230sl loss of power

[n/a]

Hi, Ive had my car for a few months now and have been
trying to diagnose a problem myself unsuccessfully, the car will
start fine and runs good until I reach normal operating temp...approx 10 to 15 miles of driving, I am still turning normal rpms and I still have normal oil pressure, however I am slowing down and when I do stop if I let my foot off the accelerater it will cut off (not always), but regardless of whether I cut it off or it cuts off it will not start again for 20 min or so...it will always start back up and run fine after it sits. I have changed sparkplugs, and the ignition coil and associated cables look in descent shape.
I am looking at some old looking wires that run to Y...one runs to the solinoid on the side of the fuel pump and the other runs to the side of the engine block...it looks so old I am just guessing here...I know I should probably just break down and find a mechanic but wanted to post here first....by the way I do hear my fuel pump running during this and also when I try to turn the engine over there is no sign of it trying to start until its ready and then it starts fine. so I am thinking something electrical but like I said I replaced my ignition coil so that was not it. thanks Scott 1966 230sl

[ja17]

Hello Mercury,
Narrow the problem down. When the car stops running, have an extra spark plug with you. Remove any spark plug wire and connect the spark plug to it. Ground the spark plug end against the engine. If it sparks when you crank the engine the problem is not likely to be ignition.
Next, hook everything back up and turn the ignition on and have someone crank the engine while you touch the starting solenoid on the intake manifold with hot wire. If the car starts temporarily or acts like it is trying to start the problem is fuel starvation.
Good Luck, report back on the results.

Joe Alexander
Blacklick, Ohio

[Benz Dr.]

This is a fuel delivery problem. It's prpbably the return line running under the car or the one inside of the fuel tank.
Disconect the return line at the tank and clamp off the fuel hose first. Use a piece of regular fuel hose and slip the one end over the steel return line at the back where you removed the clamped off hose. Place the other end into a 4 liter container and turn the ignition switch on but don't start the car. As soon as the fuel starts to come out the hose time it for 15 seconds. You should get very close to one liter of fuel during this test. If you get less than 750ml you have a restriction. If the fuel just dribbels out or has little pressure coming out you could have a number of plugged filters or lines.
There's a filter in the engine bay which can be easily changed , one in the fuel tank which can be removed out the bottom after draining the tank and a very small insert where the main fuel hose enters the fuel pump.
A small test can be done while draining the tank by watching how much and how fast the fuel drains from the tank. If it comes out at a full head and remains steady the screen is not plugged. If it comes out slowly the screen could be plugged or the short internal line running from the screen to the tank outlet could be plugged.
 You should not have a lot of fuel in the tank ( as in full ) or you may get false readings doing this test for a tank that is 1/4 full or less. During low fuel levels the fuel tank inlet dampner ( I call it the flower pot) draws all or most of its' fuel through a small hole at the bottom side right infront of the return line. If this hole is plugged the car will have a tendancy to run out of fuel prematurely or while driving on straight level highways. What happens is that there's just not enough fuel sloshing around over the top of the dampner.
You can remove the sender and using a flashlight
 ( NEVER USE A TROUBLE LIGHT !!!) and a stiff piece of wire you can often open this plugged area. There's also a fairly high chance that the return line inside of the tank is plugged. You can test this by blowing a light shot of compressed air into the return line. Make sure the fuel cap is removed. This is probably best done at the engine bay where the return line starts by using a short piece of fuel line slipped over the metal line. Use a rag around the end in case it's plugged or the fuel could spray back into your face ( do that anywhere you do this sort of test)
I've been able to clean out the return line inside of the fuel tank using a bass guitar string and an electric drill ( battery operated only) You need something that will work it's way through the rust or clogged area but be flexable enough to go around the bends in the line.
 It would be VERY wise to remove the tank and have to boiled at a rad shop and let them handle the safety problems.
If you decide to do this yourself follow all the saftey you can and have gloves, face shield, long sleeved shirt and lots of fire fighting equipment on hand. If you don't have any fire fighting equipment GET SOME! I saved my own life and my shop last week by having everything I need close at hand when a car I was working on caught on fire. I was able to put it out but I needed the right stuff and had to act quickly.
Don't ever think it can't happen to you.

Always use jack stands EVERY TIME - even once can be the time it falls on you.
Use the right tools for the job you're doing.
Always work in a ventalated  area with the engine running.
Solvents , paint and fumes from glue can explode.
Have a pail of water handy or fire fighting equipment.
Have a first aid kit ready and well stocked.
Be really carefull when working around a running engine.
Always start a car in park or with your foot on the clutch - feet inside of the car.
After the car starts , blip the throttle a few times to be sure you're linkage isn't stuck.

There's plenty more but common sense usually will work out well. Of course , it you don't KNOW that there's a danger in what you're doing - you could have big trouble ahead.

regards to all,
Dan c
SL Barn



Daniel G Caron

[n/a]

Thankyou for replying.....the only thing that does not make since tome is why the car would run that good for the 10 miles or so. If the return line was clogged would'nt it show up right away?

quote:Originally posted by Benz Dr.

This is a fuel delivery problem. It's prpbably the return line running under the car or the one inside of the fuel tank.
Disconect the return line at the tank and clamp off the fuel hose first. Use a piece of regular fuel hose and slip the one end over the steel return line at the back where you removed the clamped off hose. Place the other end into a 4 liter container and turn the ignition switch on but don't start the car. As soon as the fuel starts to come out the hose time it for 15 seconds. You should get very close to one liter of fuel during this test. If you get less than 750ml you have a restriction. If the fuel just dribbels out or has little pressure coming out you could have a number of plugged filters or lines.
There's a filter in the engine bay which can be easily changed , one in the fuel tank which can be removed out the bottom after draining the tank and a very small insert where the main fuel hose enters the fuel pump.
A small test can be done while draining the tank by watching how much and how fast the fuel drains from the tank. If it comes out at a full head and remains steady the screen is not plugged. If it comes out slowly the screen could be plugged or the short internal line running from the screen to the tank outlet could be plugged.
 You should not have a lot of fuel in the tank ( as in full ) or you may get false readings doing this test for a tank that is 1/4 full or less. During low fuel levels the fuel tank inlet dampner ( I call it the flower pot) draws all or most of its' fuel through a small hole at the bottom side right infront of the return line. If this hole is plugged the car will have a tendancy to run out of fuel prematurely or while driving on straight level highways. What happens is that there's just not enough fuel sloshing around over the top of the dampner.
You can remove the sender and using a flashlight
 ( NEVER USE A TROUBLE LIGHT !!!) and a stiff piece of wire you can often open this plugged area. There's also a fairly high chance that the return line inside of the tank is plugged. You can test this by blowing a light shot of compressed air into the return line. Make sure the fuel cap is removed. This is probably best done at the engine bay where the return line starts by using a short piece of fuel line slipped over the metal line. Use a rag around the end in case it's plugged or the fuel could spray back into your face ( do that anywhere you do this sort of test)
I've been able to clean out the return line inside of the fuel tank using a bass guitar string and an electric drill ( battery operated only) You need something that will work it's way through the rust or clogged area but be flexable enough to go around the bends in the line.
 It would be VERY wise to remove the tank and have to boiled at a rad shop and let them handle the safety problems.
If you decide to do this yourself follow all the saftey you can and have gloves, face shield, long sleeved shirt and lots of fire fighting equipment on hand. If you don't have any fire fighting equipment GET SOME! I saved my own life and my shop last week by having everything I need close at hand when a car I was working on caught on fire. I was able to put it out but I needed the right stuff and had to act quickly.
Don't ever think it can't happen to you.

Always use jack stands EVERY TIME - even once can be the time it falls on you.
Use the right tools for the job you're doing.
Always work in a ventalated  area with the engine running.
Solvents , paint and fumes from glue can explode.
Have a pail of water handy or fire fighting equipment.
Have a first aid kit ready and well stocked.
Be really carefull when working around a running engine.
Always start a car in park or with your foot on the clutch - feet inside of the car.
After the car starts , blip the throttle a few times to be sure you're linkage isn't stuck.

There's plenty more but common sense usually will work out well. Of course , it you don't KNOW that there's a danger in what you're doing - you could have big trouble ahead.

regards to all,
Dan c
SL Barn



Daniel G Caron

[CarlG]

My car did exactly the same thing when I first got it.  After much searching we found 2 things.  First the fuel filter was so clogged that fuel would not get by after it heated up.  The second was more fun and strange.  The screw holding the wire for the fuel pump in the fuse box was slightly loose and would not get a good connection when it heated up.  Good luck.

1967 230sl (stick)

[Benz Dr.]

No.
The fuel needs to return back to the tank in order to prevent the formation of air bubbles. As the fuel in the lines and pump gets hot you will start to get vapour lock.
Even on a very warm day you can place your hand on the injection pump and it will feel cool to the touch. The fuel circulating through the pump also acts as a coolant and this is why you need to circulate about a gallon a minuet to keep it running properly.
Your system has little or no circulation and as the fuel heats up you loose power. When you stop the car dies and won't start until you let it cool down.
Common problem and not that hard to cure.

Dan c
SL Barn

Daniel G Caron

[Naj ✝︎]

mercury7,
If you want to verify that it is a clogged return line, when the engine stops, undo the air bleed screw on the main fuel filter head (in the engine bay) with the ignition on. This will allow the fuel to run thru and clear the vapour lock. You will find the fuel warm to the touch but will cool down as you let some run thru.When you get the cold fuel thru, lock the screw and the car will restart and run for a few more minutes.
Voila!!
naj

65 230SL
68 280SL

[n/a]

Thank you everyone for the valuable insight....I have not even changed my fuel filter yet....not sure even where it is haha but I will definitely do that now...I appreciate the few pictures here showing the layout of certain parts, I would really like to see more pictures with all the individulal stuff labeled....I have one of those repair books but they have such close up pictures that it is hard to match up what I am seeing. I know this sounds silly that I don't know all this stuff but this is the first car I ever owned that
makes me interested to learn...I truly love my car

[rwmastel]

Scott (Mercury7),

Regarding your fuel issue, make sure you:

• lift up the rubber trunk mat
• lift the white plastic fuel sender cover in the center of the trunk
• remove the fuel sender unit (controls your fuel guage)
• use a flashlight to look inside the fuel tank for rust
• during reassembly replace the cork gasket with a new one (see vendor list)

It is very common for these 35 - 40 year old cars to have rust in the fuel tank that gunks up everything.  If you have it, just search on the forum here using key words like "fuel tank rust".  You'll get lots of discussion threads to look at.

Regarding your interest in learning about and working on your Pagoda, I highly recommend the following manuals:

• MB Workshop manual (aka Big Blue Book, BBB).  This was published in a few versions, so ask the seller (eBay?) exactly what they are selling then ask here if it's correct for your car.
• MB Spare Parts List specific for your car.  Available through your dealership or eBay.
• MB Technical Data book.  Published several times, get the right one for your car.
• Haynes manual for 230/250/280 (sedans & SL).
• Get a data card for your car from the MB Classic Center (search forum for Dillenberger(?))

This will help you out greatly.  You will always know the right procedures, the right parts, etc.

Enjoy your car!

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420