300e Still Won't Start- Steve Help! - PeachParts Mercedes-Benz Forum

Benzstar · #1 07-28-2004, 05:47 PM

1990 300E

Steve,

I am sure you can guide me to solve this mysterious problem. I have been trying to solve this problem for two months! including local MB dealer.

Car only runs after cranking few times without any hesif I pour few ounces of fuel in air intake. But, once switched off, can't restart. I have replaced the following:

1. plugs, fuel accumulator, fuel pump, dist. cap & rotor
2. Dealer said the disch. pressure & flow is okay. They told me to replace cap & rotor, but no help.

What else should be checked?

126nut · #2 07-28-2004, 06:04 PM

I think SteveB is on holiday.

What a pity!! My 126 tranny thread is fixin't to fall off the face of the earth.

Guess it's time for us lazy ass parts changers to get a book or at least a CD and start figuring this stuff out on our own??

yal · #3 07-28-2004, 06:07 PM

Sounds like the car is all the way lean. Can't it be adjusted with the adjustment screw like the M102 engine?

elusive 190E · #4 07-28-2004, 06:19 PM

Seems like a faulty accumulator or fuel pressure regulator...

Some component is allowing vapor lock to form...

Did you also replace the fuel pump check valves..?

Just trying to help, thanks.

psfred · #5 07-28-2004, 09:40 PM

you may also have a bad OPP relay or fuel pump relay, either one can cause start failure. The fuel pump relay will also cause intermittant stalling and any speed, followed by hard starts. Eventually, the pumps won't run at all, then it's tow truck time!

Basic mixture too lean will also cause hard starts -- you can check by depressing the air flow flap a bit while someone cranks -- if it start right up, you're too lean on start.

Pete

Benzstar · #6 08-03-2004, 12:49 PM

I have already replaced fuel accumulator, cap, rotor & pump. Relay is working fine.

How do you check plunger inside FD?

guitarman · #7 08-04-2004, 01:39 PM

Two things come to mind. I had the same problem on my "87 300E. Assuming yours is similar to mine. The overload protection relay located near firewall directly behind battery. There will be a plastic cover that you need to remove to see it. The relay should be aluminum with a red or yellow cover (I don't remember which). On top of it is a fuse. Check that fuse. Especially if you have jump started the car recently. Since you can get it running, go here http://www.peachparts.com/Wikka/EngineControls and check the fuel mixture. It sounds like it's lean. Hope this helps.

Benzstar · #8 08-05-2004, 10:20 AM

Thanks. I will try this.

autozen · #9 08-05-2004, 11:09 AM

I'm not clear about your post. Do I understand correctly that you can crank and put gas on the air sensor plate , and the car will continue to idle until you shut the key off even minutes later, but will not restart with the key alone? It makes a difference here.

Peter

smileymikey · #10 08-05-2004, 05:41 PM

I have a 300e (1988) with exactly the same problem I bought it from an auction yesterday and they used a far larger battery to jump start it, have spoken to a Merc breaker, who told me that he has made a fortune over the years, buying in cars where the owners had thrown a fortune at the problem to no good,replacing the fuse in the relay which is behind the battery, this would appear to be a very very common problem on these cars will change mine tomorow fingers crossed.

Benzstar · #11 08-05-2004, 06:37 PM

Autozen,

That's exactly what is happening. I, including the dealer is puzzled.

autozen · #12 08-05-2004, 10:06 PM

Benzstar,

Veeery interesting. One more question since MB has slop over years. Do you have a fuel pump relay or is everything combined in the MAS unit on your car? After I know which system you have I can do some checking in the prints. I am intimately familiar with these cars.

Peter

Benzstar · #13 08-06-2004, 12:17 PM

1990, 300E, 3.0

This car has fuel pump relay (MAS). Relay is okay, pump also runs & develops about 5.4 bar. I checked relay by jumpering two contacts ofthe relay. OVP fuse is okay.

What do you think about Fuel Distributor (FD) ? How do you test and this eliminate possibility of FD going bad? Thanks

smileymikey · #14 08-06-2004, 12:25 PM

Looked at the fuse on mine and its fine the car started and run well, but got a mile up the road and died, now wont start thinking of using it as a chicken shed at the moment

autozen · #15 08-06-2004, 08:42 PM

Benzstar,
I'm still confused. It is very dfficult to jumper a MAS unit, and I don't think the car will run without it, because key imputs to the ECM will be missing. Do you have a little black relay for a fuel pump relay or do you have a tall silver unit with a black knob on top that has to be turned to remove the unit?

Peter