Author Topic: Cold Start (Read 22527 times)

bpossel · « **on:** July 16, 2007, 06:23:51 »

Hello All!

I know..... lots & lots of postings on "cold start" issues, but none have helped so far...

Problem: when car is cold (or sits for ~1 hr), it takes many, many cranks to start it up

. When the car is warm, it starts on 1 key turn...

. Cars runs very well! Idles at ~800rpms in gear and ~ 900 out of gear. Gas mileage is ~16mpg. Spark plug color is a nice brown/grey. Cars runs great, just terrible cold starts!

Even though I tested these parts, and they seemd to work, I just went ahead and replaced them in order to try and fix my cold starts (and also as part of my overall "rolling restoration"). These are the parts I replaced:
Fuel Pump, Cold Start Valve & Solenoid, Thermo Time Switch, Injection Pump rebuilt by Hans 3 years ago, 6 new injectors, 100 & 17 degree switches, Starter (Bosch smaller version), Beckman rebuilt speed relay & speed switch, New current/working relay, Pertronix Ignitor II w/45 volt coil & Pertronix wires, New 2-way valve, Rebuilt distributor (Dan C.), New Spark Plugs, New fuel pressure damper; new fitted hoses, Linkage adjusted (did fuel, air flow test- OK). Many, many more parts, not listed.....

:?: The repair book mentions that a cold start issue could be the fuel cut-off solenoid. Any comments on this? How do I test this?
:?: Any other comments, advice on what to do next?

Thanks! 2 weeks to go till Joe's!!!

Bob
bpossel (Memphis, TN.)
'71 280SL / '97 E320

Ben · « **Reply #1 on:** July 16, 2007, 10:28:14 »

Okay so lots of new parts but have you physically verified that the CSV is actually spraying whilst cranking from cold !

Regards,
Ben in Ireland.
'64 230SL 4sp.

jeffc280sl · « **Reply #2 on:** July 16, 2007, 10:48:21 »

I'm with Ben. Wire a 12V lamp to ground and the CSV. When the car is cold and you crank the engine this lamp should be on. If it doesn't light check the operation of the silver relay box along the driver fender. Sometimes the contacts get dirty. You can take the relay apart to clean or replace it. You can also install a new style Bosch relay in the same silver shell if so inclined.

Jeff C.
1970 280SL 4-speed

George Des · « **Reply #3 on:** July 16, 2007, 11:48:40 »

Bob,

How do you try to start from cold? When I crank from cold, I do not press down on the accelerator pedal at all-usually, it will kick right over. However, when cranking after it's run a while and hot, thius technique dows not work and I do have to press down on the accelerator and it will start right up.

George Des

bpossel · « **Reply #4 on:** July 16, 2007, 12:02:19 »

Ben, Jeff,

Yes, I did the "tests". Test light lit up when did the test light test. I also flipped the CSV around and pointed it toward the fender. Held a small plastic cup over the "sprayers". Had my wife crank the engine over (disconnected coil) and the CSV produced a very nice mist spray pattern. So this appears to work.

George, when car is cold or warm, I do not step on the gas. I simply turn the key. When warm, just by turning the key, the engine fires up almost immediately.

I just cant figure out the cold start problem. I was reading back through some of the older posts regarding the shut-off solenoid. Maybe this thing is stuck?

Any other ideas?

As always, thank you for the advice!
Bob

bpossel (Memphis, TN.)
'71 280SL / '97 E320

J. Huber · « **Reply #5 on:** July 16, 2007, 12:20:00 »

Is it possible the CSV is continuing to spray?

Also -- and this might be controversial and maybe way off but have you considered going back to points and seeing what happens? You mentioned the Dist. was rebuilt -- so it seems ready for action...

James
63 230SL

enochbell · « **Reply #6 on:** July 16, 2007, 13:46:47 »

Bob,

You probably have reviewed this already, but just in case, here is the string that discusses the balast and method to go "hotter" on starting:

http://index.php?topic=4240

Best,
g

'64 230sl, fully sorted out...ooops, spoke too soon

jeffc280sl · « **Reply #7 on:** July 16, 2007, 16:27:03 »

The fuel cutoff switch is part of the emissions system and is normally in the off position. You can hook up a test lamp to the solenoid terminal and ground to confirm this. You can also disconnect the wire to take it out of the trouble shooting equation.

The solenoid is energized and fuel is shut off under cetain conditions. They are as follows:

Engine temp above 17C
Decelerating (foot off gas pedal)in drive under 1,250rpms

This solenoid is controlled by pressure switches in the auto tranny and the 8 pin relay box you had repaired. During deceleration MB wanted to minimize the release of unspent fuel emissions by shutting off the flow of fuel.

I can't say for sure but maybe your solenoid is jammed partially closed and as the car warms up it opens fully.

Jeff C.
1970 280SL 4-speed

bpossel · « **Reply #8 on:** July 17, 2007, 06:00:35 »

Hi Guys, thanks for the replies & ideas!

To summarize: When my car is cold, I turn the key on and let the fuel pump run for ~ 20 seconds. Then I turn the key further and let it crank for 6-10 cranks. Turn key off, do this again. After 3 times of these 6 or so cranks, it fires up. Then runs great!

Once the car has been started and has run for just a few minutes, I can turn off the car and the next 1 turn of the key, it fires right up.

So only initial cold starts are the issue.

Maybe to help figure the cold start issue out, we can list exactly what is different about the engine start cycle once the engine has run for a few minutes? Maybe with an understanding of the differences, I can better figure out the cold start issue?

Thanks!!!
Bob

bpossel (Memphis, TN.)
'71 280SL / '97 E320

Ben · « **Reply #9 on:** July 17, 2007, 06:15:35 »

Okay from what i have experienced, even if you do not have a functioning solenoid/relay/whatever, if your CSV sprays the car WILL try to start !

Make that SHOULD try to start.

I think your problem is elsewhere, however my next test would be to remov ethe fuse that controls the CSV and try starting without its help !

This may tell you something..................do you have a really good spark whislt cranking ? Going back to points as suggested may be the next step after the above !

Regards,
Ben in Ireland.
'64 230SL 4sp.

bpossel · « **Reply #10 on:** July 17, 2007, 06:22:13 »

Hi Ben! Thanks, that was quick! I will try this tonight after work.
Will update you.
Bob

bpossel (Memphis, TN.)
'71 280SL / '97 E320

bpossel · « **Reply #11 on:** July 18, 2007, 06:18:15 »

Last night I installed a temporary switch (what I call my viagra switch

) between the cold start solenoid and fuse #6.

Now when engine is cold... I turn the key on (fuel pump running), hit this "viagra" switch a couple of times to manually squirt some fuel into the intake.... car fires right up ! When warm, dont need to use this switch...

:oops: Not sure where to go next?[:0]

Prior to installing this temporary switch, I put a volt meter on the cold start solenoid, turn the key, and I get 12+ volts, so you would think that the solenoid is operating??? But it must not be, because when cold, car struggles to start. When warm, car fires right up!

Any ideas? Next steps? I really dont want to have to keep this manual switch if I dont need to... Would prefer the factory setup...

Thanks!
Bob

bpossel (Memphis, TN.)
'71 280SL / '97 E320

jeffc280sl · « **Reply #12 on:** July 18, 2007, 07:56:44 »

Recap

1)wife cranks the engine over (disconnected coil) and the CSV produced a very nice mist spray pattern
2)volt meter on the cold start solenoid, turn the key, and I get 12+ volts
3)hit "viagra" switch a couple of times to manually squirt some fuel into the intake.... car fires right up !

Assume 1 and 2 are continuous while cranking the engine. You said the solenoid is new.

So the car will not start under condition 1 and 2 but will start under condition 3.

It may be that the MB circuit is providing resistance such that the solenoid does not open the valve all of the way. Bypassing the circuit with the viagra switch provides sufficient current to the solenoid to completely open the valve.

I would look at the contacts in the relay. You can pry open the can and look inside. You may want to locally bypass the relay, I can help with the jumpers, to make sure the wiring is sound and not causing the resistance.

Jeff C.
1970 280SL 4-speed

enochbell · « **Reply #13 on:** July 18, 2007, 09:55:58 »

Bob,

When you tested the CSV and saw the spray did it continue, assuming you did this test with a cold engine, for longer than 1 second? Maybe the thermo-time switch thinks the car is always hot? The 1 second spray may be enough to get you started warm but not cold? Just my 2 cents.

g

'64 230sl, fully sorted out...ooops, spoke too soon

bpossel · « **Reply #14 on:** July 18, 2007, 10:33:31 »

Hi Gregg,

Actually, I didnt time it. When the gas sprayed out into the cup that I was holding around the sprayers it started to run out of the cup (had to hold on an angle due to limited space...), I had the wife stop turning the key... Maybe I need to recheck and time it?
Good idea.
Bob

quote:
Originally posted by enochbell

Bob,

When you tested the CSV and saw the spray did it continue, assuming you did this test with a cold engine, for longer than 1 second? Maybe the thermo-time switch thinks the car is always hot? The 1 second spray may be enough to get you started warm but not cold? Just my 2 cents.

g

'64 230sl, fully sorted out...ooops, spoke too soon

bpossel (Memphis, TN.)
'71 280SL / '97 E320

bpossel · « **Reply #15 on:** July 18, 2007, 10:39:02 »

Hi Jeff,

I also have replaced the relay some time back. Last night before I installed the viagra switch, I thought that maybe the new relay might be bad. So I dug my old one out of storage, took cover off and cleaned the contacts. Installed this old one and .... same results. Hard cold start. So I re-installed the new relay and put the old one away again.

I'm leaning towards wiring, resistance... like you state, not enough current. But... I do get 12 volts on the solenoid when I test it with the normal hookup? This is why I am puzzled...
Thanks again, Bob

quote:
Originally posted by jeffc280sl

Recap

1)wife cranks the engine over (disconnected coil) and the CSV produced a very nice mist spray pattern
2)volt meter on the cold start solenoid, turn the key, and I get 12+ volts
3)hit "viagra" switch a couple of times to manually squirt some fuel into the intake.... car fires right up !

Assume 1 and 2 are continuous while cranking the engine. You said the solenoid is new.

So the car will not start under condition 1 and 2 but will start under condition 3.

It may be that the MB circuit is providing resistance such that the solenoid does not open the valve all of the way. Bypassing the circuit with the viagra switch provides sufficient current to the solenoid to completely open the valve.

I would look at the contacts in the relay. You can pry open the can and look inside. You may want to locally bypass the relay, I can help with the jumpers, to make sure the wiring is sound and not causing the resistance.

Jeff C.
1970 280SL 4-speed

bpossel (Memphis, TN.)
'71 280SL / '97 E320

jeffc280sl · « **Reply #16 on:** July 18, 2007, 16:53:09 »

Bob,

This indicates the relay works. It still may not deliver the current you need for the solenoid. That would indicate a problem in the wiring between relay connector pin 87 and the solenoid or between relay pin 30 and the battery.

Try taking the viagra lead off the cold start solenoid and jumpering it to pin 87 on the cold start relay connector. Pin 87 should be the MB wire to the solenoid. Throw the switch as you crank the engine. This will simulate what the relay is supposed to do.

In another test you could connect the battery side of your switch to connector pin 30 on the relay. Throw the switch as you crank the engine.

Jeff C.
1970 280SL 4-speed

glennard · « **Reply #17 on:** July 18, 2007, 19:15:14 »

Bob, It might be the 'Timing' of the CSV on the Start switch vs. the viagra.
When you use Start, the CSV and the starter are energized at the same time. The vacuum from the pistons has to suck the meager amount of fuel from the CSV and the FI pump fuel has a time delay down the pipes. So the first couple of cylinder sparks have no fuel! Ergo, no start.
When you use viagra, you fill the intake manifold with a lot of fuel - before the starter turns. Now when the starter turns and there is the first spark - that cylinder (and all the others) has plenty of fuel. Kinda like pumping the accelerator on a carb injin pre fuel injection- get a lot of gas into the intake manifold.

With new electronic engine mgmt., they can delay 'Start' etc.

That's my story, and I'm sticking by it. Until------

wgl · « **Reply #18 on:** July 18, 2007, 20:43:25 »

I was having trouble with cold start and ideling. I took the cold start valve apart and found that the o ring that seals the selenoid to the valve had gone to dust. The o ring material had packed in around the brass plunger in the valve causing it to work poorly if at all. I cleaned it up put a new o ring in, the idle now is steady and the engine fires with 3 or 4 cranks at cold. I also replaced the o ring where the valve joins the manifold. The parts guy gave me the o ring at NC, the best deal I ever got at the Mercedes store.

Bill Lindquist
1968 280 SL

bpossel · « **Reply #19 on:** July 19, 2007, 06:03:06 »

Hey Guys!

Thanks for all of your input. Bill, good suggestion, however my CSV, Solenoid, o-ring are brand new. Also relay is new.

This morning I turned the key to the start position, started to crank, hit the viagra switch 1x and bame.... engine fired right up!

I agree, sounds like my issue is with either the timing of the OE system, and/or current (wiring)?

I may just leave this alone and see if this issue can be cured up in Blacklick. Saturday have a local MBCA car event and Sunday taking the Pagoda to Graceland for a photoshoot (Thanks Dennis!). Leave Thursday for Ohio...

If we find Elvis on Sunday, I'll bring him along to Joe & Mary's...

Regards,
Bob

bpossel (Memphis, TN.)
'71 280SL / '97 E320

glennard · « **Reply #20 on:** July 19, 2007, 06:29:34 »

Bob, I think it is all in the time delay between the crank turning at,say, 360 rpm on 'Start'(3 sparks/second) and delivery of vaporized gas to the first couple cylinders. Say #1 is TDC about to go down on the intake, then compress and fire, i. e. 1 rev. This takes 1/6 second(167 milliseconds). Don't think the electric fuel pump can deliver fuel from the tank, up the inlet to the FI pump, up the line to the CSV, thru the orifice, down the inlet manifold, past the inlet valve, into the cylinder- in 167 milliseconds?

What do you think??? guys??? Viagra switch for one or two seconds fills the the cylinder with the open inlet valve and the manifold to the others before the starter/crank turns.

Computerized engine mgmt made a solution a lot easier than mechanical/analog controls of the 50's and 60's.

Ben · « **Reply #21 on:** July 19, 2007, 08:26:51 »

With the fuel system working correctly the fuel doesn't drain away from the injectors, it remains there under pressure, the electric pump primes the lines all the way up to the injector pump.

Bob, you are mentioning the Cold start Solenoid, and relay, as well as the CSV. I would do as suggested and concentrate on the relay switching the CSV, how quick and for how long ?

The fact that your "viagra switch" ( I love it BTW) gets things working suggests the issue is with the control of this part,k as the guys say !

Regards,
Ben in Ireland.
'64 230SL 4sp.

glennard · « **Reply #22 on:** July 19, 2007, 09:30:38 »

Seems to me after 40 years the probability that here is high press at the injector is slim, especially if the car has been setting hours since last running. Prima facia evidence of -putting gasoline into the manifold w/viagra switch before hitting Start(from Run) and getting an immediate start pretty much says the engine was fuel starved in normal MB start. Bosch/MB tried to enrich at Start with 2 things- 1, Start solenoid on the FI pump throwing the rack to rich and, 2, CSV for varying number of seconds depending on the temp. Never worked too well!

bpossel · « **Reply #23 on:** July 20, 2007, 05:49:38 »

Ben, Glennard,

Thanks! Even though my injectors are new, I never had them tested. I wonder if one or more are not holding pressure?

Glennard, my version of IP does not have the start solenoid. Just the shut-off solenoid. I believe the pressure issue was solved in the later pumps with the design improvement of the check valves in the IP pump. This is supposed to keep the pressure.

In the mean time, she seems happy with the viagra switch. One or two squirts, when cold, and she fires right up!

B.

bpossel (Memphis, TN.)
'71 280SL / '97 E320

bpossel · « **Reply #24 on:** July 31, 2007, 06:46:37 »

Update...

At Blacklick University, Joe diagnosed my cold start issue. It was a bad cold start relay. Even though it was a brand new relay, it was not functioning. Joe found an old one in his spare parts collection and now the engine fires right up when cold.

Thanks Joe !!!

Now I can remove my Viagra switch and use it elsewhere…

Joe also sorted out my low idle. Believe it or not… even though I had my IP pump rebuilt 3 years ago, it was running lean, very lean… Joe ended up doing 18 clicks CW to richen up the fuel… yes, 18 clicks. I had already increased it by 3 before that, so a total of 21 clicks CW... WOW ! Now the engine really runs great! Idle and in gear!

Lessons learned at Pagoda University….

1. Joe & Mary are really great people!
2. Our club members are truly a nice group of friends and 113 enthusiasts…
3. Joe knows his stuff!
4. New parts don’t always work :oops: ! Use the tests & procedures on this site to assist with your issues.
5. Even though your IP Pump has been re-built, it needs to be adjusted for YOUR engine. Each engine is unique and different: age; mileage; overall condition; etc…
6. The homemade Viagra switch can be used elsewhere, don’t throw it away…

I really enjoyed seeing you all at Joe & Mary’s and look forward to the event again in 2 years.

Bob

bpossel (Memphis, TN.)
'71 280SL / '97 E320

News:

Author Topic: Cold Start (Read 22527 times)

bpossel

Ben

jeffc280sl

George Des

bpossel

enochbell

jeffc280sl

bpossel

Ben

bpossel

bpossel

jeffc280sl

enochbell

bpossel

bpossel

jeffc280sl

glennard

wgl

bpossel

glennard

Ben

glennard

bpossel

bpossel