L Jet Idle with Lights on, Why does it drop ? Options

[jim_hoyland]

Saw this question asked a couple of weeks back, but couldn't locate the responses. I now have everything working on the 1.8L L-jet, Idles perfect; except, when the headlights are turned on the idle drops from 900 to 200 ? Is this indicate the battery, coil, or ?? is weak.

And, what can I do to diagnose the problem ? I have a simple radio shack VM

Thanks Jim

[MartyYeoman]

I haven't had that happen to me yet.
Sounds like it's time to cleanup under the dash a bit.
Good luck

[SLITS]

It does take a modicum of engine HP to generate the amperage required to keep the lights bright (and whatever other electrical devices you have). Even though, that seems like a drastic drop...I could see a 100 rpm drop at idle, but not 700 rpm.

You would need an AMP guage to see what's happening.

[rhodyguy]

add in wipers, the radio, and fogs. it seems like a huge draw to me. my carbed car does the same thing and other members i've spoken with tell me theirs cars do as well. i wonder how accurate the tack is below 400rpm, which is about what my falls to (from a 950 idle).

k

[jim_hoyland]

How/where do you test the amperage ?

[bd1308]

pull it from the battery. get a 60-0-60 amp guage, connect the HUGE everyredwire bundle into one end of the guage, and on the other side, come out with a 8ga wire to the battery.

the needle should go over to the + side indicating your alternator is WORKING.

you know what I would do?

I would unplug the voltage regulator. Alternator doesn't "boot", doesnt draw any big current (field current) and wont drop your RPMs. Then use the amp meter to see what is going on.

Its quite possible you have just a lotta stuff you need to power, and your engine isn't your friend when you turn all of it on. (IMG:style_emoticons/default/confused24.gif)

what "I" would do is to turn everything on and set the idle at THAT point, like it says in ever manual I have read dealing with the L-jet and D-jet.

The FI system is irrevelant in this case.

b

[SLITS]

The FI system is irrevelant in this case.

b

Not the fuel pump that it needs to run Bucko...it draws a few "A"s.

[Brando]

what "I" would do is to turn everything on and set the idle at THAT point, like it says in ever manual I have read dealing with the L-jet and D-jet.

Before anyone tries doing this on an L-Jet car note: This is not the proper method of setting your idle speed/timing with L-Jet. Proper method is with both vacuum advance and vacuum retard disconnected (tubes plugged as not to read false air) from the distributor, 7.5º BTDC at 850±50 RPM.

The FI system is irrevelant in this case.

You win the dumb L-Jet answer award kiddo (IMG:style_emoticons/default/smile.gif)

L-Jet is an electronic injection system. Every time an injector fires you use power. Not sure of the amperage per injector, though. No accessories on you will have the following pulling power:

Starter (on startup)
ECU (brain)
Fuel Pump (zrrrrrrrrrrrrrrrr...)
Guages: Tach, warning light, fuel guage, oel pressure, clock, voltage meter, stereo
Dual-relay unit for injectors
Finally, the injectors.

When you turn the headlights on it creates a significant draw on our (45 amp?) alternators. You've got two beams pulling up to 30a each, not to mention all of those running lights.

My idle drops as well, too. It's because you have an electronic fuel injection system and an alternator that can barely put out enough current to supply the draw. If you turn on your foglights and/or heater at the same time you'll see the voltage guage hover between 11/12, maybe sit right at 11 with the brake lights on.

Solution: Higher output alternator, or go LED running lights with an electronic flasher unit. But you've still got both of those headlights pulling a lot of amperage each...

[SLITS]

Damn Brandon.....gettin' a little hostile these days.....Aaron ain't puttin' out anymore?

[jim_hoyland]

Thanks Brando,

I'm ok for now : the headlights are 100W; what kind of amperage do comparable cars have today ?
I've been considering going 75amp