97 plymouth slow crank No Start????

I have a 3.3 engine,took the top half off this spring to replace head
gaskets, valve cover,seals etc. Put it all back together and it ran
fine. I took it off the road to do this work so i haven’t driven it
only started it from time to time. After a few times it started
cranking real slow then it would start ok. Now its just slow. checked
connections, took the starter out and had it checked, was alittle
variable on the amps so i replaced it. still the same maybe alittle
faster. checked fuel pressure was good. has 157,000 on it and have had
it since new with no problems. I’m missing something here, any
suggestions would be great. Thanks.

 

What does fuel pressure have to do with slow crank? And I see no mention of
having the battery tested?

Glenn Beasley
Chrysler Tech

 

yes- you are missing something- the battery is dead from sitting- and
needs to be charged or replaced- also the alternator may be bad and not
charging

you need to do a charging test on the alt., and a battery load test
after it is first charged

 

Not so fast!!! I’ve been around the block a few times. It has a new
battery out of my 64 pickup. Even if the alternator was bad it still
would start. Good guess. I would not be here if it were that simple.

 

Don't listen to "shirked duty-dishonor-country" aka Charlie Nudo. He's
the resident troll.

Nippondenso starters have a characteristic problem with solenoid
contacts. If you're cranking slow and not drawing enough current to
significantly dim the interior lights, look at the solenoid contacts.
You could also check the tightness of the battery cable to the
solenoid itself, but ND starters have been prone to this sort of
failure since the '70s.

 

Use a DVOM, paper and pen.
Connect the leads measuring volts at the battery posts, crank the
engine and record your reading. You should read 10.5+ V

Next connect one lead to the neg battery post and one to the block,
crank the engine and record your reading. You should measure .1v. Just
like golf, low scores are good.

Next connect one lead to the pos battery post and the other to the
starter motor post, crank your engine and record. You should measure
3v. Again JLGLSAG

If either voltage reading is greater, move the engine side probe closer
to the battery and crank until you find your bad connection. You won't
be missing anything.

Even after you find the big problem continue testing. With the eng
running, Neg bat post to alt case should be .1v. Pos Bat to alt charge
post should be .2v

Measure the voltage differential from the battery to the body and eng
to body.

 

No, if the alternator was bad, and you ran the engine for any amount of
time, the draw from the ignition, and from repeated starts, would drain
the battery in short time.

Don't assume the battery is good just because it's "new" IYO, have a
draw test done on it. I've seen many a 5-year warranty battery give up
the ghost at 1 year and have to be returned and pro-rated, for a new
one.

You also have to do a current draw test on the starter.

 

When you have a slow crank problem and you mention checking fuel pressure
some people may question how many times you have been around the block!! Not
to degrade you in anyway but checking the battery question had to be asked
after I read that!!

Glenn

 

The DVOM voltage checks prove that the battery has sufficient capibility
under load and that battery capability is reaching the starter with an
optimal ground connection.

Most cars on the road will not pass each of these tests because of less
than optimal connections.

Once you know because you have proved with the DVOM that you have
sufficient power and ground to the starter, what is value of starter
draw info?

If the engine still cranks slow with excellent connections between a
good battery and the starter, either the starter is bad or the engine
is too hard to turn because of mechanical problems. In either case
starter draw will be beyond specs.

These tests will diagnose the cause of any slow and most no cranking
engines.

Perfoming these simple voltage tests and making repairs to high
resistance connections on vehicles without any obvios problems, will
increase reliability of every electrical component in the future.

 

Well, a good DMM with an accurate low resistance range will give you
current draw anyway. All you have to get is the DC resistance to the
same path of which you measure the voltage drop. Ohm's Law works
every time: I = E/R.

 

I must be confused by reading your post. You can call it Digital Volt
Ohm Meter or Digital Multi-Meter.

Are you answering my simple question, "what is the value of measuring
or knowing starter draw info?"

How do you use a DMM to measure starter current draw to locate
resistance? How do you test useing your low range resistance DMM to
diagnose the problem?

Ohms law formula is why the meter reads a differance from one point to
the other whenever there is resistance.

Measuring voltage at varios points under load is fast and simple. I
don't need to measure or know the amount of resistance because voltage
differance indicated by the volt meter will allow me to isolate the
resistance and prove that my repair has corrected the problem. I don't
need to measure starter draw to know if it is capable of performing its
duty.

Measuring ohms of resistance without the load may not help in
diagnosis.

 

Your procedure is the perfect way to locate a external high
resistance, looking for high IR drops. The question was how to
determine current draw, which in this case of troubleshooting, is
irrelevant unless there is a weak or dragging motor, which may be the
case here.

Measure the point-to-point resistant from, say, the battery positive .
terminal to the starter motor terminal in tenths of an ohm, more
resolution if you have a Fluke or other good DMM. Then, measure the
IR drop when the motor is cranking. Using Ohm's Law, simply divide the
IR drop (voltage) by the circuit resistance, and you have the motor's
current draw in amperes. What this WON'T show, of course, is high
internal resistances in both the motor itself (bad brushes, burned
commutator, etc.) and in the battery itself (low state of charge,
sulfated plates, plate and strap corrosion, etc.)

Exactly, and is also why you can easily calculate current draw if you
know the external resistance, with the caveats stated above. Thus, if
the IR drop between the battery and motor terminal side of the
solenoid tested good, you'd want to know just how much that load of
the motor is drawing. If current is low when IR drops are low, the
trouble is either inside the motor itself, a "floating" ground (more
common than most people realize) or a low or sulfated battery.

Oh yes you do, if your IR drop tests prove there are no high
resistances either in the positive cabling or in the ground circuit.
If that's the case, and the motor current draw is low, the trouble's
either the source (battery) or the load (motor.) A quick check of
battery positive plate voltage under load will eliminate the battery
in short order, and then proves the trouble into the motor housing
itself.

The only change in resistance will occur when the load heats up the
cabling, during which time the DC resistance of the cabling will
increase somewhat. Bad connections, such as loose bolts and nuts, as
well as battery terminals, will also heat up quickly during a high
current draw, and are usually easy to spot by feel...if you dare.

 

Thanks to all that have replied to my problem. After more checking,
Took the surpintine belt off to check the pulleys and the alternator
was locked up, stoping it from turning over. Learn something new every
day. Thanks Again