Question about 1995 Jeep Grand Cherokee
Tries to start and sounds like it will but won't.
Fine? ( 30 to 40PSI , fine, not squirt tests or sounds)
EFI demands full pressure all the time, its not like carb cars of old.
first off, no engine stated ,so all help will be poor, all cars have engine options.. to work on any car , open hood, (USA commenter) and look up see that EPA sticker there, and the engine ID< and displacement?
That is first. (ill pretend , you drove to my shop and what id do)
i ask owner, when\'s the last time car was a daily driver?, last week or last decade>? (bad fuel, etc,....happens)
i stick finger in air, its 50F, not -40F air temp, ok not in Canada. cool. er its hot...
i open hood and see a I6 4.0L engine, with EFI. ok.
2: i check all the fuses. it\'s EFI and blown fuses, will kill the show.
3: i turn the key , and check engine lamp glows, (ECU is happy)
(ecu has juice , so boots and glows CEL, to say so)
4: i crank it, it cranks over 250 RPM, sounds like normal fast cranking
we all know that sound, we dont use the tachometer...
5: i then ask owner , evah\' tune it up this decade, answer no.
i then do the tune up, plugs were ratty. all spark parts, filters.
we dont use $100/hr labor to find ratty spark parts the install them
its called a tune up.
car runs like new. (end story) no?
or it was tuned up;.
so, i check spark it is blue-white on my test spark plug (new) times 6.
i then check spark timing, it\'s dead on, good, if off i fix that first.
if timing is off on most cars i check compression as some like
to slip cam timing. (i saw a V6 once with plastic timing gears. once burned ,twice shy , i check it all) (i do a compression test on all old motors. so I can see TRUTH, and potential future LIFE of engine)
ok, spark is perfect,please note my order, good motor?, good spark?
with bad motors and spark the fuel can not burn, not fully.
then, i try "test fuel" (can-o-spray) car runs for 3 seconds. and stalls.
my gosh, the motor and spark were good. verrroooooom stall....
(btw, this here, logic flow is bad on DOHC motors, 99% true) ask
i check spark plug tips and they are dry. (wet is flooding)
i suspect low or no fuel pressure, i know from experience
that fuel pumps about 75% do not run only key on, only cranking
and running they run. so i check pressure.
i find its 10psi.
the story gets longer for flooding or injectors tests, ill skip that.. ask.
so 10psi,. i find
1: 12v to pump is really just 6v, if fix bad connector up stream from pump. done.
2: if 12v to pump cranking, mine was 11v, but the starter does that. drop so is ok. (study starting systems) , its good line voltage is good. cranking.
3: i then check the fuel pressure reg, and find the thing stuck wide open , i replace the reg. and pressure is 34 PSI (wild guess. didnt look yours up. ) car runs prefect now.
4: i find FPreg ok, but pump is weak, new pump saves day..
i have a scope and can see this pump is noisy, has a bad commutator segment, deep inside it... scopes, rule.
all above is good?
if pump pressure is at spec. cranking, then
do this long story, omitted due to fingers sore.
the pump tests and spec are all covered 100% in a real FSM.
the spec is covered at alldata.com, log in and see it.
btw, all EFI just hates low fuel pressure.
the whole system is turned for good pressure,
and many systems do not even monitor it.
To understand that read the books by, Greg Banish
the pressure must be at spec, and must regulate perfectly
or the ECU fuel tables are all TRASH.
hard starts. (fast starter) nut shell.
1: bad fuel. or running summer fuel in winter
what is your air temp, not stated, and is big factor ,if very cold.
2; no tuneups. ever done.
3: bad spark or timing off,
4: low compression.
5: bad ISC, try starting with 10% throttle ,to mimic a good ISC.
6: flooding. soaking wet spark tips.
7: under fueling, dry sparks.
try test fuel. if dry.
Posted on Dec 28, 2013
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Posted on Jan 02, 2017
it most definately is the crank shaft sensor. same exact prob i had. it costs about 60 bucks and 3 minutes to replace yourself. one bolt holds it into the transmission bell housing and one connector wire. very simple fix. call off the wrecker. just have plenty of ratchet extensions available i had to go in from behind the transfer case to reach the bolt but it was still pretty simple to install.
Posted on Jan 29, 2009
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