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Discussion Starter #1
I have been having trouble with intermittent starting problems. Every five or six times the engine just will not catch. After a minute or so of cranking it would usually start. Doesn't matter if engine is cold or hot.
I am in initial stages of t-shooting.
I have verified adequate fuel pressure at rail. Pressure actually rises quite rapidly.
I then turned to electrical issues. I measure voltage to cold start valve while cranking engine. Some very interesting observations.
Keep in mind I have fresh and verified battery.
When I initially start cranking the CSV voltage will start at 5.5 or so and slowly rise as I crank for five or so seconds to about 8.0 vdc. I give it a few seconds and start again. This time the voltage starts initially at a higher value (maybe 6 or 7 vdc) and climbs even more. After about the third time of cranking, the measured voltage will rise yet again and, when it eventually hits the 10.0 vdc mark, the car will start - every time.

I'm thinking this 10 volts is some kind of threshold voltage that is required for some ignition component to work.

There is no significant voltage drop at battery terminals during starting.

So the question is where is the voltage drop occurring?

Even with thirty plus years of fooling around with cars (foreign and domestic), this has me totally baffled.

Like I say, I'm in intial stages of t-shooting and welcome any thoughts.

Thanks guys,
Warren

:confused:
 

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1966-2013
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What's the voltage at the battery during cranking?
Anything less than 10.3~10.5 and you're wasting your time as the ECU won't come online.

As you describe voltages going up a bit on things down the line with each progressive try, it might not be beyond the realm of possibility that you're battery has had it and the increases are a result of the thing flowing a tiny bit better as it gets warmer from successive attempts. (like putting on the headlights to warm the battery when its below zero to get more available voltage)
 

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I have verified adequate fuel pressure at rail. Pressure actually rises quite rapidly.
Hmmm. So the pressure starts off low, then rises to spec? Potential problem if so. The fuel system is not retaining pressure as it should.

When I initially start cranking the CSV voltage will start at 5.5 or so
How/where is this voltage being measured?
 

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Discussion Starter #6
T-shooting harness

I have a harness that I made up with both male and female Bosch plugs. I can measure CSV, TTS, anything with that type of connector. I can read voltage while function of device is unaffected.
It also allows me to read contact states, resistances etc.
30 years experience as E&I tech in major power generating station.

Trust me on the readings.

Warren
 

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Discussion Starter #7
Clarifications

The fuel pressure rose rapidly as I had just connected pressure gauge and system was bled down. With empty lines I had pressure in an instant. It does retain pressure for quite a long time so there is no check valve issue.
I'm certain fuel pressure is not my problem.

When I measured voltage drop at battery I had already done some cranking so I may have gotten misleading readings.

The battery will be next starting point. Then I'll start chasing volts.

At least I have found the problem. And we all know how much fun intermittent electrical problems are.

Thanks for input guys,

I'll let you know.

Warren
 

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Next thing to test then is cranking voltage TO ENGINE GROUND at the CSI & TTS connectors. If cranking voltage, please see this thread. Posts 9, 15 & 17 explain how the cold start system works and how to test it.
 

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Warren,

Nice test adapter.

As others have stated, a minimum battery voltage, 10.X volts is required for the ignition controller to "turn on" and allow the car to start. Sorry, I don't know the exact voltage and it may vary slightly between cars/controllers. Measuring the battery voltage during cranking is a very good indicator. If the battery voltage during cranking is less than 10.9 volts the battery may be suspect and a full charge or healthy jump may help.

If the battery is marginal and like previously mentioned pulling some amps through the battery warms it up a little and lets it produce a little more power, then your battery is bad. If another battery is available, even if not the correct size for the car but can be hooked up and the car starts, well there is your answer.

However, more important than battery voltage is the voltage sensed by the ignition controller. You have to get the volts/amps out of the battery and to the devices.

Your troubleshooting uncovered a low initial voltage at the CSV which then rises to a sufficient value upon successive attempts at starting. Could be the battery issue but could be one or more high reisistance connections in the circuit(s). Which can act the same way as the connection heats up and material expands making better contact? the connection heats up and gets rid of any oxidized(?) insulating(?) material. Then it works better.

But you have to get the volts to the devices before anything will work.

While you are in electrical mode:

*clean and/or replace the fuse and fuse holder under the rear parcel shelf(may be behind the rear passenger's side trim panel. (it's for the fuel pump I think, but might as well get it now. It is a common problem area)

*remove the fuses under drivers's dash and clean the fuse holder contacts. Slightly squeeze them more closely together to have a better grip on the fuse ends. Replace the fuses, they are cheap and if you are right there and doing all that work, just replace them all with the pointy ended silver tipped glass fuses if you can. The lead(?) alloy strips over plastic/ceramic forms just oxidize and get hot from the bad connection right there in the fuse holder. Look at them and don't be surprised if half of them have the metal strip deformed from the heat and subsequent expansion of the fuse element itself.

*locate the fuel/ignition system grounds on the rear passenger's side of the head. Inspect, repair, clean, reinstall, etc

*locate the large 2 bolt terminal strip on the driver's side fender under the hood. Inspect, clean, etc, etc. This terminal strip is a plastic block with a couple of bolts molded into it. Lugs go on the bolts and nuts tighten up on them. I have seen where this connection gets hot, the plastic softens, the bolt moves slightly, and the connection loosens. I believe this is where battery voltage splits and connects to the rest of the car.

I don't remember if the battery cable goes to the block first then starter or to the starter then to the block but check, clean.....

Hopefully others will comment with more specific electrical advice but these have been the electrical weak points on my car.

Hopefully with a couple hours work you will have a well starting car.

Good Luck,

Wayne
 

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Your troubleshooting uncovered a low initial voltage at the CSV...
Yes, low voltage potential at the CSI. BUT the conclusion that it's a voltage supply problem is based on a test method that used the TTS as the ground. Without testing whether the TTS is providing a sufficient CSI ground, one could rewire the whole car looking for a bad connection on the supply side and still have low CSI voltage. :eek: This is why I asked how and where the voltage values were obtained. Unfortunately, no conclusion as to the problem of low CSI voltage can be reached at this time because of insufficient testing (a bad TTS heads my list though).

In order to properly diagnose a problem, one needs to know how the thing is supposed to work in the first place. Only then can one properly diagnose it when it doesn't.
 

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Discussion Starter #11
Progress report

I took the battery out of car (only had car less than a year). When I saw a date sticker if July 2007, buying a new battery was a no-brainer.
So far the car seems to be doing fine.
Tifosi, I think you had something there explaining the increasing voltage values. Definitely enering this into the memory bank.
The old battery appeared to be working fine so I had no reason at that point to suspect battery faillure.
I got focused on fuel as it appeared it would eventually start after dumping a s**tload of fuel into intake.
Having the harness I made up was a huge help in t-shooting. I highly recommend having one.
It's only been a day and a half with no problems. I would check voltage but I hate playing around with these twenty five year old connectors.
Just by the way it now starts up, I'm pretty confident.
Thanks to all for the information.

Warren
 

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Trained (ex)Professional, , 1953-2018 RIP,
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Congrats Warren. Well done.

If you PM me your email address, I'll send you the color wiring diagrams for your Spider. With your electrical experience and knowledge, you will quickly see why the test results from your really cool test harness led to the wrong conclusion. :)
 

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Cool beans on the making it go.

You're still gonna want to play with those old connectors and getcha one of them papajam diagrams while the gettin's good onnaconna going through and cleaning/tightening/dielectric greasing every contact and connection you can find will help keep the electrons flowing free and fast, which in turn will help create less strain on the battery and may even help the charging system get it rejuiced in an efficient manner (provided the alternator and regulator are up to snuff of course)

Do it now, get it over with, enjoy the car for several years.
Or, don't do it now and end up f'ing with various connections as they get stupid individually or in groups over the next several years and help to propegate the 'bad electrics' myth.
 

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Discussion Starter #14 (Edited)
Thanks

Not too long ago I wisely took advantage of Papajam's great generosity and received said circuit diagrams. I then immediately went to Office Depot and had them blown up (boy was that noisy!) and laminated.

They have been a TREMENDOUS help!

And actually my test harness did not lead me to a wrong conclusion. Moments after using it I identified the voltage problem. Troubleshooting was pretty much all downhill from there - especially with my Papajam prints in hand.

My only wrong conclusion was the initial assumption of a fuel delivery issue (pump, filter, etc.). Five minutes with a pressure gauge took care of that.

I also use the harness on my 82 911 (J-Jetronic). I wish I had thought of making one sooner. Highly recommended.

Also I have been cleaning connections all along as I go forward - especially the grounds.

Once again thanks to all,
Warren
:)
 

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My apologies Warren for not recalling that I sent you the diagrams. I email a dozen or two of these things a week and don't keep records to whom they go (that's my excuse anyway and I'm sticking to it :rolleyes: ).

As a result of this thread and the importance of knowing that the TTS provides the CSI ground (not power), I've revised the diagrams to better clarify this (and made a few graphics changes as well). If you, or anyone, would like the revised version, please PM me your email address (again).
 

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Discussion Starter #16
The results are in!

:)I didn't want to post this until I had a few days of testing. I think issue is resolved. And it appears battery was issue - however in a very unusual manner.

I think my battery had one totally dead cell and five very healthy cells. Let me explain.

I never suspected the battery. The headlights would barely dim while cranking starter (a pretty good indication of amperage pull on battery). Hence at this point I didn't see cause to put my DVM on battery. Of course I would have down it a little further down the t-shooting flowchart. However I had basically started t-shooting fuel system first.

Like I said before, after seeing the 2007 date code on battery, I immediately replaced it. Now the car will fire up instantly. I can now drive it worry-free (well almost).

The lessons learned here are

1. A ten volt battery will give you some fairly bright headlights.

2. A ten volt battery is enough to turn motor. The headlights didn't dim much either when starting.

3. These forums are invaluable as nothing beats the experiences of a bunch of gearheads who enjoy sharing information.

Thanks,
Warren
 

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3. These forums are invaluable as nothing beats the experiences of a bunch of gearheads who enjoy sharing information
I dunno man, free beer and hookers can be pretty tough to compete with :D

Still, glad its all resolved just the same.
 

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:)3. These forums are invaluable as nothing beats the experiences of a bunch of gearheads who enjoy sharing information.
I dunno man, free beer and hookers can be pretty tough to compete with...
Except there are some here ^ who share too much information...!

BTW, if you are so inclined, you can become a subscriber for ~ $20 and help toss some money towards keeping this place alive. I think it is well worth the investment.
 
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