fuel system troubles

1999 Plymouth Grand Voyager 3.3 flex fuel model...

I've had some trouble with this van's fuel delivery. The engine doesn't
idle. It can be kept running only at a higher throttle setting. Also,
it makes clouds of unburned gasoline from the exhaust.

I found that after running it for a while, the exhaust manifold is cold
at cylinder #2 and finger burningly hot at #6. Also, with my wife
keeping the engine running, when I pull the wire off of plug #6 the
engine suffers, but pulling #2 or #4 has no effect. The wires will
deliver big fat sparks to the engine block as well as the head of the
spark plug, but obviously the spark is not doing anything in the engine.

My assumption was that #2 and/or#4 injectors are delivering way too much
fuel. So my next test was to pull these two injector wires. When I do
that, the engine will idle (poorly of course because of the dead
cylinders). I assumed at first that the problem was in #2, then I
thought it might be in 2 and 4, but then I tried leaving #2 in place and
pulling #4, and it improved the situation enough to allow the engine to
idle.

Further testing showed that all 6 injectors had the proper clicking
sound with a stethoscope. Checking the system with a scan tool shows no
codes.

Questions for inquiring minds that want to know:

Would excessive fuel pressure set a fault code in the computer? If not,
I'll get a fuel pressure gauge and test it. Otherwise, I could assume
that one or possible two injectors are stuck open even though they are
getting the proper signal indicated by clicking noises.
Assuming that I have one or two bad injectors, can they be cleaned and
fixed, or do they have to be replaced? The reason I ask is because they
cost $75 each, they have to be ordered, and they won't arrive until
Monday. If the ones I have can be rehabilitated I'll give it a try.
One other thing, can anybody think of anything else that would cause
this problem besides a drooling fuel injector? Before I started
scrutinizing the injectors I had thought that it might be a vacuum leak,
but I can't find a leak anywhere.

 

Are you sure that all 6 ignition wires are routed to the right plugs? Is
the coil pack functioning properly and are the ignition wires good? Have
you tried replacing the spark plugs that are not firing? What condition
were the tips in when you pulled them? Is the Check Engine light
illuminated and are there any engine computer codes set?

Bob

 

Now that you mention it, I haven't checked that but I have no reason to
believe that they are wrong. Disconnecting #4 injector wire improves
running, so I don't suspect the ignition system. I will be checking
this, though.

Brand new plugs and wires, just finished this job yesterday. I noticed
that #4 makes bigger sparks than #2, but I don't know what that means in
this situation.

They looked pretty worn, but now the plugs are new.

No light and no codes.

 

I checked to make sure, and the wires are indeed routed correctly.

 

As bad as this vehicle is running the check engine lite should be on!!! you
mention nothing about this or even checking for fault codes.
I would think that by disconnecting the #4 injector and the fact that is
smooths out some would be the injector driver circuit is causing the
injector to remain open and dumping in to much fuel. The injector gets 12v
from the ASD relay and is grounded by the PCM. make sure the wire from the
injector (ground) to the pcm is not shorted to ground. If this were the
case a #4 injector circuit fault code would have been generated.

Just a thought

Glenn Beasley
Chrysler Tech

 

If you were to trace the wire from the injector to the PCM. disconnect the
injector#4 connector and the PCM C1 connector (LB/BR pin 16 ) and check
for a short to ground

Glenn

 

I did mention that there were no fault codes, and that the injectors
click as they should, indicating that they are getting a pulsating
signal. I forgot to mention the absence of the check engine light.

 

I don't know about 1999, but in the 96 model year the fuel pressure is
definitely NOT monitored by the computer. It can run from zero to
infinity and it won't set a fault code. I would not be surprised if
your pressure is too high, caused by a blocked return line, or
regulator system malfunction.

 

It would set a fault code if the fuel pressure was to high or to low. P0171
P0172 1/1 fuel system lean and 1/1 fuel system rich. But does not just
point to the fuel pressure. It wont just condemn the fuel pressure. You
would still have to check the basics for this code such as coolant temp,
mechanical problems and upstream 02 sensors

Glenn

 

squirt water all over the work you did including the coil to make sure none of
the wires are shorting out and then inspect the one plug for the cylinder you
have in question to make sure it is firing and if it is soaked by fuel why?

 

I know from experience that an intermittently failing/failed fuel pump
(low pressure) on a '96 will not set a fault code in 1000 miles of
drive/die/restart/drive highway travel over 2 plus days. Every dealer
within 600 miles of here knew exactly what the problem was, but none
was sure enough to replace the pump if they couldn't make it quit
while they had the pressure gauge hooked up. Never did set a code.
Also never quit with a gauge in place

As you say, IF you get a code from fuel pressure, it will be a
secondary code not directly tied to the pressure itself.

 

That's really interesting, because it is obviously getting too much
fuel, so much so that it cannot burn it. I know the spark plugs are
working because I pulled the wires off and watched the sparks jump to
the tip of the plug, meaning that there is spark in the cylinder. I
listened to the injectors clicking, meaning that they are operating
properly. So the problem is either too high fuel pressure or an
injector that doesn't close all the way. The resistance on the injector
coil is correct.

I guess I need to buy a fuel pressure gauge, unless somebody can think
of another problem that would cause excessive fuel delivery WITHOUT
setting a computer code.

 

Just because the injector is ticking does not mean it is opening and
closing. If one cylinder is getting to much fuel I don't think it would set
a fault code for high fuel pressure because it would only be effecting one
cylinder. Maybe going back to basics is needed. A compression test of the
effected cylinder? A scan test with a good scanner.

Glenn

 

It won't set a mixture code if the fuel pump just 'up and quits'. It
also won't set a code if the pressure is only slightly high or low.
With gas pouring out of the tail pipe, it will NOT set a code because
it'll likely never achieve closed loop and can't know what the mixture
is doing.

It will, however, definitely set a code if the pressure is off far
enough that the PCM can no longer correct the mixture.

If it's misfiring, it 'should' set a misfire code. However, if the
battery has been disconnected and the adaptive numerator has not been
relearned since, misfire detection will be disabled. It would also be
disabled if the engine is operating outside the normal paramaters that
misfire detection occurs in.

 

Not likely that a fuel pressure problem would affect only 1 or 2
cylinders.

 

Fuel pressure alone will not set a code. It can't set a code because
it isn't monitored. If out of spec pressure persists long enough, the
resulting symptoms 'may' eventually set a code of their own. And maybe
not.

 

OK, this is interesting because the battery has been in and out a couple
of times as I worked on basic tuneup items.

If disconnecting the power would disrupt normal codes, I'm starting to
think it may be something more obvious like an oxygen sensor.

 

My last post obviously went over your head.

While fuel pressure is not monitored, it WILL cause a code if it's
high enough, or low enough, to cause the PCM to determine it can't
keep fuel trim within spec. The resulting code would be 'Fuel system
rich' or 'Fuel system lean'.

Yes. Fuel pressure alone WILL cause a code to be set.

 

Stop right there.

Now, before you start thinking again, go back and read what you
quoted. Now, tell me where I said disconnecting power would disrupt
normal codes.

That's right, I didn't say that. I said MISFIRE DETECTION would be
disabled if the PCM hasn't relearned the adaptive numerator since the
battery was disconnected.

OK. Resume thinking and take it to somebody that knows what he's
doing.

 

So which is it? A few posts ago, you said "It won't set a mixture
code if the fuel pump just 'up and quits'. It
also won't set a code if the pressure is only slightly high or low."
Now you say it WILL cause a code to be set. I say you are wrong. It
can't cause a code to be set because it isn't monitored. Any codes
that are set are the result of follow-on symptoms, which could be
caused by any number of things other than fuel pressure. Fuel system
rich or fuel system lean are nice codes, but they are not the same as
fuel pressure high and fuel pressure low.