Looking for a cheap Auxiliary Fuel Tank solution

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Tom P

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These trucks don't need fuel pressure sensors. Even if they knew, they wouldn't be able to do anything about it. The injector flow values are based on fuel pressure, so all you really need to do is hook up a gauge to know everything is OK. You can rent them from the parts stores.

I did rent a gauge from a parts store. Only one in my town does. I got a maximum of 30psi (according to the gauge) out of a running engine. According to the GM shop manual it shouldn't be running with anything less than 44.
 

Tom P

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Pretty sure the big blocks run at 4 bar.

You are correct. 56psi is nominal, but anything below 44psi should render the engine inoperable. The rented gauge, even after repeated tests run according to this manual read 30psi. I'm guessing that rented gauge is bad. A story I've heard from other's who have rented fuel pressure gauges from other parts stores. I'm going to purchase my own now.
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Supercharged111

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You can do that dance or just see what the pressure jumps to when you crack the throttle.
 

Christian Steffen

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They will run with less than 44 psi, they just don't run well. I bet that gauge was right, or pretty close to being right.

When I had the in tank line fail on mine it only made like 20-30 psi and still ran, it just ran like ****.
 

JCribb

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I remember years ago when I had my 97 Z71, it randomly wouldn’t start so I checked the fuel pressure, and it was at like 42 or 44 psi. I got the fuel pump replaced and I was going again. I later fell victim to the failure prone 4L60E and so I sold the truck.
 

Tavi

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A bit old. But I thought I would update on this subject.

DOT rules only forbid gravity feed if the tank in question feeds directly to the carburetor or injector.

Federal Motor Carriers Safety Regulations 393.65 (6)(c).

As another note. DOT rules don’t apply to non CMV vehicles.
 

Supercharged111

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When they specify gravity feed, is that with or wihout a shutoff valve? The charcoal cans on these trucks say they'll handle about 100 gallons so it is perfectly reasonable to build a safe and properly functioning aux fuel tank.
 

Tavi

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When they specify gravity feed, is that with or wihout a shutoff valve? The charcoal cans on these trucks say they'll handle about 100 gallons so it is perfectly reasonable to build a safe and properly functioning aux fuel tank.
It does not specify. Only that it can not feed directly to the carburetor or injector.

But if you used the gravity feed into the primary tank, there should be no issues. In fact, a gravity feed seems to be a non issue for our trucks, since you will not get a constant 11-60 PSI needed to keep the TBI or spider injection happy from gravity alone.
 
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