Fuel Pressure Issues

[Wknight13]

Purchased this car a year ago and the pressure issue seems to get worse. Unfortunately every time I put a gauge at the end rail I get nothing. Is it possible for the fuel to dump straight through the regulator? I have to literally "prime" the pump a good deal before it will start. It used to hold for a day or two and now maybe a couple hours. Also not sure what the last owner was trying to accomplish but take a look at these fuel supply and return lines. I'm also including a picture of the injectors (red stripe). The pump is a Jegs sump, not sure of the pressure at this point, I can't get a damn reading. When I get it started it runs great. I've been considering changing the supply and return lines back to stock, what is the idea of such large lines (besides an abundance of fuel)? I am pretty new at this so please bear with me. thanks

 

[bpman1234]

you may have a leak in the line go through the lines from tank to regulater and rail check it all and just tighten every thing up .you should find it .if you cant find it after all that and you still want to take those lines out and go stock i will take those fuel lines if you want to sell them .let me know thanks good luck.

 

[mikestertwo]

Did you remove the valve at the end of the fuel rail before you put the gauge on?

 

[TR Custom Parts]

You need to make sure the gauge setup you use depresses the Schrader valve inside the end of the rail. Typical test gauge setup you would buy at your local parts place will depress that valve. If you are just using a hose plumbed to a regular gauge you will have to remove the Schrader valve. Just need one of those little tools with a notch in it that will remove it. But you have to make sure there is no pressure still in the rail, run the car with the fuel pump connector unplugged.

 

[DaySleeper]

If it runs fine after you get it started then the pump motor is probably okay. After the car sits for awhile, you should still have a little pressure in the rail when you depress the schrader valve, otherwise it is flowing back into the tank. It should stay put.

The pump relay is designed to prime the stock size fuel lines and those look huge. Get a gauge on it and see what's happening. If it leaks down immediately after the pump shuts off, you have a problem. I think the check valve is in the pump itself.

 

[Heg87t]

And fix that vacuum line in front of the regulator! Looks like it's only hanging on my a 1/16".

 

[Wknight13]

Got the gauge on and reading at the end of the fuel rail (took the Shraeder vavle off with eyeglass screwdriver). I am getting 30-35psi, ONLY when the car is running. As soon as I turn it off...whoosh, I lose all pressure, immediately. I don't smell any gas at all so I don't think there is a leak (it's in a closed garage, not while running though). By the way, when I prime (by use of shorting the pump relay) I don't see the pressure build up. I actually have to pump the pedal as I'm turning over. Is this pointing to the pump? Can't believe such a nice pump would have an issue already.

 

[Wknight13]

Quick question...what would happen if I loosened the nut on the regulator and turned the top screw down (what I assume would close a valve)? I would play but don't want to make matters worse.

 

[TurboBuRick]

That screw adjusts fuel pressure.

Start the car. Pull the vacuum line of the regulator and plug it with your finger. Take fuel pressure reading. This is referred to as "line off pressure". It should be between 40-43.

The fuel pressure dropping when the motor is shut off is not uncommon.

 

[Wknight13]

It only rises about 3-4 PSI to about 38-39. Does anyone think the lines may be too big for this application? Or should I incease the pressue (closing the regulator)? All I want is to not have to prime. I can install a momentary switch off the relay and activate before start but that defeats the whole purpose of EFI and still doesn't solve an issue. I'm a good student of learning, what's next to try?

thanks.

 

[DaySleeper]

The way to test the pump for certain is to get it running and watch the pressure when you give it boost. Mine used to work until it got on boost and would drop off dramatically because it didn't have enough volume. The check valve is definitely not working in the pump at all or an injector is stuck open and dribbling into the intake.

 

[S10xGN]

It only rises about 3-4 PSI to about 38-39. Does anyone think the lines may be too big for this application? Or should I incease the pressue (closing the regulator)? All I want is to not have to prime. I can install a momentary switch off the relay and activate before start but that defeats the whole purpose of EFI and still doesn't solve an issue. I'm a good student of learning, what's next to try?

thanks.

Looks like the PO has modded the regulator, could be it's not seating off. I'm in that boat right now, but my pressure holds for a few seconds and that allows me to start up without excessive cranking. I ended up porting the internal passages in my regulator which entailed removing the factory "seat" and replacing it with a larger "home-made" seat. Sounded like a good idea at the time, but failure to seat properly can cause instant bleed-off...

 

[84BuickGNYorkPA]

I would replace that regulator with a accufab billet unit to start, replace the bad vacuum lines with fresh ones and zip tie all connections. What kind of fuel mileage do you get? Do you smell gas when the car is running? How far back toward the tank do the braided lines run?

Chuck

 

[SHADOWII]

I would replace that regulator with a accufab billet unit to start, replace the bad vacuum lines with fresh ones and zip tie all connections. What kind of fuel mileage do you get? Do you smell gas when the car is running? How far back toward the tank do the braided lines run?

Chuck

I'm w/ 84, replace the regulator and use the tie-wraps. 43#f/p is about average w/vac. line on. FYI:A leaking injector can cause major problems as it can wash down the cylinder wall, leading to excessive wear/scarring of the wall and contaminate the oil.

 

[Wknight13]

I would replace that regulator with a accufab billet unit to start, replace the bad vacuum lines with fresh ones and zip tie all connections. What kind of fuel mileage do you get? Do you smell gas when the car is running? How far back toward the tank do the braided lines run?

Chuck

Braided lines are full length. I'm not smelling any gas at any time. I'm running a TT 93 street chip. As far as pressure during boost, all I can say is it seems to get there just fine, outside a bit of lag, can't tell since the pressure gauge is on the rail end. Suppose I may need to get a temp. hose extension and tape it to the windshield.

So kinda what I'm understanding is likely regulator (which may be causing the instant bleed off), stuck injector bleeding into intake (but wouldn't that allow an instant fire, like spraying starting fluid in?), or pump going on the blink. Hmmm. I hope it's not the pump, these external sumps are not cheap (and I don't actually have a reason for one).

I am not against going back to a factory setup from tank, pump, and lines. Will the factory setup work and get me good performance with the T45a turbo and these injectors (what I believe are 40lbs). With my current setup, any reason I actually need it? What could have been the goal on the PO? What is the best time I could expect with factory fuel lines?

thanks,

 

[Wknight13]

I'm w/ 84, replace the regulator and use the tie-wraps. 43#f/p is about average w/vac. line on. FYI:A leaking injector can cause major problems as it can wash down the cylinder wall, leading to excessive wear/scarring of the wall and contaminate the oil.

Is there a way to test for this? Can a leaking injector be fixed (O-rings or something of the sort)?

I'm starting to get beyond my current skills but learning this will only make me better. Gotta keep my 40 yr old brain working.

 

[Wknight13]

Contacted SX, manufacturer of the external billet pump, seems the pump was installed wrong by previous owner(s). Evidently these pumps are supposed to be mounted below the fuel line for gravity feed, push not pull. Anyone have any comments on this? Mine was installed up directly below the fill tube behind the bumper. How can I get it below the fuel line and maintain safety (not that having the fuel pump behind the bumper is very safe)? Seriously thinking about turning this thing back to an in-tank. I've read that the Walbro is the way to go? Will it accept the size of lines I currently have?

 

[Pronto]

I was going to suggest that along with a hotwire kit and new regulator. Do you know all the mods to the engine/car? What are your goals, et?

 

[Wknight13]

Currently the car has a t45a turbo, 40 lb. injectors (pictured), ATR exhaust system, ATR adjustable wastegate, one street, one strip chip. I would at least like to obtain 12 sec. at this time with current setup and work from there. It's mostly going to be a sleeper/cruiser. All of the items were from previous owners, I'm just trying to stabilize this thing with a consistant fuel supply/pressure. I do agree with you Pronto, as those items are what I'm now going after. Without dropping the fuel tank, I'm currently trying to contact the previous owner/owners to find out about the current tank if it's modified factory sump with in-tank setup still available.

 

[Wknight13]

Well, I've got a Walbro 340 on the way, going to change the car back to the stock fuel delivery system (need to quit the sump system since the pump is actually designed for gravity feed and there is no way to get it below the line). I'm going to remove the braided lines, which was also ran with a custom line. Thankfully he left the stock lines in up to just underneath the alternator area behind the drivers front tire. Here is my question. It appears to be a transition point for the up lines of both the feed and return. I don't have those lines. What size threads do I need to make the transition from those points? Are the pieces I'm seeing in Kirban and Highway Stars what I need? Just one piece from the rails to that point? Or I can make it easy and obtain stock size braided line. What are the transition thread sizes and rail size (So I know what to ask NAPA for)? Can anyone supply me a picture or diagram of the full stock fuel line system with all transition points? GREATLY appreciated.