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MG MGA - fuel pump problem

Near the end of a long(33 year resto) and can't get the fuel pump to run. Brand new pump (with a diode inside),brand new rebuilt engine , professionally rebuilt carbs,brand new battery, brand new battery cables etc etc etc. There are some changes to the fuel system.I have installed an inline fuel filter from the gas tank to the pump and this means the metal fuel line was split and a rubber hose connection was used to install the filter. I have also installed a fuel shut-off switch in the main fuel line ,again with a rubber hose connection. The fuel pump is grounded to the chassis by the spade connector (on the pump)to the small tab on the rear of the chassis. The gas tank guage is grounded to the chassis using the wiring harness connection. The fuel pump main electrical connection (from the wiring harness)is made at the terminal end of the pump bakelite cover. NB: If I remove this connection and touch the pump I get a spark so there is power in this connection. And finally the pump itself is mounted (using the two rubber plates) too the chassis.

Turn the key and.......NOTHING....NOT A PEEP (sorry tick). Any ideas.

PS: where did you guys attach the postive ground wire(from the battery) to the chassis. I think this might be my problem as mine is attach too the chassis at the floorboard bracket between the pump and the battery rack.
Gordon

Hi Gordon. Since you get a spark at the fuel pump terminal, you definitely have power getting to the the fuel pump. Question: Is your car wired for negative or positive ground, and is the pump itself negative or positive ground? This makes a BIG difference! A pump that is wired backwards wont work. Also, if you wire a solid state (electronic) pump in backwards, you will likely fry the electronics in the fuel pump. Assuming you have not wired the pump in backwards, it sounds like you have a defective fuel pump, since power is getting to it, but it refuses to run. Cheers! GLenn
Glenn

Gordon,
I know you said the pump is new, but how long have you had the pump? I bought a new pump from Moss, and didn't install or use it for about two years. When I did install it, I had the same symptoms, no ticking. I pulled the cover off, and there appeared to be a little grease or something on the points. I pulled a piece of rough paper between the points to clean them, and it has worked fine ever since.

Jeff
Jeff Schultz

Jeff's experience is very common with points style fuel pumps. The tungston contacts will develop an insulating film over time if the pump is not used. The film will build up and has a waxy appearance and will keep the pump from running. Some 400 grit sand paper will clean them off easily and as long as the pump is run on a fairly regular basis, the current through the contacts will keep the film burned off. The only way to get around this problem is to go with the all electronic SU fuel pumps or my solid state mocification, both of which eleiminate the problem because neithe approach use open points. Cheers - Dave
David DuBois

I have my car positive grounded and I do not know how to tell weather the pump is a positive or negative one. The bakelite end is wrapped in red tape.
gordon

Gordon - Red tape is 'supposed' to indicate Positive Earth, so that would be right. If you have an ohmmeter, you can pull the power lead off, and measure (on the lowest scale) between the power post and the grounding terminal. No reading indicates that either the points or coil are open, or - more likely - the points are dirty, and need a quick wipe with some fine sandpaper.

Another way is to use an instrument bulb as a test indicator. Hold the power lead from the car against the brass of the bulb, then touch the tip of the bulb to ground. The bulb should light up in your hand. Now, touch it to the power post of the pump, and it should light up again, although slightly less brightly. This trick will NOT work with a larger bulb, such as a brake light bulb.

Best of luck - - Alec
Alec Darnall

Gordon - Alec is correct, red tape indicates a positive ground pump. YOu will need to take the tape off of the pump and end cover, remove the nut ont he power terminal and take the end cover off of the pump, then take soem 400 grit sand paper and run through the points first with grit facing up and then with it facing down to clean the film off of the contacts. The pump should start running then. Good luck - Dave
David DuBois

Dave,I received you fuel pump trouble shooting email and will give it a try tonight.

Alec; I will clean the points and test the curcuits to see if that works.

Jeff: As you,I have had the pump for several years and just installed it now. I read in my manuel that it is possible for the diaphram to seize. Any chance this could be the problem?

Glenn: Definately power to the pump when I "SPARK TEST" it.My ground wire from the spade connector is solid but I am not sure if the BATTERY ground wire is OK.It is connected to the floorboard frame between the battery box and the fuel pump. I don't think this should be the problem.

And a hearty thank you to everyone for their help. Gord
gordon

Gordon - While I am not Jeff, I'll answer the question on the diaphragm. While it is not uncommon for a diaphragm to become stiff enough that the pump will not run, it almost exclusively happens to old pumps that have been used for a ong period of time, then allowed to sit, unused for an equally long period. I have never seen a new pump with a stiffened diaphragm regardless of how long it has sat unused. Over all, in 25 years of restoring pumps, I have found very few with damaged or stiff diaphragms, particularly among the later pumps (post 1985). Cheers - Dave
David DuBois

After way too many "Dealer Repairs" on my S.U. Fuel Pump, I learned to change the points myself & always carried a "Spare" WORKING Fuel Pump in the trunk beside my "Spare" distributor Cap & WORKING H.V. Cables "SET". Finally I fitted a NON-POLARIZED (POSITIVE OR NEGATIVE GROUND THE MAGNET DON'T CARE) U.S.-made "ELECTRIC AUTOPULSE" unit purchased at a Truck Stop in Virginia and had NO MORE FUEL PUMP PROBLEMS FOR 8 YEARS!. (Truckers used SEVERAL "AUTOPULSES" connected up IN PARALLEL to run their TRUCKS!) "AUTOPULSE" sold out to "HOLLEY CARBURETORS" in the 1970s, I think, and it continued life as a "HOLLEY". It put out 5-7 PSI, vs 3-5, but I never had a problem with the Float Valve, so I never had to install the "Adjustable Pressure Regulator" I had bought just in case. I'm going to check if NAPA still carries this "HOLLEY".
OLD BILL-67

OK, The pump is a positive pump with a diode in it. I removed the diode and made elctrical connection directly to the battery (ground & power) with again no results. Points have been cleaned. A friend suggested I simply reverse the wiring , too change the polarity (in case the pump is colour tape coded wrong )and try that but won't that burn out the diode. Can I try his trick if I remove the diode?
Here's the recap: new positive pump,clean points,good electical source from wiring harness,good ground from spade connector to frame,12 volts at the battery terminals,apparently good diode.
I am going to try Alec"s test but what does it mean if the light bulb when touched to the ground works but does not work when touched to the pump terminal?
The very final trial will be to install my pump in someone else's car and see if it work AT ALL.
Gordon

Gordon - Reversing the polarity to the pump won't make any difference other than to fry the diode unless the diode is removed first. Even if you do this, the basic pump, without the diode doesn't care what polarity it gets. It is not like a generator that needs to be flashed or polarized to make it work. If you did not use 400 grit sand paper on the contacts of the points, then clean them again, really grinding on the contacts with the sandpaper. Instead of installing the pump in someone elses car to test it, just hook the pump directly to a battery, positive side of the battery to the power terminal and negative side of the battery to the ground lug of the pump. Do this with the end cover off and if the pump doesn't work, thne press down on the fixed points blade right above the open area in the pedestal where they make contact with the movable points below. If thi pump still doesn't work, then you might consider returning the pump to where ever you purchased it form and get the pump replaced. Good luck - Dave
David DuBois

PROBLEM SOLVED ! It turned out to be a short in the points. One of the wires was grounding the points and stopping them from working. A friend ,who is much more electrically inclined than me (and that doesn't take much) solved the problem. It's pumping gas like a trooper now. He also was able to correct a short in my distributor which I would never have figured out. Now I have fuel & spark. The next step is to figure out why the start turns slowly and heats up. Once again I am going to say it's a short. Will find out this weekend and if all goes well my Coupe should have a running engine. A great big thanks to everyone for their help.
Gordon

This thread was discussed between 27/08/2005 and 08/09/2005

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