Pagoda SL Group
W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: MikeSimon on August 01, 2018, 18:49:10
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New member here (see introduction) and don't know if this is the right place for this question. Need some help!
I have a driveability issue with my 1970(71) 280SL.
It will start when cold and run for a while until warmed up and then shut off. Will not restart until I wait for a while for it to cool down.
Then it will start and run for a while and shut off again.
The time the car runs is getting shorter and the time I have to wait is getting longer.
When this problem first occured, I asked a lot of "experts" and tried to do some research but could not get a definite answer for a solution to the problem.
A minor thing I did was change the capacitor on the distributor.
At one time, I heard that in cars that aren't driven on a regular basis, where rust and crud deposits on the bottom of the tank, these deposits will clog up the fuel return and the fuel pump will overheat and shut off.
After the car now sat for 20 years, I have finally decided to tackle the problem.
I plan to take the fuel tank out and clean/replace it. Also will replace the fuel pump.
Before I get there, I took the cylinder head off to see, if everything inside the cylinders is still O.K. It is! (lucky me)
next is cleaning everything up and putting the head back on before I address the tank.
Anybody any thoughts?
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Could you remove the head gasket so we can see the top of your block?
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Sure can. What would the top of the block show?
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Here you go..
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Clean of the top of any piston and write down the piston size. I think it may have been rebuilt once since it looks like it has low compression stepped pistons. Looks fairly normal but it's hard to tell by looking at a couple of pictures. For sure it's a late 280 engine.
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How does this relate to the running problem? The motor at one time threw a rod bearing, but the cylinders were not touched as far as I know.
The pistons are stepped.
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Dan,
Is that a factory crown design? I Have not seen that before but have seen it on some English pistons.
Mike,
I would strongly suggest replacing the valve guides while you have the head off. The original guides have a tendency to slip down in the head and begin travelling up and down with the guides which causes a big oil leak and smoke off idle. The updated guides have a step in them to keep them from slipping down.
Have you checked for spark when the car won't start? It sounds to me like it might be the screen in the tank or the screen on the fuel pump intake. Fuel pumps to the best of my knowledge don't shut down when they get hot but if a screen gets clogged it will clear marginally when the car shuts off. I would test everything before condemning the fuel pump. New pumps are expensive.
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Thanks for the advice. I will do all the usual jobs that should be done while everything is apart.
Reading through some of the threads here, potential problem areas causing hot engine shut off are fuel filter and the WRD on the FI pump.
Don't know whether the symptoms are exactly the same, though.
What puzzles me is that the engine shuts off and requires a cool-off period to restart.
I have a new fuel pump already. Also new fuel filters and injectors. Even have a used FI pump. I had 20 years to collect parts..not knowing what I would need. ;D ;D
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When it dies does it die gradu
ally or is it like shutting off a light switch?
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MIke, this cool-off time you say the engine needs to start again often is the time gasoline needs to soak through clogged filters and fill the last filter reservoir. I think these shut-offs may be symptoms of fuel starvation.
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It dies like I flipped an a off-switch. I agree, I think it is a fuel issue. That's why I believed the theory of the fuel pump overheating and shutting off.
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As the engine dies suddenly rather than slowly, I would check the spark as I suspect an electrical/ignition culprit, more particularly the coil. If you have a spare coil I would try that. Or perhaps you have the original electronic ignition from 1970/71 that's malfunctioning.
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. Or perhaps you have the original electronic ignition from 1970/71 that's malfunctioning.
What is the "original electronic ignition"? The car has points and a distributor.
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Mike,
The search tool is your friend.
Many, if not most, issues have been written about.
1. If you car has not been modified it has a distrubutor, points, and an electronic box under the battery which basically reduced the current going through your points which increased their life.
2. Your shut down failure is described exactly as a lack of fuel flow issue. Go ahead and simply check to make sure you have spark, then you can forget about the ignition. Measure the fuel flow at various parts of the system. When I did this I found a clogged fuel return pipe going back to the fuel tank. I drove the car for years (~8) after clearing out that clog (then sold it). I know it "feels" like an electrical issue the way it shuts off, but it was a fuel issue for me.
I went through eactly what you are going through in 2009 (except I didn't take the head off ;D ).
Good Luck !!
Mark
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Dan,
Is that a factory crown design? I Have not seen that before but have seen it on some English pistons.
Mike,
I would strongly suggest replacing the valve guides while you have the head off. The original guides have a tendency to slip down in the head and begin travelling up and down with the guides which causes a big oil leak and smoke off idle. The updated guides have a step in them to keep them from slipping down.
Have you checked for spark when the car won't start? It sounds to me like it might be the screen in the tank or the screen on the fuel pump intake. Fuel pumps to the best of my knowledge don't shut down when they get hot but if a screen gets clogged it will clear marginally when the car shuts off. I would test everything before condemning the fuel pump. New pumps are expensive.
Late 230SL and some 280SL pistons only come in the stepped version. With the late 230SL you can change the connecting rods then go with the earlier version pistons which I would highly advise as the late stepped pistons will only produce about 150 PSI compression and and a 230SL needs every bit it can get. 280 stepped pistons also lower compression.
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How does this relate to the running problem? The motor at one time threw a rod bearing, but the cylinders were not touched as far as I know.
The pistons are stepped.
You removed the head so I'm commenting on that. Knowing the size of the pistons will tell you if the block has been bored.
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Mike,
The search tool is your friend.
Many, if not most, issues have been written about.
2. Your shut down failure is described exactly as a lack of fuel flow issue. When I did this I found a clogged fuel return pipe going back to the fuel tank. Mark
Thanks, Mark! That's exactly what I had heard a while ago, and it referred to a blocked return in the tank due to debris.
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You removed the head so I'm commenting on that. Knowing the size of the pistons will tell you if the block has been bored.
I removed the head to make sure the inside of the motor was OK and not rusted from sitting for 20 years.
When a motor is bored, the compression increases. You are pushing a larger swept volume into the same size compression chamber. In order to retain the same compression (ratio), it makes sense to use a piston with a lower compression crown.
I tried to measure the bore and it is difficult to do the way the motor sits installed, but it is definitely larger than stock. It looks like it is 1mm over.
Again, nothing really of consequence as far as my running issue is concerned.
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Mike,
I am not experienced like many on this site. So take this for it might or might not be worth.
not commenting on head removal.
Assuming the car starts fine when COLD and runs fine for few minutes until warm and then shuts off.
Check Cold Start Valve (CSV). If it starts cold nicely, your CSV is probably dumping fuel as it should when cold.
However, might not be shutting off so it could be flooding the engine when warm. You can test by physically blocking the fuel line at CSV. Disconnecting Elec at CSV may not stop a faulty valve so you must disconnect and plug the line to confirm you are not providing fuel. It may be harder to start cold with the line blocked but should start after longer cranking and see if it continues to run.
WRD - this is also a common culprit. You will read a lot about it, but need to make sure it shuts off when car warms.
Good luck.
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You removed the head so I'm commenting on that. Knowing the size of the pistons will tell you if the block has been bored.
Good eye, Dr Benz!
After cleaning a piston, the stamping relieved a "86.97", which should make this a 0.5 over???
What are the other marks? especially the 50 M/M ?
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Mike, the WRD is probably the easiest and quickest to check. Once you have confirmed the CSV and WRD are functioning properly you can start looking for fuel blockage. There are 3 filters to check, one in the tank, one in the fuel pump and one in the engine bay. And check the flow rate on the return to the tank with the pump running and engine off. There is lots written up about this.
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I cannot find any reference to the CSV in my manual. Where is it? What does it look like?
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Good eye, Dr Benz!
After cleaning a piston, the stamping relieved a "86.97", which should make this a 0.5 over???
What are the other marks? especially the 50 M/M ?
I'm not sure about the 50 m/m but Sp is the running clearance which looks like .03 mm. Piston sizes are .5 mm in size increases and I think standard is 86.50 mm so maybe it's indicating .50 mm over size from standard.
.50 mm oversize isn't enough to increase compression ratio on any of these engines. If anything, they never seem to have enough compression after a rebuild because replacement pistons are slightly shorter from the pin to the crown. This is so that you can mill the top of your block to clean it up. You want your new pistons to actually stick out slightly from the parting surface so trust me, you don't need to decompress the piston crown. :)
I milled about .040'' off the top of my block which gave me around 180 PSI compression. It's why we call it the Red Rocket. ;D
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CSV
https://www.sl113.org/wiki/Engine/ColdStartValve
Right side of engine bay at intake manifold.
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Cold start valve only comes into play at startup. Not the culprit.
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Cold start valve only comes into play at startup. Not the culprit.
I agree, or at least doubt that it's at fault in this case. More likely to be the fuel tank or lines going from or back through the tank.
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The easiest thing is to check for spark and rule out the ignition system entirely. My general rule of thumb is if it seems like you turned the key off it is ignition related and if it feels like you ran out of gas it is fuel related. You could very well be dealing with a cracked solder joint in the transistor module that opens up when it gets warm and closes when it cools down. I see this all the time in my work life on boats. I just fixed a module last month that caused the entire electrical grid to drop underway(no steering). I have not opened one up but I am certain there is a big transistor in there that has grown and shrunk a whole bunch of times stressing the solder joints.
In short check for spark first. If you have spark then put a fuel pressure gauge on it and drive it till it drops and see if you have fuel pressure with the key on. No? see if you can hear the wildly expensive electric pump? If yes, something is blocked. if not, you have an electrical issue that is hopefully not related to the $1700 electric fuel pump.
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Hi , I do believe it is a blocked line. I know it is a hassle but you could test by filling gas tank all the way up so gas comes over the top of the flowerpot and see if it stops, if it does not then you know that your flower pot is not getting return gas to fill it up from the engine. I am definitely NOT an expert in the fuel system, but I think I know a lot about the pumps and the pump will only overheat if it is not getting fresh gasoline to cool it. The only way the pump would suddenly stop when it is already running is if it becomes grounded, I find this to be very rare. Earthing (grounding) is a common fault which occurs when part of the winding becomes connected to the metal core of the armature. More important and likely once the armature is overheated this can cause the solder connecting the armature coils to the commutator to melt. As the armature is spinning the solder is thrown from the armature, causing the connections between the armature coils and the commutator to be broken so then even if you fix the fuel flow issue , now the pump may not turn fast enough do to the bad armature to give you the proper flow.
Bob
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It is a little difficult to diagnose how the engine shuts off when you are driving. The car is rolling and the engine stops and you don't really know if it shuts off from lack of spark or lack of fuel. The car does not accept throttle or stalls and you put it in neutral and by that time the engine has stopped.
I am not that much of an expert with the W113 -actually none at all - but I have worked on cars and engines most of my adult life and the last 20 years extensively on motorcycles. What puzzles me, is, that the car starts back up after a waiting period. So the problem is most likely temperature related.
What electrical problem, other than the coil (already replaced) and the capacitor on the distributor (already replaced) would cause "no spark".
I don't remember anymore who told me some time ago, that the fuel pump under the tank would/could shut off when overheating. If it does not, I am not sure what would cause a fuel supply problem.
What other part/component of the engine operating/control system is temperature sensitive?
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I don't remember anymore who told me some time ago, that the fuel pump under the tank would/could shut off when overheating.
Mike,
It is not the electric fuel pump near the tank that overheats. It is the FIP, mechanical Fuel Injection Pump.
It "vapor locks" when the fuel gets hot. The flow of the electric pump should be 1 liter per 15 seconds. The car only "burns" a small fraction of that. The rest of the fuel is being pumped in a big circle cooling the FIP and running back to the tank.
1. Drive car till stalls, or even better, let it idle until stalls. It was about 10 minutes for me.
2. Pop open the hood/bonnet.
3. Slap on an inductive timing light to any spark plug wire.
4. Crank engine.
5. Look for flashing light on timing light. If not light, no spark. If light, then you have spark.
Now, disconnect return fuel line to tank at the fuel tank. Turn on electric fuel pump with car NOT running. Measure how much gas flows in 15 seconds. Check against spec (1 liter per 15 seconds).
If low, you found it and send me $200 ::). I don't know why I said that, I usually don’t kid around.
If not, more diagnosis is needed.
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Thank you Mark, I should have specified, I am only talking about the fuel pump in the rear by the gas tank, I am first to say I KNOW NOTHING about the mechanical injection pump attached to the engine. Just trying to answer the questions I can. Bob
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Mike- It could be any of a number of issues, based on the input you've received from the Group so far.
I think it makes sense to start with the easy/obvious stuff first and follow a process of elimination, otherwise you're all over the place.
I had similar issues with my 280SL the day after I purchased it.
Based on advice received here I started off with the fuel tank. I'm not sure if you've done this already?
Unscrew the filter port on the underside of the fuel tank and drain the fuel into a large container and see what comes out.
If there's a whole lot of debris and rust, then you know which route to follow.....
The waiting time between restarting may have nothing to do with temperature, and possibly something to do with debris taking time to settle in the fuel tank. That's what I had. This led me onto fitting a new tank, new fuel pump, blowing compressed air through the fuel lines, and new engine fuel filter = problem solved.
Failing that, if you haven't done so already, check ignition wires from the spark plugs to the distributor, you could have faulty cables, this has also happened to me and the problem got worse as the engine heated up.
If this is all OK then move onto the more complicated stuff....
Good luck and let us know how you get on.
Best,
Mike
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I second what Mike is saying.
But I think the simplest possible test of fuel supply is: detach the return line from tank, put in into some pot, switch on the fuel pump and see how much fuel you get. You should get close o 1 liter per 15 seconds. If you do not - this is your issue. Then you check the components of the fuel system, starting from the other end - undo the hose from fuel tank to fuel pump - if you see fuel dripping rather than pouring out with a solid stream - you start from the tank, which is clogged.
The first test takes about half an hour, including lifting the car.
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I think this will be my course of action - checking fuel flow and supply from and back to the tank. I am planning to take the tank out anyway and have it redone as the car sat for 20 years and the tank is probably rusted pretty bad inside.
I will keep you all posted on what the outcome is, however, it will take a while until I get there as I do not have the time to work on the car every day.
Now I have to address the open motor first. Cleaning everything up, vapor blasting the intake manifold and valve cover, painting the exhaust manifolds, doing some jobs on the head and then putting this all together again. :o
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Hello, I have been living with this problem for 3 years. I followed the advice on this forum to find the cause. I would like to add from my experience:
- if by now the car is stalling consistently after 5-20 minutes of driving the fuel pump is full of rust particles clogging the intake screen. If you take the pump inlet connector out and if the screen has rust in it similar to the attached picture then you have your answer. Between the tank filter, the fuel pump screen and the engine bay fuel filter, the pump screen is the weakest link that gets clogged first causing stalling. Picture shows rust accumulated over 3 months.
- because I do not want to shell $800+ for a new tank I plumbed a fuel pressure gauge inside. When the pressure falls below 8 PSI it is time to change the screen.
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OK, so what "pump" are we talking about? The pump at the tank or the fuel injection pump? Where is that intake screen and how do you access it?
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.../...painting the exhaust manifolds.../...
Yes - an opportunity to paint them in the original off white finish :)
See these postings:
https://www.sl113.org/forums/index.php?topic=16880.msg116511#msg116511 (https://www.sl113.org/forums/index.php?topic=16880.msg116511#msg116511)
https://www.sl113.org/forums/index.php?topic=6139.msg38059#msg38059 (https://www.sl113.org/forums/index.php?topic=6139.msg38059#msg38059)
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OK, so what "pump" are we talking about? The pump at the tank or the fuel injection pump? Where is that intake screen and how do you access it?
We are talking fuel pump next to the fuel tank. Squeeze the fuel hose from tank to pump close to pump, so that fuel is not flowing when you disconnect it. Remove the clamp on fuel hose from tank to pump on the pump side. Get a relatively deep 27mm socket and undo the inlet fitting of the pump. You will remove the fitting with screen as you see on the picture two posts ago. If you do not have this screen in the fitting - place intermediate filter on the hose and look for a fitting with screen. It would be good if this intermittent filter has 10mm fittings as this is the inner diameter of the fuel hose. Most of the filters are 8mm, which is not enough, you'd have to add some hose pieces to make them fit.
Undoing this fitting with 27mm socket may be tough. I used an air impact gun.
You will need a 27mm aluminum sealing ring, do not use again the one that was there.
But do the flow tests first before you undo anything.
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When you do the flow test on the fuel pump (the one by the tank), you have to let it run for a few minutes, the pump initially will spin very fast but after it warms to its operating temperature (usually about 5 to 10 minutes) and the counter magnetism acts on it it will fall to its steady state that is where you measure the flow which should be 1 liter every 15 seconds.
Bob
I usually test pumps for 6 cycles of 10 minutes, 20 minutes, 1 hour, and repeat.
I have seen ones that turn way over the specification for about 2 minutes then drop due to bad armatures or worn brushes
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When you do the flow test on the fuel pump (the one by the tank), you have to let it run for a few minutes, the pump initially will spin very fast.../...
Just a reminder; do not run (spin) these pumps dry... i.e. always run them attached to hoses/pipes and with fluid flowing through
And for sure Bob; I'm not reminding you ;) I know you know
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Mike if it helps, you can send your pump to me and I can hook it up to my test bench, Gratis. Just please God drain the gas out of it and cap both ends for there are so many crevices the gas can hide and I do not want to meet another postal inspector.
Bob
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Thanks, Bob. I will come back to your offer once I get there and need it. I have accumulated quite a few parts, among them 3 fuel pumps. One, I think is almost new.
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Mike,
More than happy to lend a hand if you need it. Have presure gauges etc.