"Standard" Stude V8 fuel pump vs. Avanti R1 fuel pump

[Mark L]

What are the differences between a "standard" mechanical fuel pump for a Studebaker V8, such as a 259 or 289, versus a mechanical fuel pump for an Avanti R1 289? Is the flow rate and/or output pressure higher on a R1 pump to accomodate the Avanti's fuel return line to the gas tank?

Edited April 22 by Mark L

[Dwight FitzSimons]

The job of a high-performance engine is to consume more fuel/air mixture, and extract more HP.  For that reason the R1 fuel pump has a higher flow rate.  It is similar in construction to a 259/289 pump, but is larger (in diameter) than a 259/289 pump.  Others can quote numbers for the two fuel pumps.  For comparison purposes below is a pic of an original 259/289 fuel pump.

--Dwight

 

[Mark L]

Thanks. I had heard there were differences between the pumps, but I don't know what they are.

A few weeks ago I got the return line reconnected at the pump where it had been capped off in the past, and I installed a check valve in the return line at the tank, and replaced all the rubber lines. The test drive to fill the tank was fine. This past Saturday I drove the Avanti to a SDC chapter meeting, and it was really struggling. I punched the gas pedal to leave a four-way stop, and the engine bogged down repeatedly in a rythmic kind of way. It was fine on flat ground, but I couldn't accelerate going uphill like it was starving for gas. It was about 75 degrees on the way to lunch. On the way home, I didn't have any problems. Both the ambient temperature and the engine were about 5 degrees cooler going home.

I'm just wondering if the pump is going bad, not the correct pump, or something else I should check. This photograph will help. I also have a '62 Lark Daytona with a 259, so I'll compare the two pumps.

Edited April 23 by Mark L

[A0136]

Mark

The R1 and R2 pumps are a little larger in diameter for more volume and have a stronger diaphragm spring for higher pressure.

The fuel pump on top is the standard 61-64  3155S pump 3 1/2 to 5 1/2 psi

The second pump is an R1  3509S pump 5-7 psi

The third pump is an R2   3508S  pump 5-7 psi

 

[Mark L]

Thanks, A0136. This is very helpful.

Today I was talking to a fellow gearhead about this where I work, and he suggested I install a fuel pressure gauge and measure the output pressure under various conditions to help troubleshoot the problem. These numbers will help.

Edited April 23 by Mark L

[A0136]

Mark

There are 3 tests you will want to do.

pressure, volume and inlet vacuum 

They are outlined in the Avanti workshop manual.   

New filter?    There must be some reason the return line was capped off??? 
 

 

[Mark L]

I have a copy of the shop manual, so I'll be consulting it.

The current filter has a solid metal housing, so I can't see the condition of the filter without destroying it. I'm going to replace it to be sure it's clean. I'll cut the old one open to see what is inside.

The return line was capped off long ago, based on the patina of the plug and the poor condition of the hose. The maintenance receipts I have show the fuel pump was replaced within the past 15 years or so, but no reason as to why, or why the return line was capped off when it was replaced. It might have been the "solution" to this issue. Before I restored the return line to the original condition, it was running fine. That's why I want to test the output of the pump. It may have sufficient capacity under load with the return line capped off, but insufficient capacity under load when the return line is connected.

Edited April 23 by Mark L

[A0136]

Did you still have the original fittings.  I believe there is a restrictor in the fitting. 

[Mark L]

I don't think they are the original. Is the restrictor in the fittings at the pump for the return line? What is the inside diameter of the restrictor?

[A0136]

I don’t have a fitting that I can get to to measure the restriction. Hopefully someone else here does 

[Mark L]

Is the restrictor listed as a stand-alone part in the parts catalog?

[Dwight FitzSimons]

Mark L, which year Studebaker Avanti is your car:  '63 or '64?  The restrictor is at the fuel pump on '63s and up at the filter closer to the carb on '64s.

That the car's problem only began after you reattached the return line is suspicious.

--Dwight

Edited April 24 by Dwight FitzSimons

[mox]

If it’s of any help, I was able to purchase the fitting from Jon Myer a few years ago, he may still have them. Mine is a 63 so the fitting was on the fuel pump return.

[Rick Allen]

2 hours ago, Dwight FitzSimons said:

Mark L, which year Studebaker Avanti is your car:  '63 or '64?  The restrictor is at the fuel pump on '63s and up at the filter closer to the carb on '64s.

That the car's problem only began after you reattached the return line is suspicious.

--Dwight

Does anyone have a picture of this restrictor and return line to post?,,,

[Dwight FitzSimons]

5 hours ago, Rick Allen said:

Does anyone have a picture of this restrictor and return line to post?,,,

Which year?

[Mark L]

My Avanti is an early 1963 model with the return line coming off the side of the fuel pump. R1204.

The "T" fitting was still installed on the side of my pump. The port for the return line was plugged with a NPT pipe plug. I didn't remove the T from the pump since the line to the carburetor was still attached.

One of my suspicions was that the return line needed a restriction somewhere to maintain adequate flow to the carburetor. I mentioned I installed a check valve in the return line. I suspect the rhythmic nature of the problem may be from the fuel pump developing enough pressure in the return line to overcome the cracking pressure of the check valve. My theory is: the engine runs fine while the check valve is closed, but once it opens, the fuel flow back to the tank is unrestricted and causes reduced flow to the carburetor and the rough running. Once the pressure in the return line drops off, the check valve closes and allows fuel to resume flowing to the carburetor until pressure builds up again, then the cycle repeats.

Yes, it caused the car to buck between proper acceleration and poor acceleration as the cycle repeated itself. About one half to one second of running poor before switching back, then one half to one second of running well before switching back again. As long as I drove it easy, there was no problem.

Edited April 24 by Mark L

[A0136]

This is a picture from the work shop manual.

The second picture is a screen grab from a posting on rebuilding an R series pump.  
I had time to dig thru some boxes today and found the restrictor fitting from R1358. 
The third and fourth picture show the restrictor fitting. 
A #57 (.043) drill bit just fits snuggly. 

[A0136]

If you’re not worried about keeping original a filter like this would work. Just run a 1/4” hose down to the return line. 
this is a NAPA 3054 filter 

 

[Mark L]

I appreciate everyone's help. I'm definitely missing the return hose nipple with the .043 orifice. The one I installed is a standard nipple for a 1/4 inch inside diameter return hose. The inside diameter of the nipple is probably too large and allowing too much fuel to bypass back to the tank.

I checked my shop and parts manuals. The 0308-8 group of parts is for the return line, and one nipple p/n 1558295 is listed, but there's no other description, and the parts are not illustrated.

Is p/n 1558295 the correct nipple I'm looking for?

I'll call around to see if I can find one. If not, I imagine I can make a brass plug to fit inside a standard nipple and drill a .043 hole through it.

Edited April 25 by Mark L

[Mark L]

I called Myer's Studebaker Parts. They currently don't have any, but they make up another batch when they run out, so they'll be making more next week and sending one to me.

[Rick Allen]

On 4/24/2024 at 1:54 PM, Dwight FitzSimons said:

Which year?

Titled as a '64, round headlights, later production number, one of the last 809/810 produced, so it could be either one,,,

 

[Rick Allen]

1 hour ago, Rick Allen said:

Titled as a '64, round headlights, later production number, one of the last 809/810 produced, so it could be either one,,,

 

My car is all part, the engine is out for rebuild but I did find the fuel pump and the restrictor is on the fuel pump itself so I guess it's a '63,,,

[Dwight FitzSimons]

It sounds like your car's serial number is either R4833 or R4834, which IIRC is in the range of the "round-headlight '64s."  To me those are the most interesting Avantis of all.  Is your interior solid color and mostly like a '64?

--Dwight (R5255, R5272, R5407)

[Mark L]

From what I understand, the location of the start of the return line (at the fuel pump or closer to the carburetor at the fuel filter) is not model year dependent. It was changed at a certain serial number. The Authenticity Guide indicates return line at the filter is usually seen on later '64 models.

[Dwight FitzSimons]

13 hours ago, Mark L said:

From what I understand, the location of the start of the return line (at the fuel pump or closer to the carburetor at the fuel filter) is not model year dependent. It was changed at a certain serial number. The Authenticity Guide indicates return line at the filter is usually seen on later '64 models.

Yes, Studebaker made running changes and documented them by serial number in the Avanti Parts Catalog (a must-have for what you're doing).  Notice your car's serial number; it contains no year designation, as did all other Studebakers.  In fact, initially, Avantis DID include the model year in their serial number, starting with the first 1963 Avanti, 63R-1001.  Somewhere in the 3 thousands they removed the year from the Avanti's SN.

Those of us who have been Avanti fans since they were new generally refer to the round headlight cars as '63s, and the square headlight cars as '64s.  But, that isn't exactly precise.  The transition cars that had round headlights but mostly-64 interiors are considered by many to be '64s.  The SNs of those cars are about what yours is.

If you want to be authentic you should go by your car's SN to determine these issues in consultation with your Avanti Parts Catalog.

Years ago, I did a thorough mechanical rebuild of a '63 Avanti and had my nose in my Avanti Parts Catalog many times.  I also had taken many pictures of engine compartments of authentic '63 Avantis at Studebaker shows.  These were of invaluable help for things like the curvature of vacuum lines, type of fittings, etc.  I also had to re-create the return-line fitting as you are doing.  I can't recall the details, though, and the car is inaccessible.

Good luck.  Any of us on the AOA website (and SDC website) will be glad to help with any further issues.

--Dwight

Edited April 28 by Dwight FitzSimons