Podguy

I am attempting to sort out the wiring differences between an 86.5 fuse panel and the wiring harness on either an 87 or 88 S4 motor. I an not sure which year, but it is not an 89 and it has two presonality plugs. The 87 harness I have only has one personality plug.

Any rate looking a everything the biggest difference is the W plug. W22 has a red wire that is supposed to get power from the 30 circuit. Looking at an 85 wiring harness there is no connection in W22, but the wiring diagram shows the plug connected to relay XIV pin 87, which would be the starter relay. The difference between the real world and the wiring diagram make me a bit nervous.

Any rate I have removed the terminal from the harness and plan on providing power from another source. Other than that the W plug seems to match. The V plug is another story with considerable differences but most seem to be in providing diagnostic resources to the diagnostic plug in the engine bay.

Anyone been here before and have any suggestions. It would be helpful if anyone had the pin outs on the two main plugs to the computer. I seem to remember a diagnostic section in the manual, but I have not been able to run it down. I do have the engine turning over, but want to be sure of the voltages correct before connecting the computers.

Thanks much.

danglerb

I've been told swaps between some years require almost a total rewiring of the car, 80 hours labor from one source. No idea what its like on the model years you have. How different is the old engine wiring harness from the new one?

Vilhuer

It is doable but takes some serious work. Think all needed info is scattered around in different documents in Jim's CDs.

BC

My plan was to run the flappy with a piggyback and leave everything else alone. Do people think thats not going work? Ignition -86, Throttle sensor - 86, MAF - 86, injectors - 86. Run the 87 motor (which is just heads, intake, and flappy - sans knock sensors) in the 86 car and "don't tell it".

danglerb

I'm real curious too. How integrated are all the systems?

Should I be emailing Jim for the 2nd set of CDs with the technical stuff behond thw WSM?

At what point does some aftermarket system start looking practical, MegaSquirt etc.?

Podguy

I think I have sorted out some of the wiring issues. The W Plug is the main connection of the fuel injection to the car. The pin outs are the same between the 85-86 LH system and the 87 up with the exception of pin W22. It has a red wire going into it from the harness that requires 12 volts. The 85-86 board does not have 12 volts on pin W22. I removed the pin from the plug and jumpered it to a power source. I now have ignition. I am not sure if I have fuel pump yet sicne I am using a button to toggle the fuel pump for the inital steps.

The engine cranks and kicks but will not start. If I leave the pump running the engine will compression lock on turning over. I put on a fuel pressure gauge and am getting 55 Pounds. This is too high so I think the injection computer is dumping gas thus causing the compression lock. Cranking without the fuel pump on after a compression lock gets a mild bark, but no run on.

So the question is - why is the fuel pressure so high. I have not checked the return path because it was getting late and very cold up here (below freezing at night). The engine has headers so I am wondering if someone put high pressure injectors and a high pressure regulator. How do I tell the difference. The injectors are tan and look kind of new, but it is difficult to tell since the car has been sitting in a body shop for 7 years. What are some of the other things to look for on fuel pressure. I have a set of dampers and regulators off another enngine. Shutting off power to the pump keeps the pressue high at 55 Lbs.

I also have no history on the LH computer so I will have to dig up an S4 to test it on.

I have not yet delt with the V plug yet, but so fat it looks like it is mostly for diagnostics. So far swapping an S4 motor into a 85-86 car does not seem to be much of a big deal. Once you change the acceletator, kick down and cruise control cables and change the wiring on W22 the job looks pretty straight forward. I had a S4 motor in an 82 and it only needed a little wiring change to make it work too.

Brendan. I would consider using the 85-86 manifold if I was doing what you are doing. if you want to keep the visual looking stock then the S4 manifold is a dead give away. The better plan might be to look into changing the cam on the throttle body to give a quicker response on the lower end. This is what the 944 guys have been doing for some time. Such a change might wake the car up and give you a product to sell.

Anybody interested in a set of S4 headers. I have no interest in them. No idea who made them.

danglerb

When you put the S4 into a 82 which brain did you use?

Did everything work ok, or was it just to getting it running?

SharkSkin

Just curious... is this the car that was up for sale near the SJ airport recently?

Podguy

I bought the 82 with the S4 motor installled. It belonged to a doctor and he cracked the block when the engine flooded while driving through some water. The insurance paid off and his mechanic offered to install an S4 motor out of a wreck for the settlement. The car had the S4 computers and the main W plug was scarfed into the 82 fuse panel. He added a single electric fan running off the theromstat in the radiator. No over heating problems and the car ran well for a number of years. With the low gear differential five speed and not much interior the car got up and jumped.

When I got the car it was not running and the Doc had spent large sums of money attempting to fix an intermittant 4 cyclinder mode problem. By the time he gave up and bought a new Porsche the car barely ran. I worked on it for a few days and isolated the problem to a bad coil wire and probably some bad valve timing. I had it running pretty well when Phil Theshie bought it from me. He still owes me the front seats, but I doubt if i will ever see them.

There is not too much wiring on the S4 harness that has to connect to the car. This case the engine came out of a 91 car and had the exhaust sensors. I by passed them to get it running initally, but it turned out to not be the problem. As it turns out most of the wires on the V plug are for diagnostics. the primary inputs are on the W plug and map to the same relays on the older car pretty well.

As far as the 86 - yes this is the basket case that was near the SJ Airport. They messed with the installation to get it running and failed. What I did find is they had no power to the EZ computer and thus were not getting any spark.

There is a chance the flywheel is wrong - from the 86, but the engine is a 42 so it came out of an auto and thus I am assuming they kept the S4 flywheel. The compression is good and I get spark. Whoever installed the engine did a reasonable job. I have seen much worse work.

I am now waiting for a friend to come by with his S4 so i can test the LH computer. If the computer is good then I will continue looking at the engine and will probably pull the lower bell housing to check the flywheel.

I have the interior out and most of the surface rust removed and the metal primed. The car is getting an 86 motor and trans from the convertible. This is why I bought it to get a place to put the convertibles engine. The body is dead straight and the car has never been in a serious accident.

The interior once I removed a ton of dust looks pretty good. the A/C even has a bit of freon in it. Overall less being disassembled - which is what i do with all my cars - it is in pretty good shape. I wish the guy had not lost the 3" exhaust system, trown out the bumper covers and lost one box of door parts, but other than that most of the car is there even with a few extra parts.

Jim bailey - 928 International

OK so you want to get the S-4 engine running so you can then take it out and put back in an 86 engine...now I understand.

danglerb

Shhh now everybody will want to do it.

SharkSkin

That's what I thought -- I went to look at that for someone not too long ago.

Rich9928p

The '86 928 uses a 25 pin LH and EZF and the '87 and newer 928s use a 35 pin LH and EZF. There are many differences in the engine wiring and control sysetms, including the power source for the fuel injectors.

I'm hoping that along with the 1987 engine you have the wiring harness that includes the new LH and EZK connectors.

Podguy

The wiring harness for the engine is the 87 harness.