Author Topic: cold start lever? (Read 7113 times)

cube1980 · « **on:** October 01, 2008, 07:39:19 pm »

Ok so I'm getting used to the cold starting of my 96 golf diesel but I'm wondering if the little cold start lever is actually doing anything. I always pull it when I cold start it..and for a split second it idles around 1000 then jumps up about 200 rpm. If I close it, it doesn't do anything until the engine is completely warmed up. Is this normal? How can I check to make sure it's working? Should the engine RPM go back down right away after I push the lever back in because mine stays at around 1200 until the engine warms up then it drops on it's own...any suggestions??

neimis · « **Reply #1 on:** October 01, 2008, 10:55:13 pm »

Your cold start lever is not connected to your idle speed, rather it is an injection timing advance. You probably won't notice too much of a difference with it in or out. Sometimes, for me, on a cold engine, driveability was a little better with the lever pulled out (less stumbling and hesitation). Now that I have a Giles pump (with advanced dynamic timing) there seems to be no difference.

The cold start fast idle on your car is vacuum activated, so it takes a couple of seconds after you start the engine for the vacuum pump to develop some vacuum, at which point the diaphragm will move the lever on the fuel pump, and your idle speed will increase. After the engine is warm, or a certain amount of time has passed, the switch (located in the fenderwell behind the battery in my car) will turn off and your idle speed will drop to normal. It is not connected at all to the timing advance lever on the dashboard.

So it sounds as if everything is working correctly in your car. You could always get someone local to just visually check your setup. Half of the mechanics I have had work on my car just screw things up, leave the vacuum lines unconnected, don't have any idea how it works or what kind of mess they are making... so I wouldn't necessarily trust a professional mechanic...

P.S. Posting your location helps people respond, or offer to help

Vincent Waldon · « **Reply #2 on:** October 02, 2008, 08:29:50 am »

Agreed.... you have an AAZ engine with a vacuum-actuated fast idle system, and it sounds like it is working exactly as designed.

In terms of the cold-start handle... you can do a visual inspection: have someone move the handle in and out while you look at the back side of the injection pump (the side closest to the engine) to ensure that the cable is working and the cold-start actuator lever on the injection pump is moving back and forth.

You will also probably be able to confirm operation once the weather gets cold... the car will generally be a bit more smoky and hesitate / exhibit rough idle with the handle pushed in... pulling out the handle should make the idle to smooth out a bit and perhaps do a little less smokin' .

cube1980 · « **Reply #3 on:** October 02, 2008, 09:02:22 am »

thanks for the reply. So It's normal for it to sputter for a few seconds when starting it in cooler weather? 1 Just didn't like the vibrations t sputtering for the first 5-10 seconds. Im living in Sudbury Ontario by the way so the weather isI getting colder

Vincent Waldon · « **Reply #4 on:** October 02, 2008, 09:10:16 am »

Yup... a bit of sputter / white smoke is normal. The cylinders/pistons/pre-combustion chambers are cold... diesel needs heat to combust, so ignition is a bit dicy until things warm up a tad.

The cold start handle helps by advancing the timing... injecting the fuel earlier so that it has more time to burn.

Jolly1977 · « **Reply #5 on:** October 03, 2008, 09:00:34 am »

I'm curious what happens when you forget about the cold start lever? I've been known to forget about it, and then drive around all over town with it engaged...Oops... I'm sure its not detrimental to the engine, but maybe bad for fuel mileage? Any thoughts?

jimfoo · « **Reply #6 on:** October 03, 2008, 03:28:18 pm »

Then your timing and idle are just a little more advanced, timing at low rpm only. The lever works by pushing on the timing plunger, so it doesn't matter as soon as internal pressure starts advancing the timing, it advances it past where the cold start had it at.

burn_your_money · « **Reply #7 on:** October 03, 2008, 03:53:51 pm »

Not all AAZ pumps have a vacuum fast idle, some have the rod. Take a picture of your pump and post it. Odds are though, based on what you have described yours is vacuum controlled.

You don't want to make a habit of leaving the cold start lever out, eventually it will wear out the pin on the advance piston and it can actually write off a pump housing. This is an extreme case, and would most likely show up if you sit in traffic a lot