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Car Forum / Mitsubishi Cars / March 2005

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Help! Dodge Colt won't run.

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Eric R Snow - 14 Mar 2005 18:06 GMT
I'm getting desperate. I'm on an island. The car is a '92  Dodge Colt.
The import car fixer says my car isn't "foriegn" enough. The other guy
says it's too "foriegn". Here's what it is doing. Not running. It has
spark, compression, fuel pressure, and the timing is correct. The
manual says that if the car runs while starting and then dies when the
key springs back to the ON position then the fuel pump relay is bad.
But there is no relay where the book says to look and none anywhere I
can see. The dealership doesn't list one. He said to bring in the old
one and they would match it up. The car ran fine to work in the
morning and wouldn't start in the evening. The computer said it was a
bad mass air flow sensor. A new one is 400 bucks so my son went to the
wreckers and picked up a couple for twenty bucks. We put one on and
the car started but ran poorly. I was able to drive it about 1/4 mile
before it died. And while driving it would act like it was leaned out
real bad when I floored it. That was yesterday. Today it won't even
try to start. No matter which mass air flow sensor is connected. The
computer only returns the code now that says all is good. Any help
greatly appreciated.  
Thanks,
Eric R Snow
Stewart DIBBS - 15 Mar 2005 01:22 GMT
> ... Today it won't even try to start. No matter which mass air flow sensor
> is connected. The
> computer only returns the code now that says all is good.

OK, lets start with the basics.

Disconnect the battery for at least 30 seconds. This causes the ECU to reset
itself.

Turn on the IGN. The check engine light (CEL) should come on, then go off
after about 10 seconds. There should not be any error code output. There may
still be one (non-critical) if the CEL is off.

Try to start. It probably won't. You should hear a click from the MPI relay
(probably behind the radio).

Now to check for fuel at the engine. CAREFULLY undo (but not remove) the two
M6 bolts that secure the fuel hose to the fuel rail. Wiggle the hose: there
should be some residual fuel pressure that leaks out. I suspect you have low
to none. do the bolts up again.

Lets say yes, no fuel pressure. There's several possibilities:

1. the fuel filter (the can on the firewall end of the fuel hose) is
blocked. To check, take if off (the input pipe fitting will be a bear to
undo), and give it bang or two and reverse blast with compressed air. Can't
hurt, and often unblocks the filter until you can replace it.

2. There's crud in the fuel tank thats blocking the pump filter. As a last
resort, you can drain the tank from the drain cock on the underside of the
tank.

3. The fuel pump is not running, either because its not getting power or it
worn out. You get access to the pump from a plate under the rear seat or in
the trunk (depends on the car model).  The MPI relay is what provides power
to the pump. When you turn to START, the relay provides power to the pump,
and once the engine is running, the ECU controls the relay. So ... put a
multmeter on the wires going into the pump. You should be able to hear the
pump whirring, even from the driver's seat. If you don't have power on the
pump, trace the wires back. There's another connector block somewhere under
carpet near the B pillar. You 'll probably have to take the radio out to
check the output of the MPI relay. MPI relays do fail.

Stewart DIBBS
www.vysor.com/lancerproject
Eric R Snow - 15 Mar 2005 21:07 GMT
>> ... Today it won't even try to start. No matter which mass air flow sensor
>> is connected. The
[quoted text clipped - 41 lines]
>Stewart DIBBS
>www.vysor.com/lancerproject

Thanks for the speedy reply. It does have fuel pressure. But I only
checked it at the top of the fuel filter on the firewall. I'll check
at the fuel rail and let you know what happens.
Eric
Eric R Snow - 15 Mar 2005 22:04 GMT
>> ... Today it won't even try to start. No matter which mass air flow sensor
>> is connected. The
[quoted text clipped - 41 lines]
>Stewart DIBBS
>www.vysor.com/lancerproject

I have fuel pressure. It comes out pretty fast. Still won't run. I put
some gas, a couple tablespoons or so, into the intake manifold. THe
thing won't even pop. Now I'm really starting to suspect the spark.
Even though the plugs spark blue in open air, and even though the
plugs are new, and even though the ignition timing seems correct it
must be spark related. Is there any way to test that?
Eric
Stewart DIBBS - 16 Mar 2005 00:20 GMT
> I have fuel pressure. It comes out pretty fast. Still won't run. I put
> some gas, a couple tablespoons or so, into the intake manifold. THe
> thing won't even pop. Now I'm really starting to suspect the spark.
> Even though the plugs spark blue in open air, and even though the
> plugs are new, and even though the ignition timing seems correct it
> must be spark related.

When everything looks right, a primary assumption is wrong.  I advise taking
the cam belt cover off and verify that the cam is correctly aligned. Its not
impossible that the belt has jumped a tooth. The engine will still try to
run as the ECU will do its best to set the timing back (waaaay back).

You could also check that the coolant temp sensor (on the thermostat housing
AFAIK) has good connections to the wiring harness. Also, the sensor is
driver by either +12V or very close to +5V (I'm not sure which for the 92),
so check the wires to the sensor. This temp sensor output is critical to
getting the engine to start, esspecially when cold. On a warm day, or in a
heated garage, you can take the wires off the sensor and the engine should
start quite easily. If the sensor is shorted out (happens sometimes) the
engine can be a pig to get started.

You also need to verify that the injectors are getting power. The ECU drives
these by grounding the circuit. That is, when the IGN is ON, and certainly
on START, you should be able to detect +12v on on the larger of the injector
wires.  If there's no +12v, then I'd suspect the MPI relay, as this is where
the power comes from.  As said previously, it usually behind the radio, but
may be in the dash near the A pillar.

Stewart DIBBS
Eric R Snow - 17 Mar 2005 16:14 GMT
Greetings Stewart,
You are absolutely correct about me missing something. I will have
time saturday to do another diagnosis. It will probably show me where
I goofed when making the first. Thanks for all the help.
Eric

>> I have fuel pressure. It comes out pretty fast. Still won't run. I put
>> some gas, a couple tablespoons or so, into the intake manifold. THe
[quoted text clipped - 25 lines]
>
>Stewart DIBBS
Eric R Snow - 27 Mar 2005 18:57 GMT
>> I have fuel pressure. It comes out pretty fast. Still won't run. I put
>> some gas, a couple tablespoons or so, into the intake manifold. THe
[quoted text clipped - 25 lines]
>
>Stewart DIBBS

Greetings Stewart,
Thanks again for the advice. I checked again all the thing suggested.
It turns out that the car would not run with the old air flow sensor,
but one from the wreckers was OK. But that wasn't the only problem. I
was stymied because it had spark. And the timing light was triggered
OK, showing the timing was OK. However, the spark seemed a little
weak. I remember the first time I changed the plugs after buying the
car new was about 60,000 miles. The plug gap had increased from .030
to ,060! Yet the car still ran fine. Just hard starting at 32 degrees.
To jump the .060 plug gap meant that the spark must be pretty healthy.
And a spark like that should make noise in the open air. When the
plugs were pulled and the spark tested it was blue but not really
powerful. Not wanting to replace stuff willy-nilly and never know the
actual problem I started with new plugs and then replaced the rotor.
That did it! Putting the old rotor back in would make the car
un-startable. Putting the old air flow sensor has the same effect. So
it seems that I had two problems at the same time. Your help, and
pointing out that if I find nothing wrong I must be doing something
wrong made me look closer at that spark.
Thanks,
Eric R Snow
 
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