L-Jetronic FI harnes ('79) pictures and schematic

[furgo]

As I was preparing for the fuel line replacement and removing the AFM, S-Boot and other bits and pieces to make room, I got annoyed at the brown mass of dirt in the engine compartment. I couldn't even recognize the FI parts, let alone wire colors. So I started cleaning up a bit before doing anything else.

I then noticed the FI grounds were pretty badly corroded, so I disconnected them... and as they say one thing lead to another.

I removed the FI harness to clean it up a bit and to inspect it. I'm planning to build a new harness in the not too distant future, but in the meantime, I'll keep using the old one, and do a couple of minor fixes it needs.

When the time comes to build the new harness, there are enough really good threads here on the Samba that will help me. However, most of them follow the "nail the old harness to a board, trace the wires" approach. While a valid one, I prefer having a drawing to work with, which makes the process repeatable and allows me to keep driving the bus with the old harness while I'm building the new one. I have an Opel FI harness that I'll sacrifice for parts, which means I can also keep the original bus harness instead of butchering it to reuse the 25-pin ECU connector, double relay and injector resistor pack connectors.

In any case, consider this as additional info with lots of pictures and a schematic to complement the other great existing harness threads. The diagram is a work in progress: I did a quick sketch by hand for now, but I'll add a proper CAD drawing at some point.

Also, if a mod feels this should be merged with any of these other threads, I'll be happy for it to be done too.

Without further ado:

The harness in all its glory. The basis is a '79 Federal one, which means no full throttle switch (I wonder why they were removed and then put back on CA buses, btw), no OS2 sensor and with series resistors.

The diagram, showing approximate cable lengths (in mm). Again, it's WIP, I'll update it with a proper one at some point, but not this week.

The ECU connector. Notice the rubber seal to protect the ECU box from humidity. The connector has got a screw at its top (not seen here), which can be undone to then slide the top half of the connector off and take it apart.

The grounds to the ECU pins 16, 17 and 5 were noticeably corroded.

Note the multi-layered protective covers of the connectors, and some glue or compound used to prevent water and dirt ingress. It seems the compound has cracked and darkened from either age or temperature. It seems mostly the later to me.

Now we come to the injector connectors. They are VW-branded AMP connectors from their JPT (Junior Power Timer) line, which fortunately can still be found today. Interestingly, all of these connectors had the same VW part number, regardless of color coding. Also interesting is the fact that the connector for injector #2, depicted here, has a clearly different shade of green than the rest. The others did not have the AMP marking, so perhaps it was just chance that someone at the factory picked 3 green connectors from another OEM and one from AMP while assembling my harness.

The connectors for injectors #1, #3 and #4 in a darker shade of green, no AMP marking.

Here is the Thermo Time Switch connector, in brown. Aka "the bastard". Those who have boldly or foolishly attempted to remove it with the plenum in place will nod in agreement.

Notice the burnt and cracked sheating: it gets hot under the plenum too.

The JPT sockets have got a metal clip that fastens them to the mating connector. That's great to avoid them coming loose with vibration, but not so awesome when you are trying to undo them. Other JPT sockets have got clips that protrude and you can push with your finger to easily loosen them, but not these ones. You either need to wiggle them a bit, or dislodge the metal clip before pulling them apart.That's what I had to do with this one: barely feeling the end of the clip with a tiny screwdriver until I took it out of the recess it lies on. Easier said than done. And done after major cursing at the wretched part. After so much effort and fist shaking, I obviously had to take pictures.

The Cold Start Valve (CSV) connector was also a fun one to remove –not. It is actually accessible (check) and visible (check), but its nearly touching the distributor at its back, so it's a tight space to pull (#fail). The CSV's plastic body part scarily moves a bit in relationship to its metal part when the connector is pulled, so you definitely don't want to force it. Again, I ended up dislodging the metal clip before I pulled on the connector. And again, easier said than done.

Notice the rubber boot was broken on my CSV. I might replace it as a temp fix until I've built the new harness.

The Auxiliary Air Regulator. Not much to say on it. It's black. And came out easily by wiggling it a bit side to side, surprisingly.

The engine temp sensor (aka TSII) has seen some warm times next to cylinder 3. Notice the connector deformed and burnt to brown. It's originally transparent. Also note how these connectors work: it's simply the plastic shell that attaches to a spade connector with the little arm to keep it in place. Then you can use a regular female connector to plug into the other end. I've got a few new ones from VW, I'll add some pictures and the part # when I next go to the bus. I'll renew this one on this harness too. And check out the awesome sunset from our balcony

Finally, the double relay and injector series resistors connectors. Not much to say here either, other than to appreciate the numbers (printed, engraved, burnt?) on each of the wires. Most probably to facilitate the assembly, you can't really use them for troubleshooting, as they're not easily visible with the connectors assembled.

So that was it!, I hope the schematic and visual tour were helpful to someone

Some final questions, though - I noticed several burn marks along the harness, and I was wondering:

• Which (temperature-resistant) material was used as the external cover for the wires? In other words, what should I use for the new harness??
• Was there any better routing strategy than the spaguetti one tangled on top of the engine in other model years? No one at VW thought about the firewall?
_________________
'79 Westy, P22 interior, FI 2.0 l Federal, GE engine (hydraulic lifters)

Decode your M-Plate

[raygreenwood]

Yes.....the Junior Timer family is actually huge.

Some plugs have VW Audi #s.....some may not have any #s. By the late 70s cirtually all major FOREIGN manufacturers were using some form of L-jet derivative. These connectors were also used in certain aircraft applications.
AMP was making parts for hundreds of companies....and many companies were making parts under license.
Because of this .....but the late 70's there seemed to be no hard or fast rule that plug housings would have either part #'s you could decipher or part #'s at all.

Sadly sometimes the very best way to identify an obsure plug is to measure it and then download the blueprint from the AMP site.....which is like a 30,000 page jungle.

The outer cover.....is NOT a high temperature covering. Thats the problem with it. It was not bad for its day though as it did last a long time.
Some say its "polyolefin"....which as plastics go.....is so generic as to almost say....."its plastic".

From everything I can see....its actually a vinyl. It has the moderate temp range of about 250-270° F.....and it hardens up with age to the point of being brittle and has moderate shrinkage.

This type of sheathing is one ai am no fan of duplicsting. You can find it at places like Summit racing.....mostly in black and mostly split. Search for vinyl cable sheathing.

Im working on a harness for mine but will be using braided expandable cable sheathing from TechFlex https://www.techflex.com

I am playing with samples of their "tight weave" https://www.techflex.com/land_genpurp.asp
And their 360° wrap. https://www.techflex.com/prod_f360.asp which is not split.

The cool thing I have found that you can do if you want to:
A. Make this wrap totally weatherproof and
B. Make it look very similar to the cable sheathing the factory had (at a galnce)

.......is to take the woven flex wrap.....and insert a dowel inside that does not overly expand the sleeve but expands it a little.....like say 10%. Lube the dowel very lightly with silicone dielectric grease snd wipe off the excess. Once its installed inside the tube....wipe the outside braided surface lightly with acetone to removing any excess lube.

Then get a tight latex or nitrile glove on....and smoothly slather the whole braided tube with Permatex Ultra gray. Make sure you get all the excess ofc and fill all the holes in the braid. When its dry...remove the dowel.
You now have a moderately expandable anti-abrasion sheathing that is waterproof and dustproof for the wires.....and is very chemical resistant and good to about 500F.

The braided tube itself has a melt point of 487°F and a constant service temp of 257°F....which is much better than the factory sheathing. Ray

[aerosurfer]

[furgo]

[raygreenwood]

Anotuer way to work with the TechFlex......that I did not eant to mention because....I have not actually teated it yet... .....but it should work fine.....is to order some silicone based surgical tubing (mcmaster carr).....and slip a slightly undersized one into the braided tube.

Plug one end and put a hose clamp on it. Clamp an air fitting in the other and inflate with just enough air pressure to make it semi-rigid but not to bulge it.
The sheathing should pop right off when you deflate it.

The wood dowel also works well but you have to flex the sheathing just q bit to get it crack loose. I also have some 6' lengths of 1/4" nylon rod from mcmaster carr that work well for the small diameters.

Aerosurfer is on a good track too.....but you may need to call around and get a few samples in a few places and teat them with heat.

See.....they make heat shrink tubing in a MYRIAD of formulas, temperatures and shrink ratios. They make high ratio to low ratio shrink tube.....they make "NO" shrink tube.

And when you are lokking these up on the web......you will get the most results by searching for "polyolefin heat shrink tube", "polyolefin wire sheathing or cable wrap" etc.

The problem is this:
What IS polyolefin? Its a FAMILY of plastics.....not "A" plastic. A polyolefin is any plastic made from an olefin monomer or alkene.
Polypropylene (PP) is a polyolefin
Polyethylene (PE) is a polyolefin
EPR is a polyolefin
EPDM is a polyolefin.....

You get the picture. So.....many of the 3 intermediate companies that advertise polyolefin heats shrink and non-shrink cable sheathing......have no idea of what it is. Too many do not have much information on what its chemical proof to or what its ultimate temperature range is.
So.....try to stay with the companies that actually manufacture the tubing.
By the way....vinyl....PVC....is not an olefin. And.....polyolefins have replaced most vinyl in this application. Finding the right one is the key.

The problem with getting actual shrink tubing oversized and just shrinking it down and using that.....is that depending on what olefin its made of.....when it shrinks down it gets more dense....and stiffer....and may continue to get more brittle with age.

That's the other problem.....finding a tubing that is really made with automotive in mind so it stands up to constant heat and oil.

This company.....Mouser Electronics....has a full range of non split, non shrink wire sheathing. You will want to look at "more" under sizes
http://www.mouser.com/Mobile/Wire-Cable/Wire-Prote...s/_/N-5gh0

Ray

[Tcash]

Added to tech tips, thank you for posting.
Tech Tips

thanks to telford
Electrical Terminals FAQ

[airschooled]

A few add-ons to the thread:

The CA '79 models issued the return of the full-throttle switch to temporarily richen the mixture since the O2 sensor on those models kept the mixture so damn lean all the time. I believe the deletion of the switch around late '76 was due to emissions reasons.

--

The resistor pack plug connectors (five of them inside the one plastic block) often need cleaning. I have found that polishing them and the appropriate terminals on the resistor pack itself can bring an injector circuit back into the lower end of resistance spec after being too resistant. I'm not sure of the practical application, but I THINK there is slightly easier cold-starting to be had with a cleaner circuit there. (Could be a placebo…)

Use a little tiny jeweler's screwdriver to bend the "locking" tabs down out of the connector for polishing.

--

Your #'s 18 and 19 are switched in this pic…

Nice write-up, I look forward to seeing your harness! Perhaps someone on here has a defunct harness laying around that they would be willing to send you or cut up and measure so we could have an exact reference file online…

Robbie
_________________
Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com

[furgo]

[furgo]

[airschooled]

Oooh interesting, I didn't know about the ECU input voltage monitoring. And I didn't really consider injector opening time either. I was assuming the slightly-dropped resistance would allow slightly higher voltage to work with cold/sitting/static injectors to overcome their "influx current."

But yes... I can't think of any connection that doesn't benefit from cleanliness.

Robbie
_________________
Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com

[aerosurfer]

[furgo]

[raygreenwood]

One problem with the resistor pack and its connections. You can see this just from looking at them.

The resistor pack gets pretty hot when running. This corrodes terminals faster and also makes them brittle. It also makes them expand more and has tougher heat cycles because of this. The resistor pack terminals are notorious for getting loose because of this with time.

This affects connectivity and can affect voltage sampling by the ECU. If there were ever a conponent in the L-jet system that was begging for a sprung/dual cantilevered terminal like the fuel injectors use.....its this component.

Some of the watercooled cars used full sized dual cantilevered terminals for high heat areas like this. It would be a worthwhile modification but they are thick enough that they will be a difficult fit in the stock plug body. Ray