Mercruiser 5.7L Starting problems
David A. Lauer
hard to start when cold and impossible to start when hot. The symptoms
are a sluggish starter when cold as if the batteries are not charged.
However I have replaced them with brand new ones that I'm sure are
charged. Additionally the voltmeter on the dash only shows about 12 (or
less) volts initially after starting. It eventually gets up to about
13V after running the engine for a while but I would expect that it
would read closer to 14V when initially started and then back down to
12-13V so something could be defective in the charging circuit.
When the engine is hot it's impossible to get the starter to turn the
engine even one time, as if the batteries are completely drained. I'm
not sure if this is a problem with the charging circuit, or perhaps even
with the starter. Could there be high resistance in the starter or the
solenoid that would cause these symptoms? How can I test these
components to confirm this?
Can anyone recommend any tests I can perform in order to check out these
two problems?
Thanks,
Dave
The Loner
tested.
I had a similar problem. I removed the plugs to see if the motor would spin
easily with no compression, and, lo and behold, it spun alright. Squirting
water from the plug holes. Turned out to be blown head gaskets - glad I
caught it before the inevitable overheat.
Check your oil for water beads, maybe.
--
The Loner
"David A. Lauer" <dal...@cofs.com> wrote in message
news:3D4703B1...@cofs.com...
JR North
JR
--
--------------------------------------------------------------
Home Page: http://www.seanet.com/~jasonrnorth
Larry
Start with the negative side of the battery. Disassemble all
connections from the battery negative to the engine block. Clean them
all up with emory cloth until they are shiny. Replace anything that
is corroded and won't clean. Carefully inspect all joints where the
cable goes into a terminal lug for corrosion. Get some terminal
protector from an auto parts store and coat all of the connections
when you have reassembled them.
Leave the negative terminal off the battery for now......
Disconnect the positive terminal from the battery. Disassemble all of
the positive connections between the battery and the starter solenoid,
including BOTH connections on the starter solenoid if you can. Shine
up all the metal until it is sparkling shiny, including all the
washers, screws, terminal blocks, and nuts. Replace anything that is
corroded too bad to clean. Carefully inspect any joint where the
cable goes into a terminal lug for corrosion, any sign of green.
Replace the cable if it is corroded. We're talking about being
STRANDED in NOWHERE, not inconvenienced along a roadside, here. Use
the terminal coating spray on all reassembled connections, especially
heavily in the bilge! Reconnect all the battery posts.
Try to restart the engine. If it starts great, we've fixed it! If it
still turns way slow, we'll need a $10 pocket voltmeter from Radio
Shack next........
If you're reading here, the cleaned up terminals didn't fix it. Go to
Radio Shack, any auto parts store or any electrical supply house and
buy the cheapest little Volt-Ohm-Milliammeter you can buy, about $10.
Get someone to man the starter key for you. Your hands will be full.
Ground out the high voltage terminal on the spark coil to the engine
block. DO NOT LEAVE IT OPEN AS IT WILL DESTROY THE ELECTRONIC
IGNITION! The engine will not start, obviously, during our test, even
though we are going to crank it when we measure with the meter.
The first test we are going to make is to determine how much voltage
is actually being applied to the starter motor, itself. Set the meter
to the next higher voltage range above 12 volts DC (not AC)...probably
15VDC range. Put the positive (red) meter lead on the starter side
post of the solenoid or if you can the heavy post right on the
starter, itself, if it has one. If the solenoid is part of the
starter, put it on the battery post of the solenoid. The other
contact is inside the starter. Tell your cranker to crank the engine
while you read what the voltmeter says. Don't crank it long. The
meter will settle and you need to be ready to read the right scale.
Cranking voltage should be more than 10-11 volts at the starter. If
the cranking voltage is in this range or higher, the starter has bad
contacts, windings, bad internal solenoid, worn brushes, broken
windings, broken segments in the commutator.....You need to buy a new
starter....sorry....(d^:)
Ok, so what if the voltage on the starter is 8V DC? Then we
troubleshoot the battery and it's wiring to the starter....
Put the voltmeter directly across the battery POSTS, not the terminals
clamped to the posts. It should read over 12.5V DC with no
load....12.8 is normal. If it's less than 11 volts, try charging the
battery with a 10A charger for 24 hours before proceeding further.
With the charger across the battery, you should see about 13.5-14.0
VDC. If it never rises, the battery has a shorted cell. Replace it.
When it's been charging 14 hours or more, the voltage should be near
14V or more! Automatic battery chargers will shut themselves off on a
good battery and not on a bad battery. Disconnect the charger and let
the battery sit for 10 minutes. Measure its voltage, again.....look
for around 13VDC, not 11, not 10, not lower. Now, while we're still
watching battery voltage, have cranker crank the engine. Good
batteries will hold about 11V at cranking current. Bad batteries drop
below 10VDC. Bad or good? Bad - replace. Good? keep going........
Set the meter on the 1.5 Volt DC range (or 2VDC range if it has it).
IN all these meter tests, the perfect reading is when the meter
movement doesn't budge off zero, indicating no voltage drop across
anything. When you find the bad connection, cranking the starter will
pin the meter or make it read upscale a good bit, at least....
Put the positive (red) meter lead on the engine block on some shiny
bolt head. Put the negative (black) meter lead on the negative post
of the battery (not the terminal, the post). Watch the meter while
our cranker cranks the engine. It should read zero volts drop or very
close to zero. Practically, there may be a few tenths of a volt drop
on the cable at this current level. If the meter pegs or moves
upscale a lot, move the red meter lead to the battery terminal and
measure the cranking voltage drop from the battery post to the
terminal clamping it. Zero is perfect. If it's ok move the red meter
lead back to the next point towards the block until you find the
voltage when it is cranking.
Ok, let's assume there was little voltage drop on the negative lead.
Do the same to the positive lead. Put the positive (red) meter lead
on the + battery post. Put the negative (black) meter lead on the
battery side of the starter solenoid. Crank it. Should read low like
the negative lead did. If not start moving the black meter lead away
from the + battery post until you find the cranking voltage drop.
Ok, let's assume that didn't find it. The starter solenoid big heavy
leads have 12VDC across it when the engine is NOT cranking. So, we
DON'T connect our meter leads across these big terminals UNLESS the
motor is ALREADY cranking or the meter will peg hard. The procedure
to test the solenoid for the voltage drop is to start cranking the
engine, THEN touch the red meter lead to the battery post on the
solenoid and the black meter lead to the starter side post and look at
the meter, quickly, THEN remove the meter leads BEFORE stopping the
cranking of the engine. When the solenoid is closed, these big posts
are connected together inside the solenoid contacts and the voltage
across the posts should be near ZERO volts DC. If the voltage drop is
here....replace the solenoid, it's corroded inside and you can't fix
it....
We should have found it by now. There's nothing left in the circuit!!
larry
arthur unknown
happens with new/charged batteries). If you are a CBYM (Certified
Back Yard Mechanic :o) , disconnect, clean, and reconnect ALL
wiring in the starter circuit, including the ground strap/cable on the
engine block. It sounds like a loose/corroded connection, but could
be a bad starter. A bad starter motor will usually crap-out
completely after a few failures.
Good luck.
arthur
On Tue, 30 Jul 2002 17:22:57 -0400, "David A. Lauer"
<dal...@cofs.com> wrote:
Jim
If you can, I suggest you remove the starter and have it tested.
I had a very similar symptom on a car many years ago. It turned
out to be that one of the (silver) solder joints internally gave out
so the starter was only using half its windings. Terminology may
wrong here, but hopefully you get my drift.
-Jim
Tom Knight
comments have helped me understand what's going on "back there" and how to
begin to fix things. Good job!
Rus
Calif Bill
ride fill with copper dust and short out. A starter rebuild shop will fix
it, or first take a broken hacksaw blade (correct width) and scrap the
grooves clean.
Bill
"Tom Knight" <rus...@prexar.com> wrote in message
news:ukfnifd...@corp.supernews.com...
David A. Lauer
I made the repair over this past weekend and replaced the starter. Boy
what a PITA that was. I'm a big guy and so don't fit so well into the
small engine compartment of my 25' Monterey.
It turns out that all connections were ok, although I did take the
oppurtunity to clean them with emory cloth. I replaced the starter
motor late Sunday and that corrected the problem with the sluggish
starting, the old one had rust and corrosion, probably the original, so
I figured it was time to put a new one in there. It set me back $250.00
plus tax. ouch!
Next weekend I think I'll take a look at the engine tilt, it's not going
down.....
Dave