6 cyl drivability problem. Help please! - Page 3 - Chevy Nova Forum
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Old 5th-November-2012, 04:06 PM   #31
Rotorbolt

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I appreciate the insight and responses based on experience. Which is why I ask questions when I'm having a problem.
My dad is running this very pump and he has an edelbrock 600 4bbl on it. It has never flooded or experienced any excessive pressure issues. I'm also basing my options on what i've seen work firsthand.
I understand what you're saying though.
I just hate to have to replace the stock type mechanical pump again only to have it wear out and do the same thing in a couple years. So I'm considering an electric one instead.
what electric pump are you running in your 250 L6 68 then? Maybe thats somthing I need to use instead.
Again, I appreciate your time in helping me figure this out.
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Old 5th-November-2012, 05:16 PM   #32
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I am using the "in fuel line" Airtex E84070 from O'Reilly.

It has a max PSI of 5.75 (not 6, as previously stated) and is rated at 72 gph.

I like this design as the pump motor has gasoline circulating around it to keep it cool.

Its noisy at start up so would need super insulation, a major drawback..

I drove it on a 900 mile trip last year with no problems.
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Old 6th-November-2012, 12:12 AM   #33
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Thanks for the info on the pump you're using.
Actually, I do have one of these sitting around practically brand new.
http://www.oreillyauto.com/site/c/de...0515&ppt=C0025

It a Mr.gasket brand electric pump. Rated at 2 - 3.5 psi and 42 gph. It says its for 4 and 6 cylinder applications.
I bought this a couple years ago to use as a "tool" to pump the fuel out of my wife's saturn so I could pull the tank out to replace the pump. Only used it once to pump out a full tank of gas.
I thought about using it since I already have it. All I gotta do is put it on and no money spent.
Is this pump worth considering?
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Old 6th-November-2012, 09:16 AM   #34
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Quote:
Originally Posted by Rotorbolt View Post
a Mr.gasket brand electric pump. Rated at 2 - 3.5 psi and 42 gph. It says its for 4 and 6 cylinder applications. Is this pump worth considering?
I am not familiar with that pump - sorry.

Nothing is lost if you do try it, since it is already in your possession.
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Old 6th-November-2012, 01:52 PM   #35
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Another thing to look at is if the carbs are opening fully when you floor the pedal. If you have not had someone inside the car flooring it and visually checking the carbs it may be part of your problem.
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Old 7th-November-2012, 07:05 PM   #36
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Did some research. Stock fuel pump pressure for a 6cyl is 3 - 4.5 psi and flows 1 pint per 30-45 seconds. About 13-15GPH
Using a formula I found in the sept. 2012 issuie of Hot Rod, I calculated the GPH requirements for an electric pump.

GPH= Engine hp / 6.1 lbs/galon or

CFM= CID x max RMP x VE (.90) / 3,456
Airflow (lb/hr) = CFM x 4.38
Fuel flow (lb/hr) = Airflow x 0.077
GPH = Fuel flow (lb/hr) x 2 /6.1 lbs/gallon

I came up with around a 20-22 GPH requirement based on my engines CID, RMP and HP stock specifications referenced from factory specs in a 60's era GM shop manual.
I found this electric pump :
http://www.ebay.com/itm/Airtex-Fuel-...c933b4&vxp=mtr
Seems like a close match. 30GPH at 2.5-4.5 psi Opinions?

Last edited by Rotorbolt; 7th-November-2012 at 11:07 PM.
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Old 7th-November-2012, 08:02 PM   #37
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Any small generic pump, including the one you mentioned, should work if it is the same size as your 5/16" fuel line.
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Old 7th-November-2012, 09:06 PM   #38
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anybody know of any mechanical fuel pumps with a higher output?

arndog
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Old 7th-November-2012, 11:40 PM   #39
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I'm somewhat reluctant to use the mr. gasket 42S pump that I have. I read a bunch of reviews on it yesterday and a vast majority of them were negative. But could those bad experiences with this particular brand pump be the result of not installing the pump per the instructions? I know I did have a hard time getting this pump to actually move fuel when it was dry at start. It doesn't pull fuel too well. But once fuel is at the pump on the inlet side, it worked and didn't take long to pump out a full tank of gas. Pushes fuel pretty good. Just like the instructions said. But it does require mounting at a 45 degree angle at or below tank level no more than a foot from the tank. I've looked under the car in front of the tank area and tried to figure out a placement for it and I'm not comming up with much short of somthing that would look un-professional or wierd looking. I'm wanting to mount it flush on one of the tank strap braces as it looks like a perfect spot but that is above the tank and the pump might not work well or fail as a result.
So I'm now leaning towards this Airtex E8251 pump now. It says it for marine use, so I would imagine its more water tight and more corrosion resistant. But it doesn't come with the filter that I've seen others come with.
I'm also brainstorming the wiring. From what I understand, its best to use a relay verses running straight off the ignition switch or switched circut off the fuse block. The instructions for the 42S didn't mention the need for a relay. I'm thinking thats the better way to do it. I don't think it pulls that many AMPs. around 2 or 3 amps I think and it calls for a 5 amp fuse on a minimum of 16 guage primary feed wire.
I know, I'm thinking too much. I just need to get one and put it on.
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Old 8th-November-2012, 08:03 AM   #40
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Years ago I had the same problem on a 63 Nova SS. I finally found that the bolts/screws holding the carburetor base plate to the carb body had vibrated loose. Idled and ran fine up to a point, but above a certain rpm raw fuel was drawn down the buterfly bypassing the venturi. Drove me nuts for days until taking the air cleaner off I noticed the carb body flop. Tightened the bolts problem solved. Check those bolts.
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Old 8th-November-2012, 10:12 PM   #41
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Carbs are not loose and bolts are tight. I periodically check those and keep them snuged down. Butterflies open all the way, so no problem there.
I'm considering hooking up the 42S pump to act as a booster pump for the mechanical pump. The electric pumps instructions says I can do that.
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Old 8th-November-2012, 11:56 PM   #42
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That rust is plugging up the jets in your carbs. If I remember correct. The jets are easy to access.
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Old 9th-November-2012, 10:33 AM   #43
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I watched the video link. Man, that Chevelle wagon is bad *****...REALLY COOL

Anyway, I went ahead and took the mechanical pump off. Then I took it apart. I found a bit of fine rust sediment that had been accumulating in it. couldn't believe it got by the pickup and inline filters. Thr rubber diaphram and check valves appeared in really good shape. So I cleaned it out , reassembeled it and checked it. It seemed to work quite well when I would manually push the arm. I went aead and re installed it. I got to thinking if this much was in the pump then how much is in the carbs? i took the top of one of them off to get a look inside. Yep. same rust accumulation. Took the jet out to clean it and then took the powervalve out. There was a good bit of rust down inside the well the valve screwed into. I realize now I've got to take the carbs off and rebuild them becuse they more than likely have rust inside the various orfaces. Put the carb back together temporarily untill I can get a couple kits to go through and clean out these things. Hopefully THIS is where my problem is.

Last edited by Rotorbolt; 9th-November-2012 at 10:34 PM.
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Old 11th-November-2012, 09:17 AM   #44
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Cool

After you get the car running install a fuel pressure gauge inline to see what fuel pressure you have. I don't know how you're duel carbs are plumbed but you should be using a fuel block so fuel from the fuel pump to goes each carb individually. Heres a link for the gauge. I would install an inline T from the pump to the carb feed line,install the gauge in the T fitting. RICK
http://www.harborfreight.com/automot...ter-93547.html
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Old 16th-November-2012, 10:16 PM   #45
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Not sure it's a fuel issue.
Sounds kind'a like a coil with either a weak or burned winding.
Just a thought.
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