2002 SL55 - starts, runs for a few seconds, dies.

[davidknell]

Hi all -

I've a 2002 SL55 which has been in storage for the last few years - been started from time to time and driven a few feet forwards and back, but otherwise just sat. I went to extract it last month, and it started fine, drove it out, left it running for a few minutes to warm up, turned it off.

Now it won't run - it'll start fine, run for a few seconds and then die, sometimes coughing a couple of times on the way. First thought was stale fuel - so I added four gallons to the gallon already present (I'd put it away without much fuel in) but this hasn't made any appreciable difference.

My suspicion is still fuel - either a clogged filter or a pump incapable of delivering enough to maintain fuel rail pressure once the thing's started. Unfortunately the fuel rail pressure doesn't appear to be available through the OBD2 connector, which would have been instructive. The fuel pump relay clicks on and off when I would expect it to.

Any advice before I start groping underneath for the fuel filter?

Thanks --

Dave

 

[WG M-B]

The pumps are external to the tank. You could check they are getting 12v to run. The fuel pressure can be tested with a screw in gauge at the fuel rail

 

[davidknell]

Yes - thanks for that. I just tried starting it with a screwdriver stuck in the valve that a fuel pressure gauge would go on and got a good spray of fuel out, so I suspect that I might need to think again.

--Dave

 

[Dieselman]

Condensation in the HT side f the ignition system.

 

[davidknell]

I don't think it's the ignition system - (a) it starts and runs happily for a few seconds before dying, and (b) there's good sparks all the way until it dies.

 

[SavMan]

Is the engine getting air and/or able to get rid of it, check air filters and exhausts are clear.

Was the car left with battery disconnected?

When it does start are you able to increase rpm with throttle?

 

[davidknell]

Is the engine getting air and/or able to get rid of it, check air filters and exhausts are clear.

Thanks - have already taken a look at the air filters; can't see anything up the exhausts.

Was the car left with battery disconnected?

Service battery disconnected, starter battery connected. Starter battery still had plenty of charge.

When it does start are you able to increase rpm with throttle?

Yes, briefly, until the thing dies.

Thanks again --

Dave

 

[Dieselman]

Possibly the CPS then, but that would normally stop it starting at all.
Another alternative is the fuel pump relay, but you say you have good fuel pressure.

So we have good spark,
Good fuel pressure.

It shouldn't need anything else.

 

[Will]

With respect to the OP, I wouldn't be messing about with an SL55 - probably best to have it recovered to a good local indi for initial fault diagnosis, then up on the ramp for a re-commission, service and MOT.

If it's been standing a few years you might want a bit of re-assurance that the rest of the car is safe and any other underlying issues are addressed.

Hate to say it, but why not sell it? I expect this car has lost at least £10k in a few years standing about. Early SL55s in good condition fetch around £15-20k these days.

 

[davidknell]

Exactly. I've ordered a fuel pressure gauge - I think it's time to look at that side in a bit more detail. I'll post an update when it arrives; in the meantime, any more ideas as to things to look at gratefully received!

 

[SavMan]

Are you able to see live data on your ODB2 reader, be worth checking the throttle position. It could be stuck or in the wrong position.

Leave the keys in the ignition at position 1 for 30 mins you will hear the throttle body resetting the butterfly. There is a quicker way but it would take me a while to dig it out.

 

[SavMan]

I would still be thinking fuel / fuelling as well at this stage.

 

[andy27168]

I know you have said the fuel pump relay is operating ok, but I believe the fuel pump relay intially gets a feed from cranking then once the engine is running the pump supplied from a different supply that is dependant on when the engine is running, the symptons you describe do fit if the second supply is,nt cutting in.

 

[Mercedes man]

Hi had the same probelm on a 203 c class and was fuel pump in tank pressure would die of on fuel pressure gauge and car would stop .then when started again cycle would happen again at different times hope this helps stew

 

[BlackC55]

Make sure the battery is 100% charged and good.

Leave the ignition on for a couple of mins.

If still no luck then it needs some proper diag with a star or do you have a fuel pressure gauge?

Are you loosing fuel or spark?

 

[davidknell]

Thanks all for the advice. It looks like fuel: fuel pressure ticks up to about 4 bar when the ignition's turned on, then falls back as soon as the engine starts. Quick youtube clip showing this here:SL55 fuel pressure - YouTube

First start (not on video, unfortunately), the pressure rose to 6 bar as the engine was cranking and then fell back from there. The engine ran for significantly longer than in the clip above.

Next step, I think, is to monitor the (electrical) supply to the fuel pump..

 

[Auto-mobile]

Make sure you check both fuel pumps, is it exactly the same every time you start it? Also check the condition of the fuel in the system (drain the filter into a jar)