91 740 turbo starting problems /electrical gremlins

  • Thread starter Thread starter theo.chan
  • Start date Start date
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theo.chan

I recently purchased a 1991 740 turbo and am having some problems with
starting the car and the electrical system.
From time to time, all the electronics in the car will cut out while I
Click to expand...
am driving. This means the headlights, turn signals, a/c fan, and
radio far, power locks and mirrors, and windows will all stop working.
The ABS and SRS lights are lit up on the dash. I know when this is
*not* happening since when the lights are on, the bulb failure light
is always on (even though all the bulbs are working). When I turn off
the car and restart it, everything works fine again.

This happened the other day, so I shut off the car and when I tried to
re-start it, nothing happened. The engine did not crank or anything. I
was able to push start the car (it's a manual transmission) and drive
home. I took it to the mechanic the next morning (needed a push start
again) and he replaced the starter motor. Now when I turn the key, the
engine will crank, but it will not always turn over. Sometimes it will
turn over for a second and then stall. If I try to start it too many
times the starter motor will stop running (I'm guessing the battery is
out of juice) and the only thing that will get it going is a jump
start or a push start.

the mechanic is suggesting replacing the fuel pumps (he claims there
are two) at a cost of about $500, or at the very least replacing the
battery which he claims would give me a few more shots at getting the
starter motor to turn the engine over.

I don't really have a lot of money right now, so am thinking I may
just spring for the battery in the hopes that it'll give me enough
juice to get the engine started.

I'm wondering what the cause of the electrical and starting problems
may be, and why the old starter would have just crapped out like that.
going over the repair records for the car, the ignition was replaced
about a year ago so is relatively new.

Thanks!
 
I recently purchased a 1991 740 turbo and am having some problems with
starting the car and the electrical system.

am driving. This means the headlights, turn signals, a/c fan, and
radio far, power locks and mirrors, and windows will all stop working.
The ABS and SRS lights are lit up on the dash. I know when this is
*not* happening since when the lights are on, the bulb failure light
is always on (even though all the bulbs are working). When I turn off
the car and restart it, everything works fine again.

This happened the other day, so I shut off the car and when I tried to
re-start it, nothing happened. The engine did not crank or anything. I
was able to push start the car (it's a manual transmission) and drive
home. I took it to the mechanic the next morning (needed a push start
again) and he replaced the starter motor. Now when I turn the key, the
engine will crank, but it will not always turn over. Sometimes it will
turn over for a second and then stall. If I try to start it too many
times the starter motor will stop running (I'm guessing the battery is
out of juice) and the only thing that will get it going is a jump
start or a push start.

the mechanic is suggesting replacing the fuel pumps (he claims there
are two) at a cost of about $500, or at the very least replacing the
battery which he claims would give me a few more shots at getting the
starter motor to turn the engine over.

I don't really have a lot of money right now, so am thinking I may
just spring for the battery in the hopes that it'll give me enough
juice to get the engine started.

I'm wondering what the cause of the electrical and starting problems
may be, and why the old starter would have just crapped out like that.
going over the repair records for the car, the ignition was replaced
about a year ago so is relatively new.

Thanks!
Click to expand...
If by "ignition was replaced" you mean the ignition switch, that takes my
main suspect off the list.

If the battery connections haven't been given a good cleaning lately, now's
the time. My 85 765T has a pair of wires that attach to the positive
terminal via a ring connector, and when that makes bad contact the
electrical system cuts out. Also give each wire at the battery a little tug;
I had one wire corrode in two under the insulation (and have known a couple
other 740/760 owners with the same problem).

Mike
 
I recently purchased a 1991 740 turbo and am having some problems with
starting the car and the electrical system.

am driving. This means the headlights, turn signals, a/c fan, and
radio far, power locks and mirrors, and windows will all stop working.
The ABS and SRS lights are lit up on the dash. I know when this is
*not* happening since when the lights are on, the bulb failure light
is always on (even though all the bulbs are working). When I turn off
the car and restart it, everything works fine again.

This happened the other day, so I shut off the car and when I tried to
re-start it, nothing happened. The engine did not crank or anything. I
was able to push start the car (it's a manual transmission) and drive
home. I took it to the mechanic the next morning (needed a push start
again) and he replaced the starter motor. Now when I turn the key, the
engine will crank, but it will not always turn over. Sometimes it will
turn over for a second and then stall. If I try to start it too many
times the starter motor will stop running (I'm guessing the battery is
out of juice) and the only thing that will get it going is a jump
start or a push start.

the mechanic is suggesting replacing the fuel pumps (he claims there
are two) at a cost of about $500, or at the very least replacing the
battery which he claims would give me a few more shots at getting the
starter motor to turn the engine over.

I don't really have a lot of money right now, so am thinking I may
just spring for the battery in the hopes that it'll give me enough
juice to get the engine started.

I'm wondering what the cause of the electrical and starting problems
may be, and why the old starter would have just crapped out like that.
going over the repair records for the car, the ignition was replaced
about a year ago so is relatively new.

Thanks!
Click to expand...
I forgot to mention - the fuel pump idea is out in left field, but the
battery may not be. I've had several batteries fail intermittently. If the
brushes in the alternator are worn enough, you could lose all electrical
power occasionally.

Mike
 
Well the problem is definitely *not* the fuel pumps. I would check all the
battery cables, and the lugs where they attach to the engine block, starter,
and alternator. Don't forget to check the grounds as well, make sure nothing
is loose , corroded, or broken under the insulation.
 
Thank you everyone for your replies. I replaced the fuel pump relay
today (the one that was previously installed was original from '91!)
and the starting problems seem to have disappeared.

The electrical problem still seems to manifest itself from time to
time, such as the power mirrors do not work, but they used to a few
days ago and simply quit. If the radio is on and I press one of the
mirror buttons, I can hear the mirror motor engage for a split second
and then the radio turns completely off and the mirror does not move.

Thoughts?
 
Thank you everyone for your replies. I replaced the fuel pump relay
today (the one that was previously installed was original from '91!)
and the starting problems seem to have disappeared.

The electrical problem still seems to manifest itself from time to
time, such as the power mirrors do not work, but they used to a few
days ago and simply quit. If the radio is on and I press one of the
mirror buttons, I can hear the mirror motor engage for a split second
and then the radio turns completely off and the mirror does not move.

Thoughts?
Click to expand...


You've got some bad connections somewhere, did the fuse panel get wet? Try
pulling the radio fuse and reinserting it a few times. Also check the ground
strap from the engine to firewall.
 
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