I_am_Sam

SOLVED - FUEL PUMP

I was driving home tonight, reserve petrol warning displayed. Didn't think anything of it as I have driven home and back to work on reserve plenty of times.

About 30 mins later when I was nearly home, I crossed train tracks - a bit fast as they were pretty rough, then less than 10 seconds later I don't have any throttle response and I coast to a stop. Dash lights up like a christmas tree and engine cuts out. (Petrol was still 3 bars) Engine won't start again.

I look under bonnet for any obvious damage, but notice nothing. Try engine again and it starts.

Drive for about 5-10 mins, then it cuts out again. I get red dash telling me to take to mechanic. Petrol still showing three bars.

I leave car for over an hour and read the forum, it sounds like CPS needs replacing. Similar symptoms.

However...

I return to my car but bring some petrol as well. I try to start the car, but it cuts out each time after a few seconds. I then add some fuel, it starts a bit rough but then idles and I drive it fine. I drive to petrol station, fill up, then home and all is normal.

So did I really run out of petrol, even though the gauge indicated 3 bars and range was 20-30 kilometres. Or could the very large bump over the train tracks and a low tank cause this problem? Is there a chance it is the CPS and me adding the petrol is just a coincidence?

Thanks in advance.

megacrazy

So, your car was warning you were almost out of gas. You drive another 30 mins...hit some tracks where presumably the fuel splashes around and your car stops. You then return to the car add gas and the car drives fine. I don't see an issue here?

Our cars have a 2 gallon reserve which goes very quickly. I wouldn't consider driving another 30km a good idea. Based on how often you're hitting that reserve, you're most likely sucking up all the garbage at the bottom of the tank possibly causing what you're describing.

beejAMG

^what he said.

i personally fill up from half a tank. all the gunk, debris and dirt deposited on the tank are all at the bottom and it you drive on reserve and "shake" the tank, you are potentially putting all the dirt into your engine.

I_am_Sam

Thanks for the replies guys.

Yes it does seem plausible that I did run out of petrol from what I experienced. I just needed some confirmation before I tackle the commute and potentially **** off 20,000 people this morning if something goes wrong! haha

So if you have a min., can we tackle these points, to reassure me?

- The petrol gauge and range have always been accurate. The splashing petrol idea seems reasonable, however it would settle in seconds. But I was only able to drive less than 2k's on up to 30k's worth of indicated petrol. What reasoning would describe this? Clogged with 'gunk'? I only added about 2 litres of petrol and it started, how does this unclog the gunk?

- Does the dash light up with the red screen -"take to mechanic" (I can't remember the exact wording) if petrol runs out?

(Car serviced regularly, filters changed as needed).

I am not doubting your advice guys, I agree it seems the likely cause, but like most of us here I just like to know the technical stuff of what is actually going on.

Thanks

Rudeney

If you actually do run out of fuel, then you can cause an "air lock: in the injectors that will result in misfires. Back when I worked at the dealership, I "found" a stock MY2003 CLK500 in the back of the parking deck that had been left there by the service department over a year before (this was late 2004 when the MY2005's were already on the floor. The fuel tank was empty and the battery was dead. After fixing those problems, I drove it around and it ran like crap, throwing an MIL. The shop scanned it and said it was misfire errors and to just drive it. So I took it home for a few nights and it finally straightened out.

However, I regularly run my car down to one bar or even no bars. The gauge seems very accurate, and I know my routes. The car has a 16.4 gallon tank. I;ve never put more than 15 gallons in it and that was at zero bars on the gauge.

megacrazy

Yeah the indicator should be pretty accurate. However, the range is completely inaccurate. It simply depends on too many variables to give a good estimate. I've activated the actual fuel remaining in gallons on my cluster and I can tell you those last 2 gallons go down way faster than the estimated mileage remaining.

All in all, weird things CAN happen if you run out of gas. If the problem doesn't manifest itself anymore stop obsessing over it. There's nothing to fix

Russell Ormerod

You just ran out of fuel. Yes the red light will come on the dash when it cuts. Possibly fuel sender is reading faulty

I_am_Sam

Thanks again for your replies.
No issues since fuel top up. Sounds and seems to run as before.

....now to find out what is wrong with the A/C, as summer is here now and it has lost its cool.

Rudeney

AC is probably low refrigerant. Buy a recharge kit that has a gauge and check it. With lack of use, the seals tend to dry out and leak. Sometimes using a recharge kit with a "conditioner" can help lubricate the seals and prevent leaks. I actually just keep my AC compressor on year-round to make sure the system gets "exercised".

I_am_Sam

Yeh I would give that a try, but I live in the nanny state of Australia and you can't just buy A/C recharge kits at the local auto stores.

Thanks though. I will have to take it to a mechanic.

I_am_Sam

Well, the problem returned, multiple times, even with full tank of petrol.

It ranges from; loss of power for 5 to 15 seconds leaving from stationary in stop go traffic - but then will drive fine, to engine then running rough cutting out and not being able to be restarted....and leaving me stranded in peak hour traffic.

Before the latter break down, I had the codes checked at a mechanic, he said there were misfires reported, but he cleared them and said to return next time it happened - he wants to change the ignition coils and plugs if they do.

I've waited 24 hours since the breakdown (yesterday) and tow home and now the car starts again, running smooth.

All my searches on this forum seem to indicate, CPS or MAF.
Symptoms:
- Warm engine
- I think warm days
- Being in stop go traffic for 30-60 minutes
- Leaving from a stop, very limited throttle response, car jerks somewhat
- Engine then may cut out entirely and not be able to be restarted for a long period of time
- Engine will restart after a long wait

Additional Notes:
- I noticed corrosion on battery terminals
- I've ordered an OBD reader to check codes

If anybody would like to suggest what I should investigate, I would greatly appreciate it. Thanks.

Russell Ormerod

I am not sure what engine is fitted to your car? But it could well be cps which you will see as a fault code. It could also be low fuel pressure which would show as multiple misfires. I don't think coil replacement is necessary. I would fit a fuel pressure gauge and drive it until it plays up.

gixxerboy

missfires can be cause by many things, i wouldnt just throw plugs and coils at it with out checking first. Also no reason IMO to replace all the coils if you only have a couple bad.
Sounds like it is something more since the car dies on you. You could remove a coil and the car would still run

I_am_Sam

Engine is V6, CLK320, 2003, Australian.

- I thought the CPS didn't often throw codes, as per what I've read
- Fuel pressure, thanks. I did read about a bad relay for the fuel pump also. I will check out about a pressure gauge.
- Yeh, I don't want to replace the coils, I wasn't impressed with the mechanics plan.

Rudeney

Not starting when the engine is hot is typical of CPS failure. Try pouring cold water on the CPS. If that makes it start sooner, then it's your culprit.

Russell Ormerod

True. Hot not start usually cps. When signal is not there it should trigger a code. Cold water does do the trick..

Patton001

If you have regularly ran the car significantly past the point where the reserve fuel light comes on, chances are good that you have sucked enough of the crud out of the bottom of your fuel tank to clog your fuel filter resulting in low/no fuel pressure.

Russell Ormerod

The pick up in the tank does not move so running the tank low or even dry will have no effect on what dirt gets sucked up. Anyway the pump sits in a bowl that is constantly flushed due to the way it's designed. Picking up dirt from a low fuel level is just nonsense. Your fault lies elsewhere.

I_am_Sam

- ODB scanner reported no codes.
- I have decided I will get CPS changed and see how it goes.
- Budgeting about AUD$200 ($100 part, $100 labour....just spoke to Mercedes service centre, they want AUD$180 for part, AUD$210/hour labour)

I wish I could have tried the cold water trick when I was broken down - don't want to break down on freeway again to test though.

Thank you all for your replies. It is greatly appreciated.

I will post back results after replacement and a few weeks of Summer driving.

Rudeney

Running out of fuel can cause some issues. The fuel pump and the injectors both use the fuel to keep them cool. Overheating could damage them. When I worked at the dealership, about once a week some idiot salesperson would run a car out of gas. Only one of them actually needed any repairs - an S500. I drove it around for a week and it just kept stumbling, so I sent it into service and they ended up replacing several injectors.

Russell Ormerod

Strange that! But on a S500 with a 113 engine if you run out of fuel I would say it's a good thing to bleed the fuel rail

Rudeney

I guess if you knew you had run out of fuel and immediately shut down the engine, then bleeding at the Schrader valve on the fuel rail with the pump operating (but not the engine) would be the best thing to do. I think the problem in my case was the clueless salesperson kept trying to drive the car until it finally died. By them it had probably overheated the injectors and warped them.

Russell Ormerod

U won't overheat injectors. Without fuel it can't run so that theory makes no sense

Rudeney

Fuel injectors are basically linear servos with needle valves on the end of their stators. This needle moves quickly, and as it does, it generates heat. The fuel flowing through these valves both cools and lubricates them. If they keep pulsing but don't have fuel, they can overheat and fail. Once the engine has been starved of enough fuel and stops running and the signal for the CPS stops, the ECU will then shut down the fuel pump and the injectors. The problem is, you may have just enough fuel spitting through to barely keep the engine running, so the ECU keep pulsing the injectors, but without enough fuel in the lines to keep the injectors consistently cool and lubricated.

Russell Ormerod

I hear you but if you think about it in practice the fuel delivered is just the correct amount to make the engine run so any loss of fuel pressure is going to cause the engine to die. Even if what you say is correct and I agree the fuel does help the cooling. But we are talking about maybe a few seconds before the motor completely dies. Hardly enough time to cause overheating. I have repaired many a mercedes in the last 20 years with failed fuel pumps and engines cutting out from lack of fuel and I am yet to replace an injector. It would be interesting to know how many injectors you have replaced from overheating. I am just saying I have never had it before and I am a merc tech