Stalls after fixed time

My Plymouth Acclaim (1992, 4 cyl, 127k miles) got a new fuel pump 2 weeks
ago, when it wouldn't start (after sitting overnight). That apparently
solved the problem, since it wouldn't turn over at all before the new pump.

A few days later there was a new problem. It stalled after running on the
highway for 20 minutes. Then it wouldn't turn over. After a few minutes it
would start for 2 seconds before stalling again. Then after cooling for 10
minutes it would start and run. This is like clockwork -- it always stalls
after 20 minutes, but only if running at highway speed.

I brought it back and they couldn't find the problem since they couldn't
road-test it that long. They said the hall effect sensor had a fluctuating
resistance, so replaced it. I had them change the oil since it was about
due.

But the problem is still repeating, like clockwork, now for the 6th or 7th
time. When it happens I'm always alone so I can't ask anybody to help take
a look at the engine. The codes are just 12-55, "battery or computer
recently disconnected", which it was last week when the hall effect sensor
was replaced. (How recent does it have to be to get that code?)

 

Is your fuel tank not able to pull in air to replace spent fuel?

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

 

Do you really mean 'it wouldnt turn over', or do you mean that it will not
start and run?

 

In the places I used those words, I mean it would crank but not start.

 

I never thought of that. This problem started after replacing the pump
which is in the tank. From where does it take in air?

 

On further thought, it takes nearly 10 minutes before starting again. The
air would have to be going in very slowly.

 

Via the pressure-vacuum fuel cap. Try loosening the cap so it's just
barely on, then drive around and see if it doesn't stall. If that fixes
the problem, then replace the cap. (Alternatively, you can just drive it
until it stalls, remove the cap and then try to start the car.)

 

Ok. Vacuum in the fuel tank is the first place to look. Just loosen the
fuel filler cap and see if
the problem is solved.

I have also had electrical components that would fail within an almost
predictable time after starting and running an engine, including ignition
switch, main electronic control module, intermittent crankshaft sensor, etc.

So the thing to do is isolate whether it may be a fuel delivery problem, an
ignition problem, etc.

A squirt of starter fluid into the intake when it dies should tell you
whether fuel starvation is the
culprit.

A spark plug tester is fairly cheap, and will help you find out if you have
ignition when the car fails.

These may help you start on the way to a diagnosis.

 

Thanks. I asked the mechanic about it, and he says there is another air
inlet as well, but I'll try it.

What do you (all) think about the hall effect sensor? The mechanic saved
the old one in case that wasn't the cause of the problem (which it wasn't,
whatever the cause turns out to be). Should I have him put the old one back
even though its resistance fluctuated, or defer to his judgement since he
saw how much it fluctuated?

 

When is the last time the distributor shaft rotor button was replaced, it is
possible that the secondary voltage is grounding out on the distributor
shaft.
I have seen on many occasions that the button gets a hole burnt thru it and
will intermittently ground out the spark

Glenn Beasley
Chrysler Tech

 

That's not the case.

Was going to be my next suggestion. There is a test for the hall effect
sensor that is fully diagnostic:

When the engine stalls, remove battery negative cable *or* take apart the
main power disconnect located in the positive battery cable about 6 inches
away from the battery. Wait two minutes. Reconnect, crank the engine,
then do the 3x key flick (on off on off on) and check the codes. If you
get a code 11, replace the hall effect pickup. If you don't get a code 11,
the hall effect pickup can be presumed OK.

DS



The mechanic saved

 

?

Auto gas caps don't let air into the tank anymore- the evaporative
emissions system (charcoal canister, vent valve, purge valve, etc.)
take care of that now.

If your gas cap lets air into the tank, the evap system will fail with
a gross leak indication.

Or perhaps I didn't understand what you meant by "That's not the case".

 

You've got that entirely backwards.

The gas cap on the subject model (a Plymouth Acclaim) is of the type
nearly universal since 1970 in California and 1971 North America-wide,
known as the "Pressure-Vacuum" cap. It contains two calibrated one-way
valves (usually in a unitised single-axis valve assembly in the centre of
the cap). One of these valves allows air to be drawn into the tank at a
controlled rate (that of airflow through an unrestricted 0.040" hole)
when a certain negative pressure is reached in the tank. The other valve
allows pressure to be vented from the tank when a certain extremely large
positive pressure is reached in the tank.

The inlet valve is the one and only path for air to enter the tank to
replace the volume of fuel drawn off by the fuel pump. If this valve
becomes stuck, a vacuum will develop in the tank and cause stalling
problems and -- under certain conditions and with a robust fuel pump -- a
collapsed tank.

The outlet valve is the emergency overpressure relief valve and is the
path of last resort for fuel vapor to be unloaded before it reaches
dangerous pressures. This should seldom ever occur, because the
evaporative emission control system routes fuel tank vapors to a storage
device -- the charcoal cannister -- and thence into the intake tract where
they are consumed. So, it is only in the case of a serious spike in
the fuel tank vapor pressure that the cap's outlet valve opens. Such
spikes can occur with rapid increases in altitude above sea level and
rapid increases in ambient temperature. Of course, such spikes can also
occur if the evaporative emission control system is faulty.

No. If the gas cap's inlet or outlet valve is stuck open, THEN the failure
you describe will occur.

You understood what I said just fine. What you misunderstood was how the
fuel system works.

DS

 

I'd be checking fuel pressure after it has shut down and make sure its
keeping up with the demand .