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philk
Joined: 05 Apr 2012
Posts: 33
Location: Austin, TX
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 Posted: Wed Apr 25, 2012 12:25 pm Post subject: no crank after HD light switch short |
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the car now does not crank unless jumped...and it starts...I thought it may not have been charged well when I bought it and really haven't had a chance to really drive it to charge...
but it should at least turn over after driving about 10min....
thinking the battery cable to the starter may be dropping too much voltage .???
will have battery checked...while running I measure 14+V at the battery, so alternator should be working..
or bad starter?
nagging issue is what caused the HD light to short..? |
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edredas
Joined: 09 Dec 2004
Posts: 861
Location: Charlotte, NC
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| Posted: Thu Apr 26, 2012 7:48 am Post subject: |
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Might be time for a new battery.
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'84 944 -White, Brown interior
'84 944 -Red, Automatic
'86 944 -Garnet, Fully loaded, Koni suspension
'87 924S -Red, 300hp 951 swap
'87 924S -Red, Project Car
'88 924S -Red, Daily Driver |
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philk
Joined: 05 Apr 2012
Posts: 33
Location: Austin, TX
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| Posted: Thu Apr 26, 2012 11:43 pm Post subject: |
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naw it is realtively new - tested fine last night also.
got looking at battery cables and the insulation is dry and cracked..a piece flaked off yesterday and the outer wire is corroded...I'm guess new cables are needed..starter is new(er) supposedly too..
there are 2 connecters almost directly above the engine ground strap mounting point. I'm afraid to try moving anything before I know what it is cause its' all so brittle and fragile looking...I can see a hose out of block above the mounting point, must be coolant system (?).
do you know what those connectors might be for? |
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edredas
Joined: 09 Dec 2004
Posts: 861
Location: Charlotte, NC
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| Posted: Fri Apr 27, 2012 6:24 am Post subject: |
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The two connectors in question are for the speed and reference sensors.
_________________
'84 944 -White, Brown interior
'84 944 -Red, Automatic
'86 944 -Garnet, Fully loaded, Koni suspension
'87 924S -Red, 300hp 951 swap
'87 924S -Red, Project Car
'88 924S -Red, Daily Driver |
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11733
Location: PacNW
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| Posted: Fri Apr 27, 2012 7:36 am Post subject: |
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Phil, please look at edredas' signature and do the same. . .year and model.
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Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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philk
Joined: 05 Apr 2012
Posts: 33
Location: Austin, TX
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| Posted: Fri Apr 27, 2012 10:37 am Post subject: |
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done I think
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1987 924S project car (aka clunker) |
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joecitizennn
Joined: 12 Sep 2005
Posts: 2096
Location: no mans land
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| Posted: Sat Apr 28, 2012 1:25 am Post subject: |
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| philk wrote: | naw it is realtively new - tested fine last night also.
got looking at battery cables and the insulation is dry and cracked..a piece flaked off yesterday and the outer wire is corroded...I'm guess new cables are needed..starter is new(er) supposedly too..
there are 2 connecters almost directly above the engine ground strap mounting point. I'm afraid to try moving anything before I know what it is cause its' all so brittle and fragile looking...I can see a hose out of block above the mounting point, must be coolant system (?).
do you know what those connectors might be for? |
When a battery gets really low it takes longer for it to reach a healthy charge than you might think. Check the amps if you have a load tester, if not I would put it on a good battery charger for a couple hours. Fully charged 12 volt batteries should read at least 12.6 volts if not more. Also check your voltage when the battery is installed and the engine is running, it should be 13.5 to 14.5 volts.
_________________
87 924s
88 924SE gone
447 hp cgt clone
87 924S gone
84 944 sold
83 944 sold
89 turbo S LSD, ABS etc
86 951 white rocket
85 944 sport everything.
84 944 sold.
87 944 sold |
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philk
Joined: 05 Apr 2012
Posts: 33
Location: Austin, TX
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| Posted: Sat Apr 28, 2012 6:47 am Post subject: |
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Joe thanks, - I did have the battery tested on a load tester, pretty sure it's not the problem entirely...I plan to put it on a charger just in case..
The battery cables are really dry and cracked and I had a piece of the grnd cable to the engin flake off..when I measure from battery (+) to that spot there was and 11V drop...I pushed into the wire a bit and the 12.6V measured..so I know there's corrosion on the cables and replacing them seems prudent if not necessary..
Do you know what the 2 connector just above and to the left of where the grnd cable connects to the engine..there's a hose blocking access to the bolt also..those connectors look fragile and I want to know what they're for before messing with them..
Thanks
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1987 924S project car (aka clunker) |
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philk
Joined: 05 Apr 2012
Posts: 33
Location: Austin, TX
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| Posted: Sat Apr 28, 2012 6:49 am Post subject: |
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edredas (and JoeC) - thanks for the input on the connectors..appreciate it
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1987 924S project car (aka clunker) |
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joecitizennn
Joined: 12 Sep 2005
Posts: 2096
Location: no mans land
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| Posted: Sat Apr 28, 2012 12:28 pm Post subject: |
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| philk wrote: | ..those connectors look fragile and I want to know what they're for before messing with them..
Thanks |
They are fragile, their favorite trick is for the end of the male conncetor to break off and stay in the female end while just the prongs pull free.
This brings to mind a funny story, I went to drive a 1981 931 a few years ago and the guy said "this car usually requires a jump". He got in the drivers seat and hit the key and sure enough it did not start. So he gets his jumper pack and pops the hood... sitting there in one corner of the battery box is a 200 amp lawnmower battery 
A stranger story, I have a 924s sitting out in my barn that I never drive, but I start it on occasion. There is something wrong with the battery and it only puts out a little over 10 volts, but surprisingly enough it starts the car very reliably every time even after sitting for 2 to 3 months, it just cranks slowly. I would not have thought that the engine management system could function on 10 volts but it does well enough for it to fire and the alternator take over.
_________________
87 924s
88 924SE gone
447 hp cgt clone
87 924S gone
84 944 sold
83 944 sold
89 turbo S LSD, ABS etc
86 951 white rocket
85 944 sport everything.
84 944 sold.
87 944 sold |
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philk
Joined: 05 Apr 2012
Posts: 33
Location: Austin, TX
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| Posted: Sat Apr 28, 2012 3:29 pm Post subject: |
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joe - thanks for the lawn mower laugh -- while I got you ..what is the "reference" connect referring too?
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1987 924S project car (aka clunker) |
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joecitizennn
Joined: 12 Sep 2005
Posts: 2096
Location: no mans land
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| Posted: Sat Apr 28, 2012 10:32 pm Post subject: |
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The refrence sensor tells the computer what position the crankshaft is at, while the speed sensor tells that the engine is rotating and how fast. The plugs for these are located at the rear of the intake manifold in a metal bracket. The refrence is the top connector while the speed is below it. At the bellhousing the refrence is closest to the engine while the speed is closest to the transmission. These sensors are responsible for telling the computer to turn on the fuel, time the spark and injector pulses and operate the tach among other things.
_________________
87 924s
88 924SE gone
447 hp cgt clone
87 924S gone
84 944 sold
83 944 sold
89 turbo S LSD, ABS etc
86 951 white rocket
85 944 sport everything.
84 944 sold.
87 944 sold |
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philk
Joined: 05 Apr 2012
Posts: 33
Location: Austin, TX
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| Posted: Sat Apr 28, 2012 11:54 pm Post subject: |
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JoeC - great! that's really good info ...thanks much --
btw - you're 10V battery stroy...auto electronics are some of the most robustly built around next to radiation hardened electronics and mililtary spec'd stuff..maybe even more so cause of time and environmental changes..
usually integrated electroncis are built to specificatons to cover +/- 10% - +/- 20% supply voltage..but that's advertised operating...then margin is thrown in on top because IC manufacturers have process variations...and then engineers will throw more in if they can ...so the electronics are probably built to operate way down from 12V...
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1987 924S project car (aka clunker) |
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philk
Joined: 05 Apr 2012
Posts: 33
Location: Austin, TX
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| Posted: Sun Apr 29, 2012 7:44 am Post subject: |
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well charged up the battery and it's still not cranking..
will start by changing out the battery cables...first need to clear the way to get at the negative connection on the block
the reference sensor plug is cracked...probably should replace it at least, and possible the speed sensor too...are they the same sensor, but 2 of them? Where do you get the mating cable and what's that called?
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1987 924S project car (aka clunker) |
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joecitizennn
Joined: 12 Sep 2005
Posts: 2096
Location: no mans land
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| Posted: Sun Apr 29, 2012 9:20 am Post subject: |
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| philk wrote: | well charged up the battery and it's still not cranking..
will start by changing out the battery cables...first need to clear the way to get at the negative connection on the block
the reference sensor plug is cracked...probably should replace it at least, and possible the speed sensor too...are they the same sensor, but 2 of them? Where do you get the mating cable and what's that called? |
I would try hooking some stout jumper cables to the battery and crawling under the car hooking the neg to the bellhousing and hooking the hot to the starter. See if it cranks by key, if not take a small screwdriver and touch the small start wire post on the solenoid to the hot post.
If it cranks by key with the jumpers you have a battery cable problem.
If it cranks only when the solenoid start wire (black and red) is jumped you may have a switch or wiring problem.
If it dosent crank you have a starter or battery problem.
_________________
87 924s
88 924SE gone
447 hp cgt clone
87 924S gone
84 944 sold
83 944 sold
89 turbo S LSD, ABS etc
86 951 white rocket
85 944 sport everything.
84 944 sold.
87 944 sold |
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