[64speed]

No problems with the Edelbrock here in 6000 miles

[mgarblik]

Originally Posted by carcrazy

I'd give another vote for RobbMc....excellent products and support.

The RobbMc pump is a really nice unit. I have one on my 500 HP street Pontiac engine and it's been flawless. Plus it can be rebuilt if ever needed. Great people to deal with too. Made in USA All that said, they are expensive and don't look exactly stock. If that matters to you, I would recommend bench testing any of the stock type replacement pumps before installing them. I place a 1' pipe over the arm and operate the pump with a hose in a 5 gallon can and the outlet going to a second catch can. Make sure the pump produces a nice full stroke of fuel on each stroke. Also check the arm and pin for slop, and play at the pivot point. They are all hit or miss. They are all Chinese junk as well. I have had numerous ones that would not pump fuel right out of the box. After putting a new one on the engine, I always fill the float bowl on the carb and run the engine with a pressure gauge dead headed on the carb feed line. If between 4-7 PSI, you can live with it in this test set-up. Over 7 PSI, that's too high and the float may not be able to control the pressure. Have had several that were in the 8-9 PSI range. That's too high.

[Gator67]

Was going to swap out the fuel pump on the bird with a AC Delco 40607 I found in a spare parts box, but when I removed the vent line from the failed pump on the car, fuel poured out of the line, and kept pouring out. The car was running great before the pump died, and filled the fuel tank, but I've never had fuel gushing out of the vent line before. Wondering what the issue might be? Fuel comes out of the supply line as well, but I expected that.

[mgarblik]

You didn't mention anything about the year, make and model of your car. You have a venting system issue but need to know what type of system the car has to suggest repairs.

[Gator67]

Originally Posted by mgarblik

You didn't mention anything about the year, make and model of your car. You have a venting system issue but need to know what type of system the car has to suggest repairs.

The one with the venting issue is a 68 Firebird 400 with A/C.

[Shiny]

Not sure I would worry about fuel coming out the vent line.

Here's a section of a tall pump I saved that was published by High Performance Pontiac.

Obviously there's no guarantee your pump is built the same but probably similar, even if a short can.

I am no expert but looks like the vent line was connected to an internal tube that had a small orifice sitting in the top of the pressurized outlet chamber.

If I'm wrong, I apologize but think it would be normal for gas to flow in the vent tube, just not high volume because of the small orifice. If vapor built up in that big chamber, it could vent through the line back to the tank, which I think was the purpose.

If you think the gas in the vent line is an issue, maybe cut the pump open and see if you can figure it out? Maybe that tube broke off?

If the pump was otherwise working normally, the only other thing I could imagine is if gas somehow backed up from the tank into that vent line and headed toward the pump. I don't remember where it exits on the float assembly but is there a chance your tank isn't venting and pressure is building up in the tank?

[Gator67]

Fuel was flowing from the tank through the vent line even with the cap removed, it stopped flowing after I siphoned about 5 gallons or so from the tank.

[Shiny]

If this sender is like yours the vent line doesn't drop down into the tank so seems impossible to siphon a lot ???

Update when you figure this out...

[tstroud]

Originally Posted by HWYSTR455

Keep telling everyone, just go electric, 1/2" hard lines as much as you can, leave little rubber as possible, AN connectors, bypass regulator, in tank pump.

I went through this years ago and bailed, never looking back. Been very successful results, same with many others.

As more and more cars go efi, it's only going to get worse. And replacements will become 'specialty' items with the prices skyrocketing. It's actually surprising mech pumps are still being made, the only requirements still in place is like 7 years, manufacturers are going to dump the mech pumps soon, there's no money in it.

If you want the OE look, gut a mech pump and just run a line thru it, hide the regulator. If you're not showing the car in a judging circuit, it doesn't matter, you're just being stubborn.


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.

I have had the same results recently. I thought I made a mistake on the Q jet rebuild since It was leaking fuel and stinky rich at idle. So I bought an Aces TBI setup to replace the Q jet. I put a tanks inc. tank with a Walbro pump, AN lines, fuel pressure regulator and fuel filter on the GTO in preparation for the TBI. I regulated the fuel pressure down to 5 psi to temporarily run the Q jet and now all my carb problems seemed to go away. I had the Carter big can mechanical pump on there and I think between the higher pressure and the pulses it was overpowering the needle and seat.
It runs nice now but I’m probably still going to install the TBI since it’s setting on the bench with the warranty ticking away.

[Gator67]

Originally Posted by Shiny

If this sender is like yours the vent line doesn't drop down into the tank so seems impossible to siphon a lot ???

Update when you figure this out...

Yeah, this one has me stumped. Also, was surprised that fuel from the supply line poured out until the tank was less than 1/4 filled.

Now that there's less fuel in the tank, I'm considering trying the AC Delco pump I found, but concerned something is amiss somewhere and don't want to risk ruining another pump. Maybe I should drop the tank to check out the sending unit & lines.

[mgarblik]

I looked through the 1968 factory shop manual for you. Unfortunately, for 1968 there is really no mention at all about the fuel tank and or the engine fuel venting system. Generally, the AC cars had a return line with a restriction in the 1/4" line near the fuel pump. The restriction in the line was quite small. If memory serves around .040-.045" hole There is usually only a small dribble of fuel in the vent line. Not absolutely sure but I think 68 would have a vented gas cap, essentially open to atmosphere. The carb float bowl is vented as well as an extra vent lever operated to be open at idle. Sorry, but that is all I could find .

[Gator67]

Originally Posted by 68bird400HO

I had fuel pump issues a few years ago and started a thread on it. I had replaced my leaking fuel pump and the new one died after about 100 miles. I did find the reason for the pump failure and started discussing it at about post #58. Here is a link to the thread at page 3.

https://forums.maxperformanceinc.com...=868529&page=3

In short, the failure isn't the diaphragm, it is the arm. The repops are using the wrong arm. It appears the repops copy the Delco body but are using the Carter arm which is a little different and sits a little higher at the eccentric contact point. This puts too much pressure on the arm when compressed and they eventually break, and the car dies instantly. There are some out there with the correct arm, the "Muscle Car Fuel Pumps" from Summit or Jegs but I am not sure if they are produced anymore.

You also could try to buy a repop and swap the arm. I was messing with that a little and just don't have the correct tool to uncrimp the aluminum to get the arm pin free. I think it would slide out if you could do that, though.

BINGO!

Removed the fuel pump and found two little pieces which came from the end of the arm that depresses the spring. I removed the arm myself to make sure there were no missing pieces that could have made their way into the engine. I got lucky. Good grief...

[Shiny]

Glad you found a reason for the pump failing. Thanks for sharing the painful carnage.

You can see some forming wrinkles in the sides of the arm in the section photo right where yours broke.

Maybe the steel they use is weak or the forming operation is just bad quality?

Unfortunately, there's no way to inspect that part of the arm on a new pump. The factory probably likes that!

What brand pump? It looks brand new....

You think this has anything to do with the unexpected fuel in the vent return line? Maybe there was more destruction inside the pump?

[Gator67]

Delphi MF0154, I bought it a few weeks ago from our sponsor…less than 100 miles.

[Shiny]

Originally Posted by Gator67

Delphi MF0154, I bought it a few weeks ago from our sponsor…less than 100 miles.

I was afraid you'd say that...

Same pump I installed but have zero miles and maybe 2 hours total time...

Fingers crossed I guess....

I did just add an electric primer pump inline so there's that if my pump breaks.... but I put in a momentary switch which would take the fun out of it.

[68bird400HO]

Originally Posted by Gator67

BINGO!

Removed the fuel pump and found two little pieces which came from the end of the arm that depresses the spring. I removed the arm myself to make sure there were no missing pieces that could have made their way into the engine. I got lucky. Good grief...

Yep, I had those same broken pieces fall out of mine too. I bet if you put the correct arm on, the pump would be fine.

Any tips on getting the arm out? I was trying to uncrimp the aluminum around the pin so I could recrimp in a new arm. I'm not sure what tool to get in there with.

[Gator67]

Originally Posted by 68bird400HO

Yep, I had those same broken pieces fall out of mine too. I bet if you put the correct arm on, the pump would be fine.

Any tips on getting the arm out? I was trying to uncrimp the aluminum around the pin so I could recrimp in a new arm. I'm not sure what tool to get in there with.

I used a hammer and large screwdriver I have no plans to reuse the pump, or buy another new one. My wife drives this car around town, so it has to be reliable.

I'll probably order up a RobbMc pump for this car as well as my GTO, since that one's down with a bad Delphi pump as well.

[Shiny]

I just sent a note and thread link to Delphi about this failure mode just to find out if they will actually respond. I don't expect anything back beyond "if your part fails, return it and try again.... you might get lucky next time".

But I noticed my pump was MF0155, not MF0154. I found it odd to have a unique PN (MF0154) for 1968 applications.

Anyone know the actual differences in the pumps for 1968 vs 1970? Is it only the apparent difference in vent line configuration (straight vs elbow)?

Their online specs do show a slight performance difference, which I also found interesting and unexpected. The 68 pump says max 8 psi, the 70 says max 7 psi. Really? Does this mean the 68 pump arm is stressed more for some reason?






I also found a note in their installation instructions to grease the inside of the arm cavity. I certainly did not do this. Anyone else put grease in that cavity and how important is this?



Mike

[HWYSTR455]

I have never heard of putting grease in the cavity, and not sure it would make a diff anyway. Pump should get plenty of lube from splash, and the grease would wash out in a short period of time.

Maybe it is meant for other makes/models? Still can't think of what would use that step.

I have heard of people using grease on SBC engines, but it's just to aid in holding the pushrod while installing the pump.


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[68bird400HO]

I think pumps can vary over the years with line routing and connections.