Mechanical Fuel Pump Options
 

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'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.

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.

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

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.

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 .

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.

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.

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.

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.....

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.

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 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'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.


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I've been really impressed by robbmc products so I just ordered his 550 pump, a filter and regulator for my 460 build. Already have his 1/2" pickup and his large 100 micron filter plumbed. I expect no issues.

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've had the same issues on the same day with 2 new pumps from Napa. One died close to the house and took that one back. They warrantied it for another and it goes about 4 miles from the house and dies. Napa just gave me my money back at that point. I ordered a different brand pump and put that on, it's been fine for 3 years. Over that period I dealt with this same issue on another car lol

I've come to the conclusion these store pumps from airtek, carter, AC it doesn't seem to matter, they are hit and miss. Sometimes you get a good one and sometimes you don't. Sometimes you get 2 bad ones in a row on the same day like I did lol

So anymore if I want mechanical I do one of 2 things. I'll either buy robbmc as they have been nice pumps that are rebuildable, or I'll buy one of summits high output pumps, like a 90gph or something similar (doesn't require a regulator) and those have been rock solid for me.

If I'm not buying those then I'm sticking a walbro in the tank,....done. there are no other options as far as I'm concerned anymore when it comes to fuel systems.

If you like the reliability of the intank setups but also want stock appearances. You can put the pump back on the engine and even run a fake fuel line.

I did that on my Chevelle when I went efi. Ran the dummy pump and factory steel line up to the throttle body that was soldered shut. Fooled everyone that looked at it LOL

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.

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

No problems with the Edelbrock here in 6000 miles

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.

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.

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.

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?

https://forums.maxperformanceinc.com...1&d=1772919008

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.

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...

https://forums.maxperformanceinc.com...1&d=1772987057

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.

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.

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 .

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...

https://forums.maxperformanceinc.com...1&d=1772995145

https://forums.maxperformanceinc.com...1&d=1772995179

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?

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.

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.

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?

https://forums.maxperformanceinc.com...1&d=1773075804
https://forums.maxperformanceinc.com...1&d=1773075842



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?

https://forums.maxperformanceinc.com...1&d=1773076220

Mike

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

The robbmc mechanical pump has to have a regulator with it. I didn’t realize that,, they used to be self regulated but they changed it a few years ago

Depending on the year some pumps used 3/8 mounting bolts and some used 5/16 bolts.

Interesting. This seems to contradict the information on the website/instructions, which indicates a regulator is not typically needed with the 550hp version of the pump (it is needed on the 1100)...it says 7psi +/- 1 and that using the vapor return should reduce it by 1psi. This seems to be in the ballpark of what I need for a Qjet. Was your experience different?

The instructions also suggest that if a regulator is needed, it should be a non-return version placed between the pump and carb. The problem here is that I seem to recall to function correctly, the pressure to the regulator should be like 3psi greater than the desired pressure.

Yes sorry… the 1100 pump used to be adjustable and they did away with it the save on costs.

I installed the AC Delco pump on the bird, and took her for a quick drive. Seems fine, but the pump has been sitting for at least 20 years, so we'll see how it holds up. These pumps are pretty expensive now, so rather than looking for a spare, I ordered a couple RobbMc pumps and the fittings I'll need to make them work in the Bird (and GTO). I plan on running a factory style line from the carb, but I'll put a -6 fitting somewhere below the alternator so from the top it won't look out of place.

https://forums.maxperformanceinc.com...1&d=1773169489

RobbMC and -8 all the way and vapor return.

I installed an Airtex 40710 in the GTO...it was unused, but an older USA made one in the red and blue box. Hopefully it will hold up for a while, at least until the RobbMc pumps get here. As Mgarblik suggested, I bench tested it first.

I had to use a different hard line to the carb because the outlet port is in a slightly different location than the later 40863 style pump (i.e., Delphi MF0100 pump I replaced). I do like the location of the ports better on the later style pump...the inlet tube on a 40710 points at the steering box, which is just a few inches away, so there's a tighter than ideal bend in the hose, and the location of the outlet makes it was impossible to get any of my 5/8 flare wrenches around the tube nut on the hard line. At least the goat's running now.

I have had good luck with the Carter 6907, my fuel pressure gauge runs 6-7 for pressure.