Socal_Tom

Good morning GP, thanks for the help.

I saw some iffy stuff in the L-Jet connector so I suspect you and others are right.

Any way to tell if it is the Injector harness vs the L-Jet? Don't want to throw new parts at it randomly (beyond what I have already done which are all service items anyway such as battery and engine ground cables etc).

Callum_GT

good luck with your project

Socal_Tom

I could use some luck right about now!

I think I need to make sure I have a good injector harness before anything else otherwise I am trying to build a house on a foundation of jello.

soontobered84

Tom,
You should be able to find someone local to you that could put your L-Jet computer in their running car. This will help you determine the status of the computer. Once you find that, you can determine your next course of action. My thoughts are that your harness has been hacked up by a PO.

Socal_Tom

Good morning, thanks for the note. Looks like the injection harness needs to be replaced but is like to eliminate the L-Jet before I do that.

I still need to individually ground the new 5, 16, 17, and 35 pins. Doubt that will do it. It worth trying.

I am also hoping to learn if not having a ground on 23 is an issue. On some other makes early ignjevtikn systems the O2 sensor isn't important for the first couple minutes anyway but not sure if that is true on our 928s.

I am in Orange County if anyone is local and wouldn't mind helping out with an L-Jet.

Thanks!

hwyengr

It seem that the half of this board that doesn't live in Dallas lives in Orange County. You'll be in good hands

Socal_Tom

No takers so far, but hope springs eternal.

Per the other thread, found and clean a ground on the passenger side front near the air conditioning receiver.

Edit - I installed new Porsche fuel pump and injector relays and confirmed they are both working.

Could someone help me make sense of this ground reading? I have good ground wires going to the L-Jet connector that show basically no resistance when I connect them.

This reading however does not look correct, this is what my injector harness grounds are showing when the connector is actually attached to the L-Jet ECU.

This to my newbie-eyes suggests that the L-Jet isn't properly grounded or something in the L-Jet has more resistance than it should.

bureau13

What are you actually measuring there? What are the two points you've attached your leads to?

Socal_Tom

Hi Jeff-that is the continuity between the four Brown ground wires that go to the L jet connector, with the connector plugged into the actual LJet ECU, and a known good ground.

Side note - I had a 1987 Turbo II as well-loads of fun

bureau13

Hmmm...and the brown ground wires are not actually connected to their grounding point at that time, correct? 8.78K seems high-ish, then again there's a reason the injectors don't simply use L-Jet chassis ground, or whatever other ground connections there are there...so it might be fine. I wouldn't immediately assume this is an issue, although it wouldn't hurt to check other ground connections for the L-Jet through that harness.

I wish I had done more of my own work back when I owned those RX-7s...I am finding when you do, you really gain an appreciation and understanding of your car that you can't get any other way.

Socal_Tom

Thanks for the follow up Jeff, very much appreciated.

Correct. One test lead on the grounds connected to each other as part of the injector harness, the injector harness plugged in to the LJet, and the other test lead to a known good ground.

In other words that reading in the picture shows the resistance of the current moving through the L jet.

rjtw

Hi Tom,
Why not just replace the whole harness? FWIW I replaced mine on my 1983 (virtually identical to yours) years ago, the harness cost $300 at the dealer (not too bad all things considered) and it was pretty straightforward. Would help eliminate a few variables and clearly needs to be done anyway -- who knows what other wires are bad in there!! While you're doing that you can also check/test all the injectors very easily as well if you haven't done that already.
Cheers
Rick

Socal_Tom

Hi Rick, thanks for the note.

Taking a step back my plan was to make sure I had a healthy engine before diving in to everything else.

I am heading towards replacing the injector harness but was hoping to know for sure if it was the injection harness vs the L-Jet before throwing more parts at it. I was hoping to borrow a known to be good L-Jet to determine that but haven't had any local offers yet.

Thanks again, and Happy Friday.

rjtw

Wish you all the best on this one, Tom -- these cars can be very trying of our patience sometimes. For what it's worth though, they are incredibly sweet driving and of course I am a particular fan of the 83/84 years -- still simple, lots of buttery low end torque, nice gear ratios (love that 5th gear for effortless highway cruising), and in the bigger scheme still very lightweight, amazingly balanced cars that are super tossable and with modern tires will pull at or near 1g cornering, as good as virtually any modern sports car. I've had mine for 30 years woohoo! Simple enough for a moron like me to do all the wrenching on, but modern enough to be reliable and get great economy for a V8!!
Cheers!
Rick

Socal_Tom

Hi Rick - I know she will be worth it, climbing the walls with eagerness to get her back on the road but trying not to rush.

Sounds like yours has given you loads of enjoyment, fantastic!