Just bought my first 82 928S

[WilliamJSS]

Boy does it need some work. I am going to start a thread, and I am hoping you good people could help me like I have seen others around here. A complete restore is in the plans for this baby, but first I need to figure this out.

First issue: This all started happening last week. It was running fine, perfect except for an alignment issue, and then all of a sudden, around 25mph, normal driving I lost a LOT of power. Exactly half. Got Her home, and started to poke around. Pulled wires from front left and saw no difference on the injectors until I got past the front 2 cylinders on left/right. Somehow I have dropped my front 4.


She starts fine and stays running every single time. Plus.
She has *Almost* all Her parts. Plus.
The front 4 cylinders are getting no pulse. Minus. Rear 4 are fine, removing wires makes a difference though only on the back for (2 on either side).

I have been doing some reading, and I am seeing a lot about a Green Wire from the distributor. I have read that this is associated with a no start/spark situation. My issue is I don't know if I should start here, as I have a spark in 4 of 8, and she starts every time.

If anyone could offer a little help or a starting point that would be awesome. I don't want to ride around on just the rear cylinders.

Thank you for any help.

[medipedicman]

Hi William. Welcome to the group. We love to see pics of new members cars. What part of Georgia are you in? There is a very active group in North Atlanta and I am sure we can help.

[MPDano]

Grounds. Look in the Common Fixes thread. Might not be your year, but it will get you in the right direction.

[Danglerb]

Green wire is go/no go, not sort of go. Grounds are a good place to start, buy a noid light, inductive timing light, and a length of rubber hose is handy to listen to injector clicks.

Cleaning the grounds a good start. All the injectors are wired in parallel and fire at the same time, but do have two connections to the brain.

Alignment, worn parts, ride height set low, alignment tech raised the front end during alignment and you can't do that with a 928 unless you know how to pull down and settle the ride height.

[WilliamJSS]

@medipedicman,
-Thanks for the welcome, I will try and post up some pictures today. I am from the southeast coast, right below Savannah in between Savannah and Jacksonville Florida. Place called Brunswick.

@MPDano,
-Got a ground chart today, going to go through that with my Tech Here at work. Thank you.

@Danglerb,
I just bought a noid light and one of my Techs has a timing light as well. Going to check today.

*Update*
I see two ground wires above the passenger valve cover, but on the Driver side none, is there supposed to be anything grounded on the Drivers side? Or is it hidden.
Thanks!

[WilliamJSS]

Does anyone have some sort of wiring diagram? Not the plans type diagram, but locations diagram. Here is what I am trying to find.

There is some sort of power source that this harness runs off. I see two grounds, and one power point on the diagram. I can see the two grounds, on the passenger Valve Cover, but I am unable to locate the power/relay. It should be in the engine bay I am thinking but unsure as to where.

If anyone can help, or provide a picture of where to look that would be great. Thank you.

[WilliamJSS]

The highlighted part is what I am looking for. As you can see, I have no pulse/dead cylinders for 2 and 1 and 6 and 5

[Danglerb]

Sometimes with a 928 finding "the problem" isn't the best route, easier to just go through all the deferred PM and see if it doesn't start working when you are done. Clean all the grounds, reseat all the relays and plugs, all the basics.

Roger at www.************ has a set of CDs with manuals and wiring.

Repair mantra from Jim Bailey, relay, relay, relay. Maybe just replace the ignition relay and/or all of the common cheap relays and make up a set of jumper wires for testing.

[WilliamJSS]

Ok,
Checked the following. Relays. Tried difference ones all over, I have none bad. Fuses all look good. Checked all grounds I could find with the help of a diagram on here. Ohmed out the front 4 injectors and they are getting a pulse, but for some reason not firing.

I can't for the life of me figure out how half of a motor loses power in one second. # 1, 2, 5, 6, the front four just wont fire. She ran like a dream before with only really interior work needing to be done.

Could four of my injectors have gone out at once? What about the computer by the right hand side fender. I have an extra one of those that came with the vehicle.

I also have been reading about crank sensors on top of the bell housing that act as kind of a safe mode/limp mode, and half the cylinders will work when one of the sensors is bad. I have a parts car. Is that something I should look at?

Kinda over my head on this.

[MPDano]

To me, that sounds strange as my passenger side injectors weren't firing due to a ground on the top of the passenger side valve cover. Since yours are 2 on the drivers and 2 on the passenger side, I am wondering if your L-Jet ECU is faulty. Does your parts car have a good computer in it? If so, I would try and swap it out.

I am not an expert on efi by far, but that's something I would try. There are also places that can test and fix your ECU if it's bad, someone here can probably recommend one. Or if someone has a good one you can test with. Just throwing stuff out there.

https://answers.yahoo.com/question/index?qid=20060924065032AAtO8Al

[MPDano]

Also, can you post your engine number as the only 4.7 S in your MY is a Euro.

Here is a link to help you find the code location:

Porsche 928 Forums dot com - View topic - 928 Engine Types & Performance Data

[JhwShark]

William,

There has been some good input here. If you are still chasing the lack of Power to the bank of injectors, look a little closer at the current flow diagram you posted.

The wire that runs to the four injectors needs close inspection. From the good (your tests) Relay XVI a wire (pin 87) runs from the back of the CEP (Control Panel in Passenger foot-well) to a termination at the wire harness/plugs section then out from there in two runs to the engine; one to the four injectors in question (W2) and one to the other four (W3). Plug W needs to be checked for continuity and voltage at wire connection location W2.

Since you are getting power through W3, firing the other four injectors, you may have merely a open wire/connection (W2) at Plug W. If you have continuity and voltage at W2 then you need to look at Pin 15 & 33 at the ECU and then evaluate the ECU as Leo has suggested.

Jon

[stepson]

Originally Posted by JhwShark

The wire that runs to the four injectors needs close inspection. From the good (your tests) Relay XVI a wire (pin 87) runs from the back of the CEP (Control Panel in Passenger foot-well) to a termination at the wire harness/plugs section then out from there in two runs to the engine; one to the four injectors in question (W2) and one to the other four (W3). Plug W needs to be checked for continuity and voltage at wire connection location W2.

Since you are getting power through W3, firing the other four injectors, you may have merely a open wire/connection (W2) at Plug W. If you have continuity and voltage at W2 then you need to look at Pin 15 & 33 at the ECU and then evaluate the ECU as Leo has suggested.

Was somebody in your passenger seat when the 4 cylinder occurrence first happened? Sometimes passengers get overzealous with their brake foot on that passenger footwell brake pad and can cause strange and irritating symptoms with the 928.