Fuel pump PITA

[Rich69shortfleet]

So, the fuel pump on my sb400 in my 69 C10 started leaking pretty bad. It was probably 25-30 years old so not a huge surprise. It was a pretty run of the mill stock pump when I put it on.

So, since the engine is basically stock I got the stock replacement pump that was readily available at the local parts store. It went on without much trouble.

So, I got it running after the new pump went on and it ran fine for a while and then started flooding out the engine. Come to find out that the run of the mill replacement pumps put out 7.5-9 psi of fuel pressure which is more than a stock Quadrajet really likes. Fuel was leaking out of the carb and into the intake pretty readily.

So, I decided to rebuild the carb since it has been a while. No big deal, used a good gasket kit and installed a new float just to be thorough. Since the only pumps that put out the more reasonable psi amounts (Edelbrock and Carter) cost a ridiculous $150 or more, I decided to put a fuel pressure regulator on the system instead. This would allow me to put on a typically available pump if I had a failure out on the road and with the regulator would be able to keep it going regardless of the pump I ended up with.

So, I got it all buttoned up today and it started right up. Shut it down and checked for leaks. All was good, had the regulator set at 4.5 psi. But, while I was messing around putting the air cleaner back on and rechecking all the connections, the carb started flooding real bad again and it wouldn't start since there was so much liquid fuel in the intake.

So, either the regulator stops regulating when the engine shuts down or it isn't working in the first place. So, I"m probably left with using one of the expensive fuel pumps anyway and I'm sure I can't return the current pump or regulator at this point.

Why can't replacement part manufacturers just make parts that will work with our old stuff without having to jack around to find the right stuff, spend more than is really needed and/or having to install yet more components just to make it would like it should in the first place?

My truck used to be one of the most reliable vehilcles I've owned, but this is ruining its reputation.

[1970cstblazer]

People chuckle when I boast of running NOS AC fuel pumps on my vintage rides. They are to be trusted more than anything made today. I don't run ethanol fuel in them, so that isn't a thing.

[Accelo]

Your issue isn't uncommon.
Fuel Pressure is determined by the spring in the pump, and they don't care about getting it correct. I am assuming the new pump is the crimped-style pump.
The pumps with screws can be taken apart, and the spring trimmed to adjust the pressure.
The options seem to be an OEM pump or adding a fuel pressure regulator.
I'm guessing the pressure regulator is also China. You may be able to have someone watch the gauge while the engine is shut down.

I agree. All possible value has been removed from almost everything. Guess that is the outcome when only price matters.
I just purchased a new pair of Levis. Took the information right off my old ones.
Old Levis were made in Mexico, the new ones were manufactured in China.
They were physically lighter than the old pair.

[Rich69shortfleet]

Originally Posted by 1970cstblazer

People chuckle when I boast of running NOS AC fuel pumps on my vintage rides. They are to be trusted more than anything made today. I don't run ethanol fuel in them, so that isn't a thing.

Yeah, I had the original pump on my L79 in the Chevelle rebuilt since no aftermarket pump would ever keep the Holley happy properly.

Nothing I drive gets ethanol. Luckily I live in a rural area where gas stations make a point to sell 100% gas at most places since there are still farm equipment and trucks around that don't want ethanol in them.

But geez parts manufacturers, just make a stock replacement pump that puts out the correct 5.5 psi for a carbureted small block. QJs are the most common carburetor on the planet yet they can't make a pump any more (that isn't a specialty pump) that will work properly with a QJ?

[Rich69shortfleet]

Originally Posted by Accelo

Your issue isn't uncommon. Fuel Pressure is determined by the spring in the pump, and they don't care about getting it correct. I am assuming the new pump is the crimped-style pump.
The pumps with screws can be taken apart and the spring trimmed to adjust the pressure.
The options seem to be an OEM pump or adding a fuel pressure regulator.

Yep, crimped style pump. Couldn't find anything else that is readily available for a reasonable price. Even the supposedly "will work correctly" Carter at $150 puts out 7 psi.

[Rich69shortfleet]

The Delphi MF0001 pump is harder to find but says it runs at 5 psi. I'm skeptical and am already tired of throwing parts at this thing and smelling like gas but I'm not sure what else to try.

Has anyone had any experience with this Delphi pump?

[67 twins]

Originally Posted by Rich69shortfleet

The Delphi MF0001 pump is harder to find but says it runs at 5 psi. I'm skeptical and am already tired of throwing parts at this thing and smelling like gas but I'm not sure what else to try.

Has anyone had any experience with this Delphi pump?

Several months back I had a couple different parts stores try to order that pump only for them to tell me they couldn't get it. Good luck

[72c20customcamper]

I was told if the pressure regulator doesn’t have a return once the engine is shut down it could bump up the pressure over what it’s set at . I bought a pump from Summit when I put the new engine in . It was a Delphi unit I bought a regulator and a gage . I put the gage in first and it was running at 5.5 psi so I never did install the regulator

Edit : Just looked at my receipts and it was this pump from Rock Auto they also have the 0001 pump for no return line

[Rich69shortfleet]

My fuel system and pump has just two lines, no return.

[RichardJ]

The Carter and the Delphi are the same pump.
I just went through the same mess with a pump for my 292 6 Cyl.
Inside the Carter and the Delphi box was a clear bag with instructions and the gasket. Both bags had the same part number tag on them. I called Carter and after some back and forth, he finally admitted, they were the same pump. Basically, someone in China makes both.
The 7 psi Delphi and the 5 psi Carter, both put out 14 psi.
I have a Jegs, 4 1/2 to 9 psi, Holley style regulator set at just below 5 psi. When I turn the engine off, the pressure goes up to about 9. The carb doesn't leak and I never checked to see how long the pressure stays up.

The Carter guy made the claim that they are aware of the problem and are in the process of fixing the problem in all their mechanical pumps.

[72c20customcamper]

Originally Posted by Rich69shortfleet

My fuel system and pump has just two lines, no return.

This is the one you would need

[72c20customcamper]

On my 68 I used this one no return line . Expensive but works well no regulator needed so far

[57taskforce]

Originally Posted by RichardJ

The Carter and the Delphi are the same pump.
I just went through the same mess with a pump for my 292 6 Cyl.
Inside the Carter and the Delphi box was a clear bag with instructions and the gasket. Both bags had the same part number tag on them. I called Carter and after some back and forth, he finally admitted, they were the same pump. Basically, someone in China makes both.
The 7 psi Delphi and the 5 psi Carter, both put out 14 psi.
I have a Jegs, 4 1/2 to 9 psi, Holley style regulator set at just below 5 psi. When I turn the engine off, the pressure goes up to about 9. The carb doesn't leak and I never checked to see how long the pressure stays up.

The Carter guy made the claim that they are aware of the problem and are in the process of fixing the problem in all their mechanical pumps.

Damn you could run a tbi off of that pump. Thats crazy high for a carb. The off the shelf orielly special pump on my K20 has never given me any trouble, and im runny an eddy 1405 which is supposed to be just as picky as a quadrajet on fuel psi. seems pretty crazy to have a 5 lb pump pushing 14.

[KQQL IT]

Got a nos for a 454 and it still made 9 psi
Added a holley regulator at 5 psi runs fine now

[Hugh in NC]

I just bought and installed this one...So far, so good.

https://www.summitracing.com/parts/TSN-JM1003BK

[Rich69shortfleet]

Originally Posted by 72c20customcamper

This is the one you would need

In reading some older threads on here it appears those have now become hit or miss with many putting out 9-10 psi.

Originally Posted by 72c20customcamper

On my 68 I used this one no return line . Expensive but works well no regulator needed so far

It shows rated at 7.5 psi which would still be a little high for a QJ.

[Rich69shortfleet]

Originally Posted by Hugh in NC

I just bought and installed this one...So far, so good.

https://www.summitracing.com/parts/TSN-JM1003BK

I saw those. They are an offshore knockoff of the Edelbrock 1721. Might be a workable choice. Are you running a QJ?

The other two options appear to be:

1. Edelbrock 1721, made to work with Edelbrock carbs that don't like anything more than 6 psi.
2. Carter M6900, some say rated at 6 psi, some say rated at 7 psi. Mixed reviews on them with some saying they USED to put out 6 psi but recent versions do 9-10 psi and even Carter has acknowledged the problem.

[1970cstblazer]

The original AC part number for the small can pump is 40987.

[1970cstblazer]

Originally Posted by 70STOVEBOLT

Do you know the Delco part number for the pump that fits a 1971 402 engine?

GM 6470424 or AC 40727

[Rich69shortfleet]

Originally Posted by 1970cstblazer

The original AC part number for the small can pump is 40987.

I actually found a few NOS versions of that pump on ebay. But wouldn't they go to ruin if ethanol laced gas were used with them? Like I've said above, I use only 100% gas locally, but if I have to travel sometimes gasahol is the only choice.

[1970cstblazer]

Originally Posted by Rich69shortfleet

I actually found a few NOS versions of that pump on ebay. But wouldn't they go to ruin if ethanol laced gas were used with them? Like I've said above, I use only 100% gas locally, but if I have to travel sometimes gasahol is the only choice.

Another one of those "your results may vary". I have ran a couple of them with limited amounts of E10 in them, and no issues. If there was to be a steady diet of the corn juice in them, then yeah, you might eventually have an issue with a ruptured diaphragm. That is the ONLY advantage of the new pumps sold today.

Best scenario is to score a correct vintage logo pump, and send it out to be rebuilt with a ethanol resistant diaphragm.

[Willshook]

The problem isn’t the fuel pump or regulator; you noted you overhauled the carb at the same time; there’s a mistake in there somewhere.

Regardless - don’t guess; CHECK the pressure.

I’ve had zero issues with name-brand replacement pumps having too high fuel pressure.

[72c20customcamper]

Originally Posted by Rich69shortfleet

In reading some older threads on here it appears those have now become hit or miss with many putting out 9-10 psi.



It shows rated at 7.5 psi which would still be a little high for a QJ.

Didn’t have any problems with the 68 with the QJ. I used it for about 1k miles changed it out to an older AFB .

Only times I’ve ever had a problem was with fuel boiling in the bowls . And that was when I had to use 10% E gas . I run non E in all my carbureted vehicles

The only truck /car I have with a QJ is my 85 K20 I did change out the fuel pump a few years ago to the Delphi unit no problems at all with it . But I guess it’s like everything you buy today it’s hit and miss .

[Rich69shortfleet]

Originally Posted by Willshook

The problem isn’t the fuel pump or regulator; you noted you overhauled the carb at the same time; there’s a mistake in there somewhere.

Regardless - don’t guess; CHECK the pressure.

I’ve had zero issues with name-brand replacement pumps having too high fuel pressure.

Well let's see, it was flooding out after the new pump but before the carb rebuild. It is flooding out after the new pump after the carb rebuild. The issue is the pump, not the carb. I've rebuilt enough carbs that I know what I'm doing there.

The pressure is over 10 psi with this pump. It appears the regulator can handle it on the first start up but when the engine is shut down the pressure climbs and floods the carb making a restart nearly impossible.

You do understand how a regulator typically works, right? They typically reduce the size of the opening for fuel flow so that the pressure on the upstream side of the fuel flow is lowered. However, when the fuel stops flowing, the pressure can still build on the upstream side to equal the pressure on the downstream side. I wish I'd understood this a little better before installing the regulator.

The ultimate answer is going to be a fuel pump with the CORRECT pressure output. The trick is actually finding one where that is the case and can be trusted to be the case. It is apparent that most manufacturers are more interested in selling parts than making parts that are actually correct for the application.

[Willshook]

Originally Posted by Rich69shortfleet

The pressure is over 10 psi with this pump.

You've of course verified this with a trusted gauge.

Yes, I know how it all works, thank you

Easy enough to test using a gravity feed bottle.

Good luck!