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91 turbo current drain

Hello all, I'm a long time reader, first time posting. I'm working on a 91 turbo that has had a 3.6 engine installed. It has a constant 220 milliamp parasitic drain on the battery. It initially spikes to 800 milliamp for less than a second then levels off at 220. Obviously, this kills the battery within a few days. I've checked many things and am starting to pull my hair out. I've unplugged the tachometer as I've seen the on-board computer cause a drain before on a real 3.6 turbo but that's not it on this one. The car has been modified quite a bit:
It has a built 3.6, w many goodies that are mostly unimportant. It does have a twin-plug ignition by electromotive that was a pain to make work in this setup. I basically ran a straight signal wire to the tach from the new ignition, eliminating one of the control units under the seat that basically turned the fuel pumps on and processed the tach signal from the "mercedes type" ignition. The oxygen sensor (jetronic control unit) and the other smaller "enrichment" control unit are still in place and funtion normally. The biggest tradeoff was that the fuel pumps runs whenever the Ignition is on.(the overboost switch still works though)I performed these mods several years ago and the car has run great ever since, other than the occasional electromotive crank sensor failure. I've disconnected all the previous mentioned "wiring" and it has no effect. I've also unplugged any other aftermarket accesories (radio, etc) to no avail.

Any thoughts would be greatly appreciated, I'm starting to get frustrated with this one...
Thanks much
Old 01-26-2008, 02:07 PM
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Chances are this is not your drain, but just in case.

My '92 C2 had a very small fan behind the A/C control unit in the dash which would run continually and drain the battery in 3-4 days.

Good luck,

Hugh
Old 01-26-2008, 02:54 PM
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Thanks Hugh, I called myself checking it by holding a very small piece of tissue paper against it to see if it was running w/ key off but since you mentioned it I remember I never tried the tissue thing with it on to see if the fan even works. I'll pull out the a/c control and unlpug it and test, Thanks again!!
Old 01-26-2008, 06:34 PM
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I have the same problem with my 91. I'm running a tec2 which is getting changed to DTA so I will see if the draining still happens, rsrmike let us know if you find the problem. Hugh thanks for the help
will check the fan I get my car back..
Old 01-27-2008, 03:54 AM
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The easiest way to check current drain is to put a voltmeter on the battery. When current is being used the voltage drops when the engine is not running.
For instance take a reading and then see what happens when you open the door and the lights come on, the voltage will drop. Anyway, unplug things, remove fuses etc. until you see the voltage jump up, this will help you locate the problem.
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
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Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

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Old 01-27-2008, 10:35 AM
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Rsmike, Does this car have the stock factory alarm? If so, with your meter set up on the battery for current, hit the lock button and see if this changes anything, or I could just be an idiot to think that the earlier cars "go to sleep."
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Old 01-27-2008, 05:19 PM
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RSMike, I doubt you'll see much of a voltage difference with that amount of current drain, but since you've got a current reading already wired into your battery, I suggest you start pulling fuses.. You should be able to find the circuit that is causing it.
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Old 01-27-2008, 05:27 PM
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+1, set your multimeter to current, put in series with the battery, and pull all the fuses until the current draw drops to 0.

If it doesn't drop to zero, you at least know that whatever it is drawing the current is wired into a non-fused circuit - like the one the starter terminal is connected to.
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Old 01-27-2008, 05:31 PM
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Thanks guys. I should have mentioned I pulled all the fuses and relays weeks ago. As well as unplugging every control unit I knew of in the car. Most of you are correct in suggesting the current measuring method I mentioned earlier. A friend of mine uses a volt meter inline with either terminal to measure voltage when checking for a drain. It sorta works actually, The higher the current drain, the higher the voltage reads. I personally don't prefer this method, however, after accidentally bumping the 4-way seat switch with my knee w/ my meter set on the low amp setting, and ultimately popping a 2 amp fuse in my meter, It may not be so terrible after all. Anyway, I finally had a major breakthrough last night. I was lucky enough to have a friend near the rear of the car that heard a click when I connected the meter one time. If I repeated the click several times it would stop for quite a while. I finally went to the cheapo parts store and bought a universal horn button and some long wire to make up leads. I must have clicked that thing 100 times before I found it. It was the cold start valve!!!!!!!!!!! hooray! I now had a direction to go. After quite a bit of work I was able to get to the cold start switch in the breather plate cover(it's a 3.6T). For some reason the yellow wire coming from terminal15a on the starter is powering (+) the thermo-time switch all the time!!! Apparently my drain is the little heater circuit built into the thermo-time switch! I haven't dived further to see why the yellow wire is hot but I obtained copies of the factory manuals for 91turbo and 3.6 turbo engine pages this afternoon. It looks like it would have to be a short in the harness or something weird going on in the starter soleniod. I'll hopefully find out tonight and let you guys know! BTW with the thermo-time switch unplugged the current drain was 46ma which I believe to be perfectly normal for any 964/965. I guess I was mostly looking for encouragement to keep hunting and was definately inspired by a few of you. Thanks again!!
Old 01-29-2008, 03:12 PM
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RSRmike, Before you go nuts tearing her apart, there is a wire that goes to the starter that feeds 12 volts to something in the coldstart system, check there real quick as it is a tight space and could cross those easily. Its worth a shot and I think all the cis cars have them if I remember correctly
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Old 01-29-2008, 04:42 PM
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Just to clarify, when you check for voltage with a voltmeter at the battery. If there is current being consumed the voltage at the battery will be lower. So, when you unplug the fault, the voltmeter reading will climb up.
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

http://www.danasoft.com/sig/Iamnotanumber.jpg
Old 01-30-2008, 10:58 AM
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Thanks 930GT. You called it!! Unfortunately, I had already torn her apart locating the drain. However, the fix was at the starter. Apparently there was some starter repair work done and the small yellow wire on terminal 15a of the starter was overtightened to the point that it bent the connector (the big goofy, it can only go on one way with an 8mm hex nut connector) and it was touching the 30 terminal from the battery, it took a while to rub through the shrink-tubing so the trouble wasn't immediately apparent. What was wrong with the push-on connectors from the early days, aside from the occasional re-tightening with some pliers??
Old 01-31-2008, 03:36 PM
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That kicks a$$!
Glad you found it as that is too nice of a car to be in the garage.
Im working on a C2 turbo right now and as I was hooking up the starter I could not help but notice how bad of an idea it was to design it like that- the car I speak of is no longer in danger because I converted it to EFI and that wire got eliminated.
Well have fun with the car man.
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Old 01-31-2008, 08:27 PM
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Thats a great tip.
That wire hooks up with the thermal time switch that energizes and opens the cold start injector valve while the starter motor is running in cold weather.

The thermal time switch decides on the duration the cold start valve is energized or held open and spraying fuel just downstream of the throttle body in relation to how long you are cranking the starter motor.. by the ambient "thermal" temperature of the passenger side chain case cover.
Old 02-01-2008, 09:29 AM
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rsmike,

Glad to see you got this fixed. My 92 T has an electromotive ingnition in it as well, and still has all of the jetronic, enrichment and multifunction control unit hooked up. For some odd reason, the multifunction control unit has began clicking at 2,400 rpm, and I am hitting the overboost protection, even with the overboost wire grounded out and when connected. I don't think the overboost sensor is bad, as I have replaced it with a new one, and the random overboost has been kicking in, since I heard the clicking start.

I was able to replicate the sound in my garage, and the clicking is coming from the multifuntion control unit for sure. Since the part is a special order, and rather expensive, is there a way to test it?

I did find another 964T owner here in CO, and I am going to try his control unit, but I really don't want to do any harm to his.

Thanks,

Bill
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Old 02-01-2008, 01:07 PM
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Bill, It's smart to think that you could harm your buddies control unit. You are safer to plug yours in his instead. Maybe not at all after reading on. First off, Which control unit are you talking about? There are 3 under the driver's seat. The big one says Jetronic and the wiring diagram refers to it as oxygen sensor control unit. There are two smaller boxes behind that one, one is the acceleration enrichment control unit and it mostly compliments the jetronic control unit by manipulating the frequency valve to change fuel pressures and thus change fuel mixture. The other is referred to as turbocharger control unit in the factory wiring diagrams. I think you mean this one? This is the one that gets a trigger from the ignition and consequently turns on the fuel pump relay. This function replaces the switch on the airflow sensor plate housing on the older cars. Instead of turning on the fuel pump when the sensor plate moves, it waits for a signal from the ignition, hence no spark, no fuel. I would assume this was more to satisfy EPA. ANYWAYS, I would be really careful about plugging your friend control unit in YOUR car. I don't see how it's working to be honest with you. Your car came with more of a Mercedes type ignition than the typical Motronic setup. Porsche was actually struggling with finances in this era(hard to believe now) Which is part of the reasons the cars still ran CIS, They evidently needed a new ignition system though and the Mercedes route was the most practical. The only problem for guys like us is that the TACHOMETER signals from the ignition are quite different. I checked both of them with a lab scope with the help of an electrical engineer customer and friend. The electromotive signal works fine with most porsche tachometers, although we determined that the electrotive signal would not work well with this control unit. Nor should it in yours. Who did the install? I would love to hear more technical details. Does your tach work well? The electromotive tach output will work the tach just fine, just not filtered through the "turbo" control unit. Did someone run a straight wire to the tach from the ignition? That's what I had to do. I also had to do a few "wiring" hacks to make the other functions of this control unit work. This is what I would suggest if we are talking about the same control unit. The biggest side effect is that the fuel pumps will run anytime the ignition is on which is not terrible. Many older 911/930's have theirs unplugged to run all the time anyway. I would be happy to share the info on bypassing this control unit if you use it at your own risk!!! I am still using the overboost for protection. If you connect the white wire going to pin 1? directly to the brown/yellow wire going to pin12? The fuel pump relay should run w/key on as long as overboost switch is grounded. You could try just that one bypass and see if it fixes your overboost problem. I seemed to have installed a relay in it's place for something else but I can't remember what it was for. I could go find out if your considering this and need more advice but it's cold in there so just let me know if you actually give a ***** first I just think the tach signal from your electromotive could be freaking out the control unit in question and possibly shutting your fuel pumps down... Could be way off here, FWIW I spent about 3 days staring at the factory manuals making this all work. We took off tec2 and put on a complete CIS system sourced from Andial and then put Electromotive HPX twin-plug 'cause my boss at the time was obssesed with twin-plugging tricked-up turbos. The car split a cylinder w/ the tec2 and none of us felt qualified to tune it after we built the motor (we didn't install tec2). In hindsight, the single plug setup was probably better but it wasn't my call. Good luck! hope this helps.
Old 02-01-2008, 06:16 PM
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Nice help Mike. This is what these forums are all about
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

http://www.danasoft.com/sig/Iamnotanumber.jpg
Old 02-02-2008, 01:16 AM
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Thanks Mike, I am not talking about the enrichment unit that works in conjunction with the jetronic, but the one that controls the fuel pumps and overboost control.

The install was done somewhere in NY, and thats about all I know. I have tired my hardest to try and track down who did it, as the paperwork was pretty scarce when I bought the car. When I got it the overboost was grounded out, and the car ran just fine, al beit it really rich, and with 1.1 bar worth of springs in the tial wastegate. My mechanic pulled the engine, relocated the coils and elctromotive control unit and did a couple of other minor things. We also reconnected the overboost sensor, and with the combination of springs and the B&B headers, I was hitting it quite frequently. I pulled off the wastegate and left in only the .8 bar spring. All was good (except on the rate occasion when it was below 30 and I took the car out and drove it hard).

Fast forward to a bout a month ago, and at 2400 rpm I started hearing a clicking noise, that lasts between 2400 -3000 rpm. It doesn't matter if I am moving or not, if the engine is firing, it is making the sound. The only problem is that it isn't doing it all the time, so it was hard to diagnose. It was in the 50's last weekend, so I took the car out, and it started making the noise. I found a very quiet dead end road that I could see both the start and end of, and got into the gas in second. The clicking was there, and the overboost kicked in, or atleast the fuel pumps shut off. I pulled to the side of the road, and disconected the overboost while the car was idling to test the switch, and the car died, so I know the signal from the overboost is doing what it is supposed to. I rehooked the overboost sensor back up, and started the car, and it wasn;t making the clicking noise. It also would run strong on boost without cutting out. By the time I got home, the clicking had resumed, so I was able using my wifes help, track the sound down to this control unit.

My tach works just fine, as do all of the gauges. I have a couple of relays under the dash that say DEI on them, that don't look factory, but the car also has an aftermarket alarm system on it as well.

I do think the fuel pumps run all the time that the key is in the on position. Once I turn the car off, they don't run though.

I agree with what you are saying, but the only thing I can figure, is that the control unit has somehow crapped out.

Does this make sense?

Unfortunately my friends turbo has the engine sitting on a stand in his garage.

What do you think?

Bill
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Old 02-02-2008, 10:41 AM
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Hey Bill, Sounds like the control unit my be giving up. The DEI relays sure sound like alarm system. That may be something to consider as well. I've pulled many a aftermarket alarms off of Porsches and chunked them as far as I could. They can really lead to trouble depending upon how invasive a system it is and how crappily they were installed (scotchlocks, wires run through sheet metal with no grommets, etc.) Not sure it would affect your control unit unless whoever installed it was industrious enough to tie in some sort of fuel pump kill to your relay circuit. Probably not but you never know. Let me go get under the seat of this 91 and refresh my memory and see why that relay is there. I know the Ignition relay is mounted in the engine compartment so this obviously does something. The rest of the wiring was pretty simple once I figured out what I needed for it to run. I looked at the wiring diagram some more after my last post and noticed it tied into the ignition relay as well. I'm not sure why actually, not sure I ever figured that one out before. Now I wonder if that control unit also had some sort of time delay built in to power the ignition just a few seconds after shut down. I know the older cars had this built into the ignition relay so it's possible Porsche saw fit to include it. It certainly helps when the CIS gets older or if you've got your system pressure cranked up for hairy cams to keep it from popping upon shutdown. The mufflers catch enough hell, they don't need another ka-boom... I'll get back to you on this one
Old 02-02-2008, 02:26 PM
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I have read that it does have an ignition delay to burn the rest of the gas.

I was able to take the control unit apart, and other than the connector coming off pin 1 looking like it has gotten hot, and what kinda looks like a dried brown goo near the back of the circuit board, it unit looks good. Of course that doesn't mean much. I can post some pictures if you think that will help.

I think the relays are for the alarm, as there is an antenna under there that looks like it attaches to one of them, so good call on that.

I appreciate your help.

Bill
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Old 02-02-2008, 08:45 PM
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