Topic: 51 CM Fuel pump issues


Tracker    -- 12-23-2015 @ 10:38 AM
  After having replaced 4 fuel pumps in a 51 Mercury over a 3 year period I am asking is there a better way ?

Thinking about going to a 6v Carter Geroter fuel pump for full time service and blocking off the mechanical fuel pump or doing away with it entirely. The Geroter delivers 4-5 lbs PSI which I am told is enough for a stock 2 barrel Holley

Does any one have experience with this idea or have suggestions for improvement ? Thanks in advance for your comments. Tracker


TomO    -- 12-26-2015 @ 8:10 AM
  Tracker, what kind of problems are you having with the fuel pumps? Where are you buying them?

Airtex makes new pumps for your car in the USA and there are a few reliable re-builders that can rebuild your pump.

C&G sells a 6 volt electric pump that will push gas through your stock fuel pump as long as the diaphragm is not ruptured.

Tom


Tracker    -- 12-30-2015 @ 3:55 AM
  Tom...just returned to find your reply...the first two pumps were " rebuilds" using Viton e gaskets. Each lasted about a year before the diaphragm's turned to goo. The second two were purchased from O'Reillys. Now I buy almost exclusively from C&G Ford Parts.

Installed an in line Carter Gearotor 6v pump believing it would help or eliminate vapor lock by supplying constant pressure. It went out after 14 mos service so awaiting a replacement.Did not help what appears to be vapor lock issues ...runs fine until heats up then abruptly seems to starve for fuel. With the clutch disengaged, the engine will rev up to high rpm's...when the clutch is engaged, the engine will not make HP and starves down until it quits. It will restart in about 15 minutes and appear to idle normal but will not make hp to move the car forward clutch engaged.

My suspicion is that since the gearotor is out, the mechanical is out as well. What I have never known is
whether or not the electric pump will run the car alone and/or if the mechanical goes out will the electric pump through the mechanical. I do tons of online research before I post my questions on this forum but have not found these answers.

I have checked and re-checked for vacuum leaks but can find none. The lines to and from the tank are all SS. Add to all that, when the car first starts it drives as new until it begins to hit mid range heat temp & then I begin to notice the stumble and then the loss of fuel and then it just quits.

I am at a loss. Thanks for your suggestions .

Tracker


TomO    -- 12-30-2015 @ 7:19 AM
  Tracker,

Your car has all the symptoms of a weak spark condition. I suspect that your coil is breaking down after heating up. Check your spark when the engine is at operating temperatures for a nice blue spark, 1/2" long when a plug wire is held near a head bolt and the engine is idling.

If you install a new coil, make sure that it is a 6 volt, POS ground coil and that the + connection goes to the distributor.

The electric pump will should deliver enough gas to run the car and should pump through the mechanical pump as long as the diaphragm is not shot. If the diaphragm is bad, you stand the chance of spewing gas all over the engine compartment.

To prove it to your self that the pump is delivering enough fuel, you can perform the following fuel delivery test. On your Mercury, because the fuel line connection at the carburetor is prone to leaks, I would disconnect the fuel line at the fuel pump and use another piece of fuel line to direct the fuel into the container.

To check fuel delivery, run the engine until it is warm, stop the engine and remove the fuel line from the carburetor and direct it into a quart container with ounces marked on the container. Start the car and run it for 45 seconds. The fuel pump should have delivered at least 16 ounces of fuel.

Insufficient fuel delivery can be caused by a vacuum leak, plugged flex line, worn pivot in the pump arm, stretched diaphragm, plugged fuel line or tank pickup, plugged tank vent or wrong gas cap or a worn push rod.

I don't know who rebuilt you fuel pumps or who supplied the diaphragms, but Viton is supposed to be compatible with Ethanol and I suspect that the supplier made a mistake and delivered the old rubber coated cloth diaphragms that turned to goo when the come in contact with Ethanol.

Orielly and C&G both sell the same Airtex pump for your car.

Let me know how you make out.

Tom


Tracker    -- 12-30-2015 @ 8:37 AM
  Tom...many thanks for your reply. I replaced the coil recently with a C&G replacement but did not change the points & condenser.It started instantly and ran like it should for about 30 minutes ...then stumbled & stopped at mid heat range I did not do a spark test.

I am going to use your guidelines to get to the bottom of this & ordered new products today from C&G. I'm going to start with the distributor...when I get it started again, I'll move on to the fuel dely test & fuel pump replacements.

Thanks as always for your guidance & suggestions.

Tracker


Tracker    -- 01-10-2016 @ 8:48 AM
  I want to begin with a note of thanks to Tom O for his advice, guidance and expert diagnosis on resolving the issues described previously with my 51 Merc.

Here is what was done :

1. Replaced dead inline Carter Gearotor pump with Airtex 6volt pump. Bypassed mechanical pump. Started instantly. Hooked up again to incorporate mechanical pump...started instantly, idled perfectly, let it warm up for 20 minutes, took a test drive.

3. When the temp hit mid range, accelerated the car to 50mph....began stumbling, cutting out, popping loudly through the glass paks, engine stalled and quit. Let it sit 5 minutes, instantly started back up but would not make hp when the clutch was engaged to move the car forward. By this time, I am stone nuts.

4. Having nothing else to turn to, I again inspected the distributor ....the new Napa Pts & Condensor checked out, the coil was new....????

Using a super bright light almost by accident, I saw what appeared to be a piece of white paper buried down deep in the distributor. Tweezed it and discovered it to be a very old piece of white tape/paper. It was the primary ground distributor wire that someone long ago had had a problem with and wrapped it in some kind of insulation tape. Never seen anything like it.

The primary ground distributor wire had about a 1" gap of bare wire which my theory is that every time the distributor plate advanced the bare wire would come in contact with metal and short out the firing sequence. When the plate returned to normal, it would again start and run as normal.

4. Waiting on parts from Van Pelts who had all the rebuild components for the distributor to prove out my theory but think this will resolve the issue. The problems were twofold in my case...the dead Carter Gearotor was the second pump failure in 14 mos so I wont be a return customer & hope the Airtex is all its advertised to be. The distributor issue was the real culprit all along but who knows ? If this doesn't work, there well may be a huge bonfire in Texas !


Tracker    -- 01-10-2016 @ 11:11 AM
  Impatient as I am, I made a Primary Ground Wire,installed the dist.,let the car warm up, took it for a test drive ...got up 75 mph ...no stumbles, pops or anything other than a smooth ride.

I cannot really say it was all in the distributor since my inline electric pump had failed but I'm 90 % sure in the past I may have replaced fuel pumps that I didn't need to. The learning curve for amateurs like me can be long and costly so hopefully this drawn out post will save someone else needless grief.

Many thanks due Tom O...I was completely out of ideas when this post went out for help.

Tracker


TomO    -- 01-11-2016 @ 6:30 AM
  Tracker, you are welcome to any help that I can give.

I am glad that you found your problem and you can now enjoy your Mercury.

One of the hardest lessons to learn is that replacing parts before doing a diagnosis is not a good thing.


Tom


Tracker    -- 01-11-2016 @ 9:20 AM
  Tom

I have learned that lesson well.....I will never know as much as you do about these old Mercs but thanks to you and others on this great website I am learning and its great to share the solutions ( as others have ) with others so at least we know what to begin looking for and the means to diagnose rather than just guessing at parts changes. Loving my Merc today...I never get past the rush I get hearing that flathead rumble.

Tracker


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