Mercedes-Benz Forum banner

1 - 14 of 14 Posts

·
Registered
R170, W124
Joined
·
138 Posts
Discussion Starter #1
my friend just purchased a 90 500sl. tested drive ok, and after she brought it back and started it in the morning, it started right away, but died right away, with battery indicator light on dash. we thought it might be a bad battery, so we purchased an genuine mercedes battery. after installing it, it still had the same problem. it always started the second time, but sometimes it shook sideways when she got it started this way.
the question is, how long do you have to hold the key in start position after you start it? she suspected that it might be because she didn't hold it enough time, but i doubt it, since it always picked up the second time.
please, gurus, what should she begin to do? i will try to shoot a video of the symptom later. hopefully it is not something big, as it did not surface at test drive, or the day she brought it back.


Sent from my iPhone using Autoguide
 

·
Greek God of the R129
SL500-500SEL-190E
Joined
·
8,391 Posts
my friend just purchased a 90 500sl. tested drive ok, how long do you have to hold the key in start position after you start it?


Holding the key on start, about four seconds is normal.
Now I don't understand the key holding after it starts....

Regards,
aam.
 

·
Registered
Departed 1998 SL500 (and the Pano is in Bogota)
Joined
·
11,118 Posts
I think she should let go of the key as soon as the engine starts as it would out run the starter motor. There is a one way clutch to protect the starter to prevent damage but there is no sense to hold the key longer than needed. That apply to any cars,
 

·
Registered
R170, W124
Joined
·
138 Posts
Discussion Starter #4
my friend just purchased a 90 500sl. tested drive ok, how long do you have to hold the key in start position after you start it?


Holding the key on start, about four seconds is normal.
Now I don't understand the key holding after it starts....

Regards,
aam.
i meant on start, not after, sorry for the misunderstanding.


Sent from my iPhone using Autoguide
 

·
Registered
R170, W124
Joined
·
138 Posts
Discussion Starter #5 (Edited)
I think she should let go of the key as soon as the engine starts as it would out run the starter motor. There is a one way clutch to protect the starter to prevent damage but there is no sense to hold the key longer than needed. That apply to any cars,
ok, holding the key is not an issue any more, because the pattern of behavior is that it always starts the second time, with like a 10 second interval after the first try. but there is a "sound" difference for the two starts, ad if the second one gives a more throaty sound, the first is right up but it always immediately dies. and sometimes there is the smell of fuel.

i suspect it is a fuel delivery issue, since after the first start there might be more fuel left in the middle, and the second one pushes it to where it should go to "feed everything". if so, how should we go about checking? fuel pump relay? fuel pressure regulator? could it be low grade fuel since the seller doesn't seem to use premium?
i am just guessing, but i don't know these cars well to even start deduct things, so any advice? thank you guys so much!


Sent from my iPhone using Autoguide
 

·
Registered
Departed 1998 SL500 (and the Pano is in Bogota)
Joined
·
11,118 Posts
Sound like a fuel pressure problem. As she just bought the car, may be just replace the fuel filter and put in a tank of fresh gas to see what happens.
May also have a slight fuel leak and lost (reduced) pressure overnight, Can test it with a pressure gauge, but I have no idea what a '90 500SL should read, may be Albert (aam) knows.
 

·
Registered
R170, W124
Joined
·
138 Posts
Discussion Starter #7
Sound like a fuel pressure problem. As she just bought the car, may be just replace the fuel filter and put in a tank of fresh gas to see what happens.
May also have a slight fuel leak and lost (reduced) pressure overnight, Can test it with a pressure gauge, but I have no idea what a '90 500SL should read, may be Albert (aam) knows.
thanks. we will get more gas for it. currently it just hit the empty range below 1/4. also, one more note that it is not an overnight thing; it happens almost every time, except one time when she just turned off the car and started it like 5 mins later.
we researched the fuel filter job; that you would need to get under the car. it might be a piece of cake for you guys, but we would have to take it to a shop to do that. other than that, we will try to check here and there.


Sent from my iPhone using Autoguide
 

·
Greek God of the R129
SL500-500SEL-190E
Joined
·
8,391 Posts
It looks like you may need a fuel accumulator.
But if you don't know how to CK it is better to have it checked by a knowledgeable mechanic.
Or you will be wasting good parts money. ;)
It is a complex system, you need fuel pressure gauge to inspect.

As far as pressure goes, the injectors should hold about 40 psi, the system runs at about 95 psi.
It is a continuous electronic fuel injection/CSIE.
For the gas smell check the EHA 0 rings, rubber hose on fuel pressure regulator.
Premium gas please.

Regards,
aam.
 

·
Registered
R170, W124
Joined
·
138 Posts
Discussion Starter #9
It looks like you may need a fuel accumulator.
But if you don't know how to CK it is better to have it checked by a knowledgeable mechanic.
Or you will be wasting good parts money. ;)
It is a complex system, you need fuel pressure gauge to inspect.

As far as pressure goes, the injectors should hold about 40 psi, the system runs at about 95 psi.
It is a continuous electronic fuel injection/CSIE.
For the gas smell check the EHA 0 rings, rubber hose on fuel pressure regulator.
Premium gas please.

Regards,
aam.
did some research on the topic. some people said replacing the accumulator fixed their "hot starting problem". just wanna make sure before proceeding that i understand this correctly, since it has always been bothering me what hot, cold, and warm means in the mechanical sense of the word. are these referring to coolant temp gauge when doing things with the car? so, hot start would mean like start the car when it is over, say, 90, and "car is warm" means driving for a while and things feel smooth in the car? and cold would mean like the first start in the morning?

as for the fuel pressure gauge, would any ordinary brand work or should i get something specific?

also a small update. tonight we went to get more gas (premium, for sure) for the car until it is about 1/2. it started fine, to our joy, although it only had like a 10 min interval to the former one, with engine "warm", by which i mean 80 and a drive about 15 mins.


Sent from my iPhone using Autoguide
 

·
Greek God of the R129
SL500-500SEL-190E
Joined
·
8,391 Posts
did some research on the topic. some people said replacing the accumulator fixed their "hot starting problem". just wanna make sure before proceeding that i understand this correctly, since it has always been bothering me what hot, cold, and warm means in the mechanical sense of the word. are these referring to coolant temp gauge when doing things with the car? so, hot start would mean like start the car when it is over, say, 90, and "car is warm" means driving for a while and things feel smooth in the car? and cold would mean like the first start in the morning?

as for the fuel pressure gauge, would any ordinary brand work or should i get something specific?

also a small update. tonight we went to get more gas (premium, for sure) for the car until it is about 1/2. it started fine, to our joy, although it only had like a 10 min interval to the former one, with engine "warm", by which i mean 80 and a drive about 15 mins.


Sent from my iPhone using Autoguide
Accumulator is nothing more then, a can, a strong spring, and a diaphragm.
One hole is the IN the other is if it leaks& vibration.
(Some have more then two.)

It has on the other side of the diaphragm a small rubber hose.
The reason for that is to absorb the spring vibrations, and if the diaphragm leaks to push the extra pressurized fuel BACK in to the gas TANK.

Hot engine, STARTS with operating temperature that the thermostat OPENS, on the temperature gauge about 80-90 degrees..

Real HOT reading, is after driving more then 20 miles.
(That gives a change to burn off accumulated engine contaminants.)

When the engine is cold, like first morning start, the COLD START VALVE gets a signal from the engine temperature SENSOR to spray more gas, (about FOUR seconds ) THAT IS along with the INJECTORS.

That is provided that the MAS module senses starting RPM signal, this signal makes the FUEL pumps run for a few SECONDS to pressurize the fuel.
(A little less then 100psi.)

If the RPM SAFETY signal (some engines are also using RPM & OIL pressure.... )
Doesn't satisfy the ECU, the ECU & in your case MAS, shuts the pumps down....
(Like in an accident.)

Starting a HOT engine with a leaking ACCUMULATOR, the pressure is DOWN, the pumps, COLD start valve run for a second, the accumulator leaks BACK in to the TANK.
NO FUEL PRESSURE=Car is not starting or HARD start.
Some times if you turn the KEY FAST ON & OFF, you can outsmart the sensor.
(GIVE more pressuring time for the fuel pumps to PUMP...)

I hope that this helps you a little.

To test there special manifold hoses and gauge.

Regards,
aam.
 

·
Registered
R170, W124
Joined
·
138 Posts
Discussion Starter #12 (Edited)
Accumulator is nothing more then, a can, a strong spring, and a diaphragm.
One hole is the IN the other is if it leaks& vibration.
(Some have more then two.)

It has on the other side of the diaphragm a small rubber hose.
The reason for that is to absorb the spring vibrations, and if the diaphragm leaks to push the extra pressurized fuel BACK in to the gas TANK.

Hot engine, STARTS with operating temperature that the thermostat OPENS, on the temperature gauge about 80-90 degrees..

Real HOT reading, is after driving more then 20 miles.
(That gives a change to burn off accumulated engine contaminants.)

When the engine is cold, like first morning start, the COLD START VALVE gets a signal from the engine temperature SENSOR to spray more gas, (about FOUR seconds ) THAT IS along with the INJECTORS.

That is provided that the MAS module senses starting RPM signal, this signal makes the FUEL pumps run for a few SECONDS to pressurize the fuel.
(A little less then 100psi.)

If the RPM SAFETY signal (some engines are also using RPM & OIL pressure.... )
Doesn't satisfy the ECU, the ECU & in your case MAS, shuts the pumps down....
(Like in an accident.)

Starting a HOT engine with a leaking ACCUMULATOR, the pressure is DOWN, the pumps, COLD start valve run for a second, the accumulator leaks BACK in to the TANK.
NO FUEL PRESSURE=Car is not starting or HARD start.
Some times if you turn the KEY FAST ON & OFF, you can outsmart the sensor.
(GIVE more pressuring time for the fuel pumps to PUMP...)

I hope that this helps you a little.

To test there special manifold hoses and gauge.

Regards,
aam.
i never saw you type so many words in one post. i appreciate it and have been re-reading it to understand better. this afternoon, we tried to start it, but it was even worse than the last two days. shot a video and will post the video link. after driving for 10 mins, stopped at a grocery store for 15-20 mins, i used the "fast turn key" trick you mentioned. it started ok, with engine warm (70-80). the next two starts were both OK in similar situation, with engine temp around 80, just not cold at all.
so, now i could conclude is that it happens with cold start, but not warm or hot.
video link for this afternoon:


thanks albert (aam) and guys~

Sent from my iPhone using Autoguide
 

·
Registered
1991 500SL purch 10/2013 w/ 86,500 miles. 2001 S55 purch 9/2014 w/ 47,000 miles.
Joined
·
2,112 Posts
Iris, was your hot start problem ever fixed? Mine sometimes acts up if I let it sit for about an hour. It starts but I have to turn the key a little longer than I would like.
 
1 - 14 of 14 Posts
Top