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Difficult start?

The check engine light is on. Yesterday twice I had the situation where when I turned the key to start. The starter motor was crankin and it was not firing. I pumped the throttle a few times to let air/gas into engine. I also opened the gasoline tank cover (where you insert the nozzle to pump gas) for a few mins and then shut it and started the car. It started. After running for 20 mins it happened again. The starter motor has to crank for some 10 seconds before it fires. Then no issues. What do you think it is??? Battery is fine, starter motor is fine since its cranking away. I am suspecting fuel pump ? Any takers, ideas, comments.

You have to get the codes read to determine what is causing the no fire. There are many many possibilities. Impossible to diagnose over the net.

The next time you know this is going to happen, instead trying to start the engine right away, turn the ignition switch to on so the dash lights come on for two seconds, and then turn the ignition switch off.

Repeat this a half dozen times and then try starting the engine.

If the engine starts right up, it confirms there’s a problem with the fuel pump.


REason to build enough fuel pressure in the valve??? Does the mean the fuel pump is weak or valve is weak??

The fuel pump has an anti drain-back valve.

Does this hard starting only occur once the engine is hot?


it’s correct get the codes for the check engine light.

Get a $5 gas cap, it’s cheap, but I doubt it helps.

What you might want to try the next time it happens. Turn the key to the “on” position and leave it there for 5-10 seconds and then turn the key to “start” to start the engine. If the engine does start you likely have a check valve issue. It’s kind of expansive to repair because it is part of the fuel pump assembly inside the gas tank. The check valve prevents gas from flowing (siphoning) back into gas tank. By turning the key to “on” you are activating the fuel pump wanting to deliver fuel to the engine.

If that is your problem, you do not have to repair it, but have to live with the “new” start procedure.

Turning the ignition on for ten seconds does no good as the fuel pump only runs for a second or two and then shuts off.

The fuel pump must be cycled many times in order to reprime a fuel injection fuel system.


My wife’s Acura the pump stays on as long as they key is in the on position. I can actually hear it humm inside the gas tank and some years ago I pulled the fuel supply line to the fuel injection and it kept squirting out fuel as we turned the key to “on”. Perhaps the one or two seconds you speak of are model dependent?

If the fuel pump stays on as long is the key is in the on position without the engine running, this is a safety issue and there’s something wrong with the fuel pump circuit.


Do you also have a problem with the vehicle stalling?

Agree with the others . . . get those codes read and please post them for us to review

I agree. I have not had a fuel pump buzz for more than 2 seconds. I use that 2 seconds to scan the warning lights to ensure they are functional then start the vehicle.

Thanks all of you for your comments. I have not taken the car into the dealership since i have been traveling on work. I promise to post the engine code that comees up when I take into the dealership. I have not been near the car for the past many days since I have been out. I have not even tested the fuel pump clue with “turn engine on for a few mins” routine. Will post details.

You can get the codes read anywhere. An auto parts store can do it today or over the weekend. You borrow the code scanner from them, read the codes, return the scanner to them, and they print the codes for you. What year is you E-series, what engine, and how many miles on it?

car is 500E 4 matic 2006 model. I started the car today following the directions given here on site - turned the engine on left for 1 min and then started ignition - started beautiful, A few more times and that will confirm

Now that you’ve mentioned the year and model, I know what engine you have

Anyways, on that engine, the crankshaft position sensor was well known for failing . . . often intermittently, and without any kind of warning

And often without any kind of codes

Get the codes read again . . . if if says something along the lines of CKP sensor, just replace it outright. I wouldn’t recommend you do it yourself, unless you WANT to get burnt. You will need extensions, a swivel, and some torx sockets.

Even if there is no code for the sensor, it doesn’t mean it’s okay

It could very well be the fuel pump, but I’m just telling you of a very real possibility, at least on this engine

Ok. But why would it affect the start? Does the CKP sensor come into play only at start?

I said the fuel pump may well be THE problem

But neither I nor the others are present with the vehicle to properly diagnose and repair it

I clearly said I was alerting you to a possibility, now that I know what car and engine you have

The CKP sensor does not come into play only at start. It can cause no-start and it can also cause stalling at any time, without warning

The problem with internet advice is you have to choose who to listen to, and who to disregard

And internet advice is not the same thing as paying a shop to diagnose and repair the car

I never said that the ckp sensor IS the problem

I said it COULD be the problem

I still think you should get those codes read and post them for us

Another bit of advice . . . you have a saddle tank. One side has a fuel pump and sending unit. The other side has only a sending unit. If it turns out the pump IS the problem, I would advise replacing both sides, so to speak

Finally the shit hit the fan. Last morning while driving in the city - the engine went dead. But started again and I drove. It did this twice. Finally in the afternoon it wend dead at a traffic signal and motor woudl not start. Had to call flatbed to get me home. Does it sound like fuel pump or other stuff? Have to take it to dealership/service.

I think the best thing you can do is to have it towed to either a dealer or an independent which specializes in Mercedes-Benz. The independent should be fine. Slightly lower labor rates, moderately lower parts prices, and they’ll have had plenty of experience with your car, because lots of cars just like yours were sold, so undoubtedly they’ve already worked on several

Be simple about it, though. Tell them your symptoms, and that you’d like to have it diagnosed and repaired. Don’t make any suggestions, as to what the problem might be. You’re paying them to figure it out. Don’t try to influence their thought processes.

I had it towed to the dealer who has so far done a good job at good prices for me. Car needs a crank position sensor which is causing it to die. Estimate is $529 before discount. after discount game to 478.00

Also other codes in computer for purge valve and cooling fan but I was told that I will not need to worry about these at this point unless engine light comes back.

Also they found fuel level sensors leaking and they replaced fuel tank under warranty. That fuel tank replacement came to 2512.00 totally paid by Mercedes. Great for a 2005 car.