How to ID a CCKW carb

[pfarber]

If its does not have a SIGHT PLUG, PASS!!!!

I can cross reference this part to AT LEAST two TMs.

Its in the ORD 9 SNL (1945) an the part numbers are

DIE CAST:
PLUG Sight Level GM-2196082

CAST IRON:
PLUG GM-2178496

Neither part was superseded or deleted/replaced as per the SNL dater July 45 (this is just ONE MONTH PRIOR to all CCKW contracts being canceled in August of 45 (when we won the war!)

Here is the figure out of TM9-1826C Zenith 28 Series carbs:

carbplug.jpg (130.7 KiB) Viewed 18589 times

[pfarber]

AKA How to tell if you have an ORIGINAL CCKW carb:

It seems that 'original' carbs are for sale.

But they lack the all important SIGHT PLUG. I've been told that they were not needed, replaced, removed from manufacturer etc etc etc.

Well... if your 28AV11 (die cast) or 30 BW 11GM (cast iron) carb does not have a SIGHT PLUG how are you going to perform Paragraph 49 (ENGINE FAILS TO START) e 3?

Which reads:

(1) Remove float level sight plug from carbureter bowl (on engine side).
(2) If no fuel can be seen, remove drain plug from bottom of
bowl. If no fuel flows out, make check as itemized in (6) below.
(3) If fuel is level with sight plug hole, failure to start may be
caused by flooded combustion chambers due to excessive use of
choke, or by fuel not reaching the cylinder due to a dirty carbureter.
Check choke mechanism or remove carbureter and clean (par. 94).
(4) If fuel flows out of sight plug hole, carbureter float needs
adjustment (par. 94) or fuel pump pressure is excessive (par. 97).
(5) If fuel does not flow out of sight plug hole, but does flow out
of drain plug hole, check fuel pump for operation (par. 97) or check
adjustment of carbureter float level (par. 94).
(6) If fuel is not reaching carbureter as in (2), check fuel pump
operation; check line between fuel pump and fuel filter, clean fuel
filter, check lines between fuel filter and fuel tank.

Its all in TM9-801 the 1944 version.

[pfarber]

The die cast and cast iron carbs have fuel level sight plugs. The official nomenclature is PLUG, sight level GM-2196082 (die cast 28AV11 carb) or PLUG GM-2178496 (cast iron GM-2137474). These plugs are to allow line mechanics to troubleshoot engine failure to start issues. The first reference I can find of a sight plug on the April 1943 TM9-801. Since this TM covers the first of the open cabs, one can assume that the carb was in place before the April 1943 publication date.

The previous TM published is TM10-1563 contains no reference to the sight plug or any picture clearly showing it.

The die cast carb is Zenith Model 28AV11 PN 9778. Gm Part number 2135998. This part number is used through out the ENTIRE CCKW production. The fuel bowl PN is 2143816. This number also never changes through production. The first CCKWs through CCKW-321078 used the die cast carb. CCKWs after that had cast iron carbs.

I am confident in saying that the fuel bowl WAS changed to incorporate the sight plug in early 1943. There are several reasons why I say this.

First the TM9 for April 1943 clearly shows the plug in place. Trucks in this production run used the May, 1943 TM10-1562. I do not have this TM but the production of carbs would have been started before the TMs printing. Or at least coincide with its release.

Second, the 43 TM9 has a table showing what echelons of maintenance can perform what actions. For all but a select few items 2nd echelon (Company/battalion level) was restricted to REPLACING parts. Repairs were done 3rd echelon and higher. So the TM would not include detail descriptions of troubleshooting problems. The 43 TM9 only covers how to remove the carb.. no servicing was allowed. This is opposite of previous and future TMs that included either detailed repair instructions or advanced troubleshooting tips. I believe that the sight plug was added to allow 'future' 2nd echelon mechanics the ability to diagnose fuel system problems without the need to disturb the carburetor by having to disassemble it to check for proper fuel level.

Here's a list of TMs, dates, and part numbers:

1941 TM 10-1500 page 13 Group 03 FUEL SYSTEM

0301 Carbureter, Air Cleaner

2135998 Carbureter Assembly (Zenith #9778)
2143816 Bowl Assembly

No mention of the sight plug or pictures of it.


1941 TM10-1501 First Series Closed cab civie dash

Make and Model Zenith 28AV11
ID Plate 2135998-9778

No mention of slight plug in carb rebuild or fuel level adjustment section.


1942 TM10-1563 Closed cab Military Dash

Make and Model Zenith 28AV11
ID Plate 2135998-9778

No mention of slight plug in carb rebuild or fuel level adjustment section.

Jan 1943 TM10-1563 Closed cab Military Dash
Make and Model Zenith 28AV11
ID Plate 2135998-9778

April 1943 TM9-801

Pg102 Fig 40. Fuel plug CLEARLY visible.
Page 89 "Organizational Instructions"
Second Level maintenance was NOT presecribed anything more than REPLACE a carb.

TM10-1563 May 1943 - Do Not own.

I bet is shows the first incarnation of the sight plug on die cast carbs.


April 1944 TM9-801

Page 140 Para 49(e)(1) CLEARLY calls out carb fuel plug in several steps to diagnose engine starting problem.


1944 TM9-1826C Ordenance Maintenae Carburetors (Zenith)
Lists 28AV11 O-97778 A,B Venturi size 29 Float setting 1 31/64
Only unique setting Pump Stroke 1/2 all other 28AV11 3/4

1945 SNL-G508 All parts list

Carbureter GM-2103965 Die Cast CCKWX Figure 01-3 page 34
Carbureter GM-2135998 Die Cast CCKW Prior to CCKW-321078
Carbureter GM-2137474 Cast Iron CCKW After CCKW-321078

So if someone says that they have a die cast CCKW carb WITHOUT a fuel bowl sight plug its either a very early production (1941/1942) or is a civilian model 28AV11. No reference has been found that shows the cast iron carb without the sight plug.

A few further points that must be mentioned is that the 28AV11 was a civilian carb. It was used on many civilian vehicles like the CC450 truck. The cast iron carb GM-2137474 was a 'milspec' carb. That means it was designed to withstand the CCKWs rough driving techniques. The early dis cast carbs has problems with the air filter flange breaking off, and spilling oil all over engine causing fires. The cast iron carbs were stronger and less complicated.

[pfarber]

In searching for NOS 28AV11 carbs (zenith part #Z-9778 with the sight plug) I think that its informative to like all the zenith part numbers that fall under the 28AV series of carbs. This list is probably incomplete:

S616, A, B, S971, 8518, 8519, 8533, 8534,
8535, 8539, 8686, 8811, 8821, 9018, 9019,
9020, 9030, 9031, 9032, 9036, 9038, A, B,
C, D, 9040, 9041, 9042, 9043, A, B, C, D,
9044, 9045, 9046, 9048, 9050, A, 9051,
9052, 9060, 9074, 9077, 9082, 9149, 9241,
9293, 9428, 9429, 9445, 9453, 9454, 9472,
9489, 9508, 9565, 9579, A, B, C, 9580, A, B,
9778, A, B, 9829, A, B, 9866, 9867, 9868,
9890, 9894, 9899, A, B, 10342, 10527, A,
10528, 10529, 10831, 10898, A,
10899, A, 10920, 11147, 11148, A, B, 11377,
11440, 11441, A, 11442, 11503, A, 11576,
11577, 11578, 11579, 11618, 11658, 11659,
11742, 11743, A, 11779, 11780, 11781,
11851, 11852, 11853, 11854, 11855, 11856,
11963, 11964, A, 11965, 11966, A, 11967,
11968, A, 12027, 12057, 12058, 12059,
12219, 12488, 12489, 12496

What are the differences? Who knows? But 28AV11 is a series, and 9778 is a specific model.

[pfarber]

The only sure fire way to ID a zenith made in the USA carburetor is by the ID disk riveted to the fuel bowl cover.

"Zenith carburetors produced from about 1932 to 1980 have a round tag, approximately the size of a US dime, riveted to the body of the carburetor. Original equipment carburetors will have two numbers stamped on this tag. The outer circle will be the O.E. part number (ie Allis Chalmers, GMC, IHC, etc.). The inner circle will be the Zenith number. Aftermarket carburetors made during this period will have the Zenith part number only on the tag."

What does the 28AV11 model decode to? Zenith says:

A – designates a carburetor where the throttle shaft is parallel to the air shutter shaft (with normal air intake).
V – vacuum operated power jet if the standard of the series has mechanical pump or no pump

28 and 11 are simply model numbers.

Zenith seems to be the hardest carbs to ID. "Identification of Zeniths other than above is difficult."

http://www.thecarburetorshop.com/Carburetor_ID.htm

[pfarber]

More images of the fuel bowl plug. These are from the JULY 1945 version of the SNL. This is one month before the war ended and all CCKW production was canceled.

cp2.jpg (46.48 KiB) Viewed 18587 times

In the engine ID section we have the plug clearly visible. If its not that important a part, why take the time to draw it?

cp3.jpg (77.25 KiB) Viewed 17472 times

Here it is again. This is 1940s tech. These drawings were hand drawn, they simply didn't click the 'rotate 90 degrees' button on their CAD computer and get new view.... it was hand drawn in.

cp1.jpg (24.98 KiB) Viewed 18587 times

This drawing is EXTREMELY interesting because it does not deal with the carb AT ALL. Its an exploded engine diagram.. yet they STILL drawn in a sight plug.

So the next time someone tries to explain that the CCKW carbs didn't have sight plugs on them ask them what proof do THEY HAVE? I bet you get excuses, conjecture, stories about their military training.. everything but PROOF.

[pfarber]

I'll probably consolidate these posts into a single thread, but yet ANOTHER bit of historical evidence for the CCKW fuel bowl sight plugs has been found.

Please see GM Technical bulletin G-98 regarding the 'new' cast iron carbs.

From the SB Cast iron carbs started production in Feb 1944 (no date or SN given) and the service bulletin CLEARLY shows the fuel level sight plug in Figure 1 and Figure 2 (plate numbers TP0202 and 0203). The July 45 SNL gives a SN start number of 321078 .

So, it seems the time line for the sight plugs is complete.

From start of production to approx Feb/Mar 1943 there was a standard GM-2135998 WITHOUT the fuel bowl sight glass. (TM10-1563 Jan 15, 1943)

From Feb/Mar 1943 through Feb 1944 the carb was GM-2135998 WITH the fuel bowl sight plug. (TM9-801 April 1943)

From Feb 1944 end of production the cast iron carb GM-2137474 WITH fuel bowl sight plug.

So when some nut job says they have ORIGINAL NOS CCKW production carbs remember than after Feb 1944 the die cast was phased out. The die cast was only used for the first 2 years of production.

g98.jpg (23.26 KiB) Viewed 18600 times

g981.jpg (23.66 KiB) Viewed 18600 times

[pfarber]

Well it seems that the 'elusive' fuel level sight plug has finally been spotted in an official GM publication! I missed it at first but while on the crapper reading the SBs again I noticed the 'Mona Lisa' of fuel plug portraits! Side by side die cast and cast iron picture that showed the fuel bowl AND the plugs!

Here we go.. smile for the camera!

plug1.jpg (40.78 KiB) Viewed 18591 times

Hers a blown up shot of the die cast plug:

plugdc.jpg (28.99 KiB) Viewed 18591 times

Now to correct any possible questions:

NO they are not the fuel inlets, both carbs have the fuel inlet on the TOP COVER so the float needle can regulate flow.
YES that is the fuel bowl. The cover is above it and has the floats attached to it.

So I think my quest is finally over. I have at least 5 official documents for at least 2 different sources that are dated and include part numbers.

Why would a company 'produce' a carb that was superseded by the manufacture as some have mentioned? They didn't. The GM-2135998 was replaced by GM-2137474. The original 5998 carbs were pure civilian in origin, were modified to miltary use with the fuel level sight plug in early 43 and then completely replaced with a 'military standard' 7474 carb from Feb 44 till the end of production.

MANY GMC civilian trucks used the 270 and the 'civvi' 5998 carb (no fuel level sight plug) and THOSE are being marketed as NOS CCKW.

The 1941 and 1942 CCKWs (approx 150,000 trucks out of 527,000 total) were the only trucks to use the civvi (non fuel level sight plug) die cast carbs. The reason that there are so many civvi (no sight plug) 5998 carbs around is that they were used extensively POST WAR on GMC trucks/buses because the 270 was finally available to the public. The 7474 was a military design and I could not find many references to vehicles that used it... unlike the 5998 that was pretty numerous.

[pfarber]

Here's a tid bit from Zenith Series 28 and 228 Operation and Service Bulletin Z-190-B dated August 1950.. this Bulletin supersedes the December 1948 Z-190-A .

The illustrations are pretty much identical to the ones in the TM9's. The parts breakdown are identical to the SNL for the die cast.

While the parts diagram does call out a fuel level plug and washer (65, 66) nothing else is mentioned about them.

A good thing about the Bulletin is that it does list the tools requires and information on reaming cast iron base for bushing the throttle shaft.

[pfarber]

If your fuel bowl has 'BENDIX Zenith" its post war. Bendix is more of a logo while Zenith is in all caps.

If it just has 'Zenith' in all caps, but the 'Z' is lager than the other letters, then shes a keeper!

Also, the idle jet passage cast into the fuel bowl assembly (just under the idle set screw) should only have ONE step. If there are two distinct 'steps' before the passage meets the throttle body, question it.

Pics will follow.

[pfarber]

Got a new Parts Manual, TM10-1562 , 1 May 1943.

Wanna guess what the fuel bowl has on the side? HINT ZZ 2196082 Plug Sight Level (you knew that was coming).

A here's the pic:

[pfarber]

Did a little more digging.

Looking through the TM-10 from 1941 and all of 1942 were fruitless. They simply show the same disassembly/assembly photos rearranged. So the images from the 41 TM10 are used all the way up through the end of 1942.

The FIRST parts manual to show the sight level plug is the TM10-1562 *EFFECTIVE DATE* 1 May 1943. But on the inside cover is a nugget of info:

Note the date of the authorization letter: January 26th, 1943

The TM did not become 'effective' (this is the ONLY parts manual I have the says: Effective: rather than Published:) 1 May 1943.... 4 MONTHS LATER!

So this seems to clarify the start of the fuel level sight plug a bit... DEPENDING on how you read the above. Since the FIRST mention of an open cab CCKW in TMs was in the May 1, 43 TM10-1562. It was not until the April 43 TM9-801 (open cabs started in late 42, August) thats 8 MONTHS after start of production that a maintenance manual was EFFECIVE, but less than 5 months from when the TM10-1562 was completed and the War Dept signed off on it.

The TM10 simply states (pg 160):
"NOTE: Following is a complete list of parts for the GMC Model 1619 CAB, used on CCKW-352 and 353."

No chassis SN

I'm saying that the best I can put the START of the fuel level sight plug would be August, 1942, when the 1619 Open Cab was put into production.

Anyone have anything to add that might narrow that down a bit????

[pfarber]

The August 42 date also makes more sense when you consider that late 42 was around the time that the Army was moving to the ECHELON system of maintenance. Previously units at the Regimental/Divisional level would have the ability to make in depth repairs (this is why the TM10's are so much more detailed, including rebuild instructions while the later TM9-801s were simple operator and Preventative Maintenance manuals).

This change was huge.. no longer could battalion level mechanics rebuild a carb, it was to be swapped with a spare and then sent up the line to 3rd or 4th echelon units for repair.

The fuel level sight plug was a DIRECT development to allow 1st and 2nd echelon maintenance personal to troubleshoot a carb issue (the process is fully laid out in an early post).

[retro-roco]

Paul,

I'm not sure what your stance is for sure regarding sight plugs. Initially I thought you were declaring that all war time CCKW carbs should have them. It looks now like you're trying to determine when they were added? The manual I mentioned to you recently, TM 10-1562, Parts List, 2 1/2 ton 6x6, July 1, 1942, Form X-142001, shows parts for two carbs.

The first is 2135998, CARBURETOR ASSY. (Zenith 9778). It neither shows, nor lists the Sight Plug. The parts diagram is very similar (virtually identical) to the diagram you posted above from Parts Manual, TM10-1562 , 1 May 1943. The only differences that I note are the lack of a sight plug; and the throttle plate and shaft are rotated about the shaft 180 degrees (ie the shaft lever points down, NOT up. No where listed is 2196082 Plug Sight Level.

The second carb listed is 2137474, CARBURETOR ASSY. (Zenith Model 30 BW-11, Stock List #10046). It is noted as "NOTE: Following Carburetor not Used at Time of Publication." No where listed is the sight plug, GM-2178496

So between July 1, 1942, and May 1, 1943, sight plugs appear to have been added?? So forms or both carbs might exist both with and without sight plugs??!?

[pfarber]

You are correct. Initially I believed that the sight plug was always there.

I never knew of the parts manual you mention, till you mentioned it. The TM10 series was based on CONTRACTS, so new TM10s didn't make earlier TM10s obsolete like the later SNLs and TM9s did.

The Zenith model 30 is the CAST IRON CARB. The PN is 2137474 (double check your PN... are you missing a '4' at the end - 213747 ??) I just scanned in the TM9-1826C to post later this week.

The Model 30 went onto CCKWs in Feb 1944. This was a pure Military design, whereas the 28AV11 was an off the shelf civvy product.

But since I acquire more and more TMs/AMs/SNLs etc it seems that there was a short period (maybe 10-15% of production, 41 till mid/late 42) that had a 28AV11 without a fuel level sight plug.

SNL-G-508 p108 does list these:

GM-2143816	Z-A3-52	Bowl, Fuel, Carburetor Assembly, Superseded by BOWL GM-2198543
GM-2198543	Z-A3-52F	Bowl, Fuel, Carburetor Assembly

Gotta wonder what the 'F' stands for... and when it was put into production!

But I gotta give a LOT of weight to the evidence that is pointing to a mid/late 42 appearance of the sight level plug.