Fuel Pump Push Rod Adjustment for 1966 Beetle

[colonel biggs]

Except for Thanksgiving, the trip to Mass. to install my daughter's new fuel pump was a bust. Because the phenolic stand is in good shape, and because I don't want to risk destroying it on attempting a removal, it turned out that the max push rod height (with no top gasket on the stand) turned out to be 12.65 mm. Hence, I need to sand down the top of the stand by 0.35 mm to reach the 13.0 mm desired max height for the push rod. (The push rod is exactly 108.0 mm.)

It has been suggested that this task is more easily accomplished if one removes the two fuel pump studs. In the Model A Ford world I have tightened two nuts onto an engine stud, and then turned the nut closer to the block ccw to remove the stud. Not having worked the VW mechanical trade before, is this an acceptable approach to removing the fuel pump studs from the case? With the fuel pump stand in place, I am not able to use some penetrant (like Kroil) on the studs. Or, is a stud removal tool a more effective approach?

The last thing that I want to do (being 300 miles from my NJ shop) is to snap off one of the studs. (What is the length/pitch of these studs, if I have to replace one?) If this is a strong possibility, because of the age of these cars, the alternative is to carefully remove the existing plastic stand. (I have a backup from WW. VW is stamped onto the stand, but it is 12.7 mm in thickness, as opposed to 14 mm for the stand now in place.) I presume that this is accomplished by tapping around the bottom edges where the gasket is sealed to the case and to the stand. Will a putty knife, or equivalent, do the trick?

When measuring max and min push rod height, I noticed that the travel between the two heights is approximately 6 mm. I have read that a travel of 4-5 mm is the desired range. Are there any negative implications from this discrepancy?

Sorry for all of the questions!

[aquifer]

I’m not an expert but I wouldn’t worry about.35mm, especially being on the short side of 13mm. I would probably find really thin gasket material and cut a gasket to fit and call it good. Whatever you used to measure is probably off by more than .35mm!
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Current hobby vehicles:
1967 Beetle
1973 Beetle
1998 Jaguar XJR, restored myself, in near-immaculate condition

[zerotofifty]

On the VW I have removed a many a stud by locking two nuts together as you suggest. The steel stud is very unlikely to break unless the stud is damaged by extensive corrosion or such, which is not likely the case for this stud. Exhaust studs are the ones more likely to break do to the heat induced corrosion.
The case is soft magnesium

Some penetrating fluid wont hurt, it may well work its way down to the case

The stud is 8 mm.

Sometimes the pump spacer comes out easy, other times they break during attempts to remove, The spacer is fragile, and does not take kindly to being wacked and pried.

Now for your issue.

The factory manual states the rod should stick up 13 mm at highest point, and 8 mm at lowest point. the manual also states the stroke should be "about between 4 mm to 5 mm."

13 mm - 8 mm = 5 mm. However the stroke should be "about between 4 mm to 5 mm"

Given that the specification for highest stick out is "13 mm" Id simply round the highest point you got to the nearest millimeter You measure 12.65 So round that to 13 mm, and there fore you is ok!!! Note the tolerance of the manuals highest point, it is 13 mm, NOT 13.0 mm With no decimal after the 13 mm, that implies that the measurement is to the nearest millimeter. It is thus allowable to round to the nearest millimeter.

Leave well enough alone, run it as is.

Sanding the spacer is going to be a pain, and it has to be done in a nice flat plane

Your highest point measurement is within the tolerance given. 12.65 is 13 mm sure it aint 13.0 mm nor 13.00000 mm but that is not what is specified. What is specified is 13 mm, which means the tolerance is to the nearest millimeter, in this case 13. 12.5 mm is acceptable, as is 13.4999 mm.

Heck the stroke has a 1 mm tolerance.

See how that works?
So go ahead and run it with the spacer as it is, no worries.

[Glenn]

Leave it along, you're gonna cause more of a problem than you already have.

Install the pump and add a Tee and pressure gauge to see what you have.
_________________
Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"

Member #1009

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עַם יִשְׂרָאֵל חַי

[Cusser]

[VW_Jimbo]

[RWK]

X4, most pumps I have recently installed had too high pressure, you will probably have to install a few gaskets to get the pressure down, that's all that matters.
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73 Type 181
63 Type 113
63 Type 261- 428 071
62 Type 241-378 025 178 530

[Cusser]

In 2018 I installed Import Direct fuel pump #M16102 from O'Reilly into my 1970 Beetle, and it measured 3.2 psi.

I now notice that this same part number is no longer listed though.

No clamp on fuel pump outlet, to route in the pressure tester.

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1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297

[colonel biggs]

What an overwhelming set of responses! Had I posted my questions prior to my trip I would have a running bug. I appreciate the inputs immensely. Zerotofifty did an excellent Job of placing the push rod measurements in perspective. I had often wondered how folks measure mm to the nearest hundredth of a mm. Then it dawned on me that I could take my inch-scale calipers and convert the readings to millimeters. (I have restored Model A Ford carburetors for 20 years. There are four jets, and each is assigned a given rate of flow in milliliters, but as a range, not as an exact number.)

Cusser: thanks for your fuel-measuring photos. How do you obtain a reading if the fuel inlet port on the pump is not connected? Using the standard gasket for the top of the stand, do you have any guess as to how one gasket affects the psi change?

Glenn: I don't need a broken stud when I am 300 miles from my shop, so I take your advice whole heartedly! You also identified this engine several months ago as having the generator mounted 90 degrees out of sync. That was a bear getting those lower shroud bolts installed. I would not want to try that now with the 20-degree weather. The fuel pump stud is an M8, if I recall correctly. What is its length, in case one day in milder weather I attempt
to remove a stud? Also, the existing carb is off the car (fuel bowl empty). Is it desirable to fill the bowl before cranking up, or will the starter rapidly do the job for me?

Zerotofifty: your numerous comments from several months ago were greatly appreciated. I also like your sense of humor when referring to push rod measurements. They will make me feel better when I do my flow testing of Model A carb jets.

[scrivyscriv]

Here's a little bit to add to the mix!

In lieu of removing material from the fuel pump pedestal, if you **REALLY** want to get that last little bit of pump movement, you can weld the tip of the pump pushrod.

I'm not saying you *SHOULD*

I personally would not worry that much about it. The 1/4"(ish) fuel line from tank to pump is only going to flow so much fuel, and the small carburetor is only going to let so much in. Were pushrod length an issue here, you'd see it manifest as a fuel delivery volume problem, not so much a fuel pressure problem. In this case, checking fuel pressure will only show you if you had a gross pump failure. Checking volume according to the Bentley manual will positively tell you if you're pumping enough fuel or not.
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Robert in Memphis
Dünkelgrügen 1967 Java Green bug thread
Engine rebuild thread
If you're ever in the Memphis area, you are welcome to stop by for advice and help.

[Cusser]

Let's just note that I've had my 1970 for 52 years and my 1971 for 48 years, and I've never measured either their fuel pushrod lengths or their travel.....
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1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297