[Gator67]

I replaced the fuel pumps on two of my cars in January (Delphi MF0154 on my 68 Firebird, Delphi MF0100 on my 67 GTO) and neither lasted 100 miles. The former just died while idling in my garage...it doesn't pump any fuel at all. The latter just delivers weak spurts. I've replaced both pumps roughly 2 years ago as well for similar issues. Are there any good options for mechanical fuel pumps these days? I've set-up high quality fuel systems for our fuel injected pro-touring cars, but really wanted to keep these cars simple and factory appearing.

[moneypit]

I've had good luck with the Carter high performance mechanical pump. I run one on my 467 with dual Edelbrock 750's. 3/8" line, inline filter between tank and pump and pump to carbs.

[nUcLeArEnVoY]

I just use a Carter stock replacement pump for my W72 400 and it's been fine after 5+ years. If I recall from when I tested it; it puts out like 8.0-9.0 PSI of pressure. That happens to be right in line with the spec per the service manual. The later 70's Qjets with the smaller nitrophyl floats ran under higher pressures.

[JBanna]

I use a Carter Street pump on my 78, and it seems to do the trick ...

[srmmmm]

I am running an Edelbrock Performer mechanical pump. No issues in 2600 miles over the course of 18 months. 110 gph with an internal regulated 6 psi.

[steve25]

So many of what you call pump failures in about a two
Year span leads me to believe you have other issues going on in both of those cars, like the the pumps are sucking air .

[JLMounce]

Agree with Steve on this. If they are failing repeatedly and that quickly, I'd be looking for a downstream cause.

How old are the fuel lines? When was the last time the sock on the sending units was changed? Those original socks, or socks from as late as the early 90's can become brittle and cause a starvation issue when E10 fuel is being used.

[P@blo]

Been through this on a few of my cars. Start by replacing the fuel tank and sending unit, then work your way through the lines if necessary. No issues with Delphi big can pumps here either.

[Gator67]

Installed a new tank and new fuel lines in the goat about 15 years ago. I replaced the sending unit two years ago along with all the rubber hoses when the first pump failed. Essentially the same deal with the Firebird, although the tank and lines are a few years newer. I'll replace the lines again I guess, along with the socks. I ran a camera down both tanks and they look pristine.

[65 Lamnas]

Originally Posted by Gator67

I replaced the fuel pumps on two of my cars in January (Delphi MF0154 on my 68 Firebird, Delphi MF0100 on my 67 GTO) and neither lasted 100 miles. The former just died while idling in my garage...it doesn't pump any fuel at all. The latter just delivers weak spurts. I've replaced both pumps roughly 2 years ago as well for similar issues. Are there any good options for mechanical fuel pumps these days? I've set-up high quality fuel systems for our fuel injected pro-touring cars, but really wanted to keep these cars simple and factory appearing.

I haven't tried their fuel pumps, but I've been VERY impressed with everything I've bought from RobbMc. I think they offer 2 different mechanical pumps for our Pontiacs.

https://www.robbmcperformance.com/pr...ontiac550.html
https://www.robbmcperformance.com/pr...ntiac1100.html

I saw your desire to keep it "factory appearing", and these 2 pumps probably aren't, but the other suggestion would be to keep an eye out for an NOS AC-Delco pump on marketplace or E-Rape.....

[steve25]

Keep in mind that new everything does not guarantee that the clamps on any hose to steel line connection points are as tight as they need to be.

Many times I have seen a air suction point yet no discernible fuel leak.

[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.


.



.

[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.


.



.

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.

[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 .

[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.

[HWYSTR455]

I've seen the roll pin come out of the arms before, maybe that's because the arm was under too much pressure from being the wrong arm, dunno, but makes sense.


.

[Shiny]

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.

I remember seeing this post and it didn't sink in.

Thanks for bringing this up again!


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So when I installed a Delphi pump that had low enough pressure to avoid overpowering my carb inlet, I may have also sentenced it to a short life?

Hmmm.... I will have to check this!

Do you know if the difference in arm geometry affects the pump stroke?

If so, I now wonder if these new aftermarket pumps have reduced pump volume because of the "wrong" arm? If so, maybe this contributed to the amount of cranking I experienced to fill my carb when the bowl was dry?

I kind of doubt it because of the flow ratings but it's a thought....

Mike

[68bird400HO]

Originally Posted by Shiny

I remember seeing this post and it didn't sink in.

Thanks for bringing this up again!


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So when I installed a Delphi pump that had low enough pressure to avoid overpowering my carb inlet, I may have also sentenced it to a short life?

Hmmm.... I will have to check this!

Do you know if the difference in arm geometry affects the pump stroke?

If so, I now wonder if these new aftermarket pumps have reduced pump volume because of the "wrong" arm? If so, maybe this contributed to the amount of cranking I experienced to fill my carb when the bowl was dry?

I kind of doubt it because of the flow ratings but it's a thought....

Mike

I don't think the arm difference affects the flow or volume. My bird was running the same as with the old pump for the 100 miles that the new pump lasted.

[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?