1993 928 GTS hesitation
06-05-2012, 11:45 AM
#47
Rennlist Member
Join Date: Jun 2006
Location: Vancouver, Canada
Posts: 165
Likes: 0
Received 0 Likes
on
0 Posts
When I first got my car a few years ago I had similar issues and it turned out to be the ground that's inside the front passenger side nook near where the transmission cooler lines are. It's a tough one to find but it was loose and the engine was cutting in and out.
Also, this past weekend I removed my passenger side ignition coil and when I installed it one of the wires (+ or -) grounded against the frame and melted the coil? Might want o check the coil leads are not rubbing on anything.
Also, this past weekend I removed my passenger side ignition coil and when I installed it one of the wires (+ or -) grounded against the frame and melted the coil? Might want o check the coil leads are not rubbing on anything.
06-05-2012, 12:50 PM
#48
Rennlist Member
Well, if the main engine ground is not the problem, then hopefully it can steer you towards the correct answer to the problem.
It was amazing to me to what ends my car would attempt to find a sufficient ground before it would not run. But when it wouldn't find a ground, it simply would not run.
Good Luck.
It was amazing to me to what ends my car would attempt to find a sufficient ground before it would not run. But when it wouldn't find a ground, it simply would not run.
Good Luck.
06-05-2012, 01:02 PM
#49
Advanced
Join Date: Dec 2005
Location: Vernon BC
Posts: 67
Likes: 0
Received 0 Likes
on
0 Posts
Who knows which ground point the fans are supposed to be using?
If something with a high draw is grounded at the wrong point, will this interfere with other things that are supposed to be grounded there?
Can you "overload" a ground point causing electrons with no place to go? (except straight into my ignition system), or would it just be bad or corroded ground connections?
Steve
If something with a high draw is grounded at the wrong point, will this interfere with other things that are supposed to be grounded there?
Can you "overload" a ground point causing electrons with no place to go? (except straight into my ignition system), or would it just be bad or corroded ground connections?
Steve
06-05-2012, 02:02 PM
#50
Rennlist Member
Who knows which ground point the fans are supposed to be using?
If something with a high draw is grounded at the wrong point, will this interfere with other things that are supposed to be grounded there?
Can you "overload" a ground point causing electrons with no place to go? (except straight into my ignition system), or would it just be bad or corroded ground connections?
Steve
If something with a high draw is grounded at the wrong point, will this interfere with other things that are supposed to be grounded there?
Can you "overload" a ground point causing electrons with no place to go? (except straight into my ignition system), or would it just be bad or corroded ground connections?
Steve
There are two ground points at the front of the engine bay, one just behind the igntion amps and the other as described above. These are used by lights, fans and the ignition amps.
And yes, if there is corrosion or a loose connection then there will be a voltage drop with high current loads, which will effect other circuits sharing the same ground point.
Let's say you had a resistance of 0.5 ohms at a ground point, almost too small to measure with a meter. But when the fans are running, with (say) a 10-amp load, that's a 5-volt drop. So the ignition amps suddenly see 5 volts on the ground connections. The trigger pulse from from the EZK is a 5-volt signal IIRC, measured to ground. But if the ground itself jumps up to 5 volts, you've got nothing.
I would disassemble both of those grounds, clean and reassemble.
06-05-2012, 02:05 PM
#51
Under the Lift
Lifetime Rennlist
Member
Lifetime Rennlist
Member
On left hand drive, the ground for the radiator fans is GP II - in engine compartment on the right side inner fender just in front of the radiator. In my car the auto trans fluid cooler lines obstruct the view of that area, so this is the best shot I can get.
06-05-2012, 02:18 PM
#53
Nordschleife Master
Thread Starter
Jim,
Are you sure on the grounds?
93GTS (early and late) show fans LHD are GP II, but final stages use GPIII.
GPIII is located above the hidden coil.
Steve is going to clean both, and we will hope that will solve this issue.
However these two do not share the same ground, so the problem would then lie in a broken wire possibly inside the front chassis harness. Luckily for us, this could be repaired properly and easily without fully disassembling the entire car with a few new short leads.
Are you sure on the grounds?
93GTS (early and late) show fans LHD are GP II, but final stages use GPIII.
GPIII is located above the hidden coil.
Steve is going to clean both, and we will hope that will solve this issue.
However these two do not share the same ground, so the problem would then lie in a broken wire possibly inside the front chassis harness. Luckily for us, this could be repaired properly and easily without fully disassembling the entire car with a few new short leads.
06-05-2012, 02:21 PM
#54
Nordschleife Master
Thread Starter
GP II is only for LHD cars! RHD is GP I according to the manual. Luckily the car in question is LHD.
Also for 93+ the WSM lists them as GP, not MP. They finally wrote them for the english speaking market too.
Also for 93+ the WSM lists them as GP, not MP. They finally wrote them for the english speaking market too.
06-05-2012, 02:40 PM
#57
Nordschleife Master
Thread Starter
They are factory units (bosch) with only as you can see 16,000 km on them. We also took the units which run perfectly in my high mile car out, and put them in his, no change.