Idling/starting woes

[230slhouston]

Hi all,
I need some help troubleshooting. I have the same problem second time round.

Initially, the car was started (after 20 years), it idled fine without any miss. It had new plugs (Bosch W7DRC). I drove to the gas station, 1 mile and then drove it round trip for 7 miles. It started missing and did not want to idle. Reached a point were it did not start at all. I figured out that the distributor should be a retard type not advance, since the throttle body was a retard.
I bought a retard distributor, the car still did not start. Changed the coil and ballast as well. Seemed like it would take but just won't start.

I changed the plugs to NGK BP6ES. The car started without a misfire, backfire through the intake or anything. Fired on all cylinders. It idled at about 6 RPM but I could not increase/decrease the RPM through air or the enrichment screw on the rear of the pump.

There was no change in RPM's when gear selected. I drove to the gas station and drove three miles, no problem. Then felt a loss in power, came home and the idle was barley 500RPM. I could not adjust it at all. Gradually, it started to misfire and the misfire got worse. It starts by backfires through the intake, misfires and won't idle.

Any one had similar experiences? Is this fuel or electrical, I am not sure anymore.

The car was standing for 20 years. Prior to starting the first time, I had the tank cleaned (RENU process), new filters, oil, transmission etc.

Thanks
Maistran.


Maistran (MB)
230sl

[Raymond]

I'll bet its fuel.  Getting the idle and mixture right is an exact iterative process.  There is a ton of explanation on this site.  Search for linkage adjustment and start there.  The linkage has to be perfect in order to begin any kind of trouble-shooting or adjustment on fuel injection or mixture.  

The Bosch plug number you gave is a resistor plug and that is wrong for the car.  Search for Spark Plug threads, you'll find plenty.  You want non-resistor plugs.  (I think those NGKs are non-resistor, but may be one step too cold.)  Bosch are W7DC, W8DC, or W9DC.  There should be no R in the number.  The numeral indicates the heat range.  7 is for very healthy engines.



Ray
'68 280SL 4-spd Coupe

[merrill]

so,
Maistran,

sounds like you have adjusted many things. I have learned to only mess with one item at a time.

1. what is the dwell reading?
2. what is your timing?  set it for about 3 deg btdc with the distro at the number one to get a basic setting.
3. I assume the valves are good.
4. have you verified the linkage set up.  see the linkage  tour for deatails.

5. if you kept track put the inj pump adjster screw back to where you started.
6. your idle adjuster screw only has a small range to affect idle.

when you screw it in the idle will eventually slow, then as you unscrew the idle will increase then start to drop again. (cause you have leanded out the mixture)

I would put evertything  back to the starting point.
get the car warm.

then if you get the car to idle at 750 - 800 rpm, disconnect the cross linkage from the inj pump. slowly open the cross linkage (tb) and the idle should only increase 50 - 100 rpm.

if it goes up more, turn off car, reduce the inj pump mixture screw one click try again.  

it should only take a few clicks to get the richness test to dial in.

Note:  Unless your linkages are correct this will not help you as much as it should

it took me a while to get my sl dialed in.



Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[rwmastel]

quote:Originally posted by 230slhouston

Initially, the car was started (after 20 years), it idled fine without any miss. It had new plugs (Bosch W7DRC). I drove to the gas station, 1 mile and then drove it round trip for 7 miles. It started missing and did not want to idle. Reached a point were it did not start at all.

Several forum members have had fuel distribution problems that have this symptom of failure after driving several miles.

1.  Make sure all fuel filters are clean.  Main filter screen in fuel tank.  Filter screen at inlet of electric fuel pump.  Main fuel filter in engine bay.  Also, you said you had your fuel tank cleaned with the RENU process.  Perhaps they blocked a fuel passage in the tank?  Check these links:
http://index.php?topic=1712
http://www.sl113.org/wiki/pmwiki.php?n=Fuel.Pump

2.  Make sure the flow pressure and rate are appropriate.
The pressure generated by the pump should be about 14 psi.  Measure this (somehow) at the outlet of the pump and at the return line to the fuel tank.  Both times, with the electric pump running, but the engine not.
The flow rate should be 1 liter in 15 seconds.  Drop the fuel tank return line into a glass jar and run the pump as described above.  It should be pushing fuel back to the gas tank at that rate.

quote:I figured out that the distributor should be a retard type not advance, since the throttle body was a retard. I bought a retard distributor, the car still did not start.

What exactly did you buy?

quote:Changed the coil and ballast as well. Seemed like it would take but just won't start.

What exactly did you buy?

quote:I changed the plugs to NGK BP6ES. The car started without a misfire, backfire through the intake or anything. Fired on all cylinders. It idled at about 6 RPM but I could not increase/decrease the RPM through air or the enrichment screw on the rear of the pump.

Idle should only be adjusted at the screw on the intake mainfold, where the small air hose from the air filter box joins the manifold.  Changing the enrichment screw on the rear of the injection pump is usually just covering up for other incorrect adjustments.

quote:There was no change in RPM's when gear selected. I drove to the gas station and drove three miles, no problem. Then felt a loss in power, came home and the idle was barley 500RPM. I could not adjust it at all. Gradually, it started to misfire and the misfire got worse. It starts by backfires through the intake, misfires and won't idle.

I would recommend:

1.  Check the fuel filters and perform the fuel pressure & rate tests described above.  That can find a weak fuel pump, fuel line blockages, etc.
2.  Ensure your linkages are set correct and have no slop.  You can buy a new set of ball/socket linkage ends if necessary.  Read this thread:
http://index.php?topic=5003
3.  Try to get your injection pump adjustment screws back to "neutral" or "default" position.

If this doesn't help, then:

4.  Ensure your timing & dwell is set per the manual.
5.  Ensure your combination of ignition parts are a correct match for each other (coil, ballast resistor, distributor, etc).

Beyond that, you get into fuel shutoff relays, leaking cold start injectors, and other things.  Don't worry.  If you detail the change in symptoms that follow each adjustment, the Group will eventually help you solve the problem.

Rodd
Pagoda Technical Manual
please contibute: http://www.sl113.org/wiki/pmwiki.php
1966 230SL
2006 C230 Sport Sedan

[rogerh113]

Hello,

I did have a similar problem, and it turned out to be the fuel tank (also had the RENU process done on the tank, and it worked for a while).  There was a similar intermittent fuel starvation type problem, which I ultimately concluded was the tank. I ended up getting a new tank, and it did resolve the problem.  My guess is that some of the coating was moving around and restricting the fuel passages in the coated tank.  There was a recent posting on fuel tank coating, with other opinions on this process (as well as mine).

The fuel tank happened early on in my ownership (maybe 9 years ago).  I recently had a similar power loss issue, and it turned out to be my aging fuel pump. It was working, but evidently not delivering sufficient fuel flow.  Once that was rebuilt, all ran well again.

The idle screw adjustment will only increase idle if the injection unit is running sufficiently rich - there is also a fairly recent post on how to adjust the idle screw on the pump to achieve a correctly rich mixture.  If the fuel input is restricted to the injection pump, I would guess that the idle could be impacted in the way you are experiencing and the adjustment screw would have no effect (aside from maybe killing the idle with too much air).

As mentioned in the several earlier posts, there are a number of other things that could be causing your problem. One good/bad thing about our cars is that components do not generally just fail - they fail gracefully, which makes diagnosis difficult some times.  Given that you now have the correct plugs in, I would suspect a weakness in your fuel delivery system. You can 'measure' the fuel output at the fuel filter, which would cover both your tank and fuel pump.  A LOT comes out when the system is running right, and I am not sure how easy it is to accurately measure it......  Given my experience, I would suspect the tank/RENU job......

Good luck -- Roger

[230slhouston]

Hi All,

This morning, I tried starting the car and it won't start (went from fine to rough idle to nothing), typical wants to take when I cranked the engine but will not start.

I did the fuel flow rate test, it was 3 liters in 30 secs.

I removed the plugs, they seemed to be flooded with fuel. I put in a new set NGK BP6ES. The car  fired up immediately and idles/sounds like a dream.

I am going to check the dwell and timing like Mat suggested but find it surprising, this is the second time I had to change plugs after 7 mile trips to start the car again. I have a new coil, ballast resistor and plug wires.

Any suggestions?

Thanks
Maistran.

Maistran (MB)
230sl

[230slhouston]

Update, I set the dwell to 38 degrees, the timing 8 BDC, and it is idling at about 650 RPM. Not a misfire and sound great.

Adjusting the enrichment screw (CCW or CW) has no effect on the idle, turning in the air screw cuts the idle but at a point when unscrewing, there is no impact to the idle, it remains steady.

Any suggestions?

Maistran

Maistran (MB)
230sl

[merrill]

so, I am figuring this out recently as well.

the idle air screw will only have a small impact on the idle, in reality, you can screw it in till it cuts off the air or you can unscrew it till it has no effect.  There is a happy medium that the experts understand.

what I would do is let the car idle, and do a richness test. that will give you an idea how rich or lean the pump is.

once you get the car reasonably running, you can use a co2 meter to check where you are.  any time you mess with the idle air screw you mess up the air fuel ratio and with a co2 meter you can see where you are. (this is assuming your idle is within specs)

note: if your pump is too rich the idle will increase a lot when you unscrew the idle screw if too lean it will have little affect.  your idle may ever wander up an down till the car dies.

make sure you only make adjustmens when the car is wamed up. this way you eliminate the cold start circuit.



Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[ja17]

Hello Maistran,

The fact that your car runs great everytime you install fresh spark plugs, leads me to believe that the usual fuel tank problem may not be your issue. A stuck WRD (warm running device) or a leaky starting solenoid could be at fault if the used plugs are fuel fouled. Do you need guidance here or have you checked to see if these items are working correctly?

Joe Alexander
Blacklick, Ohio

[230slhouston]

Joe,
In a previous thread, you explained how to test the WRD to me. Once warm, there is barely any vacuum  sucked through the WRD inlet. I could not troubleshoot with the pipe as stethoscopes.

I would appreciate it if you can guide me on the starting solenoid. Is this the one behind the IP?

I took of the small bolt on the CSV and there is no fuel out once the car is started.

Thanks

Maistran (MB)
230sl

[ja17]

Hello Maistran,

Your problem seems to be over rich at start or not enough spark at start.

The WRD can also be checked also by removing the small air filter on the injection pump and placing your finger over the opening in the WRD. As the engine warms up the "suction" will disappear or become very, very slight.

The other fuel issue, which you have already checked, is the cold start valve.

The issue could also be ignition. You may want to use an ohm meter on your spark plug wire set to make sure you are getting good spark.

Make sure your ignition points are in good condition.  

We cannot completely rule out a fuel tank problem yet, but it seems you could have two issues or something other than fuel supply.

Joe Alexander
Blacklick, Ohio

[230slhouston]

Hi Joe,
I drove the car today for 15 miles, it still idles fine, no repeat of the first two trips. I am baffled, should I be grateful of confused in that the problem will reappear.

I took Matts advice and reset the dwell and timing. 38 degrees dwell and  8 BTC.

I took of the filter from the WRD, barely any suction once the car is warm.

I set the linkages, when I remove the IP linkage and then open the throttle, the RPM's go up to 1600 RPM. Is this too rich, I have the enrichment screw CCW by 8 turns. Should I turn it CCW even more, how many turns are typical?

I am going to post another thread on the transmission and revs.

Thanks to everyone.

Maistran (MB)
230sl

[ja17]

Hello Maistran,

Yes, a 1600 rpm increase is an indication of a very rich mixture.
The next test is a little more difficult. Let the engine warm up to running temperature. Split the linkages as before. Now raise the rpms to 2500 to 3000 keeping the linkages separate but aligned. Now increase the linkage going to the venturi. If the rpms increase significantly, your injection is running rich at more than just the lower speed range and a simple thumbscrew adjustment at the IP will not be adequate.

Removal of a shim under the WRD (oval shim between the WRD and the IP housing) will lean all speed ranges if needed.

Joe Alexander
Blacklick, Ohio

[hands_aus]

Have you checked the oil level in the injection pump reservoir?



Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[230slhouston]

Hi Bob and Joe,
I did check the oil in the reservoir, it was correct.

Joe, I did the test you recommend, I had to get over the psychological barrier of revving the engine to 3000 RPM under no load. At 3000 RPM, I opened the throttle more and the revs increased much higher with the fuel linkage held in the 3000rpm position.

I guess your theory burning rich at all RPMs is true. The last time I took of the WRD, there was a verrrrry thin space, will removing this make a huge difference?

Thanks
Maistran.

Maistran (MB)
230sl

[230slhouston]

Update, I removed the shims from the WRD, they are very thin. still, I get 1400rpm with the linkage split and throttle gently open. Idle speed is 750 RPM. The enrichment screw on the IP is about 12 clicks CCW. I almost had it to the end but turned it in a couple of clicks.

I drove it 12 miles today and took it up to 60MPH (first time in 20 years). It drove with a vibration and felt solid on the rode.

Any suggestions of setting the rich idle?

Thanks

Maistran (MB)
230sl

[mrfatboy]

check out this thread.  Play around with temporary adjustment bolt and see if you can get it any leaner.  I'm sure you can.

http://index.php?topic=8328

1969 280sl
Signal Red

[230slhouston]

Update,
I took of the spacer out from the barometric compensator and was able to reduce the richness. The spacer was about 1.5mm plus two thin shims. With the 1.5mm spacer, removed, I think the car was too lean and the rev was not spontaneous. I added a 1mm brass spacer, this improved the responsiveness. Now with the split linkage and opening the throttle, I get an increase of about 150RPM before it cuts out. I also have the shims removed from the WRD, I will add them back this coming weekend.

Thanks for the help thus far.
Took it for a drive and seems OK. I will now tinker a little more.

Maistran (MB)
230sl

[mrfatboy]

I only had a 2mm washer/spacer under the BC.  With the washer  it was too rich but but when I removed it the car was way too lean and undriveable.  So less than 2mm but more then 0mm is the perfect setting At least for me.

Good luck

1969 280sl
Signal Red

[hands_aus]

230sl and MrFB
Did both of you test the WRD thermostat to make sure it is working correctly? The thermostat can become lazy as it ages.

There is a description of testing the thermostats in the BBB.

If the thermostat is not working properly the pin does not move enough and that does not move the WRD valve.

230sl inj pump thermostats are expensive but 250,280sl thermostats are inexpensive.

Replacing the thermostat in my Injection pump WRD allowed me to replace the removed shims and make adjustments via the sprung knob on the back of the inj pump.
I did not adjust the Altitude compensator.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[mrfatboy]

Yes, my WRD works fine.  It sucks in air when the engine is cold and stops sucking in air when the car is warmed up.

The reason I used the "bolt method" on the BC was so I can fine tune the engine mixture on the fly.  It's faster, easier, and more precise then removing the WRD shims.  

But if you want your IP to look stock like most of us do you are ultimately going to have to take the bolt out, measure the depth of where you set the bolt and then replace with shims.

1969 280sl
Signal Red