993 conversion wiring help - 3 questions

DW SD · 01:34 PM

1. my tub is a '71, but has an '86 wiring harness and gauges. Is the oil pressure sender - part #928-606-203-01-M82 - between the '95 engine and '86 gauge compatible?

NOTE***: The newer sender provides signal for the oil pressure gauge and oil pressure idiot light. If I installed the early sender, I lose the idiot light. This thread tipped me off that I may have compatibility issue, but Ted has a different gauge setup than I: Correct oil pressure sender for a 3.6 conversion?

OLD sender (84 to 89): http://www.pelicanparts.com/cgi-bin/smart/imgdsply.cgi?pn=91160613500-M100

NEW sender (90 to 98): http://www.pelicanparts.com/cgi-bin/smart/imgdsply.cgi?pn=92860620301-M323

2. I've wired in the Patrick Motorsports DME conversion harness, but not yet installed the computer or attached all the sensor connections at the engine. the DME conversion harness is simple, one lead to power on, second to switched power (+ one to tach and second to fuel pump).

Should the DME relay click closed, just by turning the ignition on OR does everything else need to be connected for it to click closed?

Note*** I did install two different DME relays, completely connected the conversion harness (including ground) and at the DME relay have ground at connector pin 87 and 12V at the relay pins: 86 and 30. I don't find switched power (switch by ignition switch) at any of the relay pins. Maybe some other logic device provides signal to the DME relays? I'm just trying to test as I go.

3. what is this white connector for on the '95 DME engine harness?

NOTE***It is found inside the electrical housing - my finger is on it, next to the large 40A fuse. Looks like another relay connection - maybe for a blower motor relay?

As always, thank you very much!

Doug

DW SD · 03-14-2006, 04:49 PM

East Coast primetime BUMP; it's project night for me in the garage - would love some good advice.
Thank you,

Doug

jevvy · 03-15-2006, 12:13 AM

Hi Doug, cant help with all your questions but can make a few observations.

I used the sender that came with my 95 engine and I think it reads high on my gauge - almost double I would say but as bill says in the other thread I think I will live with it for now, at least it tells me I DO have pressure!

Not sure about the DME clicking closed without other items connected however I did notice 1 difference between my 3.2 & 3.6 setup in that with the 3.2 when ignition was switched on I would hear the fuel pump prime then stop however the 3.6 doesnt fire the fule pump until it recieves a signal from the flywheel sensor. I hot-wired the pump to get the system up to pressure before I tried to fire the car.

I got the switched live from a spare black wire that came out from under the drivers seat however I think this is 87 onwards.

I dont remember seeing or using the white plug in your pic so cant really help there.

If you can be assed please report back as to whether you got an oil pressure sender to read right with your gauge.

ischmitz · ischmitz's Garage

The VDO senders come in two basic varieties (0-5 bar and 0-10 bar) for their 6 to 130 Ohm range. The older gauges/senders are 0 - 10 bar (0 - 160 PSI). The 964 and 993 engines have 0 - 5 bar sending units. If you connect a later sending unit to an earlier 160PSI gauge your readings will be double. You either need to buy an early sending unit or have a shop convert your gauge. I think VDO makes 0-5 bar with pressure switch. Check North Holywood Speedometer or others VDO shops as source.

The DME relay on a stock setup has two stages. Stage one is controlled by the ignition switch. It is turned on when you turn the ignition to ON. It powers stage two, the DME box, and the ignitors. Stage two is controlled by the DME box. The DME switches stage two on when it detects flywheel movement at the reference sensor (cranking). Stage two powers the fuel pump and the O2 sensor heaters. It's a safety feature: If the engine stalls the fuel pumps shuts down instantly preventing excessive fuel spillage.

I noticed that some conversion setups do not use stage two and coninue to power the fuel pump by the ignition switch. While you can do that I prefer to do it the right way.

Hope that helps.
Ingo

jevvy · 03-15-2006, 04:38 AM

There you go...a proper answer from a man who knows!

DW SD · 03-15-2006, 05:44 AM

Quote:

Originally posted by ischmitz

The DME relay on a stock setup has two stages. Stage one is controlled by the ignition switch. It is turned on when you turn the ignition to ON. It powers stage two, the DME box, and the ignitors. Stage two is controlled by the DME box. The DME switches stage two on when it detects flywheel movement at the reference sensor (cranking). Stage two powers the fuel pump and the O2 sensor heaters. It's a safety feature: If the engine stalls the fuel pumps shuts down instantly preventing excessive fuel spillage.

Hope that helps.
Ingo

Jevvy and Ingo -
Thanks very much for your replies! It definitely helps!

Ingo,
I thought one stage of the DME was ignition controlled - I believed it was in my 3.2. I'm not getting any click when I turn on the ignition, though I have the conversion harness wired in properly. Unfortunately, the harness doesn't come with a wiring diagram, so I'm at a loss for the moment.

Do either of you have a wiring diagram for the conversion harness?

Also, any guesses as to what the white connector is for?

I intend to install this in the safest way possible.

Thanks again,

Doug

ischmitz · ischmitz's Garage

Doug,

Yes, one stage is controlled by the ignition and the other by the computer exactly like in the 3.2. Check if you get ground and +12 volt at the proper pins of the DME relay socket with the ignition turned to ON.

I don't know how the PMS harness is configured. I guess you need to ask them what the white socket is for if you didn't get a schematic. Give them a call

Good luck,
Ingo

jevvy · 03-15-2006, 08:57 AM

I think that white plug looks like its part of the harnes you got with the engine right? If so my harness didnt come with one so its either a US specific thing or even something aftermarket that was fitted to the car you got the engine from - just a guess.

1 thing you should check is if your ECU has a part number "993.618.124.xx". the 124 bit is the bugger since it means it is drive blocked - I didnt find this out until I was trying to fire it up and it just wouldnt start. I farily quickly sourced an ECU with a "993.618.123.xx" part number and it all worked spot on.

Do you have the Igniter from the 3.6 engine too - dont forget to fit a heat sink to it and dont bolt it flat on the floor - it gets a bit hot for that!

DW SD · 08:01 PM

Jevvy,

More good advice! I'm quite sure drive block is not part of the '95 993 system. I'll check the part # on the computer.

I reviewed the 993 wiring diagram today in more detail. It is a pain in the A$$ to read these things. I found that the 40A fuse is part of the secondary air injection system and I believe the white relay harness is the corresponding relay. Those are US only - I think.

Ingo & All,
I reviewed the DME circuit very closely on the 993 wiring diagram. Seems the two triggers (controller signals) for each relay within the DME relays are grounds and go to the computer itself. I assume the computer would ground PIN 3 & PIN 27 to control the DME relays. Source power is always on for the first circuits and the power circuit. Like Ingo, I thought one would be switched with the ignition.

Can anyone verify if I'm reading the wiring schematic properly?

Thank you,

Doug

DW SD · 03-15-2006, 09:25 PM

"Can anyone verify if I'm reading the wiring schematic properly?"

I guess I can verify.

Though the engine is just in trial position, I fitted the connectors to the engine, hooked up grounds, igniter, coils, computer. The DME makes noise! I didn't try to crank it over, since there is no starter and I didn't want to make any spark (not sure if it would spark anyways).

The first DME relay activates! Good sign. Won't be able to try phase 2 until the motor is ready to fire.

Doug