4.7L Hard Starting
S. Miller
I have a 2001 Dakota 4.7/auto with 42k miles that has always started
immediately anytime, warm or cold. Recently however I have needed fairly
long cranking times to get the engine started whenever the vehicle has not
run for a few hours or more. Once started with a long cranking run I can
immediately shut off the engine and it will restart normally (immediately)
until the engine has set for several hours, then again a long cranking
period will be required to get it started. It doesn't seem to make any
difference whether the engine is cold or warm, and there are no other
drivability problems, the idle is fine, etc. No trouble codes are being
set.
Due to the time element nature of the problem I first thought that this
might be due to the fuel pressure leaking down too quickly due to a leaky
injector or check valve, but a look at the service manual reveals (in bold
type, no less) that a fuel pressure of zero in the fuel rail is perfectly
normal for a cold engine, so it would appear that fuel pressure leakdown is
not the cause of the problem.
I have also read of similar problems being caused by the throttle position
sensor or the crank position sensor, but the fact that the engine will
re-start immediately and that there are no other drivability issues and no
trouble codes would seem to lead one away from these causes.
Any thoughts or pointers would be appreciated...
- Seth
wrnch61
react to temp. changes(either directly or indirectly) the codes often will
not show up til a sensor is completely bad while a marginal one will still
cause you problems. let us know what you find out wrnch61
"S. Miller" <smail-pleas...@gstarusa.com> wrote in message
news:3F971102...@gstarusa.com...
Paul Johnson
>
> I have a 2001 Dakota 4.7/auto with 42k miles that has always started
> immediately anytime, warm or cold. Recently however I have needed fairly
> long cranking times to get the engine started whenever the vehicle has not
> run for a few hours or more. Once started with a long cranking run I can
> immediately shut off the engine and it will restart normally (immediately)
> until the engine has set for several hours, then again a long cranking
> ...I first thought that this
> might be due to the fuel pressure leaking down too quickly due to a leaky
> injector or check valve, but a look at the service manual reveals (in bold
> type, no less) that a fuel pressure of zero in the fuel rail is perfectly
> normal for a cold engine, so it would appear that fuel pressure leakdown
is
> not the cause of the problem.
>
pump- was allowing fuel to bleed back. New fuel pump (under warranty
fortunately) completely solved the problem.
Paul Johnson
Steve
I had the same problem with a 86 Dak, but it ended up being the sensor
that told the computer how warm/cold the engine was. Not sure what
the sensor was called. The truck always thought it was warm so it did
not get the correct mixture for a cold start.
Steve
da...@spamattbi.com
(remove "spam" for E-mail)
Unknown
originally shipped with these trucks had some know issues. I had to
replace mine twice.
DC redesigned the fuel pump because of the number of problems being
fixed under warranty, but there is no recall or TSB for this.
On Thu, 23 Oct 2003 13:48:21 GMT, "Paul Johnson"
<thejo...@frontiernet.net> wrote:
Ron S.
I have a 94 Dakota with the 3.9 and it sort of does the same thing.
Just turning the key to the ON position and waiting a few seconds
while I put my seatbelt on lets the fuel pump build up pressure and
it will start in an instant, hot or cold. If I don't give it that little bit
of time, it still starts okay, but the cranking time is longer.
Ron
nItpIk
"wrnch61" <b...@earthlink.net> wrote in message
news:wbIlb.13729$W16....@newsread2.news.atl.earthlink.net...
S. Miller
Hi Paul and Twix,
Thanks for your comments.
I certainly don't doubt your experiences, but I don't see how it would be
possible for the fuel pump to be the culprit in my case. If I turn the ignition
to 'on' without starting I can hear the fuel pump run for a few seconds and then
shut off as soon as the fuel rail comes up to the proper pressure (just as it is
supposed to do). If I try to start the engine at that point I will still
experience the hard starting problem, even though the fuel pressure is up to
normal. And as I mentioned earlier, the DC service manual states that it is not
even necessary for the fuel rail to maintain pressure in order to provide a
normal start.
Again, I'm not doubting your experience and I'm not trying to debate anything or
say that you're wrong, but it seems that in my case it is very unlikely that low
fuel pressure could possibly be the problem.
- Seth
Tbone
the injectors. If that is happening, then the truck will not start until
the air is purged out through the injectors and that takes a little time.
--
If at first you don't succeed, you're not cut out for skydiving
"S. Miller" <smail-pleas...@gstarusa.com> wrote in message
news:3F99C304...@gstarusa.com...
RedNeck TookOver Hell
>Again, I'm not doubting your experience and I'm not trying to debate anything
>or
>say that you're wrong, but it seems that in my case it is very unlikely that
>low
>fuel pressure could possibly be the problem.
>
A simple test is to "cycle" the key several times without engaging the starter
from off to on when the vehicle has sat for at least several hours.
If it starts right up after the last "cycle" it's the fuel pump, if not, then
it's something else
I'll start watching reality TV shows, when I can vote people off the planet.
S. Miller
Hmmm, yep... good point... and I think you're right... see my response to
Redneck below...
S. Miller
Bingo. Cycling the ignition (and thus the fuel pump) through a few cycles (rather
than just once as I had been trying) will result in the engine starting
normally... thanks much for the tip and also thanks to the others who suggested
the fuel pump or a fuel-related problem as it looks as though you were all on the
mark.
I'll try this test again through a few more cold start cycles and if the results
hold up then I guess I'll let the dealer take a look at it because it looks like
the culprit could actually be many things... check valve in the fuel pump, check
valve in the pressure/regulator, maybe just a leaking injector (I hope) and some
of these parts are pretty expensive and thus maybe not such a good idea to shotgun
this one. Maybe I'll get a fuel pressure gauge and one of those adapter rigs that
goes between the fuel line and fuel rail so I can isolate the problem in one
direction or the other... if it's just a leaky injector I can take care of that
one pretty easily myself. Would not look forward to dropping the tank...
Damn, I remember when the fuel pump was mounted right on the front of the engine
and cost $12.95 at Pep Boys...
Roy
See what happens when ya get off "the machine" ???
<BFG>
Roy
"S. Miller" <smail-pleas...@gstarusa.com> wrote in message
news:3F9A8B83...@gstarusa.com...
Jim
Dakota has occasionally required longer cranking to start. It started
doing this about 18 months ago. Not a problem since it rarely
occurred. A new distributor cap seemed to eliminate the problem for a
while. However, the last couple of weeks, after a 700 mile trip, it
has gotten very frequent, hot or cold, day or night, recent start or
no recent start. I took it to Goodyear and they said everything is
okay, within spec -- might be carbon build up absorbing the initial
fuel load. I pulled a plug and it looked fine. The ignition wire
ends look good. I do about 1/2 highway driving and 1/2 local driving.
Does anyone have any suggestions? (Please post response since my
mailbox is full of trash spam and I don't dare go near it.)
TIA.
Jim
"Roy" <R...@home.net> wrote in message news:<Vuxmb.25529$e01.51759@attbi_s02>...