Rotary Vane pump can be a problem

Park_W

FYI, folks: I've been battling a fuel delivery-rate problem with my '47 C8 for some time now. After several tests and corrective measures to eliminate other possible sources of the problem, with only partial success, I've finaly found the heart of the problem ... a restriction in the fuel line. And the restriction is the Carter rotary vane electric fuel pump. It works great to fill the carb before starting, etc. But when it's not running, it's a significant restriction to flow. Try blowing through one. I had thought the pump design had enough clearance in the vane and housing structure to allow the main pump to draw through it with no problem. Not the case. I measured suction at the tank with and without the elec. pump in the line. Vacuum reading with the pump removed was twice that with the pump in the line.



My planned solution is to install a bypass line around the elec. pump, with a check valve in the bypass so the engine pump can draw through the bypass line, but when the elec. pump is on, the added pressure will close the check valve so the elec. pump isn't merely pumping fuel in a circle, around the bypass loop. I've fould a nice brass check valve with 1/4" pipe connections for less than $10. Will post the results here when I get it installed.

[Deleted User]

Park,



I experienced the same thing with the pump I bought from Fifth Avenue. I mounted it in-line by the gas tank. The car ran fine when it was on, but turn it off and the car would quit. I called and talked to Randy and these pumps are made to run all the time like a new car.

When I put one on my 36 Terraplane, I did as you suggested, and put in a by-pass line with a check valve to keep it from pumping back into the tank, so now I can turn it off. These are great pumps and last forever.

[Deleted User]

I'm just curious, what do you guys have against eliminating the engine mounted fuel pump and running the electric pump full time?



Allan

Park_W

Scott, thanks for the confirmation that the "check-valve bypass" works the solution OK. Allan, I just wanted it to look original under the hood.

[Deleted User]

Other than having it crank longer before the engine starts, why have an electric pump?

jjbubaboy

Hey Matt,

The advantages I have found are not only to fill the regular pump after sitting, but in case the regular one quits you can get home with the electric, and its also a great cure if you have any vapor lock issues.

Jeff

SuperDave

Running both pumps at the time runs the risk of the mechanical pump diaphram failing and the electric pump will dilute the engine oil and cause bearing failure. It's your car..gamble if you choose.

[Deleted User]

The Carter/Federal-Mogul rotary vane pumps are, and NEVER were intended to be used as a booster pump for a STOCK mechanical fuel pump!! It's all, or nothing with these, as the stock mechanical pump will not pull gas through the rotary vane pump when it is turned off.



See the attached JPG scan of the installation instructions... this subject is specifically addressed in both the "Important Notice" box at the top of the sheet, as well as the main body of the instructions.



I have found these pumps to be the most trouble free electric fuel pumps currently on the market when correctly installed. The biggest advantage is they are not effected by any of the fuel additives, or alcohol that is blended in today's gas which can ruin the diaphragm type pumps. The motor is also cooled by the fuel itself while it is running which adds greatly to the life-span of these pumps.



I personally ran one of these for more than 20.000 miles on my '46 Hudson Pickup before I sold it, and never had a single problem, but you must remove, or bypass the original mechanical pump.



The attached instruction sheet does tell you how you can leave the original pump on the engine which may be preferred if you have a double action pump that boosts the vacuum for the wipers, by plugging the outlet, and bypassing it.



Dad, (53Jetman) will most likely chime in here on this subject, as we have been running one of these pumps on his Super Jet for many trouble free miles as well.



Hope this helps answer some of these questions! These pumps are an excellent product!!

53jetman

Hudson308 wrote:

That's exactly what I've done, with great results for the last ten years using the same pump. A couple diaphragm (electric) pumps in the same location near the tank only lasted a year or two each. The lack of a mechanical pump doesn't look stock when you open the hood, but then neither does the rest of my engine.

I too have had the rotary vain pump installed on my Super Jet for at least eight years with no problems. I don't even have a mechanical pump on the engine any more - just put a plate over the mounting hole in the block.



Jerry

53jetman

Geoff

I concur that if the diaphragm in your mechanical pump fails, you must by-pass it, otherwise you will pump fuel into the crankcase., if you have an electric pump back further. I carry a flexible fuel line with fittings that will screw into the inlet and outlet pipes after disconnecting these off the mechanical pump. Have only had to use it once. My experience of electric fuel pumps is such that I don;t trust them that much, but I*'m talking about Lucas models, so the ones referred to should be much better. However, the Carter mechanical fuel pumps seem to have notoriously leaky vlaves which let the fuel drain back after about three days, so an auxilary electric pump overcomes that.

Geoff.

RonS

Park,I had a parrelel fuel line in my hornet until recently. The fuel line branched off after a common filter. One line went to the AC mech pump,the other to a E8011 solenoid pump(Airtex). The two lines met , with a tee, after the AC outlet and resume as a single line to the carbs. Both pumps have check valves. I switched to a Carter P60430 and ran the line through the AC pump along with the vacuum line and removed the cam arm. Can't tell that the mech pump is a dummy. I was concerned with the old system, that gas could get into the crankcase. The elec pump can't pump gas into the engine cause the hole is blocked. No more fuel starving in Arizona summers.

[Deleted User]

http://www.mcmaster.com/# Is where I got my check valves.

Park_W

Geoff, my bypass line is around the electric pump, so it won't be a hindrance to flow when it's not running. Ron, I've thought about the diaphragm failure issue and pumping gas into the crankcase, but figure that's a low-probability event. Worth considering though. Your dummy pump idea is a good way to work the "original look" issue (unless one has a dual pump and wants to retain the vacuum pump function). I'm getting my check valve from McMaster-Carr also. Using the one with female 1/4" pipe threads at both ends, and only 1/3 psi needed to open the valve. Price is about $12.

RonS

The original mech pump has check valves already,and so do any electrical ones.However, due to the elec pump location in the rear,Napa sells various inline check valves. Just go to Napa on line, and seek inline fuel line check valves.While there, check out vacuum storage tanks. They fit nicely on the right fender liner and are about the size of a softball. Need the one with 2 vacuum ports(in & out from the wipers). The tank can be removed in a minute. Cost $13.

Park_W

Ron, I think the Carter rotary vane pump doesn't have check valves. Or valves of any sort. No need for them in that type pump.



Here's what I got from NAPA online on the check valves: "We're sorry, but no matching products were found for "inline fuel line check valve". " Pretty much what I've come to expect there. Not that they don't have the item, but that the search tool is often worthless in finding it.

RonS

Park, I stand corrected it was Summit racing parts.The one I like is the Carter G1691002 -$21.40. And your right about Napa they have a online, but it's usless as ...on a bull. They want you to go to the store. You can't even browse if you don't have a specific modern car in mind.

Unknown

RonS wrote:

Park,I had a parrelel fuel line in my hornet until recently. The fuel line branched off after a common filter. One line went to the AC mech pump,the other to a E8011 solenoid pump(Airtex). The two lines met , with a tee, after the AC outlet and resume as a single line to the carbs. Both pumps have check valves. I switched to a Carter P60430 and ran the line through the AC pump along with the vacuum line and removed the cam arm. Can't tell that the mech pump is a dummy. I was concerned with the old system, that gas could get into the crankcase. The elec pump can't pump gas into the engine cause the hole is blocked. No more fuel starving in Arizona summers.

That's exactly what a friend of mine did on his '41 Packard. You can't tell the difference from original and every looks stock. He did install a flat block off plate between the pump and the block to ensure that no fuel can get into the crankcase in case something inside the mechanical pump decides to leak.



Personally, I dumped the mechanical pump altogether and went with an electric fuel pump with a block off plate on the block. You can't go wrong with it and the whole thing looks so much cleaner now. But again, I'm not 100% originality minded, either.

Park_W

Here's the finished installation.

Richie

Sweet looking setup Park, I like that. Richie.

RonS

Park,nice job, is the check valve the Carter that I spoke of before? Where did you get it?

53jetman

Park W wrote:

Here's the finished installation.

Park - I'm surprised that you are using copper line. I've been told by someone smarter than I that we should convert our fuel lines to steel, or stainless steel.



Jerry

53jetman

Park_W

Jerry, I'm not aware of any reason to drop the use of copper tubing. Maybe I've missed something. It's sure a lot easier to work with (sharp bends, etc.) than steel pipe.



Ron, that's the $12.50 valve from McMaster-Carr. Only 1/3 psi to unseat it in the forward direction, says the spec. I've not taken it out for a proof test run yet (too darned cold today!)

onerare39

Very very nice installation Park.



John



P.S. McMaster Carr has a lots and lots of great stuff, it's the first place I look when I need something that I can't find something locally.

[Deleted User]

When I bought my car it came with an electronic fuel pump in addition to the mechanical pump. Is there an easy way to tell just by looking at it to tell the style?



It does not seem to restrict flow when not turned on, but I have noticed my oil thinning like some gas is getting in.

Park_W

I think it's safe to say that any "click-click" pump has built-in check valves in order to work properly, so shouldn't cause any flow restriction problems. If the fuel seems to be getting thinned and you're using the electric pump sometimes, that could indeed indicate you've got a bad diaphragm in the engine's mechanical pump (And if you don't think a leaky diaphragm can be trouble, I hope your wife isn't of child-bearing age!)

RonS

I 'm interested in installing a check valve. I like the ones at Mcmaster-Carr. I want to place it in line with the pressure regulator. Should I put the regulator first in series, or the check valve? By the way, Michael, that is a solenoid type pump, probably by Airtex. Gas will pass through it when off, with little restriction, but when they fail they they block the flow and even though the motor hums, nothing passes. Reliability is spotty, I am told.

Park_W

Ron, what's the nature of your installation, and objective of the check valve ? That might dictate where the check valve would go.

RonS

Park, Right now, I have an elec (gear driven)pump by the gas tank and a straight run to the carbs with only a pressure reg in between. The regulator is just behind the cowl support Where the fuel line begins its' rise to the engine compartment..out of sight of engine and chassis judges. When the engine shuts down I would like to cut down on the liklihood of a long travel for gas to be pushed to the carbs. Especially when restarted after only a few hours. My thought, by placing a check valve before the reg, fuel will "crack open " the valve quicker and enter the reg to reduce pressure to the carbs(6-7 psi without a reg). Mcmaster-carr has just the right valve to thread into the regulator.

Park_W

Well, after a few days of yucky weather, I took advantage of a sunny day to finally run a proof test of the electric pump check-valve bypass arrangement. It seems to have eliminated the restriction problem. Ran the ol' (but "new engined") C8 out on I-77 and ran it up to 75 mph, accelerating and climbing a bit of a hill. Nary a hint of fuel starvation. So at long last, all is well.

[Deleted User]

Congrats Park,

I know how you feel, when I first got my 51 Com 8 on the road I would get about a mile from home and the engine would quit. I would flip on the fuel pump and it would run for a little while and quit again. I finally figured out the pump was the restriction. I parked next to you at the Nationals in the black 51 Com 8.

I did the exact same thing with a check valve when I put another pump in my 36 Terraplane. It seems to work OK, but I haven't road tested it yet.

RonS

Put a check valve on my hornet this week as well. Park, I installed the 1 psi cracking valve from Mcmaster-carr, female inlet, male outlet, into the 1/8npt pressure reg. Ran great and after 4 days fired right up and again after sitting 3 hours instantly started. the gas is staying up in the line now. Need to wait to the Arizona summer to verify elimination of fuel starvation. Ron