Fuel issue - Stumped

Ribbedroof

Comic Book Super Hero
Supporting Member
Jan 4, 2009
4,930
7,073
113
Wellston, OK
All great questions, yes. Yes, and yes.

Crawling under last night, it looks like I used a REALLY cheap POS fuel hose from the sending unit. I could pinch it between my fingers.
Couple of years ago I had a knucklehead at Autozone (it was closest store) sell me "fuel hose" that turned out to be trans cooler hose. Couple days of exposure to fuel it was pretty soft.

Lesson learned: ALWAYS double check when buying hose
 
  • Like
Reactions: 1 users

starliner

Not-quite-so-new-guy
Dec 25, 2023
23
26
13
The most common issue with new replacement pumps is higher than stock or spec fuel pressure. Excess fuel pressure can lift the needle of its seat and cause rich running or flooding, especially with hipo large seats.

Qjets came with several different sizes of fuel inlet seats depending on the application. Qjet guru Cliff often suggests using a .135 seat for most setups. Some of the cheap rebuild kits come with restrictive seats, sometings even werid ones with caged needles.
That is interesting for sure. I was careful because I think I read that the secondary metering rods are tough to replace in the 78 turbo. The rebuild itself was pretty easy, (thanks to some online videos).
Now you have me wondering what seat I got.
Too late to check now.
 

starliner

Not-quite-so-new-guy
Dec 25, 2023
23
26
13
And stop going to Aut
Couple of years ago I had a knucklehead at Autozone (it was closest store) sell me "fuel hose" that turned out to be trans cooler hose. Couple days of exposure to fuel it was pretty soft.

Lesson learned: ALWAYS double check when buying ho
 

starliner

Not-quite-so-new-guy
Dec 25, 2023
23
26
13
And stop going to Autozone. Here in Framingham, MA. they suck. Employees going in and out of the store, indicating product shrinkage, 4 of them crouded around a personal car while I'm waiting 15 minutes for a basic part while the sun is setting. Bad management.

20240430_190943.jpg
 

Ernest

G-Body Guru
Apr 28, 2016
767
1,056
93
Texas
The most common issue with new replacement pumps is higher than stock or spec fuel pressure. Excess fuel pressure can lift the needle of its seat and cause rich running or flooding, especially with hipo large seats.
I can atest to that... bought a carter brand stock type replacement pump once for a typical SBC for my ZZ4 engine, that pump was pegging the needle (15psi max) on the mr gasket fuel pressure guage.

After a couple of months, the guage itself started leaking, it was a gonner, but my holley 670 SA carb took it like a champ though, i now run with a Carter M6900 mechanical fuel pump, internally set to 6psi pressure, works like it should.
 

starliner

Not-quite-so-new-guy
Dec 25, 2023
23
26
13
This saga is never ending.

Before changing the fuel pump, rebuilding the carb, replacing fuel hoses, dropping the tank and checking the sending unit, this "suck out" problem already existed.

Agaun, it first runs fine, the tubo kicks in too, but then it acts like it is out of gas. Then I either feather the pedal, or shut it off and restart.

So its back to dropping the tank again, hoping that the replacement fuel hose on the tank is junk out of the box and collapsing.

Reminder, this car was sitting in a garage for 20 years.

Thanks.

20240504_115637.jpg
 
  • Like
Reactions: 2 users

69hurstolds

Geezer
Supporting Member
Jan 2, 2006
8,254
17,767
113
Did you try "back puffing" the line with air while the tank was out? Might be something (a little rust build up) partially clogging the metal line along the frame? If you have a portable air tank or small compressor, it makes it super easy to do.

Worth a try. It's free and costs you nothing but time just to make sure the line is clear.
 
  • Like
Reactions: 1 users

CopperNick

Comic Book Super Hero
Supporting Member
Feb 20, 2018
3,396
3,061
113
Canada
Back on the topic of hose for just a skinny minute here, Do you happen to know the diameters of the hard lines that were fabricated or installed to handle fuel delivery and return? Coming from the factory, what may have been installed could have been a 5/16ths steel fuel delivery, plus two other associated lines, one for the return itself and the other for the vent line that gets attached to the charcoal canister for emissions.

What might be causing your starvation is that the steel delivery line is undersized for the amount of fuel that the motor is demanding. I am not a turbo guru by any means but with as much air being stuffed into the manifold as a turbo can be capable of, having sufficient fuel on hand to mix with it is probably extremely critical. Should the factory have, for whatever reason, gone with the same sizes of fuel lines for your turbo as they did for a naturally aspirated car, then they may not have anticipated an owner who would wish to explore the outer limits of turbo action.

Remember this is 1978 here and the mfgrs are looking for anything they can add that would both attract buyers and appease the EPA/CARB at the same time. They'd be touting the turbo as being fuel efficient and environmentally friendly and all that eco-jazz. If the turbo that is currently resident in your engine bay is not what may have come with the car from the factory, it may just require larger fuel lines in order to deliver sufficent fuel to the engine to keep it running.

Just a thought here.



Nick
 
  • Like
Reactions: 1 user

melloelky

Comic Book Super Hero
Oct 22, 2017
4,182
9,633
113
mass
that's a clean ride.shot in the dark but try driving with the gas cap removed,vented gas cap/vapor lock issues aren't as popular as they used to be but it's worth a try.
 
  • Like
  • Agree
Reactions: 2 users

starliner

Not-quite-so-new-guy
Dec 25, 2023
23
26
13
Did you try "back puffing" the line with air while the tank was out? Might be something (a little rust build up) partially clogging the metal line along the frame? If you have a portable air tank or small compressor, it makes it super easy to do.

Worth a try. It's free and costs you nothing but time just to make sure the line is clear.

Definitely, I will do that when the tank is down tomorrow. No, I did not do that before.
Thanks
 

GBodyForum is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com. Amazon, the Amazon logo, AmazonSupply, and the AmazonSupply logo are trademarks of Amazon.com, Inc. or its affiliates.

Please support GBodyForum Sponsors

Classic Truck Consoles Dixie Restoration Depot UMI Performance

Contact [email protected] for info on becoming a sponsor