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hotrod1932
Novice
Mar 30, 2021, 8:00 PM
Post #1 of 16
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fuel delivery problem
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I have a streetrod running a 340 mopar engine. Holley 670 carburetor not getting fuel in the float bowls. Has a new electric fuel pump and pump is pumping a good steady stream of gas up to the carburetor through the gas line at 7 psi but very little is getting into the float bowls. i have never seen anything like this before. Engine started stumbling bad but you could keep it running by pumping accelerator. Car has always ran great. Removed sight plugs and very little fuel is getting into the front primary bowl or the secondary bowl. Also I have changed both internal filters in the carburetor at the fuel line intakes. Can not find any blockage in the line. Beats me! Any ideas?
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Tom Greenleaf
Ultimate Carjunky
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Mar 31, 2021, 2:39 AM
Post #2 of 16
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Re: fuel delivery problem
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Where is the fuel filter for this set up? Check flow after that of course.
No fuel to carb it also has to vent fuel vapor somewhere in order to fill up and maintain fuel level in bowl/bowls - fundamental carb 101 if you will.
Bet it not? That "Holley" may or may not do it same way as ancient carbs but should provide a way to run those vapors to reburn them a canister or however set up.
No vent, not easy to fill up just like a fuel tank or about any container.
Are you able to take just the top of this carb off and run it? Forgive me, been ages was good at carbs not exact Holly's made carbs for others too without their brand name for OE engines.
Smacks of not venting so far just look up top for where it vents if a rod is supposed to push down or hose to return vapors isn't working blow thru it bet it doesn't work at all?
T
(edit in adjustments - a link to this carb. Vent is a tube that would be inside air cleaner housing if used see diagrams in this PDF if it shows for you. If just like that spray carb cleaner right down that: > 199r10487-1rev6.pdf (holley.com) <
(This post was edited by Tom Greenleaf on Mar 31, 2021, 3:10 AM)
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Tom Greenleaf
Ultimate Carjunky
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Mar 31, 2021, 3:27 AM
Post #3 of 16
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Re: fuel delivery problem
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Another post - sorry. Low use street rod or low use alone. If anything can make rust - fuel lines or where you go fuel carbs will make a rust mud in bottom of fuel bowls. It get thru most fuel filters like coffee if you boiled that down get instant coffee but rust is/was common to me for carbs lots stuck inside fuel bowls.
It came out using carb spray (top off carbs) and a magnet or buy the kit and redo the carb. You shouldn't need to readjust just clean it all out. Add filters now especially if where you are uses "ethanol" fuel is not filtered where you buy it!! If those tanks are iron there's your source IMO not allowed where I am I think tanks in ground must be a fiberglass or non rustable??
IDK what I'd do now probably get a glass bowl filter (look for those) that you see the mud and just dump it out! I own one now is just what I do.
It would help if you can buy non ethanol fuel AKA farm fuel, equipment fuel or something not easy where I am is also way over $20 a gallon in hardware stores!
Spray down that vent it may run well but isn't fixed it's rust mud fuel went dry gets like clay in fuel bowls,
Tom
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Hammer Time
Ultimate Carjunky
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Mar 31, 2021, 3:47 AM
Post #4 of 16
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Re: fuel delivery problem
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Back to basics
Where is the electric pump located?
Electric pumps are designed to push, not pull which means they have to be located close to the fuel source.
Also make sure the tank is vented to allow air in as the fuel leaves.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
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Mar 31, 2021, 4:30 AM
Post #5 of 16
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Re: fuel delivery problem
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? Electric fuel pumps ? I use a "diaphragm" one for fuel exchange and to empty tanks or fill from one vehicle to another. It's not spinning and can run dry does pull fuel up. For just like this if it was done right with right pump rated for 4-7 lbs pressure. Funky but it's a mechanical pump and diaphragm not impeller driven for "push" only. IDK what or how this is rigged up,
Tom
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hotrod1932
Novice
Mar 31, 2021, 5:51 AM
Post #6 of 16
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Re: fuel delivery problem
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Fuel pump is near and mounted below the gas tank. I have ran it this way for several years. The only thing I changed was the fuel pump and filters. Holley was rebuilt about 6 months ago. Carburetor is clean. Never had this problem. I took gas line off at carb and ran fuel pump into a gallon jug. Pumped gas fine. Fuel pump is a Holley red pump. I have used Holley catburetors for several years. Never had a venting problem. Thanks for all the info. I will find the answer.
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hotrod1932
Novice
Mar 31, 2021, 5:55 AM
Post #7 of 16
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Re: fuel delivery problem
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I will check the vented gas cap too.
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Tom Greenleaf
Ultimate Carjunky
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Mar 31, 2021, 6:27 AM
Post #9 of 16
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Re: fuel delivery problem
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More! They make gas caps (pre screw on) that are full vent but don't if splashed at with gas. Look or ask for one I forget part # was long ago. They matter but it isn't your problem.
Just what are you using for fuel and filter? Pump is easy it either "thumps" or buzzes either way you saw it work. Filters go after pumps.
Fuel can go bad and or if using ethanol included fuel that can be hell on certain plastics and rubber destroys that. Results would usually be carb flooding all over the place or needled valves can stick?
Don't do this I didn't write this but tapping on carbs once freed up stuck needle valve ALSO can't use metal as that makes a spark or might. AYOR - folks reading just don't too much to explain.
Old gas starts at about 3 months IMO none of it is pure and doubt ever was. Test what you use in a glass jar, metal lid out of harm's way would be very informative. If it separates like salad dressing use something else.
That can happen to new things so the rebuild isn't out of the question who knows what was used if you didn't do it all bets off that just isn't ruled out.
Good grief, why did you need to rebuild it? They can last decades or not something causes the problem. It's 99% just cleaning the things if settings are way off WHY?
This is custom so open book for lots of things you happen to be dealing with close or over 100 years of hands on experience just Hammer and myself never mind others that haven't chimed in.
This or anything is always harder when not in person doing checks and observations.
Do know something about carbs MOST DON'T! They don't push fuel into engine to burn the pump does. The pull fuel in via the Venturi effect pump not needed really if fuel is overhead where tanks where placed eons ago so is my 1948 engine on a machine - no pump at all, glass bowl and a screen. Updraft carb so fuel flows downhill. Drain out normal water like with radiator drains all over the thing when you see it in glass bowl. Kinda works like a canning jar with a metal bail was the way to judge fuel attitude issues and fix without tools you could see it,
We'll find out why your carb isn't taking in fuel it just hasn't been fully checked out by you yet,
Tom
Tom
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hotrod1932
Novice
Mar 31, 2021, 7:03 AM
Post #10 of 16
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Re: fuel delivery problem
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Tom, Still checking things out. Carburetor only had about 5000 miles on it when I rebuilt it. I dont drive the car at all in the winter except around a big block to warm it up every week or two. I had to get into it because the front needle valve was leaking so while I was in there I just put a kit in it. (gaskets, both needle and seats and a new power valve that all came in the kit.) Had the float levels set perfect and was surprised to see levels were very low when I took the sight plugs out yesterday. I try to check things and probably do replace more parts than I need to just trying to be safe when we do travel with the car. Thanks
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hotrod1932
Novice
Mar 31, 2021, 7:16 AM
Post #11 of 16
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Re: fuel delivery problem
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oh, one more thing, I used the same filters I always used. They were the standard in line canister filters. One before and after the fuel pump. I drove the car a few times after the fuel pump and filter change and it ran fine until now.
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Tom Greenleaf
Ultimate Carjunky
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Mar 31, 2021, 7:31 AM
Post #12 of 16
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Re: fuel delivery problem
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Quote you ">Had the float levels set perfect and was surprised to see levels were very low when I took the sight plugs out yesterday.<"
Hmmm. On to something there. Back to it can't vent or fill bowls or some maybe plastic of needle valves bloated or floats bloated not liking something?
I actually forget if you can just take top off of these and watch holding the floats so they work? The worlds b*tch was a Quadrajet OMG best carb ever made but nobody could fix them nor could Rochester make two the same!!! Adjusting them new all the time no 2 ever right on the money NEW!
You did it if not long ago it should come apart again to reset it without wrecking gaskets AYOR at that but I would with that observation.
Holly if still owned by them made carbs for others allowed the other to name it.
I'm thinking, bear with me. That vent tube and the sight plugs? Wonder if you could fill bowls ever so slow see fuel come out. Put plugs back + run that out see if same problem is there?
If so that mean back apart again you should see the problem by eye point of needle or floats of a plastic (should have kept brass ones) have changed? Carb kit should have listed floats by how much they weigh so need a very accurate scale! If heavy would flood or too rich if bloated IDK might do this??
At any rate NOW YOU KNOW YOUR PROBLEM! Fuel level too low will almost not run if far off this whole massive missive is now finding out why that's the problem! Yeah - now we can't work on why if not obvious then IDK another set of needle valves or maybe find floats if too nasty you decide if some other carb is a better idea if wrecked inside,
Tom
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hotrod1932
Novice
Mar 31, 2021, 7:46 AM
Post #13 of 16
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Re: fuel delivery problem
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The next thing was opening it up again and checking everything. i have an extra set of needle valves and also a new power valve.
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hotrod1932
Novice
Mar 31, 2021, 7:48 AM
Post #14 of 16
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Re: fuel delivery problem
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No you cant take the top off of a Holley. The fuel bowls come off the front and back.
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Tom Greenleaf
Ultimate Carjunky
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Mar 31, 2021, 7:55 AM
Post #15 of 16
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Re: fuel delivery problem
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Sorry - didn't see post on filters: Hmmm. Measure output at carb and pressure right there. IDK on freaking filters which tolerate what but yard machines use inline ones do screw up IDK blaming the dang ethanol! It get crap for MPG or hours of use of things vs ~$5 a qt for "pure fuel" in a can! I use that for seasonal stuff says it's stable for two years or more on label.
An FYI, that TMK there are over 200 formulas for fuel we buy! I'm in MA has it's head where sun don't shine if I buy gas out of state get 10% more in vehicles - how smart is that?
Another site suggested measure a perfect gallon by weight! OMG, never thought of that should be the same bust isn't at all. If diluted with crap it's more or less now your floats don't behave it's lighter fuel than when you checked it! How to win that game?
The answer was fuel inject everything but what can you do if that's the problem? Buy that equipment fuel (so named as it's not street legal here or CA) but is elsewhere I think?
If you live where you take this off the road or don't use it (me too for many) IDK what's in them and do run them (way too many things and cars) just till fully warmed up like you said you do.
We know the problem it may not be your fault now I'm on a learning curve to weigh gas see how much difference I get MA uses Summer and Winter formulas if not near a large city can maybe get real fuel + be the same all the time.
Was heading to NH today may not. It's close saw pure 110 octane fuel was $9.10 9/10ths of course there! Yikes! If I go I'll check today bet it's well over $10 bucks?
Tom
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Hammer Time
Ultimate Carjunky
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Mar 31, 2021, 8:15 AM
Post #16 of 16
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Re: fuel delivery problem
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You should have external adjustable float levels on that carb. Are they adjusted correctly?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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