450 SL Still Won't Start - PeachParts Mercedes-Benz Forum

GAMMTKA · #1 03-23-2003, 06:25 AM

After unsuccessfully trying to start my 1976 450SL after winter storage I tried poring a little gas down the air intake and all I got was a little backfire. The car seems to want to run, but it only lopes on what seems to be maybe one cylinder briefly for a few seconds. Last year before storage it ran great, except that even after replacing all injectors, plugs, sparkplug wire, coil and fuel filter, cylinder seven gives intermitant problems. Sometimes this plug gets fouled)

I had a battery charger on most of the day yesterday and tried every couple of hours to start it to no avail. Interestingly, after all that cranking, there was no perceptible smell of gas. You would think I would have flooded the engine at some point and would have smelled gas.

I haven't checked for adequate spark, as I don't know how to do this. One of my questions is, is there a fuse or fusible link for the fuel pump? I checked the fuse panel under the passenger kick panel and all fuses appeared to be ok. My brother, who is a body man, said I may have blown a fuse it there was some ice in the pump when I tried to start it (It was about 35 degrees here yesterday morning.

Is there a simple way to test if the fuel pump is working? I have the Haynes manual, but my automotive skills aren't that good. If I could get the car running, I would drive it to one of the local shops that works on mercedes here in the Minneapolis area.

Does anyone have recommendations as to which shop is good? I don't feel good about one of the local MB dealers as they charged my $1,000 to replace a rear wheel bearing last fall and I thought that was pretty high

Any suggestions would be appreciated.

cbdo · #2 03-23-2003, 08:11 AM

Don't have any detailed instructions for you, but at least a couple of things to check.
First, the fuses sometimes don't easily show that they're blown.
Check the relevant fuse(s) with a VOM to show continuity (resistance should be about 0 ohms), and make sure the fuse connections are clean. If there's enough power to turn over the starter vigorously, the battery and its main connections should be fine. Also, turn the ignition on and listen for the fuel pump to run, at least for a few seconds; it's behind the rear differential and should be audible if you've got the car door open. Someone more expert than I am can instruct on actually checking fuel pump output.
If there's an ice problem, the car will need to have been in warm enough conditions long enough to melt same--but then you'll have the problem of dewatering. If you added stabilizer to the gas before storing (you DID do that, didn't you?), that's less likely to be an issue.
That's a start--hope it helps!

GAMMTKA · #3 03-23-2003, 08:15 AM

Yes, I put stable in the gas before storing. No sound from fuel pump. If anyone knows what specific fuse to check, it would be appreciated. Engine turns over just fine, but shakes.

cbdo · #4 03-23-2003, 08:24 AM

My 560SL doesn't list the fuses in the owner's manual, but does have a label on the fuse cover listing the circuits. If all else fails, taking a fuse out and checking for 0 ohms on a meter is a quick process; you'll go through all of them in 10 minutes or less. Take one out, check it and replace if good; if not, WRITE DOWN which slot it came from and what size it is (don't ask me how I know this!). If you don't have a VOM (volt-ohm-ammeter), under 20 bucks at Radio Shack will fix that.
Apologies if I'm pointing out stuff you already know.

GAMMTKA · #5 03-24-2003, 07:18 AM

All fuese are good. Is there any other advice from members before I have the car towed in?

neileg · #6 03-24-2003, 08:48 AM

I don't know about your car, but most Mercedes have a relay to control the fuel pump. Failure of these relays is not unknown. If no one chimes in here try posting on the SL forum.