logically tracking down a fuel flow problem



logically tracking down a fuel flow problem

Postby grumpyvette » January 27th, 2013, 6:20 pm

My BROTHER-IN-LAW called with a complaint, his 1974 big block corvette stopped running.

READ THESE RELATED THREADS AND LINKS


http://www.corvettefaq.com/c3/sending/sending.html

http://www.mamotorworks.com/corvette/su ... el-tanks-1

http://www.corvettemagazine.com/tech-ar ... placement/

viewtopic.php?f=55&t=211

viewtopic.php?f=55&t=1939

viewtopic.php?f=55&t=635

viewtopic.php?f=55&t=58

viewtopic.php?f=55&t=6105&p=18854&hilit=fuel+filters#p18854


BTW I WONDER IF VERY MANY GUYS BOTHER TO READ INSTRUCTIONS
http://www.jegs.com/i/JEGS-Performance- ... 2/10002/-1
heres a fuel filter I see some guy installed on his 750 holley carb equipped car and he wonders why he runs out of fuel in third gear,think about it, hes got a fuel filter rated at 130 gallons per hour , certainly adequate...until you realize hes using a manual fuel pump that produces maybe 9psi and the filter flow rates rated at 75 psi, , more than 8.3 times the pressure, so hes likely getting 1/6-1/8th the flow at 9 psi



I came over to help diagnose the problem,so we started on a step by step isolate and verify approach to the problem.

(1) the first indication was the car had good ignition spark and spun over with the started but the carburetor didn,t seem to be getting fuel fed from the fuel tank,
(2) so we confirmed the fuel tank was more than 1/2 -to-3/4 full by looking into the rear fuel fill access door in the rear deck, with a flash light.
(3) removing the fuel line from the carburetor and cranking the engine on the starter, while we had a 6 ft section of 3/8" clear vinyl tubing and a hose clamp to extend the fuel line into a 2 litter bottle so we would not spill and fuel showed we were getting zero fuel pressure at the carburetor inlet.
(4) so we know its got fuel in the tank but its not reaching the engine, so we know either the pumps not working or the feed to the fuel pumps blocked.
(5) The next step I took is disconnecting the fuel feed line into the fuel pump inlet port (which resulted in fuel draining out slowly but I was not sure the line was clear, and I hooked a temporary section of 3/8" vinyl fuel line to the fuel feed line going back to the tank and used my air compressor to pressurize the fuel feed line from the tank,for testing which resulted in a mass of bubbles bubbling up in the tank, and obviously indicating the fuel feed line was fairly clear and the fuel strainer sock in the tank was not seriously blocked. removing the air pressure resulted in in a very slight increase in fuel drain rates, probably resulting from the fuel sock in the fuel tank being slightly less clogged from the recent surge of air pressure flowing thru in the reverse of normal fuel flow direction.
looking into the tank with a strong LED light showed years of accumulated crud so we decided to order a new tank and fuel gauge sensor assembly.
(6) now this is a fair indication the fuel lines fairly free so the next step was to use an adapter fitting in the fuel pumps inlet port with a 6 ft section of 3/8" clear vinyl tubing and a hose clamp to extend the fuel line into a 2 liter bottle we filled 3/4 with fuel to test if the fuel pump would suck and pressurize fuel, as expected the fuel pump proved to be defective as it would not move the fuel.
(7) so the choice at this point is to replace the existing manual pump
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or replace the manual fuel pump with an electric fuel pump.
HAVING SOME BRASS, FUEL LINE TEST FITTINGS TO USE WITH THE CLEAR VINYL TUBE, IT HELPS WHEN TESTING BUT SWAP TO REAL FUEL LINE ONCE YOUR ACTUALLY INSTALLING A FUEL SYSTEM
keep in mind this corvette is not going to be used for anything but cruising , so he has zero interest in anything but a nice looking corvette that runs smoothly, and has good passing power on the high way, he has zero interest in racing, our concern here is simply getting the car to run correctly , in stages as he can aquire the required components and allow the cars engine too make decent power in the 1200rpm-5000rpm power band, he has several issues but we will be replacing the ENTIRE fuel system, tank, lines, fuel pump,regulator, intake and carburetor..

ONCE we got all the lines, fuel pump and fuel pressure regulator installed my brother-in-law wanted to take the car for a test drive....it ran like crap , because of several reasons, the main one is a rusty old fuel tank full of loose crud , that will soon be replaced (ITS ON ORDER) so we installed the fuel pressure gauge on the line running between the regulator and the carb and found we had 9 psi of fuel pressure, adjusting the fuel pressure to a much more reasonable 5 psi made a HUGE improvement in the cars power.[/size][/b]


BTW, while it doesn,t apply here in this particular case, one factor I see guys ignore at times is when a in tank fuel pump goes bad, guys read the instructions about dropping the fuel tank to get access to the in tank fuel pump to replace it, which in some cars makes the replacement procedure a HUGE P.I.T.A. and start thinking ,...hey Ill just tap into the fuel line and install one of the outside mount electric fuel pumps and avoid all that work, FORGETTING that the defective in tank fuel pumps going to significantly restrict fuel flow, as its still in the fuel line in the tank


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http://www.harborfreight.com/40-piece-h ... 67578.html
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clear vinyl 3/8" tube is worthless for anything but testing, but its great for testing because you can see the fluid travel thru it during testing
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many guys will go the cheaper route with standard fuel line and hose clamps and that will work in many applications,but if you go this route of using rubber type fuel line ID STRONGLY suggest the better quality 300 psi rated fuel line thats compatible with alcohol in the fuel, most hydraulic hose supply and performance shops have it at only slightly higher cost. my brother -in-law ran two parallel sections of 3/8" inside diam, 300 psi rated fuel line along the route of the factory fuel lines, and mounted the fuel pump on rubber bushings to reduce noise back on the rear inside pass side frame next to the fuel tank, and mounted the fuel pressure regulator up on a custom fabricated bracket that bolted to the rear pass side intake manifold
the existing fuel lines basically follow the upper inside edge outer surface of the pass side frame from the fuel tank to the engine compartment, and duplicating this route will keep the lines well away from the headers

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properly sized and fabricated braided fuel line of the correct size is ideal

http://www.youtube.com/watch?feature=pl ... uIoAa5RRBs

MY brother-in-law decided to go with the electric fuel pump and bye-pass regulator and install a fuel pressure gauge, the pump will be mounted on the frame near the fuel tank, the fuel pressure regulator placed near to the carburetor on a support bracket, so you can easily see the fuel pressure the carburetor sees at the fuel inlet

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READ THRU THESE THREADS

viewtopic.php?f=55&t=4381&p=14833#p14833

viewtopic.php?f=55&t=1939

viewtopic.php?f=55&t=211

viewtopic.php?f=55&t=635

http://www.summitracing.com/parts/hly-1 ... structions
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http://www.summitracing.com/parts/hly-12-454-13
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do fuel lines yours look like this,
THEY SHOULD match this config.!

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for some reason no one reads instructions and thinks the fuel return lines, supposed to be located at the bottom of the regulator and fuel should flow strait thru the regulator from side to side...WRONG! the fuel feeds up from the bottom center, and for some reason i always seem to get more consistent results with the lines hooked up as posted in the picture

BE AWARE THE FUEL PRESSURE REGULATOR MUST BE HOOKED TO AN UNRESTRICTED FLOW RETURN LINE BACK TO THE TANK TO ALLOW THE FUEL PRESSURE REGULATOR TO FUNCTION AND YOU MUST VERIFY THAT RETURN LINE IS UNRESTRICTED, IF THE RETURN LINES BLOCKED THE REGULATOR WON,T FUNCTION, BUT THE FUEL PRESSURE GAUGE MUST BE ON THE SAME SIDE OF THE FUEL PRESSURE REGULATOR THAT FEEDS THE CARBURETOR, the FEED FROM THE FUEL PUMP FEEDS THE LOWER CENTER PORT, THE LEFT SIDE IN THIS DIAGRAM FLOWS UNRESTRICTED BACK TO THE FUEL TANK, THE RIGHT SIDE FEEDS THE CARB AND FUEL PRESSURE GAUGE
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http://www.keenparts.com/pages/Catalog3 ... &year=1974

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It is best to run the tank as low on fuel as possible prior to removing the tank.

1963-74 Models
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Disconnect the battery cables at the battery.
Remove the gas cap and the filler neck boot from the top of the tank. Disconnect the drain tube.
Raise the vehicle and support it safely with jackstands.
Remove the spare tire compartment (if applicable), spare tire, and spare tire carrier.
Loosen the U-clamps and separate the exhaust systems at the transmission crossmember. Disconnect the muffler support brackets and slide the exhaust system rearward.
Remove the fuel tank strap bolts and disconnect the gauge unit wiring.
Disconnect the fuel lines and allow the fuel to drain into a clean container.
Unbolt and remove the tank support. Lower the tank, rotating it toward the front of the vehicle to remove it.
Installation is the reverse of the previous steps.
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: logically tracking down a fuel flow problem

Postby grumpyvette » April 20th, 2013, 7:49 pm

well I spent several hours today helping my brother in law replace the fuel tank and install a 3/8' feed and return line using flex fuel line rated at 300 psi because hes had intermittent fuel supply and pressure issues that we could not completely eliminate, after removing the original tank it became rather obvious why, the original hard fuel lines were kinked in several not easily located places and the tank had a couple cups full of loose debris that would shift around and at times partly clog up the fuel inlet screen.
keep in mind this BIG BLOCK corvette is being built as a car to cruise in not race so the cars engine will probably rarely see rpms over 5500rpm.
we had cleaned the tank previously but it was 40 years old and the interior surface was in poor condition, and since a new replacement tank was found at a local supplier for $140, he decided to swap out the old tank that had been giving him problems.
then I helped replace the four power steering pump hoses, and tune the corvette, the difference in how the corvette now runs is a noticeable improvement.
I DON,T KNOW HOW YOU GUYS FEEL, BUT I always get a sense of satisfaction knowing the complete fuel systems been checked and fitted with components that you know are going to function rather than hoping that 40 year old parts are going to hold up, which they may not, in the case of fuel lines even if they test good.

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HE has ordered a decent fuel filter, with a built in water separator,and drain to make testing and checking for fuel related problems easier, but its not yet arrived

http://www.amazon.com/Moeller-Separatin ... d_sbs_sg_1
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IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: logically tracking down a fuel flow problem

Postby 87vette81big » April 20th, 2013, 8:48 pm

I have driven and owned used vehicles most of my adult life.
Thinking it through, the #1 problem as a majority has been fuel system problems.
Be surprised how many decent cars, trucks, and SUVs are scrapped because of in tank rust, fuel lines rusted out, broken corroded brake lines.
It can be real grungy and filthy dirty work making repairs.
But like you said Grumpy, its satisfying knowing the job knowing the job is done right and will last for the next 20 years.
Fuel delivery, correct volume and pressure imperative on any performance or race car.

I like the fuel and water separator Grumpy.
Any specs on it ?
Gallons per hour capacity?
Cost?

Brian R.
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Re: logically tracking down a fuel flow problem

Postby grumpyvette » April 21st, 2013, 8:55 am

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if you do a bit of research youll find that those combo water separator & fuel filter combos come in dozens of different configurations and flow ratings.
these are ideally mounted near the fuel tank where you can easily access and replace parts,
that particular one pictured first,below is rated at 90 gph which for the application is adequate.
youll find this type filter mostly listed in marine applications and for diesel fuel, but they can be used for gas in carb applications.
be aware that you must carefully read the fine print on specs ,some of these filters Ive seen ar 4" in diam. and 14" tall, some are 2" diam. and 4" tall making them more reasonable for automotive use, some have CLEAR fuel bowls with a drain, sone have a drain but you can,t see the fuel thru the filter, most cars use 1/4" or 3/8" NPT or smaller fuel hose fittings some of the marine filters have fittings up to 1" NPT which by automotive standards is HUGE!

http://www.amazon.com/Moeller-Separatin ... _sbs_sg_12

http://www.amazon.com/Moeller-Separatin ... d_sbs_sg_1
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http://www.amazon.com/RACOR-500FG-EQUIV ... _sbs_sg_16
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http://www.amazon.com/Racor-320R-Rac-Se ... _sbs_sg_11

http://www.jamestowndistributors.com/us ... 378&AMAZON

http://www.amazon.com/RACOR-320R-RAC-01 ... d_sbs_sg_9
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: logically tracking down a fuel flow problem

Postby 87vette81big » April 21st, 2013, 9:03 am

I see and service those fuel and water separators often on big rig diesel semi trucks.
Sometimes there are 3 inline series - parallel flow. Bio diesel.
Think its a great addition for a daily driver on todays E10 ethanol tainted gasoline.
I will research Grumpy.
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Re: logically tracking down a fuel flow problem

Postby grumpyvette » May 4th, 2013, 7:42 pm

I spent the majority of the day assisting my brother-in-law replacing the stock quadra-jet carburetor and cast iron intake on his 1974 corvette with a edelbrock torker II low rise single plane, oval port intake and a Holley 750 cfm double feed carburetor , and a couple tall chrome valve covers for appearance.
plus some tuning issues, because its obviously a new intake and carb combo. the result was about as expected the car easily lost 30 plus lbs of front end weight and picked up a bit more rpm in the upper mid range, gaining about 1200 rpm of useable torque without any real loss in low rpm torque.over the stock intake in the useable power band, but keep in mind the 454 is a low compression version with a very mild cam in the 1974 , no where close to what the better 1970 version of the corvettes 454 BBC engine was, and its basically a dump truck power band , with the engine running out of breath even with the better intake and headers by 5500rpm.
I could easily have suggested a cam swap that would have gained 30-40 hp, but my brother-in-law wants to keep the engine as stock in that area as he can because he will never do anything but cruise around in the car, and hes perfectly happy with an engine that can smoke the stock tires thru all of first gear and most of second gear, but then is about as far up in the power band as he needs to reach about 70mph, and I doubt he will do much driving over that speed.

BTW heres a very helpful hint, when you allow a cars owner whos not really mechanically inclined too glue valve cover gaskets to valve covers , the night before you intend to install them, inspect them very carefully before you start,....BECAUSE you WILL need to carefully cut the plastic sticky, rubber like crud out of those holes in the valve cover gaskets to allow the bolts too go thru, where the mount bolts are intended to secure the valve covers to the cylinder heads, because they are, rather difficult to install if filled solid with silicone, making the valve cover install almost impossible until you notice that and drill out the silicone from those valve cover mount holes"
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http://www.summitracing.com/parts/pro-141-813
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http://www.summitracing.com/parts/edl-5061
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http://www.summitracing.com/parts/hly-0 ... dia/images
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he took the 1974 bbc vette home last night and reported back on the phone that it now runs a bit cooler and smoother and generally has improved performance now that the entire fuel system,.....
fuel tank ,
fuel lines
,fuel pump,
carburetor,
fuel pressure regulator,
and intake manifold
have been replaced

these threads, I linked to below might be rather useful, if your running into a fuel line routing issue on your c3 corvette.

If you can,t think of a good solution, Id suggest you bend a piece of stiff welding rod or similar material into the shape and size /length required and bring it to a GOOD local hydraulic hose fabrication supply shop with a sample of the thread sizes at both ends and have them custom fabricate a hose for you., they can fabricate something with either AN fittings or high pressure fuel line that won,t kink with swivel ends if required.
theres an easy solution , you just don,t know all your options.
theres 90 , 135 degree and 180 degree AN fittings, swivel connections, steel hydraulic hose, braided hose and a dozen other options


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viewtopic.php?f=55&t=7787&p=28271&hilit=flex+fuel+line#p28271

viewtopic.php?f=55&t=4381&p=16285&hilit=flex+fuel+line#p16285

http://www.corvettemagazine.com/tech-ar ... placement/
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: logically tracking down a fuel flow problem

Postby 87vette81big » May 4th, 2013, 7:54 pm

A camshaft swap Grumpy.
I am sure you a very good cam profile in mind, picked out.
:)
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