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switched from low pressure to tbi pressure now issues

RootBreaker

RootBreaker

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Ok so in 1999 I put a 1991 caprice police roller 350 in my truck. Nothing special but it doesn't have the lobe on the cam for the fuel pump so had to put a fuel pump on the frame. It sucked.. it was junky... clattered on the frame, etc...

finally got around to installing a 1987 tank and sender unit with fuel pump, as yall helped, and got it running.
has been ok, all well and good for a few weeks, start it here and there with no issues.

this weekend I was cleaning the garage and fired up the truck. Well as I was cleaning, I turned and saw it pouring under my truck in 3 places. One under the motor, 2 under the bed...
walked over and looked..

front fuel line next to water pump leaking...
walk to back of truck.. looked... and OH SHIT!!! RUN AND SHUT TRUCK OFF

one was leaking in one spot that I didn't get to see too well as the other caught my eye...
fuel POURING onto my muffler!!!!! and my exhaust exits under the truck and fuel was pouring in front of the exhaust exit!!!!! a backfire and she goes up!!!!!!!!!!

so over years and the swap as I just told you, things got changed a bit.

went from the 4-6psi to 15psi (regulated back down to 5psi)… I think that extra 10psi back pressure Is just causing havoc and making fuel spew out of certain areas.

what I have noticed is those locations are where I have cut the metal line and attached a rubber hose with clamp.
all place with the (dunno what to call it) but the nipple end, penile end, whatever u wanna call it... are all good.

I am guessing that is due to fuel hose going over and clamp, clamping down and the pressure cant pull it back over that hump....


so do they make a flaring tool to make that so I can take a straight cut piece and not have this happen?

I am working on a 2001 8.1L with 145k miles on it... guy was supposed to pull it but his mom broke her hip so im patiently waiting. Want the truck running as when I get the motor, im still gathering parts... and want to drive the truck...

so looking for advice on how or what to replace with. Can do high pressure braided lines if that is worth it. Just don't want to drop a fortune to redo it...
 
They make better clamps made for FI. Those alone would probably help.

It's hard on a retrofit, but I'm a huge fan of running the stock TBI (or any GM of that vintage fuel line, TPI works as well) lines. Pickups used hose/clamp on the tank side of TBI, at least for our R/V trucks, while Suburbans and K5's did not, which I believe is due to passenger safety.

I don't like messing around with fuel. As you've found, anything goes wrong, and it takes nothing for the truck to burn to the ground. There are multiple ways to tackle the beast, mine is not necessarily the best way, just my way.

When I box the frame and have to make new lines, I'm spending the ~$300 on the Mastercool 71475 to be able to use solid line and make the Saginaw flares (GM fuel flare for TBI/TPI) in it.
 
As @dyeager535 points out, flaring the ends properly won't be cheap. Flaring the ends cheaply, like borrowing the tool from the parts store, will lead to leaks. I tried the cheap flaring way, and got lucky, like you.

Buying braided line and fittings, ones that will even fasten to the hard lines you cut, can be done for less than $150 if you do want to go that route.

Whichever route you choose, don't go for the cheap way, go for the safe way. You got your break once, I wouldn't risk it again. If you decide to do braided lines and fittings, go with reliable brands from summit/jegs/etc, not cheap no-names off ebay.

If you've already got the upgraded tank and can install a high pressure pump when you get the 8.1, I would plan on getting something like the ep381 in tank pump where your braided line fittings can screw right on. You can then attach the line right to your hard line, with the correct fittings or run the braided line all the way up.

@skunked has done it all with his truck and a big block (using after market efi rather than GM, but the high pressure fuel line/pump was still needed), so definitely take a look there for inspiration:
https://ck5.com/forums/threads/84-k10-white-lightning-rollcage-seats.310302/

RootBreaker said:
I think that extra 10psi back pressure Is just causing havoc and making fuel spew out of certain areas.
Click to expand...
And I thought regulators diverted the extra pressure back to the tank, not leaving it in the line? My guess would be after enough time the lines wore on the hard lines and fuel was able to get out from the wear and tear.
 
They also make fuel injection rubber hose for your patch points

The solution is better lines, either hard or rubber.
But the FI rubber lines are an ok temporary solution



Also, if your not injected, what are you running with the 15 psi?

Most carbs are happy 7-9psi
 
Bent77 said:
Also, if your not injected, what are you running with the 15 psi?

Most carbs are happy 7-9psi
Click to expand...


Not yet. As said.. originally did 1987 tbi pump sender and tank as i had to replace and am looking at going 8.1L. If i dont...LS swap if my 8.1L falls through. So 63+psi will be there.

Agreed on doing it right hence why i asked. My current 87 sender just takes rubber lines. I dont have dual tanks setup and oem stock selector wont handle the pressure so maybe take all the lines/dual tank stuff out and just run new up drivers side and to motor vs passenger side.
 
RootBreaker said:
Not yet. As said.. originally did 1987 tbi pump sender and tank as i had to replace and am looking at going 8.1L. If i dont...LS swap if my 8.1L falls through. So 63+psi will be there.

Agreed on doing it right hence why i asked. My current 87 sender just takes rubber lines. I dont have dual tanks setup and oem stock selector wont handle the pressure so maybe take all the lines/dual tank stuff out and just run new up drivers side and to motor vs passenger side.
Click to expand...
But you’re running a carb now since the 8.1 isn’t there?
 
for a cheap fix I would probably grab some of the EFI rated rubber hose and correct hose clamps and make new runs. There's several hard line and braided systems you can run but I wouldn't buy a bunch of fittings $$ to find out you can't run them on a new setup.
 
ekajkrats said:
And I thought regulators diverted the extra pressure back to the tank, not leaving it in the line? My guess would be after enough time the lines wore on the hard lines and fuel was able to get out from the wear and tear.
Click to expand...

Some but not all have a provision for a return, most do not.

RootBreaker said:
Here is the regulator im running. Gotta find install instructions and see if return...

https://www.jegs.com/i/Spectre/865/...cDt0eZ-f0gAUB9IVz7uipZg1D6VtXNZhoCRr8QAvD_BwE
Click to expand...

This is not a return style regulator, 1x inlet and 2x outlets.
 
Last edited:
AN fittings from the TBI sender, steel braided fuel hose rated for E85, and up to the motor.

You will need this anyway with the 8.1 swap that it sounds like you’re doing.

Why not do it now?
 
You can use the double flare adapter button in a flaring tool to just make the first "bubble" ,that will make the line bulge out enough so fuel cant sneak past the clamp...you can double up on the worm gear clamps or use the fuel injection ones without the serrations in the band to get a better seal..I'd be sure to get hose rated for fuel injection too..

You could also use compression unions to splice in new sections of steel line,they even supply those on the repair kits sold for EFI with much higher pressures,they are safe to about 500 psi--or you can just double flare the lines and use a coupling and two line nuts..
 
nvrenuf said:
Some but not all have a provision for a return, most do not.



This is not a return style regulator, 1x inlet and 2x outlets.
Click to expand...
Like nvrenuf points out the regulator you are using has no return to tank. There are basically two types of regulators. The type you have will let just enough fuel through it to keep the outlet pressure at say 6 psi. Everything behind it is 'dead headed'. That means it has nowhere to go and builds up max pressure. The second type of regulator has a blow off valve so to speak. It uses a return to the tank. Think of it this way. You have a straight line from pump to carb/TBI or EFI. Now put a spring loaded blow off valve in it with a tee. Once the pressure comes up to the spring pressure in the blow off valve (regulator) it will open and let fuel return to the tank. This keeps the pressure in the line at the set pressure from the pump to carb. A TBI has this type of regulator with a return line on the throttle body. The problem with the dead head type like you have is the pump pressure is probably way higher than you think. Most of the TBI pumps I have hooked a pressure gauge on and dead headed the pump to see what they would max at would hit 50-70 PSI. EFI pumps will go about 100 PSI. Where I'm going is I bet you have about 50 PSI in your fuel line to the regulator and that's why it's blowing out all over the place.
 
AV8TER said:
Like nvrenuf points out the regulator you are using has no return to tank. There are basically two types of regulators. The type you have will let just enough fuel through it to keep the outlet pressure at say 6 psi. Everything behind it is 'dead headed'. That means it has nowhere to go and builds up max pressure. The second type of regulator has a blow off valve so to speak. It uses a return to the tank. Think of it this way. You have a straight line from pump to carb/TBI or EFI. Now put a spring loaded blow off valve in it with a tee. Once the pressure comes up to the spring pressure in the blow off valve (regulator) it will open and let fuel return to the tank. This keeps the pressure in the line at the set pressure from the pump to carb. A TBI has this type of regulator with a return line on the throttle body. The problem with the dead head type like you have is the pump pressure is probably way higher than you think. Most of the TBI pumps I have hooked a pressure gauge on and dead headed the pump to see what they would max at would hit 50-70 PSI. EFI pumps will go about 100 PSI. Where I'm going is I bet you have about 50 PSI in your fuel line to the regulator and that's why it's blowing out all over the place.
Click to expand...
Exactly
 
yeah I get all that. including that having the pump sit there with back pressure is hard on it as well. This is a temporary deal until I get the 8.1L in and then when I decide to start tearing my truck apart. I just want to get it together and run for now...

so this guy is lagging around pulling this 8.1.. if he don't hurry I'm gonna say screw it and go fi-tech or holley inject....
 
so still waiting on the dude with the 8.1L.. I think its going to fall through. I want the truck running...

fuel line shows up today.. an6 fittings, etc...

so new question to it...

I had dual tanks but not going to be running them as I only have one tank right now...

so should I take the fuel feed off the sender and send it up the drivers side and figure out where it is safe to cross over up to the motor? right now it does that from drivers side over to passenger side to a dual tank selector valve then up the passenger side to the motor....

the piece that connects left and right side, I cut it to put a fuel filter in thus part of what is leaking... so not like connecting to that metal piece that crosses the truck is good anymore...
 
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