Fuel Pin Problem

[rebel horseman]

I wonder if I have a problem. When I pulled the diaphragm and pin tonight it was very reluctant to come out of the pump housing. Is this a normal issue with an aftermarket fuel pin?

When I pulled it out I found scoring in the face of the pin:








The first thing that jumps out at me is that I'm not getting full travel from my pin and I'm no where near the bottom where the fueling rate is the greatest.

What was surprising is the scoring that is there. The scoring was pretty deep at what I'm assuming is the idle position of the pin; the farther the pin travels downward, the lighter the scoring.

So is this normal? If not, what could be the problem?

[dazedandconfused]

I read on another forum about one of the companies having issues with a bad batch of material they received but don't remember who it was.

[Richie O]

If its a Denny T pin contact him and he will replace it. He did get a bum shipment of steel and as far as I know he has shipped a new one out to everyone who has contacted him.

[burnt_servo]

i'd just polish it out , put a dab of white lithium grease on it and put it back in

[KTA]

Probably nothing wrong with the steel. Just a failure to heat treat it. Even tool steels do not come in the proper Rockwell hardness for fuel cones in the standard bar stock shape you get from a metals supplier. If they were as hard as they need to be they would wreck all the tooling to machine them with unless you used a grinder to machine it, but its hard to cut threads with one of those.LOL I don't know what metal they use but you might could grind it smooth, then heat it dull red with a torch and the oil quench it in some vegtable oil. That would probably get the hardness where it needs to be. Depending on how it was made though it might bend like spaghetti when you do that, but that is a standard heat treating issue. If it does then you probably need to temper it so you could bend and straighten it. Its a lot of trouble for something that won't fuel any more max over a ground stock cone.

[Richie O]

Probably nothing wrong with the steel. Just a failure to heat treat it. Even tool steels do not come in the proper Rockwell hardness for fuel cones in the standard bar stock shape you get from a metals supplier. If they were as hard as they need to be they would wreck all the tooling to machine them with unless you used a grinder to machine it, but its hard to cut threads with one of those.LOL I don't know what metal they use but you might could grind it smooth, then heat it dull red with a torch and the oil quench it in some vegtable oil. That would probably get the hardness where it needs to be. Depending on how it was made though it might bend like spaghetti when you do that, but that is a standard heat treating issue. If it does then you probably need to temper it so you could bend and straighten it. Its a lot of trouble for something that won't fuel any more max over a ground stock cone.

Do you say that because the small pin does not touch the deepest part of a aftermarket " cone ". Like it is maxed out before the new " cone " pin gets to the bottom. My MH#2 is way deeper then a stock one that is ground. Thanks.

[KTA]

Yes the lever inside the pump can only push the pin out so far before it bottoms out against the boss that holds the pin. A stock cone can be ground to allow the pin to come out as far as the lever inside the pump can push it. This is one of the reasons a lot of aftermarket pins allow fuel to leak out as they allow the pin to travel to far. No extra fueling is gained because the lever inside the pump is still bottomed out. if you ever have a pump top off putting a gov spring in you can see exactly what I am talking about. You can also verify that your cone allows full pin travel at that time, or that it allows overtravel. In order to take advantage of the extra depth a aftermarket cone allows you need a longer pin. Of course this still doesn't allow any more fueling in and of itself, but it can reduce fueling at low boost which is benefecial when you have big injectors.

[Richie O]

Cool. Out comes the grinder.