V-band clamp for GM fuel pump

[Bitsyncmaster]

I have the Bosch 67317 fuel pump and was looking how the V-band clamp works with our tank.

Our tank lip where the V-band clamp mounts has a taper (wider near the tank, getting narrow at the top). So the V-band clamp will tend to pull up as it is tightened until it hits the little lip at the top of the tank opening.

My fuel pump thickness with the gasket non-compressed is 0.275".

My measurement with the V-band clamp (DMCH part) with the clamp lifted to the tank lip is 0.43". So if you press down on the pump as you tighten the clamp, that clamp will try to lift because of the taper. So have people had any leaking when you overfill the tank?

By the way my pump plate is 4.58" dia. and the gasket which came with the pump is a perfect fit for our tank. I was wondering if the DMC pump thickness is more than mine.

V-band clamps can be bought with that "V" thickness less then the DMC part. Was wondering if I should get another V-band clamp with that thickness (known as INSERT APEX WIDTH).

What V-band clamp part numbers have you users that bought for your GM fuel pumps?

[dmcnc]

I have the same DMCH clamp, and I usually hold the clamp itself down instead of the pump with the top end of the V-clamp flushing with the top of the pump (but over it, since it has a smaller diameter). I then tighten while holding the clamp to where the bottom side of the V-clamp will squeeze the neck enough against the pump to where neither will move. It will slip if you over-tighten. I've never had leaks (knock on wood).

I've seen folks use other style clamps like Hervey uses a flat one.

[Bitsyncmaster]

I have the same DMCH clamp, and I usually hold the clamp itself down instead of the pump with the top end of the V-clamp flushing with the top of the pump (but over it, since it has a smaller diameter). I then tighten while holding the clamp to where the bottom side of the V-clamp will squeeze the neck enough against the pump to where neither will move. It will slip if you over-tighten. I've never had leaks (knock on wood).

I've seen folks use other style clamps like Hervey uses a flat one.

That is probably the best way to hold it down. My rubber ring on the pump fits in the tank very tight so probably not much would splash out. It's just if someone overfills the tank where the seal is important.

[Bitsyncmaster]

I gave this some more thought and there really is no way the V-band clamp can apply downward force on the pump except for you putting pressure on the pump as you install it. These clamps are designed to apply clamping force when both sides have a large taper so when the clamp is tighten it clamps together without bottoming out on the "pipes".

I may come up with something but it seems to be working for others as is.

[Bitsyncmaster]

I pulled the OEM baffle out of the tank and put the new pump in. It is really tight and did not seem to get the pump seaded down all the way. I will have to look closer when I get time.

By the way this pump has the pickup cylinder offset from center. The DMC pump is centered. I wonder if the offset is enough to clear that stud that holds the OEM baffle. The offset can be removed by carefully taking the pump apart an putting the guide rods into the other holes.

Have any of you owner cut that stud out of the tank? I would guess is limits how low the new pump will sit.

By the way this pump has only one spring on one of guide rods.

[Bitsyncmaster]

Well I pumped the tank "dry" with the new pump. The tank was about half full and pumping was pretty quick then but the flow slowed quite a bit as the level got low. Not sure if that is normal or something is wrong with my setup. What I plan to do it test primary pressure when I have everything ready to start testing the fuel sender values.

That offset of the pump may be a good thing. I pulled the old fuel sender so I could look into the tank and that stud has about one inch of clearance from the new pump pickup fixture. That is when the pump pipes are pointed to the drivers side of the car like the DMCH pump is orientated.

I have not put the sender float on yet so that is my next test to verify it does not have clearance problems with the sides of the tank.

[dmcnc]

The tank was about half full and pumping was pretty quick then but the flow slowed quite a bit as the level got low. Not sure if that is normal or something is wrong with my setup.

Mine did this as well when I emptied the tank at the very end. Likely too much air in the pump to push the very last bit?

[Bitsyncmaster]

Mine did this as well when I emptied the tank at the very end. Likely too much air in the pump to push the very last bit?

It was pretty much a dribble at the end. It do however pretty much empty the tank. This was pumping into a 25 foot hose. It's nice to have the hose quick release so you can move from the drain hose to the car's hose.

[Bitsyncmaster]

I measured the clearance from the pump to the stud with my unmodified Bosch pump and it is 0.8".

So if the pump is modified putting it directly under the tank opening it would not clear unless you can rotate the modification to where there is the flat areas of the pump pickup. I may need to do that depending on how the float sits in the tank with the unmodified setup.

You can see if there is a clearance problem by looking in the OEM sender hole but you may need and empty tank to see it clearly. The other option is to cut off that stud. Remember you don't want any sparks made by a cutting tool. I would guess you could just use a hack saw blade cutting it by hand.

I also really had to pull hard on the pump to remove it from the tank. I think I will try some grease on the rubber ring to see if that will let it install and remove with less force.

[Bitsyncmaster]

Well there is only 4 inches of clearance at the front and passenger side of the tank from the pump opening. So if you want to use the sender, you have to rotate this pump pickup so the sender is facing the back of the tank. You pull the bottom white plastic off (held by two clips) and rotate the bottom to existing "rod holes". I also pulled the pump hose clamps off so I could rotate the hoses but you may be able to rotate them with the clamps on (wish I checked that). The bottom of those hoses are not clamped and wonder if they should be.

So it's not for a lot of owners since you have to be very careful not to break that plastic with the rework. If you need a replacement on the road you would install it as it comes and not put the float on until you get home to do the rework.

I wonder if there is a model that comes already pointed the correct way. Does the DMCH pump have the sender at the back?

This rework did put the pump directly under the tank hole. The large flat is at the back and it does just hit that stud in the tank. You can tilt the pump a little to clear the stud and probably be fine but then the pump sits at a very small angle from perfectly vertical. Not sure if I will cut that stud yet.