98 concorde starting problems

On close analysis, that explanation makes no sense (some of the heat
will be removed to ambient in the travel back to the tank, the tank is a
huge heat sink, so if nothing else, it buys you a lot of time (more than
no recirc) before temps at the rail rise significantly.

OK - but why was recirculating fuel system design used in the first
place - it obviously costs the motherfacturers more to run a return line
instaed of dumping it at the pressure regulator in the tank? There must
be a reason for its use since they could save money by not doing it. Or
was this a lesson-learned in the industry?

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

 

Ok some other people have mentioned some TSBs so you may already have
this info.

There are several TSBs for a 98 Concorde which may apply to your problem.

18-14-98 In Stock/Transit Flash Update to Minimize Vapor Lock Concerns.

- and -

18-09-98B (6/12/1998) NO RESTART/ROUGH IDLE AFTER A HOT SOAK - PCM - REVISED

This second TSB supercedes two earlier TSBs with the same title
18-09-98 (Feb 27 1998) 18-09-98A (March 13 1998) Be sure you're
looking at the last version.

----------------------------------------
TSB 18-09-98B NO RESTART/ROUGH IDLE AFTER A HOT SOAK -PCM- REVISED
(Jun 12 98)
Applies to all vehicles built before May 12, 1998. (2.7L t'stat mod
applies to vehicles built after Apr 20, 1998). Check your VIN if you're
not sure when your vehicle was built.

Symptom: Hot engine no start, hot engine restart w/ rough idle, or hot
engine start/die-out. May have misfire DTCs. ... May not restart until
cools. Fuel vapor build up in the fuel rail may be the cause.

The summary diagnosis for 18-09-98B basically is to Check codes and
repair as necessary prior to proceeding. Cold soak the vehicle for min.
of 8 hours. Connect a fuel pressure gauge (Miller Tool # C4799) to svc
port. Switch key to RUN while monitoring pressure but do NOT start
engine. Allow fuel pressure to stabilize (48-50 psi) and switch to OFF.
Monitor pressure for 15 mins. If fuel pressure drops 20 psi or more
perform flash update repair procedure only. Additionally if vehicle
has 2.7L perform thermostat mod. and heater hose mod. repair procedures.

The fix-it section starts with replacing the fuel pump module (if
necessary per diagnostics I paraphrased above) and then flashing the
PCM. [Release 21 or higher and TIL CD Release 1161 or higher]. For
the 2.7L engine (which I don't think you have b/c you said Concorde LXi
not LX) there are additional mods to the cooling system involving hoses.
The full procedures are too detailed to post here.

-----------------------------
TSB 18-14-98 Flash Update to Minimize Vapor Lock Concerns. (Mar 13 1998)
This TSB applies to 3.2 L engine vehicles built prior to Feb 16 1998 MDH
(0216XX) and 2.7L engine vehicles built prior to Mar 9 1998 MDH (0309XX).

There is no diagnosis section. Basically it has step by step
instructions to erase and reprogram the PCM and seems to be a subset of
the TSB 18-09-98B above, except it was written a little earlier so it
has a lower software release number specified as the minimum to use. It
lists that the MDS and DRB must have Release 21 or higher and TIL CD
release 1153 or higher.

 

Then how does it work?


Matt

 

I don't know any fuel system design engineers personally. Do you? This
is exactly opposite everything I've read. It would be very hard to heat
up all of the gas in the tank by enough to get anywhere near enough
vapor pressure to cause vapor lock. It is much easier to just heat the
slow moving fuel in a non recirculation system. This is pretty simple
physics. I'd like to hear your explanation as to why a non recirc
system will pick up less heat in the fuel before it reaches the injector.


Matt

 

Maybe if the fuel tank was almost empty and the little amount of fuel
returning to the pump was enough to almost make a measurable change in
temperature to the fuel in the pump. Otherwise I don't see how that
would be much of an issue. The advantage of a return line is that you
can pump plenty of liquid gasoline through the system to keep it
continuously cool enough to avoid vaporization in the lines. This is
similar to a garden hose sitting in the sun that is full of hot water
but if you keep running fresh water though it, it stays fairly cool even
though it is still in the sun.

Vapor lock has been a hot starting issue for some piston aircraft
engines with fuel injected engines. When return lines are used it
becomes less of an issue as running the electric fuel pumps for a short
while is an item on the pre-start checklist.

I'm not sure what the PCM update (mentioned in the TSB I posted in a
separate message) does, but it probably turns on the fuel pump a little
longer before cranking or some similar trick. On my 99 (built after
they fixed the problem in the TSB) I can hear the fuel pump come on for
a second or two when I turn the key to ON before START. On the other
hand I have a California Emissions-Certified vehicle that needs a leak
detection pump which may work differently then vehicles sold in the
other 45 or so states that did not use this type of pump.

 

I think you're forgetting that this car does not do recirc (I don't
count pressure relief valve dumping at the tank a true recirc).

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

 

Does designing fuel pumps for 8 years count?

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

 

What are the necessary components to create a vapor lock?

Is heated fuel one of them?

 

Personally as in ; I visit their home at least once a week for
dinner? The answer would be no. Why would it be necessary to
know one personally? Does one need to have a personal
relationship with an engineer in order to avail themselves on how
a (any) system works? I hope not, otherwise there is probably
only a handful a people out there who are capable of servicing
any given component or assembly on an automobile.
Do I know any engineers? Yes.
Do I know any Chrysler/GM/Ford engineers? Yes, I've met them on a
regular basis during various training
sessions/conferences/committee meetings, etc.
Are there Chrysler engineers here, lurking? Yes
Are they/do they laugh at the pomposity that is posted here? You
betcha!

before you commit to that Matt, you might want to familiarize
yourself with the criteria set for monitoring EVAP pressures on
any vehicle built to 1996 or later OBD2 standards, because fuel
heating is a very major component used in the EVAP strategy.

Please explain how the fuel in the tank is heated by engine heat
in a non recirculating system.

It would be much more interesting to hear why you think a
recirculating system -wouldn't- raise the temperature of the fuel
in the tank in spite of the fact that a portion of the fuel has
traveled to the engine compartment, sat in the fuel rail for a
period of time soaking up heat, and was returned to the tank
repeatedly. Especially since it -is- a known occurrence and is
something that has to be dealt with in the OBD2 EVAP strategy.

 

The fuel ahead of the pump is at 35-40 psi, at that pressure, it
isn't at all susceptible to vapor lock. Doesn't mean it can't
happen, but as it's been since the advent of EFI, usually the
only time vapor lock becomes an issue is when the gasoline supply
is blended for winter and a geographic area receives an unusual
for the season warm/hot spell which makes it a specific function
of the gasoline's vapor pressure.

Not at all like a garden hose, the fuel lines do not sit in the
sun like your garden hose does, soaking up heat. Also, once
purged of the hot water from the sun soak, your garden hoses
supply of water comes from underground where the ambient ground
temperature keeps it cool(er).
Bad analogy

A purge function which is separate from the causing event.
Run the aircraft for enough hours to sufficiently heat the fuel
and the problem will return I suspect.

Or; they increase the pulse width of the injectors to purge
vapors. Running the fuel pump longer would do nothing since
there's no recirculation involved, so what if anything would it
do?

Same as any other EFI car.

Nope. AFAIK, LDPs are used federally also, I see enough of them
for service here in Wi.

 

Oh yeah, that fuel sure is going to cool down in the whole three
seconds that it resides in the return line.

You're implying that heat sinks do not warm up.

Where did 'temps at the fuel rail" become an issue?
Why would they be/
The fuel rail is under pressure where as the inlet to the pump is
not.

Proximity of the fuel pressure regulator and the attendant
manifold vacuum source, for one. Complexity and the lack of (to
that point,) OBD2 regulations.

I think it's pretty obvious that the industry as a whole has been
evolutionary, a large part of which has been because of lessons
learned.

 

Just the pumps? Without knowing more specifics about who and
what application, no.

I know a whole gaggle of electrical engineers who design electric
motors, most of them can't even install a simple 4 wire trailer
light connector.

 

Yep, but you aren't the guy who claimed that a recirc system is MORE
susceptible to vapor lock!

Matt

 

It is the main one. Your point?


Matt

 

Then let one of them weigh in on this topic.

It isn't, but then vapor lock doesn't occur in the tank in occurs in the
engine compartment typically where the fuel line runs past a hot
component such as the exhaust manifold.

I don't think that it won't heat the fuel in the tank. However, since
that is largely irrelevant to vapor lock, what does it matter? What
matters is when the fuel in the fuel line vaporizes before reaching the
carbuertor or fuel injector. And the temperature of the fuel in the
fuel lines in the engine compartment will be much higher in a
non-recirculating system that has a low flow rate and thus higher dwell
time near the hot components of the engine.


Matt

 

the whole of retuirnless is the carmaker is saving money by not having a fuel
line running bac to the tank from the engine
that is alos why u see more window switches in the center console as in
libertys and pt bruisers less wiring since it runs onma bus circuit

 

Not in my control.

I would (belatedly) interject here that apparently all you've
got to go on is what you've read, and it's certain that you may
not have read all that is necessary, and it's also certain that
you lack practical experience.

So, apparently it is not "very hard to heat up all the gas in the
tank by enough to get anywhere near enough vapor pressure to
cause vapor lock." If you knew anything about OBD2 EVAP
criteria, you'd be familiar with the pressure built and the
conditions where they are maximum.

That equals a head start as far as the fuel system is concerned.

Hog wash. Vapor lock is more likely to occur on the suction side
of the pump and is virtually non existent on the pressure side of
the pump up too the point where there is a component problem such
as a failing fuel pump.
You could easily win this by describing in detail the precise
movements of the fuel in the tank to the pump, from the pump to
the filter/regulator and its return to the fuel tank in an LH
chassis and include the where and why that causes the (cited in
TSB by Greg Houston) vapor lock condition. IOWs, cite the
specific failure mode that contributes to the vapor lock.
(hint, it's got nothing to do with anything you or Bill have
posted so far). I'll tell you this much; Chryslers description
using the words "vapor lock" is a bit disingenuous.

I'm under the hoods of a lot of LH cars, exactly where is this?

Fuel temperature is "irrelevant" to vapor lock?
Does raising the pressure of a liquid tend to increase or
decrease its boiling point?
Pick a point in the fuel system where the fuel goes from a
negative pressure to a positive pressure and then cite why the
side under positive pressure is (according to you) more likely to
boil of form into a vapor.

Again, vapor lock on the pressure side of the fuel is quite rare
and would probably take some pretty extreme temperatures to
facilitate. And, in the case of the LH cars, it doesn't occur
there to begin with, it starts at the inlet to the fuel pump.
(you can go ahead and do the math since I already know what the
root cause of the LH vapor lock is)

This totally ignores the fact that the fuel can pick up heat on
the return path from things like the pavement and/or the exhaust
system. But then, you -did- say that fuel temperature was
"irrelevant."

 

There is no indication of that all, either in your posting or the Chrysler
service bulletin regarding the vehicle in question.

Exactly which OBD2 criteria are you referring to?

There are service bulletins issued by Chrysler for vapor lock conditions on the
pressure side in the pump (more specifically inside the engine compartment) for
some M.Y. 1998 LH vehicles.

The hot component cited for sure is the engine cooling lines, at least for the
2.7L engine.

I don't think he indicated anything like the question you propose.

The vapor lock problem occurs while the engine is off. If pressure is not
maintained while the engine is off (but the engine is still warm) the vapor lock
problem can occur. The first step for diagnosis in Chrysler's service bulletins
is to check if fuel pressure is maintained for 15 minutes after the fuel pump is
turned on, then off.

Careful there, your statement is resembling begging the question. First Chrysler
published a TSB for vapor lock conditions on the pressure side of the fuel pump.
Second, what math are you referring to? If you honestly know some math which
supports your position don't be afraid to post it. You may already "know" what
the root cause of the LH vapor lock is, but Chrysler published a service
bulletin that disagrees with your diagnosis. Given the choice, I'll lean
toward Chrysler's analysis and repair.

To be fair, you've made an irrelevant conclusion policy here. His "irrelevant"
comment was only referring to the temperature of gasoline in the Fuel Tank, not
any fuel temperature anywhere. As stated in Chrysler's own bulletin, the vapor
lock problem occurs near the hot engine, not in the tank. However according to
the TSB the fuel pump module is a source of the problem due to its inability to
maintain fuel pressure after being switched OFF.

 

It's only at 35-40 psi after the engine is shut off (while the engine remains
warm) IF the fuel module is working properly.

Actually the fuel line is adjacent to warm engine components, where they can
soak up heat. The TSB states as much as well. It is also why the TSB refers
to modifying engine cooling lines. The combination of the fuel lines
absorbing engine heat and a malfuntioning fuel pump that doesn't keep pressure
high enough after it is shut off causes the vapor lock condition.

Not at all. Running the fuel pump is a warm engine start checklist item.
(i.e. after the aircraft has been run for hours.)

With the LDP you can also hear the LDP sequence (only when starting an engine
that is cold [it doesn't do it when it is really really cold in the winter).
In later years CA cars used another technology in lieu of the LDP--I think
around MY 2001 or 2002.

According to the Chrysler '99 LH service manual the LDP was only on CA
emissions cars, at least for that MY.

 

Oops, strike that last sentence. I just confirmed with my copy of the LH manual.
Leak Detection Pumps may be found on non-CA emissions cert. vehicles.