Fuel Injection Swaps

by Richard Atwell
(c) Copyright 2004-2011

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There is a Fuel Injection (Bosch Parts Interchange) cross reference at the Type.2com website that is a great resource. I've summarized the information into table format below to make it easier to understand at a glance how Fi components are shared between the models.


Configurations:

Bosch L-Jetronic is a simple system compared to the earlier designs like Bosch D-Jetronic on the Type 3 VWs and the D-Jet 914s. Compared to those systems, the parts are more readily available, they are simpler to diagnose and the connectors are more robust. Although a vehicle hasn't left the factory with L-Jet the technology in over 2 decades, it lives on in the Bosch Motronic engine management systems available in newer cars.

VW Baywindow L-Jet configurations can be broken down into 4 groups:

79 CA models are unique because they have an O2 sensor and special ECU with a built-in rev limiter. All of the other models rely on a rev limiting rotor in the distributor to limit the RPMs to 5400.

76 1/2 - 78 models and 79 Fed models are the most common. The sales numbers were the highest and you are more likely to find these models at the junkyard than any other models. The all have a 7-pin AFM and a mechanical EGR valve. The late 76 models have their own harness and a microswitch on the throttle but are otherwise the same. The 7th pin is for an air temperature sensor inside the AFM.

75 - 76 1/2 models models have a 6-pin AFM and an electro-vacuum EGR valve. Because they lack the air temp sensor, these models have an intake air preheat pipe that is part of the cross over pipe that's seen on the original exhaust setup.

74 CA Automatic models are very rare. They have a 1 year only harness and no decel valve.


Baywindow Compatibility:

When you go to the junkyard, take this table along to help you pick out compatible parts without having to memorize the Bosch part numbers.

When I write Shared 020 I mean that the Bosch part ending in 020 is shared between those model years in the table.

Part Abbr. 79 CA 79 Fed 78 77 late 76 early 76 75 74
Air Flow meter AFM 022 Shared 020 Shared 018 Shared 012
Auxiliary Air Regulator NLA AAR Universal 022 906 045A
Cold Start Valve CSV Universal 022 906 171B (Type 2 only)
Decel Value NLA Unique Unique Shared *1 Shared *2 n/a
Double Relay DR 13-pin version Shared 11-pin 071 906 059 (was 022 906 059)
Electronic Control Unit ECU 4 combinations/year (manual/auto x federal/CA)
Fuel Filter Universal 133 133 511
Fuel Injectors Universal 022 906 031
Injector seals small Universal 311 133 261A
Injector seals large Universal 311 133 263
Fuel Injection Harness NLA 1 yr only Shared 1/2 yr only Shared 1 yr only
Fuel Pump Universal 043 906 091
Pressure Regulator PR Universal 022 906 035
Series Resistors SR n/a Universal 022 906 079
Temp Sensor II TS2 Universal 311 906 041A
Thermo Time Switch TTS Universal 043 906 163A (Type 2 only)*3 043 906 163 063 906 163 022 906 163 311-906-163C
Oxygen sensor O2S 1 yr only n/a

Universal also means you can use this part from a FI beetle unless the part number is followed by (Type 2 only).

*1 - See this Type2.com article for part numbers for high altitude and automatic only versions of the Decel Valve.

*2 - Automatics used electrically controlled decel valve otherwise used same Decel Valve as later manuals.

*3 - The 043 906 143A TTS supersedes all other versions so it's compatible throughout.

See my TS2 article for all the part numbers I'm come across for this seemingly identical part.


Aircooled Vanagons:

Vanagon AFMs and Decel values are different than baywindow versions but the rest of the components are the same as the 79 Federal models with the exception of the Oxygen sensor which is shared with the 79 CA model. The ECUs (all 4 of them) are the same as the 79 models.

Part Abbr. 83 CA 82 CA 81 CA 80 CA 83 Fed 82 Fed 81 Fed 80 Fed
Air Flow meter AFM Shared 030 Unique 025 Unique 038 Shared 032
Electronic Control Unit ECU 4 combinations total (manual/auto x federal/CA)
Decel Valve Shared 319 Shared 317
Double Relay DR Shared 13-pin version Shared 11-pin version
Oxygen sensor O2S Shared n/a

Watercooled Vanagons:

What about waterboxers? Yep there are a few compatible and no doubt low mileage parts:

Part Abbr. Bosch number Models
Fuel Pump 0 580 463 016 84-91
Aux Air Regulator AAR 0 280 140 101 84-85

Keep in mind that although Vanagons went watercooled mid way though 83 those models weren't available in the US until 84.


FI Beetle:

The intake boot and harness obviously won't fit a bus but many of the universal components listed in the first table will. Here are some of the beetle part number so you can distinguish them from the bus part because they look similar. The CSV is easy to spot because it only has an inlet and no outlet.

Part Abbr. 75-79
Air Flow meter AFM 043 906 301
Electronic Control Unit ECU 043 906 021
Cold Start Valve CSV 043 906 171
Decel Valve 311 133 551
Thermo Time Switch TTS 043 906 163

Part swaps:

Certainly there exists a lot of confusion with regard to parts especially in the case of the ECU since so many versions exists. Since Bosch does not publish technical details about these components bus owners have had to make guesses and experiment with component swaps.

  1. Can I put a 2.0L FI system from a 76-79 bus onto a 75 bus with the 1800cc engine? The easy answer judging by the shared components is yes. L-Jet doesn't seem to care about the displacement because it's delivering a fuel quantity based on an air flow quantity. Assuming that a 1.8L engine pumps slightly less air than a 2.0L engine on each stroke and the CA/Fed/automatic/manual ECU differences aside, the ECU seems to be able to deliver the correct quantity of fuel. The L-Jet is flexible up to a point: if you bore out your engine you will find that it will limit the horsepower you are able to make because of the lack of sensitivity in the AFM at higher RPMs and the fixed size of the throttle body.
  1. Can I disable the EGR? Yes, because the system is not an input to the ECU. If you have the mechanical style you have no issues. If you have the electro-vacuum style, just leave the harness connector dangling. Either way you must seal the EGR system so vacuum leaks do not occur and lean out the fuel mixture.
  1. Can I use this ECU and AFM? The simple answer is limited by the harness that you have. If you have a 6-pin AFM harness and a 7-pin AFM then the answer is no. See the next question for a finer point.
  1. Can I use this 79 CA harness? There are no series resistors in this setup because the resistance is built into the ECU itself forcing you to use the ECU and the O2 sensor.
  1. Can I use beetle fuel injectors? Yes, they have the same flow rate although they might not have the same style of hose (curved vs. straight) but that's easy to fix.
  1. Are 018 and 020 AFMs are interchangeable? Yes, despite the apparent flip flop mention of the swap in the supplementary section of the yellow workshop manual. Several bus owners have verified the compatibility.
  1. The most important question: can I use this CA ECU on my Fed bus or this Manual ECU on my Automatic bus? What I've read is that the automatic ECU works best with an automatic. It's fuel map is geared to the shift points in the transmission. If you swap in a manual ECU the bus will still run but apparently you can tell the difference and will notice that the mileage suffers. The ECU rebuilders say that a manual bus can run an auto ECU without any problems.

    What I can speculate about is that the CA buses have catalytic converters and it's important that they run hot so the ECU may prefer leaner mixtures. As for the automatics I have to assume they are paired with the differing decel valves and perform a fuel cut off function during deceleration at different rpms.
  1. Given the wide range of adjustability of every AFM, I still don't have a definitive answer as to what makes the 022 different from 020 (aside from CA spec). I have measured a NOS unit with these results:


    Based on this data, the 022 AFM appears the same as the 020 as far as Bentley is concerned but I suspect that graphing pins 7 and 8 for every flap position may produce a different mixture curve than the 020 AFM.

ECU parts numbers:

Model Year California Manual California Automatic Federal Manual Federal Automatic
1974 n/a 022-906-021K n/a
1975 022-906-021L 022-906-021M 022-906-021H 022-906-021J
1976 022-906-021Q 022-906-021R 022-906-021N 022-906-021P
1977 022-906-021AA 022-906-021AB 022-906-021S 022-906-021T
1978 022-906-021AE 022-906-021AF 022-906-021AG 022-906-021AH
1979 039-906-021D 039-906-021E 039-906-021B 039-906-021C
Vanagon 071-906-021B 039-906-021E 039-906-021C

I don't recommend getting a replacement ECU from the VW dealer. Aside from paying too much you'll probably get a unit remanufactured by Robert Bosch Corp. for VWoA instead of the new unit you paid the price for. Look for an X after the VW number and/or REV after the Bosch number if there is no other indication on the box.


References:

History:

08/12/04 - Created
09/28/04 - Added unique 79 CA AFM
10/31/04 - Added FI beetle parts and correct aircooled Vanagon info
09/07/11 - Fixed broken photos, added translate button, updated footer
09/19/11 - Fixed 77 and 76 AFM slots in table (thanks Joe)