A 521 in Massachusetts

[Crashtd420]

1 hour ago, d.p said:

Oh and my passenger side door spring broke yesterday and I think I almost prefer them without it.  My drivers side never had one and the door was always much easier to open and close and not my passenger side is too.  

Those springs should not effect how you door opens or closes.... it only keeps it open if you open the door all the way.... 

 

[d.p]

1 hour ago, Crashtd420 said:

Those springs should not effect how you door opens or closes.... it only keeps it open if you open the door all the way.... 

 

 

They defiantly apply some resistance when you open it, or at least I assume it did with the difference between my driver and passenger doors having one or not having one.  

[Crashtd420]

So my fuel system still hates me, I took it for a ride last night and by the time I got back home I had just about no fuel pressure.... 

I had initially not added a restrictor in the return line because I was able to achieve fuel flow and 3.5 psi at the carburetor.... 

I still think the Carter doesnt like an external regulator.. so I bypassed the regulator and added a restrictor... 

Last night just idling I had 3.5 psi like I wanted. Then this morning I had about 5 or 6 psi.... 

The only good thing was the pressure stayed consistent,  so I'll try a slightly larger restrictor and see if I can get it to maintain closer to 3 psi... I'm actually using my spare air correctors, they fit perfect inside a 1/4 inch hose....

[Charlie69]

Sounds like the Carter pump pressure is all over the place.

 

Have you changed to a meter restrictor like the OEM one or are you trying by restrict with an adjustable valve?

 

Is your tank and pickup tube clean?  Reason I ask is I just had a 71 521 tank that the pick up tube was completely blocked.  I had to unsweat the tube from the tank and clamp it in a vise  and hammer a stiff rod through to get some flow.  Then I had to take a map gas torch and heat the tube red hot to born out the rest of the tank sealer.  This is why I do not recommend or use tank sealers.  With all the chemicals in the gas today I do not know of any that with stand the chemicals in the gas of today.

[Crashtd420]

2 hours ago, Charlie69 said:

Sounds like the Carter pump pressure is all over the place.

 

Have you changed to a meter restrictor like the OEM one or are you trying by restrict with an adjustable valve?

 

Is your tank and pickup tube clean?  Reason I ask is I just had a 71 521 tank that the pick up tube was completely blocked.  I had to unsweat the tube from the tank and clamp it in a vise  and hammer a stiff rod through to get some flow.  Then I had to take a map gas torch and heat the tube red hot to born out the rest of the tank sealer.  This is why I do not recommend or use tank sealers.  With all the chemicals in the gas today I do not know of any that with stand the chemicals in the gas of today.

Ya I'm not a fan of the Carter pump anymore. I'm planning to get one of those facet pumps you mentioned before .... 

 

And yes I'm trying to mimic an oem setup, I am using a restrictor now... 

The reason i used the adjustable valve was to troubleshoot.... 

 

As far as the tank it's good, I had the tank cleaned and sealed years ago and when I did the modifications last winter I did reseal it with some stuff called redkote  ... same as what the shop used before, good stuff.... 

This did not mess up my pickup tube because mine is actually removable. When I cleaned the tank I removed the old pickup tube and had them weld an NPT bung in place. I then used a threaded marine grade pickup tube, its trim to length and wont rust... 

[Charlie69]

Good idea on hte bung.  The original pickup pipe is silver soldered in.

[Stoffregen Motorsports]

Back to voltage drop. When you first start an engine with an alternator, sometimes the alternator doesn't excite until it reaches a certain RPM. When you experienced low pressure, was that after you revved the engine, or right after startup? Or was the engine even running?

 

I would check again with the engine running after a few blips of the throttle.

[Crashtd420]

4 minutes ago, Stoffregen Motorsports said:

Back to voltage drop. When you first start an engine with an alternator, sometimes the alternator doesn't excite until it reaches a certain RPM. When you experienced low pressure, was that after you revved the engine, or right after startup? Or was the engine even running?

 

I would check again with the engine running after a few blips of the throttle.

No the voltage is fine.... 

I actually thing the Carter pump doesnt like having a regulator after it.. 

Since I got rid of the regulator and placed the return line at the carburetor the psi has stayed more consistent.. with the current size restrictor I have in the return line I have had a consistent 4psi....

I'm hoping I can open the restrictor up a little and get the psi down to the 3.5.... 

Raining today so I'm hoping to get back into it this weekend.... 

[Crashtd420]

I also found this little write up about fuel filters... I always assumed I should see it full till I read this.....

 

"Most clear plastic fuel filters have the outlet pipe down inside the paper cone, so when the filter is upright, the fuel only has to touch the bottom of the filter paper to get through to the outlet.

But as the filter paper clogs up, the fuel has to climb higher to find clean filter paper.

So for those filters, a near empty filter is good, but a full filter is toast and should be replaced.

If the filter is mounted horizontally, all that still applies except that when new it will look about 1/2 full.

The filter itself is telling you if it's still good or not."

 

This basically what I have seen, so it makes sense to me....

 

[mainer311]

I concur. The wicking effect of the paper allows it to still be effective even without being submerged.

[Crashtd420]

27 minutes ago, mainer311 said:

I concur. The wicking effect of the paper allows it to still be effective even without being submerged.

For my own sanity I plan on cutting my old filter open just to see how it is constructed.... atleast I can stop obsessing over something that doesn't matter.....

Hopefully the psi remains constant and I can be done with this.....

[Crashtd420]

So far things are working out.... 

Psi seems to be where I want it, still need to take it out today and see what it's like after a drive.....

Also the way the wix gas filter is made you definitely want the outlet facing down not up, its flush with the bottom of the filter....  so I switched it back to where I had it originally...

[Crashtd420]

Back to driving myself crazy.....

After a ride around town pressure on the gauge went from 4 to 2.... 

When I got back I decided to go to a smaller restrictor.... this did increase the pressure but then I remembered something and also wondered....

Does heat effect the gauge?

There is a small plug on the side which the instructions say to pierce with a pin.... I think that has something to do with ambient air temperature.... so for the hell of it I made sure the hole was good.....

 

 

[Stoffregen Motorsports]

You've got something funky going on. I've never had as much trouble with fuel pressure as you are having.

[Crashtd420]

8 minutes ago, Stoffregen Motorsports said:

You've got something funky going on. I've never had as much trouble with fuel pressure as you are having.

I might just be me... 

It's getting better in my opinion, driving wise but I agree something is up.... 

That's why I started wondering about the gauge.... I was using a really cheap gauge before and dont remember seeing the fluctuation but it hazed over and I couldn't read it anymore. So I decided to get what I thought was a better gauge which was oil filled... might not be the right choice.... maybe I'll get another non oil filled gauge and see if the readings change....

[Crashtd420]

Son of bitch seems I may have been right about the heat......

Did some reading and found some information.....

 

"Bottom line, a common liquid filled pressure gauge is very susceptible to heat, changing its reading with the temperature of the gauge. Imagine that; engine bay temperatures can rise as much as 200-deg. Fahrenheit from cold to hot and we're using a fuel pressure gauge that changes it's reading with temperature... how does this happen? The simple explanation is when the glycerin used to fill the gauge heats up it expands, and being inside a sealed container (the gauge case), the internal case pressure rises. Internal gauge case pressure can increase as much as 1-9 PSI above atmospheric pressure when hot.

 

What difference does it make? Well, for every 1-PSI of pressure rise inside the case, the needle will fall 1-PSI. Of course, the higher the oil temperature, the higher the internal pressure, and the deeper the reading on the gauge falls. In extreme examples the result is like entering the "Twilight Zone"; take a carbureted engine with 8-PSI fuel pressure, and a hot gauge with 8 PSI of internal pressure, the pressure gauge went from reading 8 PSI to 0 (zero) PSI... is it any wonder racers get a little tense now and then?

 

Not every liquid filled gauge will get that hot and drop that far, but experience shows it's common for enough temperature rise to create the illusion of a 3-5 PSI drop"....

 

[datzenmike]

Just so you know, the restriction in the return is not intended to adjust the fuel pressure. It's only large enough so some  cool fuel circulates past the carburetor and small enough that the pump has to push against it to build pressure. The pump should have it's own regulator OR a regulator added but only to drop the pressure. If you increase the restriction hole size the pump will only pump harder/faster trying to reach it's regulated pressure. Taken to an extreme and the restriction removed, the pump would run at full tilt never reaching any usable pressure.

[Crashtd420]

31 minutes ago, datzenmike said:

Just so you know, the restriction in the return is not intended to adjust the fuel pressure. It's only large enough so some  cool fuel circulates past the carburetor and small enough that the pump has to push against it to build pressure. The pump should have it's own regulator OR a regulator added but only to drop the pressure. If you increase the restriction hole size the pump will only pump harder/faster trying to reach it's regulated pressure. Taken to an extreme and the restriction removed, the pump would run at full tilt never reaching any usable pressure.

Ya I'm starting to understand it more and more.... 

Any idea what a stock diameter hole is for a return line restriction ?

I have it currently drilled to .090 diameter.... 

I'm fairly certain it's been the gauge messing with me this whole time...

[Charlie69]

Crashed I think I have a spare L20B fuel return "Y" pipe.   I will look tomorrow.  I think I know where it is in my garage.  LOL

[Stoffregen Motorsports]

18 hours ago, Crashtd420 said:

Ya I'm starting to understand it more and more.... 

Any idea what a stock diameter hole is for a return line restriction ?

I have it currently drilled to .090 diameter.... 

I'm fairly certain it's been the gauge messing with me this whole time...

Stock went out the window when you installed a Weber and an electric fuel pump, so the stock size orifice is not going to be the answer. The right answer for you is still to be determined...

 

Starting over, I would keep the Carter pump, ditch all the restrictors and return lines, run a good quality low pressure regulator with the gauge mounted on the regulator, have one hose going to the carb and call it done. Built this setup dozens of times, never had a problem with pressure.

 

 

 

[Crashtd420]

2 hours ago, Stoffregen Motorsports said:

Stock went out the window when you installed a Weber and an electric fuel pump, so the stock size orifice is not going to be the answer. The right answer for you is still to be determined...

 

Starting over, I would keep the Carter pump, ditch all the restrictors and return lines, run a good quality low pressure regulator with the gauge mounted on the regulator, have one hose going to the carb and call it done. Built this setup dozens of times, never had a problem with pressure.

 

 

 

I know what you're saying but I kind of like the return line to keep the fuel moving.... 

As far as starting over I'm going to start with a new gauge first and see what that tells me....

all ready ordered.

After that I can plumb this any way I want if I need to ....

Its become more of a science experiment to me know.... 

Truck still hasn't left me stranded but before if I did a long full throttle pull getting on the highway it would actually seem like its was running out of fuel, after I let out it would recover and drive normal....

I haven't really had that issue since these changes, but I know I'm chasing that pressure number from a fluctuating gauge.....

I'll get it eventually....

[Charlie69]

21 hours ago, Stoffregen Motorsports said:

Stock went out the window when you installed a Weber and an electric fuel pump, so the stock size orifice is not going to be the answer. The right answer for you is still to be determined...

 

Starting over, I would keep the Carter pump, ditch all the restrictors and return lines, run a good quality low pressure regulator with the gauge mounted on the regulator, have one hose going to the carb and call it done. Built this setup dozens of times, never had a problem with pressure.

 

 

 

Using the stock L20B fuel "Y" on my 70 521 and on my 84 and 86 720s using the stock Z24 fuel "Y" works fine with the Weber swap.

 

The way these work is the metered orifice is sized to restrict the flow of fuel returning to the tank and there in that process creates approximately 3.5lbs back pressure even at WOT.  This does not mean that you can use a fuel that puts out more than 4lbs pressure, because much over 3.5 lbs pressure will push fuel past the needle and seat.  By having the metered orifice fuel return to the tank this vastly improves the fuel delivery to the carb by helping to keep cooler fuel going into the carb.  

 

On the L20B fuel "Y" I suggest taking a piece of fuel hose the length of the fuel pipe on the Fuel "Y" and split the hose length wise to slip over the pipe to help with vapor locking.  In theory the moving cool fuel should "not" vapor lock but on 122^O days I have had my L20B vapor lock.  The stock placement of the L20B fuel pipe is just above the intake manifold.  This happened with married intake and exhaust manifolds and has not happened since I changed out to a set of unmarried manifolds.  I still wrap the fuel delivery pipe with fuel hose as a precautionary measure.   I hate to wait on the side of the road for my fuel line to cool down enough to drive again.

Edited September 28, 2021 by Charlie69

[Stoffregen Motorsports]

A lot of new cars and trucks do not use a return anymore. The theory is that friction from moving fuel causes it to heat up, whereas in the past, it was thought that flowing fuel is what kept it cool. Not true anymore.

[Crashtd420]

Took a picture this morning,  you can see the datsun warming up on a 45 degree morning,  Nissan will be staying home.... 

 

[Charlie69]

Someone likes black!  LOL Looks good.