c3 high fuel pressure
Thread Starter
Instructor
Joined: Jun 2014
Posts: 126
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c3 high fuel pressure please help
Hello this my first time I hav a 1977e corvette ("e" early) 383 stroker engine holley double pumper 750 carb I just put in a mr gasket hp electric fuel pump but it flooded my carb. I rebuilt the carb but to adjust it I need less than 7psi. This is my 3rd regulator (holley12-803bp) I cant not get it lower than 8 & half psi please help tanxxx
Last edited by hardmansonfan; Jun 15, 2014 at 09:43 AM. Reason: first time
Le Mans Master
Joined: Jul 2000
Posts: 6,664
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From: columbia city in
lets start with why do you have a electric fuel pump instead of the mechanical?does the directions for the regulator say that you can turn it down that low ?I would go with a mechanical pump ,problem solved or look into a regulator that I know can be adjusted for a much lower psi.
Burning Brakes
Joined: Oct 2008
Posts: 1,037
Likes: 14
From: Mobile Alabama
Cant see your setup without pictures. You may have something wrong other than the regulator. It is probably set to ~7psi in the box. I think "BP" means by-pass, so you have to have it connected correctly, and have a good by-pass (no restriction). You have a good gauge between regulator and carb? You know how to adjust float levels, and they are correct?
Thread Starter
Instructor
Joined: Jun 2014
Posts: 126
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lets start with why do you have a electric fuel pump instead of the mechanical?does the directions for the regulator say that you can turn it down that low ?I would go with a mechanical pump ,problem solved or look into a regulator that I know can be adjusted for a much lower psi.
Last edited by hardmansonfan; Jun 15, 2014 at 11:54 AM. Reason: misspell
Thread Starter
Instructor
Joined: Jun 2014
Posts: 126
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Cant see your setup without pictures. You may have something wrong other than the regulator. It is probably set to ~7psi in the box. I think "BP" means by-pass, so you have to have it connected correctly, and have a good by-pass (no restriction). You have a good gauge between regulator and carb? You know how to adjust float levels, and they are correct?
Last edited by hardmansonfan; Jun 15, 2014 at 12:07 PM. Reason: misspell
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Burning Brakes
Joined: Oct 2008
Posts: 1,037
Likes: 14
From: Mobile Alabama
It looks like picture #3 shows the by-pass being reduced down - my guess. If you know for sure that the floats are adjusted correctly, try running the by-pass line to a container and see if the bypass line is your restriction. Some high volume pumps need a by-pass the same size as the supply line. You should be able to turn the regulator down, then turn on the pump without the engine running and adjust the regulator up to 7psi.
Again -- you have to be able to set the float level correctly.
Again -- you have to be able to set the float level correctly.
Thread Starter
Instructor
Joined: Jun 2014
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It looks like picture #3 shows the by-pass being reduced down - my guess. If you know for sure that the floats are adjusted correctly, try running the by-pass line to a container and see if the bypass line is your restriction. Some high volume pumps need a by-pass the same size as the supply line. You should be able to turn the regulator down, then turn on the pump without the engine running and adjust the regulator up to 7psi.
Again -- you have to be able to set the float level correctly.
Again -- you have to be able to set the float level correctly.
Thread Starter
Instructor
Joined: Jun 2014
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I hav 3/8 hose all around carb,gauge,regulator,pump setup untill I get to that picture. From that picture I followed it to the tank its all metal (original?? Never changed ?? "Not sure") but they are all metal and the same size could that be contributing to the problem ??
If I do change them can I use fuel rated rubber hoses??
Last edited by hardmansonfan; Jun 16, 2014 at 09:20 AM. Reason: misspell
Melting Slicks
Joined: Jan 2004
Posts: 3,247
Likes: 210
From: Detroit MI
Normally electric pumps are mounted near the tank to push the fuel forward rather than pull it. I'm not sure if the close proximity of the pump to the regulator has anything to do with it, but I run a Holley black pump (140gph?) mounted under the tank and have no trouble regulating it down to 6-7 psi.
Found this Mallory fuel pump troubleshooting guide, I know you're not using a Mallory but it has some general information regarding electric pump systems that may be helpful.
http://mallory-ignition.com/media/in...edure_0010.pdf
If all else fails, call Mr. Gasket.
Found this Mallory fuel pump troubleshooting guide, I know you're not using a Mallory but it has some general information regarding electric pump systems that may be helpful.
http://mallory-ignition.com/media/in...edure_0010.pdf
If all else fails, call Mr. Gasket.
Melting Slicks
Joined: Jan 2004
Posts: 3,247
Likes: 210
From: Detroit MI
I just looked at the fuel pump installed pic again. Are you feeding the fuel into the regulator in one of the outlets? My Holley regulator inlet is on the bottom and the two side ports are the outlets....
edit: Holley instruction manual shows the return line coming off the bottom of the regulator so that probably isn't the problem.
http://www.holley.com/data/Products/...7914-3rev6.pdf
edit: Holley instruction manual shows the return line coming off the bottom of the regulator so that probably isn't the problem.
http://www.holley.com/data/Products/...7914-3rev6.pdf
Last edited by 69autoXr; Jun 16, 2014 at 10:06 AM.
Burning Brakes
Joined: Oct 2008
Posts: 1,037
Likes: 14
From: Mobile Alabama
Yes, an electric pump should be near the tank as it is better at “pushing” than “pulling”. But - the regulator doesn’t know where the pump is, it just regulates the pressure. I am assuming you have the regulator connected properly (in, out, and bypass). The regulator bleeds the excess pressure to the return line. If return line has restriction, (blockage, or too small for the amount of flow) the pressure cannot be bled off and will be too high. That is why I said to run the by-pass to a container to check if you can regulate pressure with it basically open. You said you tried three regulators and can’t get it to work, so something in the system must be wrong. Yes, you can run rubber lines, but it is not the best for a permanent situation. Metal or nylon (like late models use) would be better. Copper/Nickel alloy lines are easier to form than steel or stainless and don’t corrode.
Melting Slicks
Joined: Jan 2004
Posts: 3,247
Likes: 210
From: Detroit MI
Agree, looks like the bypass 3/8" rubber hose is connected to the factory return line which I think is 1/4" i.d. This could cause a restriction.
Thread Starter
Instructor
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Tanxxx guys I used a drill bit & inserted it into both lines. (Dont know how to measure lines "hopefully this is a good way") The fuel supply line is 1/4 & the return line is 5/32 smaller than supply line. If I change both lines to a bigger size I think it should resolve the pressure problem
Last edited by hardmansonfan; Jun 17, 2014 at 02:34 PM. Reason: misspell
Thread Starter
Instructor
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I also disconnected the return line on the regulator from the metal return line put a bucket & turned on the pump I can easily set it (which I have) about 6 1/4 psi so the problem lies in the metal return line. If I get a new return line (probably be better if I buy both return & supply line) I should resolve both the clogged & narrow situation
Last edited by hardmansonfan; Jun 17, 2014 at 02:35 PM.
Thread Starter
Instructor
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Now I have 2 questions. Where can I get lines that are bigger than what I got. Also am I gonna have a problem connecting a bigger line to the tank. Do I need to make the hole in tank bigger. Is there some kind of adapter I can get for the bigger line if so will that cause a restriction if I cant make the tank hole bigger
Again tanxxx alot u guys are really helping me through this
Again tanxxx alot u guys are really helping me through this
Burning Brakes
Joined: Oct 2008
Posts: 1,037
Likes: 14
From: Mobile Alabama
I am pretty sure you have 3/8 feed line and 1/4 return. If you cannot get it to the work with the small factory return, the best way would be to replace the return fitting at the tank with a 3/8 piece of tubing. The problem here is you upgraded one part of the system, and other parts are not matched - bigger is not always better. If your engine would work with a lower flow pump, (that would work with the stock return), that is easy - just swap the pump. I have upgraded the return line on cars and it is not hard, just a lot of work. Here are two options:
1. Pull your tank and remove the plate on top that has the feed and return line. Remove the return, drive a tapered punch in the empty return hole, to enlarge it. Form a piece of 3/8 tube, solder it in place.
2. Remove the tank and plate, and drill a hole to bolt in a bulkhead fitting to use as the return. Plug off the old return.
1. Pull your tank and remove the plate on top that has the feed and return line. Remove the return, drive a tapered punch in the empty return hole, to enlarge it. Form a piece of 3/8 tube, solder it in place.
2. Remove the tank and plate, and drill a hole to bolt in a bulkhead fitting to use as the return. Plug off the old return.
