Pagoda SL Group
W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: sardalani on April 07, 2024, 15:01:56
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Hello, everyone. I’m posting this on behalf of my father, as he has a 1968 280SL. Recently we tried turning it on and the car turns over but will only stay on if your foot is on the gas pedal, revving the engine. If you take your foot off the gas pedal, it hesitates to stay on and then quickly shuts off. This is all happening in park, of course. Has anyone had a similar issue? Or possibly know the cause? Thank you in advance.
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first advice is to go through the linkage tour and double check everything is setup right. It's a very simple but well thought out process for checking all the proper adjustments. you will easily find it in the tech manual section or search tool.
a simple thing to try first :
Find out if it can idle better after it warms up so if you can keep it running long enough to get hot and it improves its idle, then that points you to the cold starting systems which the linkage tour will help you adjust.
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I was thinking it was fuel related (fuel pump) or perhaps a tuneup (plugs, cap, rotor, wires etc). The car does spend most of its time sitting in the garage. But I will definitely look into that, at least now I have a place to begin looking. Thank you!
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Sardalani,
Welcome to our Group. We've been online 20 years, so this forum is full of answers to problems. Learning to use the search feature will provide you lots of information.
The linkage tour is a great place to start to ensure the linkage is setup correctly. But, not knowing what has changed recently, I would start with fuel delivery.
It's a fully circular system with excess fuel returning from the mechanical fuel injection pump to the fuel tank. The fuel flow rate should be measured at the fuel tank return rubber line. Search for the liters per second flow requirement. Regarding pressure, I believe people generally connect a gage by removing an access bolt on top of the main fuel filter housing. Search for the correct minimum pressure.
If these tests don't meet minimums, clean the screen in the bottom of the tank, inspect the fuel tank for rust through this hole and the fuel gage sending unit hole, clean the screen at the electrical fuel pump inlet, and replace the main fuel filter.
As you get test results and info, post here for further help.
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Please note that the 'linkage tour' is only accessible to paying (= 'Full') members.
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There's a Linkage Tour thread pinned to the top of this sub-forum. Is that only visible to us Full Members?
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Hi Sardalani, Welcome to the the group,
It sounds to me like you father's car sits a lot. The first questions that comes to my mind are, how old is the fuel and did it have ethanol in it?
Both can cause some real problems. For starters, I'd sure want to know it has relatively fresh fuel in the tank.
Ed Riefstahl
1966 230SL (Ms Magoo)
1970 280S (Miss Daisy)
1999 BMW Z3 5 speed
1991 BMW 318I 5 Speed
1997 Toyota Paseo Convertible - One of 1000, (have you ever seen one?)
1997 Ford Ranger step side (Mater)
2023 Mazda CX 5
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I will look into the linkage tour! I just saw that it is pinned on top. Thank you
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Hi Sardalani, Welcome to the the group,
It sounds to me like you father's car sits a lot. The first questions that comes to my mind are, how old is the fuel and did it have ethanol in it?
Both can cause some real problems. For starters, I'd sure want to know it has relatively fresh fuel in the tank.
Ed Riefstahl
1966 230SL (Ms Magoo)
1970 280S (Miss Daisy)
1999 BMW Z3 5 speed
1991 BMW 318I 5 Speed
1997 Toyota Paseo Convertible - One of 1000, (have you ever seen one?)
1997 Ford Ranger step side (Mater)
2023 Mazda CX 5
It did sit for quite some time (a little over a year) as he was recovering from hip surgery. We put fresh 93 fuel in it yesterday and it took a couple of cranks but she fired up but would only stay on if you are revving it. Shuts off when you let go of the gas. I thought maybe it was a fuel pump issue
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There's a Linkage Tour thread pinned to the top of this sub-forum. Is that only visible to us Full Members?
I had underdtood access was limited; if not, my mistake and so much the better.
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We have a Wikipedia style technical manual here that is for Full Members (paying members) only, and it has a linkage tour and much, much more.
https://www.sl113.org/wiki/
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If you have two solenoids on the back of your fuel injection pump, the lower one is a "fuel shut-off". This is part of early emission system to reduce rich fuel conditions during de-celeration. If there is a malfunction, your IP can be stuck in the "shut Off" condition allowing no fuel to the enjectors. Try disconnecting the wire to the lower solenoid. Other possibilities are the IP rack could be stuck or the WRD on the injection pump can be stuck.
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Hello again, Sardalani,
I'm still wondering how much old fuel was in the tank before you topped it off, and how old the fuel was before the car was parked?
Did you actually run the car long enough to get the old fuel out of the system?
While you were trying to keep it running, did it seem to be firing on all 6 cylinders?
I'll share my experience from a few years ago with my 1970 280S. Granted, it has carbs. With some health issues, the car sat for a while, but not for years. In the spring I decided to take the car out for a drive. It started up, but it ran so poorly I could hardly keep it running. So, i didn't even get to drive it.
To make a long story short, I was talking with a friend the next day who happened to recently have the same problem with a vintage BMW motorcycle. He said his problem turned out to be from the ethanol in the fuel. He told me to go purchase some Star Tron Enzyme Fuel treatment from NAPA. I thought, yeah sure, but stopped at NAPA and bought some.
I added the initial recommended 1 oz / gal. and started the car and managed to keep it running until it reached the carbs. Within a very short time the car began to run better and better and better until it sat there and idled. I was then able to take it out on road. I've never done a single thing to the car since, other than I always try to run non-ethanol fuel in the car. I absolutely never park any of my 5 collector cars for the winter (6 months in northern PA) without filling the tanks with ethanol-free fuel first. I also keep a bottle of Star Tron in the trunk.
In my experience, mechanical adjustments don't typically change over night or just from sitting. However I've have had several strange things happen over the years, like the above, or like a mouse making a nest inside the air cleaner of my wife's Paseo. Also, rodents also love to chew things. Mice will usually leave some tell tale droppings under the hood, if you have a critter problem.
Just my 2 cents.
Keep us posted.
Ed Riefstahl
1966 230SL (Ms Magoo)
1970 280S (Miss Daisy)
1999 BMW Z3 5 speed
1991 BMW 318I 5 Speed
1997 Toyota Paseo Convertible - One of 1000, (have you ever seen one?)
1997 Ford Ranger step side (Mater)
2023 Mazda CX 5
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It did sit for quite some time (a little over a year) as he was recovering from hip surgery.
I'm still wondering how much old fuel was in the tank before you topped it off, and how old the fuel was before the car was parked?
Ed,
Hope this helps.
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If you have two solenoids on the back of your fuel injection pump, the lower one is a "fuel shut-off". This is part of early emission system to reduce rich fuel conditions during de-celeration. If there is a malfunction, your IP can be stuck in the "shut Off" condition allowing no fuel to the enjectors. Try disconnecting the wire to the lower solenoid. Other possibilities are the IP rack could be stuck or the WRD on the injection pump can be stuck.
Good starting point, I will look into that. Thank you!
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Hello again, Sardalani,
I'm still wondering how much old fuel was in the tank before you topped it off, and how old the fuel was before the car was parked?
Did you actually run the car long enough to get the old fuel out of the system?
While you were trying to keep it running, did it seem to be firing on all 6 cylinders?
I'll share my experience from a few years ago with my 1970 280S. Granted, it has carbs. With some health issues, the car sat for a while, but not for years. In the spring I decided to take the car out for a drive. It started up, but it ran so poorly I could hardly keep it running. So, i didn't even get to drive it.
To make a long story short, I was talking with a friend the next day who happened to recently have the same problem with a vintage BMW motorcycle. He said his problem turned out to be from the ethanol in the fuel. He told me to go purchase some Star Tron Enzyme Fuel treatment from NAPA. I thought, yeah sure, but stopped at NAPA and bought some.
I added the initial recommended 1 oz / gal. and started the car and managed to keep it running until it reached the carbs. Within a very short time the car began to run better and better and better until it sat there and idled. I was then able to take it out on road. I've never done a single thing to the car since, other than I always try to run non-ethanol fuel in the car. I absolutely never park any of my 5 collector cars for the winter (6 months in northern PA) without filling the tanks with ethanol-free fuel first. I also keep a bottle of Star Tron in the trunk.
In my experience, mechanical adjustments don't typically change over night or just from sitting. However I've have had several strange things happen over the years, like the above, or like a mouse making a nest inside the air cleaner of my wife's Paseo. Also, rodents also love to chew things. Mice will usually leave some tell tale droppings under the hood, if you have a critter problem.
Just my 2 cents.
Keep us posted.
Ed Riefstahl
1966 230SL (Ms Magoo)
1970 280S (Miss Daisy)
1999 BMW Z3 5 speed
1991 BMW 318I 5 Speed
1997 Toyota Paseo Convertible - One of 1000, (have you ever seen one?)
1997 Ford Ranger step side (Mater)
2023 Mazda CX 5
Very informative, Ed! The car sat for about a year and a half. The tank had less than 1/4 in it. We use 93 octane gas in the 280SL and I believe 93 octane contains 10% ethanol in it, if I am not mistaken. When the engine fires up, it sounds healthy and strong (granted I am revving it because that is the only way it stays on at the moment). It is the first time I hear of star tron, based on the reviews it sounds like a good product. I bought a bottle of Chevront Techron high mileage fuel system cleaner, and I am going to pour the bottle inside to see if it helps any. I am hoping that may solve the issue, but I really have not had much luck with any of these injector cleaners like others have had.
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Hey Sardalan,
Make sure you get the right stuff. The product you want is Star Tron Enzyme Fuel Treatment. It will treat the ethanol in the tank.
The Pennsylvania Training Center has a recent interesting article on ethanol. autotraining.edu. Here is a quote.
"IS ETHANOL AFFECTING MY CAR?"
"Do you let your car sit without driving it for long periods of time? If so, the answer is more likely to be yes, especially if you drive an older vehicle. Ethanol gasoline is made as a through product, ideally to be used within 30 days inside your gas tank.?
Incidentally, my brother In-law owns the NAPA store. He told me at the time I was having my problems that he could hardly keep the stuff on the shelf. I hate ethanol in the gas. I've had to rebuild the carb on my 1952 Farmall 3 times, before a local station started selling ethanol-free fuel. It's about a buck a gallon more to leave the ethanol out, but I no longer let my vehicles sit for the winter with eth-gas in the tank.
Good luck and keep us posted.
Ed Riefstahl
1966 230SL (Ms Magoo)
1970 280S (Miss Daisy)
1999 BMW Z3 5 speed
1991 BMW 318I 5 Speed
1997 Toyota Paseo Convertible - One of 1000, (have you ever seen one?)
1997 Ford Ranger step side (Mater)
2023 Mazda CX 5
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I had underdtood access was limited; if not, my mistake and so much the better.
Access to the forums (including the Linkage Tour) is not restricted. Only the Full Member forum is restricted to full members. However the linkage tour in the Technical Manual is better structured, and easier to follow. It does not have posts asking questions, or "noise", which the reader has to filter out. So it is still worthwhile to become a Full Member.
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What are thoughts about higher octane (93) with ethanol vs. lower octane (88) without ethanol?
I drive my 280 most weekends and refill the tank about once a month or so, so the fuel isn't sitting for long periods.
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It sounds to me like the Warm Running Device (WRD) is stuck in the "warm" position. So when you crank the starter, the engine gets a squirt from the Cold Start Valve which will allow it to start. But the stuck WRD is not allowing enough fuel and air to keep it running at idle so you need to give it throttle to keep it running.
One thing to try is to keep the engine running long enough to get it fully warmed-up. Then give the WRD thermostat housing a few sharp raps with a hammer to try to free up the slide. If that doesn't work, the WRD should be removed, cleaned, and lubricated. Lots of posts on how to do this.
The WRD is also known as the Won't Run Device for good reason.
Cheers,
CT
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It could also have a stuck rack in the IP from the ethanol fuel. This is an easy item to check off your list of possibilities. Start with the easy and inexpensive items first!
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Good advice Joe, and pretty easy to check. I wonder how sardalani is making out?
Ethanol is said to be hygroscopic. Wikipedia says "hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature."
In our area ethanol is still at 10% However, we are 5 miles from the NY state line and while traveling have seen pumps that say may contain up to 15%.
At any rate, it's certainly not a bad idea for folks who own vintage vehicles to be aware of what problems ethanol in the fuel can cause if it sits in the tank for a while.
Ed Riefstahl
1966 230SL (Ms Magoo)
1970 280S (Miss Daisy)
1999 BMW Z3 5 speed
1991 BMW 318I 5 Speed
1997 Toyota Paseo Convertible - One of 1000, (have you ever seen one?)
1997 Ford Ranger step side (Mater)
2023 Mazda CX 5
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My SL sits for years, starts no problem with 87 regular. It is a gas quantity issue on warm up. My 1st guess would be in the injection pump cold idle controls. This is not going to be easy for a newby because the throttle linkage and injection pump warmup process are subtle and don't look at all familiar or similar to any other motor. You can easily determine if it is too little or too much gas by disconnecting the pump link and giving it more or less gas.
Its good that is starts and runs with your foot on the gas. That tells me several things are good: spark, compression, Gas on start, fuel pump, and the initial start function on the injection pump. I suspect the fuel is not rich enough once the cold start solenoid turns off, and the cold start solenoid is working to start the motor. It stays on for a few seconds. Its on the far side on the intake manifold with a wire and a metal tube going to it.
So, the next step is why does it start but then need more gas? There is heated coolant piped to the warmup valve on top of the IP (injection pump) It is the metal cylinder with two hose connections and two pipes going in parallel to it. My guess is the thermo expansion bulb inside that cylinder is stuck in the hot motor position: extended. As it heats up, a copper ampule pushes a metal pin out of a rubber chamber, which pushes a lever in the ip that reduces the extra gas needed for the cold motor. When cold that ampule retracts the pin to enrich the fuel mixture. You may be familiar with a carburetor choke enriching the fuel mixture by reducing the air. Fuel injection enriches the mixture by increasing the gas. On cold start the manifold gets a spray of gas from the electric start valve and the thermo valve should be retracted causing the ip to give extra gas while the motor warms up. As the motor warms the ampule pushes the pin out, gradually decreasing the extra gas needed by the cold motor. Pretty slick?
It doesn't take too long for the motor to warm up to where it doesn't need the extra gas. Just a few minutes and the coolant starts warming up. First thing I would try is keeping it running until the motor temp is up. You can do that on the motor with the linkage and feel the heat warming that cylinder on the ip with your hand. It warms up pretty fast. It warms up to due to the coolant flowing through the two connections on it. One supplies coolant, the other feeds the coolant back to the motor.
If after warmed up the motor is ball park idling, you found the problem. You need to carefully remove the two flat head screws connecting the cylinder to the ip. Don't let it get too hot, the coolant will get pressurized and you'll have to wait for the cool down. Some warm coolant will be lost, not much. The copper ampule is inside the cylinder and available on line or the dealer. When replacing it make sure the cylinder is aligned up and down with equal tightening of the two screws. And get a good seal. the seal requires the screws to be pretty snug and they probabably have been xposed to the eliments for a long time. I think I had to use vice grips on a big screw driver to get mine out at about 100K miles on mine. It doesn't take that much tightening to to reseal.
There is much help in the W113 forums on calibrating, correctly adjusting, the throttle linkage. Hopefully it is just the ampule, they don't last for ever and they usually fail in the extended position (not retracted to give extra fuel).
Good luck,
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Well, minor update. We went ahead and started with the very basics and that was to drain the old fuel completely and pour fresh 93 octane gas with a bottle of techron in it, and it seemed to help just a little bit. By that I mean, it does not die as fast when you let your foot off the gas, it hesitates for some seconds and sounds like it wants to stay on but ultimately still shuts off.
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Please troubleshoot this by testing things. Test solenoids, fuel pump pressure and flow rates, cold start valve function, and the like. Put the WRD in water and boil it to see if it moves and how far. Many people give advice based on their experiences, but that may not be relevant to your situation. Test. Get facts. Eliminate possible causes. And yes, as JA17 recommends, start with the simplest, cheapest tests first.
And, join as a full member. Read the linkage adjustment tour. The section on starting aids (systems) would be important right now. Best $30 you'll spend, if you like to read, research, and learn new stuff.
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What are signs of a faulty WRD?
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One test is to listen whether the air suction stops when the engine warms up from cold. Place a piece of hose next to the small air filter that sits on the side of the injection pump and hold the other end to your ear; as the engine reaches operating temperature, the air suction noise should slowly stop. That is your confirmation that the little thermostat inside the WRD has extended and shut off the airflow, and reduced also (if I am not mistaken) the fuel flow to the engine.