380SL Fuel Accumulator

[R107-1981]

Hi--

I have a warm/hot start problem with my 380 SL if it has been sitting for about an hour. Cold starts and 5-10 minute sitting hot starts are no problem.

This sounds like a fuel accumulator problem, but they are about $110 each.

I understand that Mercedes has devised a check valve that is placed in the line to solve the leaking fuel accumulator problem without having to change the accumulator. The check valve is reportedly about $15.

Does anyone know about this, and what it's called and/or part number?

Thanks in advance for your help.

Joe

[meltedpanda]

i would make sure your injectors and CSV are not leaking before I would go to the fuel delivery side. Do you have a gas smell? What is the plug tip color? make sure all the vacuum lines are in tact, no leaks. make sure your timing is correct

[dingobait]

It's most likely your "fuel accumulator". I have the exact same problem. It's easy to check. Just remove the clamp securing the fuel accumulator "drain line" to the fuel damper, but first make sure you've got something to press against the opening to keep the fuel from the tank from shooting out of the damper. I used a piece of hard rubber and just pressed it against the damper. With that line disconnected, start the car. If fuel comes out of that drain line, the accumulator is bad. The Mercedes manual calls it the "fuel reservoir". It's a simple mechanism comprised of a diaphragm and a spring. It's hooked up to the pressure side of the pump. The fuel pressure pushes on the diaphragm and compresses the spring. When you turn the car off, the spring gradually releases the fuel pressure "to prevent vapor lock and to help in hot-starting the car". What happens is that the diaphragm starts to leak. The drain line is there just for that purpose. It routes the fuel back to the fuel line so that it doesn't leak out onto the ground. Believe me, I had the "exact" same problem you've described. The thing is that when the diaphragm starts to leak more, the car will die on you while you're driving it, since the leaking diaphragm is lowering the overall fuel system pressure. The accumulator is located above the fuel pump and the fuel filter at the rear of the car. There's a hard fitting on one end, and a standard rubber fuel hose at the other end. That rubber hose is the drain line, and the bottom end of that line is connected to the fuel damper with a small clamp you can remove with a screwdriver.

[abiby]

Originally Posted by R107-1981

Hi--

I have a warm/hot start problem with my 380 SL if it has been sitting for about an hour. Cold starts and 5-10 minute sitting hot starts are no problem.

This sounds like a fuel accumulator problem, but they are about $110 each.

I understand that Mercedes has devised a check valve that is placed in the line to solve the leaking fuel accumulator problem without having to change the accumulator. The check valve is reportedly about $15.

Does anyone know about this, and what it's called and/or part number?

Thanks in advance for your help.

Joe

If you used the check valve to negate the issues from a leaky accumulator, I believe you would allow pressure to equalize on each side of the diaphragm, keeping the accumulator from serving its purpose.

IMO, if you are sure it is a bad accumulator, and I'm not, you might as well bite the bullet and replace it.

Alan

[Strife]

I'd check for leaky injectors and put a gauge on the fuel distributor first. Shotgunning problems on these cars with new parts is getting expensive.

[dingobait]

Just follow my post from earlier today and you'll know 100% whether your accumulator is bad. All you have to do is loosen one screw on a clamp that is easily accessible, pull the rubber hose off, block the hole so that the fuel from the tank doesn't gravity force itself out, then start the car and see if fuel comes out of the drain line. If it does, then you are 100% sure the accumulator is bad. If you use a check-valve in its place, you'll negate the reason the accumulator is there, which is to prevent vapor lock and to enable hot-starting, by lowering the fuel pressure "gradually" when the engine is turned off.

$110.00 is a good price. The dealer sells the part for $394.00. You can find even better prices on the internet. Just google "fuel accumulator for whatever year and model yours is.

If you're having the hot-start problem, this is a very simple way to figure out if it's your accumulator, and there is no substitute for replacing it. The system was designed with the accumulator, not a check valve. A check valve likely won't solve the problem since it won't hold pressure on the system at all, and the vapor lock issue is caused by the fuel pressure decreasing rapidly when the engine is turned off.

Also search Craig's list for your area...

Good luck. Don't make it hard.

[dingobait]

I just looked in the Mercedes repair manual. The "check valve" is a fix for when the fuel pump is leaking internally and letting the pressure bleed off that way. Check the accumulator as I described. If that's not it, it's possible that your pump is leaking internally. I bet you find that the accumulator has failed.

Best of luck to you.

Mark

[dingobait]

If the accumulator is bad, the check valve won't fix it. The check valve gets installed on the pressure side fitting of the fuel pump. If the accumulator is the bad part, the check valve will have zero effect.

[R107-1981]

Hi--

I replaced the accumulator today, and all is well again.

Thanks to all for your help!


Joe