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silent knight
Dodge Dakota
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7/24/2008
00:40:15
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 Subject: 3.9 not firing
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Last week bought a 94 SLT with a 3.9 auto and 140,000 mi. Pretty clean truck. Has had a rebuilt tranny & Mopar obc, timing chain, & fuel pump all done about 3 years ago, at 130k. Truck's been sitting mostly since then. Been starting fine for me until yesterday. Seemed like valves were a little noisy but previous owner and Tuffy Auto said it was normal on this model, even with a new chain. Something about not enough oil pressure to lube the upper end???
Yesterday it started and died immediately. Cranks over fine but wont pop at all. Spark was weak so I put new coil, plugs, cap, rotor & pick up plate on. New O2 sensor. Checked rail pressure while key on = 40 psi. Gauge needle bounces while cranking, not sure if thats ok. Fuel pressure gauge does not drop when key off so injectors aren't leaky. Voltmeter on #1 injector solonoid coil shows it's getting pulses. Tried starting fluid in the throttle body throat. Did not help. Tried another ob computer. Still nothing. Any ideas?
By the way the codes flashed on the dash were a 12 - lost memory and a 52 - rich 02 sensor. Old plugs were Bosch Platnums - and they were coal black with carbon, threw them out. Put in Champions.
Hate to try another fuel pump or pressure regulator but that's what I'm thinking.
Haynes isn't much help.
Help me,
Silent knight in Ohio
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daddio
Dodge Dakota
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7/24/2008
08:34:51
|  RE: 3.9 not firing
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could be the CPS(crank position sensor)
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?
Dodge Dakota
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7/24/2008
08:40:35
| RE: 3.9 not firing
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That C.P.S. is at rear of engine , passenger side
just behind the EGR valve.
Another thing to go for is that infamous
splice in the harness - just below the underhood
fuse/relay box - need to unwrap the tape for about 6 to 8 inches to find a splice of 3 or 4 wires - re do this splice- solder and tape , or at least a better quality butt connector..
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Bob Lincoln
Dodge Dakota
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7/24/2008
08:43:15
| RE: 3.9 not firing
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+1 CPS failure is not uncommon here. Check also to see if it smells too strongly of gas. Maybe an injector or two is leaking and flooding out. The O2 sensor may have been fouled by another problem, but failure of it does not prevent starting, so it was premature to replace that until you could resolve the real problem and get it started.
The bit about the valvetrain noise is not true. It's a quiet motor.
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silent knight
Dodge Dakota
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7/24/2008
09:36:25
| RE: 3.9 not firing
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I've got good spark when cranking, could it still be the cps?
Still silent..
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daddio
Dodge Dakota
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7/24/2008
10:03:59
| RE: 3.9 not firing
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no it wouldn't be the CPS if you have spark. is it a good strong spark? are you sure you have fuel?
the previous owner and that Tuffy Auto are feeding you a line of crap. as Bob stated these engines are quiet. depending on the oil & filter or age of the truck, you may get a little lifter tick at start up but what your describing sounds like a pinging issue. that fix can come later. first thing is to get the truck running again.
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silent knight
Dodge Dakota
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7/24/2008
10:35:56
| RE: 3.9 not firing
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Daddio,
Good fat spark. I also eyeballed the #1 cylinder tdc while I was installing the rotor. It seemed close but it could be off a little. If the chain jumped a couple of teeth wouldn't it be pretty obvious on the rotor position?
It wonder if maybe the problem might be fuel or fuel timing. Is there a way to check anything without pulling the rails? If it's not getting fuel wouldn't starting fluid at least get the engine to bump a little while cranking?
By the way, I pulled the plug off the cps and checked for spark when cranking. It still sparked. Maybe I don't have the right sensor. It was an inch or 2 from the distributor, towards the passenger side, vertically screwed into the block - two wires. Almost impossible to see...
Thanks in advance,
silent..
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ya
Dodge Dakota
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7/24/2008
11:08:31
| RE: 3.9 not firing
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can check for fuel right at the schrader valve on the rail
(drivers side, looks just like a tire valve stem)
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Holy Knight
Dodge Dakota
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7/24/2008
11:10:38
| RE: 3.9 not firing
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Forgot to mention
get hold of a fuel pressure test'er
and check it out if you do have fuel @ the rail
all is calm
all is bright
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silent knight
Dodge Dakota
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7/24/2008
12:11:47
| RE: 3.9 not firing
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Guys,
I'm about to go over to the dark side - I just don't want to give up yet.
I've got good spark. I've got 40 psi pressure w/ key on, at schrader valve. Slight needle pulse on gauge when cranking. Clean fuel flows into glass jar from gauge releif hose when I open it during cranking.
The splice under the fuse box looks like it was redone recently = fresh tape from the box to about 16" down harness. If the splice went bad would it kill the spark?
Whats with the original harness cloth tape? Most of it just crumbles when I touch it at any of the engine compartment wiring.
Sorry to take so much of your time but thanks a million.
Silent, (but not deadly)
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daddio
Dodge Dakota
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7/24/2008
12:56:57
| RE: 3.9 not firing
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did someone try turning the distributor to set the timing? i hope not because the PCM controls that. you turn the distributor to set injector sync. and yes if it's out far enough it will not start.
as far as jumping time, if the chain install was done properly it should last more than the 10k miles you've put on it since it was "supposedly changed".
turn the engine to get #1 to TDC making sure it's on the compression stroke(both valves closed) then check your rotor alignment.
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Holy Knight
Dodge Dakota
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7/24/2008
13:10:27
|  RE: 3.9 not firing
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hey if they did move the dist. he's in luck
its a 94 he can set it manually
and hey bud
i personally wouldnt trust someones work with out looking it over
your only talking a few more minutes
un-do that splice and have a look under that tape
2ndly as daddio said or asked
did someone turn the distributor?
if so let us know so we can help you get the fuel inc sync set again
Holy Infant So Tender an Mild
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daddio
Dodge Dakota
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7/24/2008
14:06:37
| RE: 3.9 not firing
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Message:
Holy Knight, i could be wrong but it was my understanding that on all the Mag motors the timing was controlled by the pcm. i was thinking only the carbed motors had adjustable timing.
as they say, you learn something new everyday.
thanks.
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Holy Knight
Dodge Dakota
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7/24/2008
14:31:38
| RE: 3.9 not firing
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Message:
Yes
and I was asking him as you did,
Thinking/asking if someone tried to set the timing by turning the distributor. If so all they did was throw the fuel inj. Sync. out of whack.
The good thing I was saying is 92 - 96 the inj. syn. can be set manually.
Its also a nice Mod for these year motors.
Sleep in Heavenly Peace
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daddio
Dodge Dakota
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7/24/2008
15:45:29
| RE: 3.9 not firing
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AH, i see. Well i did tweak the sync a little on my '00 using a procedure that was lined out on a post some time back. it did seem to help some. but the best way is with the scantool.
we definitely need to know if someone turned his distributor or not.
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silent knight
Dodge Dakota
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7/24/2008
17:23:13
| RE: 3.9 not firing
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Nobody's touched the distributer. It was running for me all week just fine. Pulled into Kroger to get some ice for the cooler for fishin'. Was idling a little rough but didn't quit. Shut it off, got the grub and when I tried to start it, started right up but died after 1 - 2 seconds. Cranked over fine but wouldnt hit at all. Had no tools with me but a gas can. As I stated up front, this has been sitting around for 3 years. The tank was a little above empty. Maybe I pulled in some water or sludge into the injectors. All I could do in the parking lot was add a couple of gallons of gas and a couple of table spoons to the t.b. It didn't help. Had to tow it home. Shouldn't a prime like that get the engine to fire if the timing is ok?
Ps. My wife did catch a 26" channel cat that afternoon so the night wasn't all bad ;)
Silent night...
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J and J Auto
GenII
7/24/2008
23:38:01
| RE: 3.9 not firing
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Message:
when it does not start are the plugs wet
The pickup in the dist tells the injectors when
to fire
If the dist was not urned you can check to see if
the timing chain jumped very easy
Put the vibration damper on 0 TDC compresion
stroke
If its 180 off turn around again should be
pointing at #1 wire drivers side front is #1
Always turn clockwise if you pass it up keep
going around do not turn back and with just a
little finger pressure just push back on the rotor
towards counter clockwise
turning dist clockwise moves sync towards -
turning counterclockwise advances towards +
Now remove the air cleaner so you can get to the
dist cap there is a line on the pickup marked cyl
the rotor should be within the thicknes of the
tab on the end of the rotor back edge or front
edge with this line if it is farthaer away either
it was turned of the chain did jump
If you center the rotor tab over this cyl line
that is 0 they run best right around +3
looking from the front of truck and straight down
over the rotor the back edge should be lined with
this line that is +3 back edge is the edge
closest to you looking from front
tab behind this line towards front of truck is on
the - side
= sign will be rotor tab - will be cyl line
.. just to move it over to give you an idea of
how it should be
= rotor
.- cyl line
looking from front this is on the + side
.- cyl line
= rotor
this is on the minus side
center 0
front edge closest to fire wall wit the cyl line
is -
back edge of tab with cyl line edge closest to you
looking from front + side this is aprox +3
within 1 degree either way
I have mine at +5 because my hotter cam opens
5 degrees sooner stock cams run best at +3
Hope this will help you check this if its way of
someone turned dist or the chain did jump
use a good light when checking this so you can see
it good
Also on your 94 check these 2 computer pins
#3 and #9
1 has power all the time
1 on/off with key
this will tell you if the splice is bad
If you have the haynes manual also check the ASD ground
and ASD power wire from relay other side comp to
be sure this is good with ohm meter
cant remember the pin #'s off hand I am at home
sitting on the couch with my laptop no books or
info handy LOL
Larry
J&J Auto
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silent knight
Dodge Dakota
JOIN HERE
7/25/2008
11:52:58
| RE: 3.9 not firing
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Message:
Larry, I put the damper at TDC. Pulled the distributer cap. The rotor is sitting squarely under post #1. (The post is about 1/2 inch counter clockwise from the =cyl mark on the pickup plate.) I can turn the damper clockwise to line up the rotor tab with the =cyl mark, but then the grove on the damper is about 3 inches from the TDC mark on the block.
Does that mean the chain jumped?
Silent..
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