cold start weirdness

Dan Cordon cord4530 at uidaho.edu
Sat Jan 17 17:43:03 EST 2004


SJ wrote:

> > From: Dan Cordon <cord4530 at uidaho.edu>
>
> > My 87 5k has just the opposite problem. Long starts when normal temps
> > outside, but super quick starts when cold. My problem seems to be leaky
> > injectors. When it's cold outside (anywhere from ~30° to -13°) it fires
> > right up, but runs slightly rough for the first second or two until the
> > main injectors start going.
> **** First and foremost . . .. you have a predictable problem. It happens
> this way every time.
> My problem(no start after short warmup) is intermittant. With environmental
> conditions the same . . .sometimes I have the problem, most of the time I
> dont.

>  I dont understand why leaky injectors would cause this problem. Are you
> saying that residual fuel pressure is the problem . .the injectors bleed off
> the pressure over time?
> If you turn ignition on, but dont start the engine. Does'nt the fuel pump
> pressurize the system?
> If you wait a few seconds before starting the engine, is not the system
> fully pressurized now? Why would a leaky injector have an effect on not
> starting? Leaky injector might provide a richer mixture . .. but that is
> exactly what you want . . .firing the CSV adds that additional fuel and the
> engine fires up. If the injectors leaked more, you wouldnt need the CSV to
> start the engine.
> If I remember correctly, leaky injectors will cause hard starting when
> engine is hot and then shut off and left to sit for a while. The drop in
> pressure causes vapor lock in the lines.

Not entirely. Leaky injectors will cause the mixture to be rich after a short
sit, but after a long sit the lines to the injectors are mostly empty. Turning
the fuel pump on will bleed the system up to the fuel distributor, but not from
the distributor to the injectors. My cold start valve line does not leak though.
When cold, the CSV works correctly and the car starts almost instantly (though
very lean) on that fuel alone. Within 1-2 seconds, the main injector lines are
all pressurized and the injectors start squirting....which is good because
that's about when the CSV stops firing.

However, after it's sat over a few hours and the temperature isn't cold enough
for the CSV to fire, that's when I have the long cranking. That's why I had
related the CSV to the starter signal....to get the CSV to fire when it wasn't
really cold outside (it would already fire when cold, so no change there).

>
>
> Your problem appears to be no signal to the CSV for extra fuel. The ECU is
> not grounding out the CSV. Its like a switch shut off in the ECU. The temp
> sensor should read about 5000 ohms at 30 degrees F, 14,000 ohms at -2 F. At
> 60 F, it should read 3,000 ohms.
> Easy enough to check the resistance of the temperature sensor.

No, the CSV works great when it's cold. For that matter, it works like it's
designed too :o)

<snip lots of stuff>

>
> I just thought of another idea . . .attach an LED to the pushbutton switch.
> The LED bridges the CSV terminals . . . you need 3 wires to do this. When
> ECU shorts out the CSV to fire it, the LED  lights up. If the LED dont light
> up, you know what the problem is . .and hit the switch.
> The LED would be useful to see how long the CSV stays on for different
> temperatures.

My problem isn't related to yours at all. I understand that. I was just saying
that my relating the start signal to the CSV worked. Mostly I was just trying to
support you in that you can definitely hook a momentary switch up to the CSV. I
really like your idea of adding an LED to it too. It could go in one of the
blanks in the center of the dash. One switch and one LED.

>
> Whats a multimeter/spark tester? I did a search and all I can find is an
> in-line spark tester for around $7. I might get one of these . .. easy way
> to determine if you have spark. Looks like it works by lighting up a neon
> bulb.
>
> SJ

The multi meter is something I'm sure you already have. Just your basic
Voltmeter and Ampmeter. That would allow you to see if there was voltage at the
coil when the car wouldn't start, or voltage across the CSV wires, etc. The
spark tester is just what you found. It goes between the end of a spark plug
wire and the plug. It will have a little light that goes off when it gets spark.
Just a quick visual way to see if there's spark when you don't have someone to
crank the car while you hold the wire :oP

So, in the end, I'd say "go for it" with the momentary switch and LED.

--
Dan Cordon
Mechanical Engineer - Engine Research Facility
University of Idaho




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