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Fuel pump points Why did they pit

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KevinR

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My first real road trip in the BN7 was going to be to the dedication of the original road coarse at road america. half way there the car started to act as if it was running out of fuel. It stalled an then started before I could even come to a stop. Not knowing what to expect I turned tail and went home. Talk about the honeymoon being over.

After a few diagnostic drives I have come to realize the pump was working intermitantly. I looked at the points tonight and they were burned black. I filed them clean an reinstalled but now it is raining and I havent test driven the car.
This pump is the stock SU from Moss and has only 800 miles on it. Is this well below normal? do I realy need to clean these points every 800 miles? how loud is the facet style pump relative to the SU? I wanted to keep the car stock but refuse to service this item every 800 miles. The car is negative ground if this matters

Any thoughts on this are appreciated
Kevin R
1959 BN7
 
You have multiple options to solve your problem. There are electronic points available for these pumps. Being solid state they are reliable and don't have points to burn up. You could also add a catch diode across the pump solenoid and capacitor across the points to minimize the burining you see. Both of these fixes take place under the dust cover so your pump still looks original.
 
I thought SU fuel pumps added capacitors and later diode/resistors a long time ago to minimize the current across the points. There was something about removing the diode for positive ground cars but yours is negative ground.

https://www.team.net/sol/tech/supump.html

Does yours have a diode under the cap like the one in the attached picture?

Cheers,
John
 

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That's right. If the fuel pump has an arc surpression diode, then the polarity would have to be swapped when the car is changed over to negative ground. If not, then the diode cannot perform it's intended function of arc surpression and the result would be a set of burnt points. Look and see if your fuel pump is the kind with the diode. Some have a capacitor and they are not polarity sensitive.
 
Hi Kevin, I have been wondering how the current points type SU pumps supplied now are not polarity sensitive.Perhaps the "Manufacturer" has reverted to an earlier mistake and removed the arc suppresion components from the pump.I would stay with the SU pump but use the electronic version, they will give you years of trouble free service.---Fwiw---Keoke
 
I have posted Bob bridger's excellent article (with pictures) on making fuel pump transistorized.

I have converted 5-6 and the process is easy and the results are great.

Forget the Archer Part Numbers and just get the generic parts from your local Radio Shack or electronics store.
Shouldn't cost more than $2-$3.

Here's a link - It is Tech Tip # 21

https://www.ntahc.org/techtips/TechTips1.htm

Tim
 
To all, attached is picture of the internals of the pump. although I am hazy on the terms diode and capacitor this pump does have an item between the pump body and points. it does not appear to have any terminals left over where a diode was removed. the tech article looks fairly simple and I may go in this direction.

I purchased this pump as specific to a negative ground car. the price difference is what made the decision to go with points assuming they have worked for the past 50 years.

When I bought and restored this car I thought I would only put on a few hundred miles a year. now that I realize how cool of a car this is a few thousand a year is more likely.

thank you for your help. I will update with the findings

Kevin R
 

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Kevin, We needed some more Healeys at RA! It has become increasingly obvious that when when installing a new SU pump, one needs to clean the points before installing. There may even be something like that in the installation instructions. Perhaps the coating they use, or some oxidation happens, but whatever, many new pumps succumb just as yours did. I now clean every new one when I "hand it over" Peter C.
 
Hi Kevin, if that is all the components under the cap in your pump then my suspicions might be correct. The "Manufacturer" has removed the arc suppresion components from the pump to allow its application to each ground system. The addition of a Mylar; 0.047 Micro Fd Capacitor with a peak inverse voltage of ~ 600 Volts across the points will solve its problem. --Fwiw---Keoke
 
Kevin,
In your pic of your fuel pump, what is the light blue item in the middle of the green wires ? Is it a side view of a little capacitor ? Are there numbers on it ? In your pic this item looks like the side view of a small capacitor. We are just curious what the current stock is using....
All of this doesn't help you get your problem fixed. What will help is for you to convert it with the power transistor as shown in Cottontop's link. Then it should't fail for another 120 years or so. Make good notes of your work so your great grandson will know what those " old fashioned " electronic parts are for !
 
Gotta agree with Peter C., gents. And I no longer get mine from US suppliers as I just plain do NOT like to "new" "universal" fitment crud.

And I do check points in every one before it goes "out the door"!! /ubbthreads/images/graemlins/confused.gif

/ubbthreads/images/graemlins/cheers.gif
Ed
 
So where do you get them?. They all come from one single "Manufacturer".---Keoke- /ubbthreads/images/graemlins/confused.gif
 
This is only my opinion, some will disagree.
The SU pumps with points and arc suppression diode will last for many years without trouble.

Arc suppression diodes come in two varities for negative ground & positive ground. Moss number 377-135 for positive ground pumps & number 377-145 for negative ground. The only difference is the polarity & lead colors. The polarity of either diode can be reversed by simply reversing the two lead connections red for black. Since the two models have slightly different lug connections on their ends the lugs also need to be interchanged. It's easier to just buy the correct diode for your intended pump ground, positive or negative.

If a positive ground pump with diode is connected as negative ground, the diode will immediately blow, you will unknowingly have no arc suppression & the points will burn. SU replacement point kits are readily available if you need them.

It's been rumored that "some" resellers simply remove the diode all together & sell the same pump as positive or negative ground. The points usually last just long enough to get beyond any guarantee or return policy.

Some sellers may convert the newer pumps to universal ground connections by replacing the diode with the earlier capacitor arc suppression. This will likely last fairly well but not do as good a job as the diode suppression method.

There are several schemes on the net to replace the points with transistors, or to add transistors with the points to reduce the point wear. SU converted some of their pumps to transistor switching which didn't work very well & later modified the circuits for more reliable "solid state" operation. One major vendor refused to sell the SU version of the transistor switching type pump until SU corrected their design.

If a transistor conversion with points is attempted, the circuit design must take care to not have too little point current or the points will fail to make reliable contact.

I believe one of our forum members (Dave D.) does a solid state conversion which also replaces the points with a mercury switch & gives the best of both worlds.

Each of these "fixes" has enthusiastic followers & I won't attempt to argue their merits. As said above, I believe that a points type pump with the "correct" diode will last a very long time & is the lowest cost alternative.

Each can make their choice. The whole subject is somewhat like "what is the best motor oil"
D
 
Hi Dave,

As usual, great info.

I have a few diodes from previous rebuilds or pos/neg conversions. Is there a simple test to determine if they are still good or not? (obviously, I'm not a whiz with electrical testing but can usually follow simple directions /ubbthreads/images/graemlins/grin.gif )

Cheers,
John
 
Yep John, take an Ohm Meter and set it up for a resistance check.Diode will read a short in one direction and virtually open circuited in the other.---Keoke
 
Well yeah thats true Dave.However, when choosing the diode over the Mylar capacitor some thought needs to be given to the failure modes of the two components. In the event the diode fails it is just that it is failed.On The Otherhand,the Mylar Capacitor has the ability to heal itself.Additionlly,the ability of the Mylar capacitor to accept charge is much much better than the old wax paper ones and they are very effective in this role.---Keoke
 
Keoke, FYI:

Diodes can fail open or shorted, Mylar Capacitors can, self heal, fail open or shorted. Neither are the best choice alone. The combination is much better (even if the failure probability goes up because the're are two components). Purchase overrated components like you mention earlier and the probability of failure will be small AND your points will live a long, slow pitting life. IMHO go the total electronic route and you're 5 to 10 times better off than with those mechanical points.
 
GEEZ Thom P, There for a while I thought you were gonna disagree with me.--Keoke- /ubbthreads/images/graemlins/laugh.gif
 
[ QUOTE ]
...read a short in one direction and virtually open circuited in the other...

[/ QUOTE ]

Thanks Keoke .. I was able to chuck most of the diodes. At least the one I put in the pump checked out o.k.!

/ubbthreads/images/graemlins/cheers.gif
John
 
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