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1938 fuel pump installation--what is wrong?


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Restoring a 1938 Special from California. This is the pump that came with the 248 engine. We rebuilt it with a kit and installed it but the fuel line is too short. What is wrong? Should it be a two-stage pump? Which way does the fuel pump arm point when installed? Up or down? Been too many months since the engine was back together!

Pete Phillips

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You need to look at the 1938 Dealer Service Bulletins. There were two different fuel pumps available. One is the inverted bowl the other is the traditional style. Either you have the wrong fuel pump, or else it is upside down. If that pump came on the car, you have it upside down. I can't tell from your photo, will it bolt on the other way? The two fuel pumps take different fuel supply lines, so if the fuel pump came from elsewhere, it might be upside down, or it may be the wrong pump. I don't know enough about 1938 40 series to know from looking at your photo. 

 

 

IMG_20210803_233430441.jpg

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i agree the pump shown by Don and Gary would be the one i am familiar with for 38 Series 40.

 

@Pete Phillips I believe I may have one if needed. Let me know and I will check my parts bins.  If I do it would need a rebuild, however it is clean and in good condition.

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I suspect that may be installed upside down- to get the correct orientation the actuating lever should be pointing up.  Also note I think the “bowl” section of the pump can be removed and re-installed to get the correct location of the pump outlet.

Edited by Ray34
Correct text (see edit history)
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Pete,

 

One other choice- It has been rebuilt, The good-all AC castings and the original number is on the flange. The bad-The diaphragm was probably pre ethanol so I would replace it and it is painted silver. $50 plus medium flat rate postage.

 

Dave

 

  

421 AC.jpg

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Dear Pete,

Here is a good supplier of antique Buick fuel pumps:

Then&Now Parts

Tom Hannaford jr 

447 Washington St 

S Weymouth  Mass 02188 

781 335 1579

Email ourt1932@aol.com

Tom has been providing 31 Buick pumps for me for many years. Chuck Straub    straub31@charter.net

 

 

 

 

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On 8/4/2021 at 10:13 PM, Ray34 said:

I suspect that may be installed upside down- to get the correct orientation the actuating lever should be pointing up.  Also note I think the “bowl” section of the pump can be removed and re-installed to get the correct location of the pump outlet.

Ray34, you are correct, we reinstalled the pump with the glass bowl pointing up, rotated the bowl section slightly to get a closer fit with the metal fuel lines, and it is working fine but we have a bit of an oil leak at the block where fuel pump mates up to it, so this may not be the correct pump, but it was on this car when it arrived last year.

Pete Phillips

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Pete,

 

Does the pump have a part number on it? If it is Part number 1523703, that would be the correct Inverted pump for a 1938 40 Series Buick. It is possible that the gasket might be the cause of your slight oil leak if it is the correct pump. I think the inverted pump must be fairly rare. If that is one of them, please post a photo. It would be helpful for people to see what it looks like mounted on the engine. 

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The mounting boss on the engine itself is upside down when comparing Pete Phillips' engine to Gary W's engine. Anyone else notice that? It's hard to tell in Ray34's picture.

 

I suspect the pump on Pete Phillips' car is wrong, and we have not got to the bottom of this problem yet.

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From some online searching, it appears that Buick part number 1523703 seems to cross reference as an AC 504 fuel pump. Photos online for an AC 504 fuel pump appear to be the same as the fuel pump that you have. I think it is the correct inverted fuel pump used on later 1938 Buick 40 series. If you happen to take it off, you might find the part number stamped on the side of the arm. That seems to be where the part number should be. 

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A429 is stamped on the flange of the pump where it mates to the engine block. There is no brand name on it. Number on pump arm is badly worn but first few numbers are 1523___ so it does not appear to be the correct pump. I think Dave39MD is correct, it is a Chevrolet fuel pump.

Pete Phillips

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Pete: I know I am late to the party on this topic as you have solved your problem. Just had to comment, though.  The  A429 on the flange is a rebuild # stamped on by the rebuilder. Airtex maybe??  Most rebuilders ground off the OEM # stamped on the flange and put on their own. As Matt Hinson nicely posted the picture of the Service Bulletin, Buick changed the original "W" series AC pump (which interchanges with the 37-52 Chevy), to the inverted bowl AF series after around 40,000 engines were used.

This same AF series pump was used on 1939 series 40 for one year. 1940 saw the use of the combination AJ series pump on the Series 40 and later.  

Out of curiosity do the numbers stamped on the block show that it is a 38 engine?

Great Bugle by the way.

 

 

 

 

 

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JIC,   if you still have a problem,   I got an early '50' fuel pump the had the vacuum boost pump on to and the fuel pump below.   That pump is readily avail at your NAPA store.    I got it and bypassed the vacuum pump by hooking the input  to the output.    Also,  you can not purchase any pumps with the glass bowl...  Old ones and rebuilt ones are still around.   The fuel pump manufacturers  stopped them for safety reasons.   There are good reasons as you might break it in a crash and have gas coming out the opening.  Fire is very scarry.... Just a thought - - -  

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  • 4 weeks later...

Pete:

 

If you have not solved your fuel pump issue.  I have an NOS AC Fuel Pump Type 421 in the original box and packaging.  I cannot use this type of fuel pump on my 1938 Buick Model 41 Self-Shifter.  There was approximately over 4,000 fuel and vacuum units (AC 3927) installed the 1938 Buick Specials that did not have the semi-automatic transmission installed to be used up at the factory during production.  There was more than one type of AC Fuel Pumps used on 1938 Buicks.  See AC Fuel Pump Sheet for pump type #.

 

Lawrence

AC Fuel Pump Sheet.jpg

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