Decoding VINs and Repairing Fuel Sending Units - Technically Speaking

James Berry Apr 30, 2014 0 Comment(s)
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Serial Number Plate Attached Points and VINs Decoded

Q: I need a bit of advice. I purchased a '62 Corvette several years ago that needed some work. I did not register the car immediately because it was not road worthy. I have done some research on the '62 models and noticed that the VIN location changed from the driver's door to the steering column by this time. My VIN is screwed on the driver-side door post. I have a clear title that reflects the VIN in the door. The first digit in my VIN starts with a 2, but I thought all first- generation Corvette VINs started with a 1. Now I am scared this may not be a '62 Corvette VIN. Is there any way to tell? Do you think this will this be a big deal when I go to register the car? Could this be a stolen vehicle? Thanks.

Greg

A: Greg, you are correct. The Vehicle Identification Number (VIN) is not screwed into the door jamb on a '62 Corvette. It is typically spot welded to the top of the steering-column-mast cover. There is the possibility that the vehicle in question may have been stolen, but I have seen some VINs moved during restoration and for various other reasons.

You can check the frame to see if the VIN on the vehicle's frame matches your VIN plate. Starting in '60 to present day, the VIN should be stamped on the front passenger side of the engine block if the vehicle retains its original engine. Also inspect to see if there are any traces of spot welds on the steering-column cover where the VIN could have been originally attached. The VIN for your vehicle should have rounded corners. Some reproductions have square corners.

Corvette Vehicle Identification Number

1953-55: The early-'53 serial-number plate also known as the VIN plate is composed of magnetic stainless steel with rounded corners and the attaching holes were drilled by hand. The later-'53 serial-number plates were made out of aluminum with machine-stamped attachment holes. On '53 Corvettes, the VIN plates and screw heads were coated with a plastic resin to discourage tampering.

1956 through Early-1960: In '56, the VIN plate remained on the driver-side door-hinge pillar, but moved just below the upper hinge. These serial-number plates were made out of aluminum. They feature machine-stamped attachment holes and rounded corners. They are attached with Phillips head screws.

Early-1960 through 1962: The VIN plate remained on the front of the left door post until approximately November 24, 1959, when the serial-number plate was moved to the steering-column-mast jacket, where it was spot welded approximately 13 inches rearward of the steering-gear housing and resided there through the end of '62 production year. These serial number-plates were made out of stainless-steel.

1963-1964: The VIN plate was moved to the body-hinge-pillar brace below the right-hand-side glovebox compartment where it was spot welded. This was a new design plate with rounded corners and entered production approximately June 15,1963. These plates included letters “DD,” indicating the Delivery Date with a blank space provided for the dealer to stamp the delivery date of the vehicle. It is not uncommon for these VINs to not contain the delivery-date stamping.

1965-67: The VIN plates remained mounted to the body hinge pillar brace below the right-hand side glove box compartment but were riveted in place instead of spot-welded. The change was implemented since some VIN-plate welds were broken by dealers when stamping the delivery date into the plate. Early-'65 VIN plates are attached with normal circular-head rivets, and later in the run the rivet heads were rosette shaped. In '65 a new plate with square corners was put into service.

1968-82: The VIN plates were attached with rosette-head rivets to the inner vertical surface of the left-hand windshield pillar. A Federal law stated VINs must be visible from outside the vehicle to benefit the police. In '81 a 17-digit VIN was made standard.

Greg, I hope this helps and good luck with getting you vehicle registered so you can enjoy driving it after owning it for so long.

Corvette Vin Decoded

1953 to 1959 10-digit VIN
Position Code
1 Series E or J = Chevrolet Corvette
2 & 3 Model Year 53 = 1953, 54 = 1954, 55 = 1955, 56 = 1956, 57 = 1957, 58 = 1958, 59 = 1959
4 Assembly plant S = St. Louis F = Flint
5 to 10 Production sequence number 000000
1960 to 1964 12-digit VIN
Position Code
1 Model Year 0 = 1960, 1 = 1961, 2 = 1962, 3 = 1963, 4 = 1964
2 to 5 Series 0867 = Chevrolet Corvette
6 Assembly plant S = St. Louis
7 to 12 Production sequence number 000000
1965 to 1971 13-digit VIN
Position Code
1 GM division 1 = Chevrolet
2 Car line or series 9 = Corvette
3 Engine type 4 = V-8
4 & 5 Body style 37 = two door coupe, 67 = two door convertible
6 Model year 5 = 1965, 6 = 1966, 7 = 1967, 8 = 1968, 9 = 196, 0 = 1970, 1 = 1971
7 Assembly plant S = St. Louis
8 to 13 Production sequence number 000000
1972 to 1980 13-digit VIN
Position Code
1 GM division 1 = Chevrolet
2 Car line or series Z = Corvette
3 & 4 Body style 37 = two-door coupe, 87 = two-door coupe ('78 to '80), 67 = two-door convertible
5 Engine type 1972 -> K = base, L = LT1, W = LS5
1973 -> J = L48, T = L82, Z = LS4
1974 -> J = L48, T = L82, Z = LS4
1975 -> J = L48, T = L82
1976 -> L = L48, X = L82
1977 -> L = L48, X = L82
1978 -> L = L48, 4 = L82
1979 -> 8 = L48, 4 = L82
1980 -> H = LG4, 8 = L48, 6 = L82
6 Model year 2 = 1972, 3 = 1973, 4 = 1974, 5 = 1975, 6 = 1976, 7 = 1977, 8 = 1978, 9 = 1979, A = 1980
7 Assembly plant S = St. Louis
8 to 13 Production sequence number 000000
1981 to Present Standardized 17-digit VIN
Position Code
1 Country the vehicle was manufactured in 1 = USA
2 Corporation that built the car G = GM
3 Make of the car 1 = Chevrolet
4 Car line or series Y = Y-body series
5 Additional information Usually a Y but a Z = ZR1
6 Body style 1 = two door coupe, 3 = convertible
7 Restraint system 3 = late-model seat belts warning and air bags
8 Engine type 8 = L98, P = LT1, J = ZR1, 5 = LT4
9 Randomly generated digit 0 - 9
10 Model year B = 1981, C = 1982, D = 1983, E = 1984, F = 1985, G = 1986, H = 1987, J = 1988, K = 1989, L = 1990, M = 1991, N = 1992, P = 1993, R = 1994, S = 1995, T = 1996, V = 1997, W = 1998, X = 1999, Y = 2000, 1 = 2001, 2 = 2002, 3 = 2003, 4 = 2004, 5 = 2005, 6 = 2006, 7 = 2007, 8 = 2008, 9 = 2009, A = 2010, B = 2011
11 Assembly plant 5 = Bowling Green
12 to 17 Production sequence number Example: 000000


C4 Fuel Sending Unit Repair

Q: My '90 Corvette fuel gauge will display a full tank of gas until the tank is a little less than half empty. Then the gauge appears to read correctly until it is time to fill the tank again. I'm concerned that the gauge may stop reading properly at all and I don't want to run the vehicle out of fuel. I only drive it on nice weekends and sometimes I don't remember exactly how much fuel was left in the car from week to week. Do you think this is a gauge or wiring problem? Thanks.

Mike P.
via question at a Corvette seminar

A: Mike, as we discussed at the seminar, the most common cause for this problem on older vehicles is the fuel-tank sending unit has an internal fault. This is generally caused by certain types of gasoline that can cause deposits to build up on the fuel-sending-unit potentiometer (variably resistor). This can cause the fuel gauge to be erratic or even non-functional. Remember fuels have changed tremendously over the last few years and some components on older vehicles were not designed with today's blends of fuels in mind.

To repair this problem, the fuel-sending unit will need to be removed from the fuel tank. After removal, the resistor and wiper can be accessed by bending back three small metal tabs and removing the cover.

Upon visual inspection you will notice that the small metal wiper slides up and down across a resistor. If you observe wear marks or a buildup of gray residue on the resistor, take some fine Scotch-Brite (or its equivalent) and gently clean the face of the resistor assembly and the face of the wiper contact. Take care not to damage any of the components during cleaning.

Also inspect for broken wires on the resistor, weak resistor-spring tension, or a fuel float that has become heavy due to fuel saturation.

After performing the repair you can check your work with a Digital Volt Ohm Meter (DVOM). With the float resting at the bottom of its travel, you should get a low resistance. Slowly raise the float toward the top of its travel. You should get a steady increase in resistance with no flat spots. Flat spots are locations where the resistance drops to zero momentarily. Once the reading is steady with no flat spots, the repair is complete.

Mike, sometimes these fuel-sending units cannot be repaired and will need to be replaced. Some of them, such as the one in my C4 ZR-1, can be very expensive, so if you can repair it and save a little bit of money, I am all for it. Good luck.

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