Linkages Checked now Cold Start Problem

[Nic J]

Hi,

I checked all the linkages on my engine as I was having walm idle problems, the butterfly in the Ventri needed adjusted as did the CSS and everything is all playing nice when walm now with a happy 800 rpm idle.

However how when I start the engine cold it fires then dies, the only way to keep it running until walm is to keep my foot on the Accelerator a little. 

I can't be 100% sure that my CSV and thermostat are working correctly but previous to tinkering with the linkages the car would idle at 1100 RPM before falling to 900 when warm.  It would also start both cold and warm with no problem at all.

As the engine will start and run fine if the venturi butterfly is a little open (as previous setting) but the idle will still reduce once warm does this mean the CSV and thermostat are functioning correctly? 

The only thing that has changed by me fiddling is ensuring the venturi butterfly is closed and adjusting the warm idle and CSS.

Can anyone point me in the correct direction for some diagnostic tests to get a correctly functioning cold start.  I have changed the settings for both the idle air and fuel settings to get a nice smooth warm idle.

Thanks,

Nic

[Peter van Es]

Have a look at this: http://www.sl113.org/forums/index.php?topic=5486

If you are a Full Member then you can find this information, but better organised, here: http://www.sl113.org/wiki/Restricted/Engine-starting-aid-tour

Peter

[ja17]

Hello,

By opening the venturi you are actually leaning the fuel mixture.  The engine is telling you that it needs more air because it is running rich. The incorrectly adjusted linkage was compensating for the problem, and was not fixing the problem. You will have to verify, that your engine is running rich by perfoming the "split linkage" CO test. You can do it when the engine is cold and then after warm up.  If you are not familiar with the test let us know. We will fill you in.

[Nic J]

Thanks for the replies,

I think changing the idle stop screw on the venturi moves the whole linkage adjusting both fuel and air,  The previous setting would have given additional gas and air?

I will check the split linkage test but I am starting to wonder if by coincidence my warm running device or thermostat has failed whilst looking at the linkage setup.  If the linkages are incorrectly adjusted using the idle stop on the venturi to increase idle then I would expect higher RPM at both cold and warm?  At present the only way I can get the car to start is to use the idle stop  on the venturi, to add gas and air.  On starting the engine idles at 1100 but then climbs to 1500 when warm, is this indicative of a failed warm running device or themostat?

Regarding the idle fuel screw on the fuel injection pump, does this control all idle functions both cold and hot or is it by passed when the engine is cold?

I will try to run through some diagnostics but I think it might be good to get the car put into the shop for a full check over including timing and tappets, i'm fast getting out of my comfort zone

Kind Regards,

Nic

[ja17]

Hello Nic,

Correct adjusting the venturi screw should move both the venturi and the injection pump rod as long as your linkages are not worn. If worn, only the air flap will move at first.

The idle thumb screw will adjust fuel mixture, hot or cold, up to around 1700 rpms.

You may find that the fellow in "the shop" who will be working on your car may not know as much as you!

[Nic J]

Thanks, could it be possible that when I have adjusted the venturi stop to where is should be then set the idle warm, the engine does not have enough fuel for starting cold?  Or is this indicative of a deeper problem?

Ill do anything to not have to try and diagnose a problem with the cold start system

Nic

[twistedtree]

Have you been adjusting the idle air bypass screw to set your idle mixture?  You should not be setting the idle speed with the venturi stop.  The stop just keeps the butterfly flap from jaming closed.  Idle fuel gets set at the FI pump, and idle air gets set with the separate idle air bypass screw on the intake manifold.  Definitely check out the engine starting aids section of the technical manual (members only).

[ja17]

Hello Nic,

Even if your starting aids are not working at all, over richening the whole injection system will help the engine start, but will run way too rich when it does. You may need to check those starting aids. A simple 12 volt test light or a volt meter will work.

Also after a lot of messing around with bad fuel mixture, even a new set of spark plugs may foul. Consider getting a fresh set to start off with again. Sometimes this makes all the difference in the world. You can always use the other set later if they prove to be good.

[ctaylor738]

Checking the cold start system is simple.

With a cold engine:

- Test for power at the cold start valve when you crank the starter by connecting a test light between the wire connection and ground
- Same for the solenoid on the back of the IP
- Remove the CSV completely and reconnect it so it squirts into a plastic bag or cup and verify that it squirts when you crank the starter
- Remove the little air filter on the warm running device.  Start the engine and put your finger over the hole where the filter screws in.  You should feel suction that diminishes completely when the temp hits 80.

I also recommend that you check the level of the oil in the inection pump. 

I had the exact same issue on my 230.  The major problem turned out to be a clogged CSV, followed by a grossly over-filled IP.

[Nic J]

Thanks,

I will give these a try before taking it to the shop as a last resort

Kind Regards,

Nic

[hands_aus]

what about the WRD?