A new one today. Early this morning, hard acceleration from a traffic light. I shifted through the gears into 4th. I thought I missed the gear because the engine seem to lose power. Put it into neutral and pumped the gas, which didn't seem to do anything. Then it stalled out completely. I rolled into a 7-Eleven parking lot and the car would not start back up again. After a while it started again, but still stumbled, and then stalled again. Got it towed home and took a look. Fuel bowl was completely empty. I disconnected the fuel line below the filter. The line was completely empty. No fuel coming from the fuel pump. I sprayed carb cleaner in the carb and it started up for a second. Then I poured some gas in the carb and it ran for about 10 seconds.

Did the fuel pump catastrophically fail from a hard acceleration?

1972 Cp. SB 383 4 sp

 

You may have dislodged rust or a piece of disintegrated sock at the sender. You can easily shine a light into the tank to inspect for schmutz on the bottom (and an adequate level of fuel ), then pull the S-hose at the pump end of the line that comes from the tank to see if the line is free-flowing. Next disconnect the fuel inlet at the carb and crank the engine – you should get a healthy flow of fuel (catch it however you can so it doesn't jet across the garage).

If you have fuel at the S-hose but no fuel at the carb, then the pump died somehow. If you have a pressure gauge that you can test the fuel pressure at the carb, it should be ~7 lbs, +/-.

 

I agree I would start by shining a light into the tank. If everything appears OK. Then I would pull the S hose, (at the end of the hard line on the frame rail) between the hard line and the fuel pump. Does fuel flow out of the line? If not, try blowing a short shot of compressed air backwards up the line. What happens? Look in the tank again.
Still no flow out the line. Investigate that first before buying a pump.
Connect a short section of fuel line to the pump in place of the S line. Put the end in a gas can. Crank engine. Does the pump pull fuel out of the gas can?

 

So it was a blown up fuel pump after all. The connection between the rocker arm and the push rod broke.

I got a new pump from NAPA, but the fitting for the hard line from the pump to the carburetor was a different size. I think the old pump is a half inch connector, but the new one is a 3/8. What is correct? The old pump was jerry-rigged by another mechanic to function. I like to get the correct OEM hardline.

 

The outlet of the fuel pump is for 3/8" hard line. It is an inverted flare connection, and uses a straight-thread 5/8-18 thread size.

They should have sold you part number DFP MF0026. This is the pump with the 3 connections, which allows for the fuel return line hookup. It should cost $40.00. What did they sell you?

Your fuel line should look like this:




Lars

 

Yep. I believe that's the one I purchased.AMF0026 Delphi


I purchased a generic hard line from autozone, but the nipple on the end of the flare is not long enough to seat inside the fuel pump fitting.

can I assume that the OEM Hardline will work?

 

Buy the correct hard line. Autozone does not sell Corvette fuel lines. If you want to fabricate your own line, buy the pre-flared 3/8" inverted flare brake line sections. They have the correct 5/8-18 inverted flare fittings installed.

 

Thanks for the quick replies Lars,

I think that's what I purchased. But the threaded ends were not long enough. It needs to be about a quarter inch longer than this one. Was just trying to get the car back on the road for the weekend, but at this point that's not happening. So I want to get the correct setup.

Also, now that I've gotten more into it, I realized it might not even be the correct pump for my carburetor. I have a Brawler 670, that recommends 6.5 psi. The Delphi pump has a range of 7 to 10 psi.

 

That's the normal, standard length of an inverted flare fitting - you're not going to find anything, or need anything, longer than that. If that fitting, assuming it's the right size, does not seat against the pump's inverted flare sealing cone, you have a problem with the pump. But I've never seen that happen.

But is that really a 3/8" diameter fuel line..? Looks like 5/16"... have you checked it? Is your inverted flare fitting a 5/8" thread fitting? It looks like 1/2", which won't work... you can't thread a 1/2" fitting into a 5/8" threaded hole.

...And you can't use an OEM hard line for a Brawler carb. You have to fabricate your own custom line for the custom carb, and you'll need to run an in-line filter if you are not running the dual in-carb filters on the Brawler. You can e-mail me for my fuel line fabrication paper for some fabrication techniques and ideas.

That's also the only psi spec you're going to get on a new replacement pump. It will work fine with the Brawler, but it can cause problems with a Q-Jet, which won't take much more than 7.

 

Thank you again for the feedback Lars.

​​​​​​Here is where I'm at. The Delphi pump am0026 from AutoZone does indeed use the half inch threaded fitting with a 5/16 hose. Also, the female connector mounted to the bottom of the pump is too deep for a standard flare fitting. I looked at another one from AutoZone and it was the same way. So it seems it's a problem with their stock.

I could just grind down the end of the female fitting on the AutoZone pump, to reduce the depth and allow it to properly see the 5/16 - 1/2-in repair fitting that I have, but I would rather have the correct pump in the first place. I assume if I order one from a reputable distributor like Summit, Top Flight ,or Ecklers it would have the correct size female fitting. I also realize that the stock fuel line won't match up exactly, but I'm planning on modifying the top end of it to use an inline filter and connect to the carb. I didn't realize that the Brawler capable of having internal filters. So I'll look into that as well.

While I'm always up for buying new tools, and I'd love to fabricate my own lines, I have an event coming up in a few weeks and I'm not sure I'll have the time for that.

Original fitting on the right. New fitting on the left that threads into the AutoZone pump, but isn't long enough to seat correctly


Thanks again, Scott

 

The Delphi pump should not have a 1/2" thread. It is 5/8". If it's 1/2", it's wrong.

 

I can't speak for all of them, but the two I got from AutoZone were definitely incorrect. Any thoughts on other brands?

 

I have two of them here in the shop, and they are both correct. If you can't find a good Delphi, use Carter part number M6955. I've never seen one of those pumps with a 1/2" threaded outlet. They are all 5/8" for a 3/8" fuel line. I think you have a line and fitting problem - not a pump problem. How are you measuring the pump female threads? Are you measuring across the minor diameter of the female threads? If so, the 5/8" threads will measure at 1/2". You have to measure the threads on the major diameter, which will be 5/8". They don't make that fuel pump with a 1/2" threaded outlet.

 

I do believe I have entered an alternate universe. Or something.

I got a Carter pump m6955. It is still not the same as my old pump. It uses the smaller sized fitting. Which is 1/2 in threaded on a 5/16 tube. It also seems to be missing an insert for the flare to seat against. Which would explain why the flare isn't seating inside the pump fitting. Here are photos of both pumps and tubes. Photos rotated when I uploaded. in the first photo The Carter pump is on top the old pump is on the bottom. You can see the fitting in the new pump is completely bottomed out and still not seated. The old pump seats before all the threads are in.

My old pump and flare line are on the top, the new Carter pump and smaller flared line are on the bottom


My original pump on the left. The new Carter on the right. There seems to be a seat inserted in the fitting on the old pump, but not on the carter.

Closer look at the Carter pump

This is my old pump.

Here two flare lines again. My old one on the left with 5/8 thread on a 3/8 tube. On the right the one that fits in the Carter pump, half inch thread on a 5/16 tube