use the one I bought (link above) appears to be weak for that application...
Also the Carburetor has a leak towards the front of the engine not sure if the fuel pressure is high or it needs a rebuilt...
Thanks
If that Holly in the pic is the inline fuel pump …..your inline fuel pump is way too far from the tank to do any good. I dont think it can siphon from that far away at least. It with that pump anyway. If you want a strong inline fuel pump designed for inline external mounted function, use a Ford 7.3 diesel inline fuel pump made by Bosch. The part number is 69136. They run about 80/90 bucks and I believe it’s rated for 70 PSI. Theire good enough for stage 2 injectors on a diesel for fuel supply. They also run forever. Hook up is a piece of cake with a positive and negative lug. I would remove the factory fuel pump and lengthen the pick up tubes to go down further to the bottom of the tank. Install a screen or fuel sock on there. That fuel pump is a ton of restriction. You’re doing the equivalent of trying to suck a thick milkshake through a coffee stir straw.
Last edited by ThatFordGuy; 07-13-2021 at 11:38 PM.
03-04-2021, 06:03 PM
