Car will not start, wait 2 hour and it will; what's going on
 

1992 300 TE

Car will not start when it is not driven for a few days.
Here's what happens:
-battery will crank engine but engine will not start.
-no fuel when I check spark plugs
-no fuel when I crack gas line going to fuel distributor.
**wait a few hours maybe 2 hours, go out car will starat no problem.

What might be going on, anyone have this happen?

Only thing I could think of is fuel pump and check valve attache thereto.

I do hear the pump making sound for a few seconds when I turn key but not all the way.

1. Try cycling the fuel pump 3, 4, 5 times by turning the key to "on" (but not start), letting the pump run until it shuts off, then again, and again. If there is a defective accumulator, fuel pressure will bleed off over a long period of inactivity. Repeated pump cycling may bring up enough pressure to start.
2. The inlet screen in the fuel distributor (FD) may be almost clogged. When you make an attempt to start, enough fuel pressure may be built up to eventually fill the FD, so that it will start after a 2 hr. wait.

Fuel Pump Relay. It's right behind the battery where a plastic cover resides. If it's the fuel pump relay, there should be pressure going to the fuel distributor after cycling the key a few times. STRONG pressure.

Not trying to be a smartass but if the relay is bad there will not be pressure by cycling the key. The pump relay is designed to only pump for a few seconds if the engine is not running. That's why with a good relay you can build pressure by cycling the key even though the engine doesn't start.

I have previously tried the repeated cycling which did not help.

I will check the inlet screen in the fuel FD when I find it's location.

I meant to say if the pump relay is replaced with a good unit, the key should be cycled at least once then check the line at the fuel distributor and close the line and crank. Close the line first then crank. Fuel should spew out but be sure to put something under the line. It most likely IS the fuel pump relay.

I dunno that model (or relay) specifically, but I DO know that on another car we had, the relay had 2 "stages" one to prime the line before starting (or build pressure or whatever), and another to run the pump after ignition and the car was running. The prob we had (If I recall correctly) was that our car would crank and crank and not start, then it would start and run fine. Then the next time we tried it- it would crank and crank again. So if it was me, I might take a look at the relay as previously discussed.

I found genuine MB fuel pump relays on eBay $40.00 free shipping from California.
eBay Fuel Pump Relay Link $40.00

Check the inlet screen first as its free to clean it.


My 190E quit running the other day and cleaning the inlet screen with brake cleaner got it running again in under 5 minutes.

Two big lines that at 17mm iirc go into the fuel distributor. On an m102 its the line closer to the fire wall. Take the line off the fuel distributor. You will see a fitting still in the fuel distributor that is the same size, take it out. It should have a tiny little conical screen in it. Blow some air and or brake cleaner through it from both directions.

If the fitting you pull out doesn't have a screen in it, you've got the wrong side. Just pull out the other fitting.

Pull your current relay and check for corrosion on the posts. My OVP in my e320 caused the same symptoms you are describing. I bought a new ovp but its still in the box as cleaning the old relay with a wire brush did the trick.

Thanks for all the help.

Based on the advice I replaced the OVP with a spare. I cleaned the little filter at the fuel distributor with brake clean and then blew it out with compressed air.

After doing this I reassembled and turned the key and the car started right away. I know there was previously no pressure in system because it bled off when I accessed the fuel distributor.

Hopeful this will fix the problem. Really the only way to know is let it sit for 5 or so days and then try to start.

Also check (and replace if needed) fuel pressure accumulator. It's responsible for maintaining fuel pressure when engine is off. If it's bad, it shows symptoms similar to what you're having, due to loss of fuel pressure in system.

Re: Accumulator

Please see post #2.

Now the situation is the car will not start at all.

Battery will crank starter.

Fuel will get to distributor from fuel pumps.

Fuel will not get to spark plugs, they are completely dry.

Now what?

Check to make sure the plunger in the Fuel Distributor isn't stuck. Remove the air cleaner and check the travel of the round plate.