1984 380SEL no fuel questions - PeachParts Mercedes-Benz Forum

Douge · #1 05-24-2009, 06:27 PM

Found another abused car. The cool news is that my son, after seeing me work on these beautiful old cars, wants to have a go.

He can buy the car for 400, it is straight with 135k two owner miles. Car is not running as it has been sitting for over a year. Now I know that a diesel would probably fire pretty willingly after that amount of time but a gas car? I think not.

My only real question is that I am concerned that it might be that $500 fuel distributor and want to know how likely is it that that particular part would have failed after sitting. Though I don't have any direct experience with this part, it seems that if usually begins to fail and cause the car to run poortly rather than failing completely and disabling the car. The car will turn over with a bit gas right down the pipe, but it will not stay running so it it not getting fuel.

We figure we need to go from tank to injectors with seafoam hopefully but may be replacing filters and maybe the fuel pump and other components along the way. Any pointers or opinions are always welcomed and of course much appreciated.

Doug

Mike D · #2 05-25-2009, 08:53 AM

I'm going through the same thing with an '85 500SEL ($300 delivered to my door in a "non-start" condition).

Check the forum posts for CIS problems.

The first thing to check is the fuel pump relay. Jumper the relay (it is located in the fuse box on the driver's side fender wall on my car). Pull the relay, (large black plastic box with a round "cap" on it), connect a jumper between the two rearmost side by side pair of contacts, and see if the pump engages. You will hear the pump "whir". Make SURE you have all the fuel lines TIGHT! Those vane style pumps spin the pressure up to 50 psi in no time flat.

If you hear the pump engage, disconnect the jumper, undo the fuel supply line to the distributor's front, left side (17mm wrench and a hold down bolt with a 10 mm head) and fit a rubber fuel hose over the end of the flair, I think a 3/8" hose will fit. Run the end of the hose into a 1 liter bottle sitting well away from the fuse box area, down on the ground or over on the other side of the engine, connect the jumper and check the flow. It should fill the liter bottle in about 30-40 seconds. Use a clear bottle and you will also have a view as to the condition of the fuel you are pumping. While you have the line disconnected, pull the fitting it goes into. You will find a strainer inside the fitting. Clean it out.

If you don't have the proper flow then change the filter. Do NOT bypass the filter or you will be making more problems than you already have! Go ahead and ask!

That's the FIRST steps to diagnosing the CIS systems. Do this first before attempting anything else.

Mike D · #3 05-25-2009, 09:06 AM

The next thing to do BEFORE you do anything to the fuel system is to pull all the spark plugs and do a compression test. The M117 engines have a known weakness with the timing chain guide rails. If the rails have broken it is very possible it has bent valves or a "holed" piston. They are "interference" fit engines and a loose chain can be a catastrophic event.

While you have the plugs out, check for spark from the plug wires. The transistor box is a known weakness on all the early Benz'es.

tyl604 · #4 05-25-2009, 09:57 AM

What does "interference" fit mean?

Mike D · #5 05-25-2009, 10:24 AM

Minimum clearance between the closed valves and the piston in the top position. essentially. There is no room for error if the chain stretches or jumps a tooth.

Douge · #6 05-26-2009, 11:47 PM

Quote:

Originally Posted by Mike D

While you have the plugs out, check for spark from the plug wires. The transistor box is a known weakness on all the early Benz'es.

OK we went ahead and bought this car. When I looked at it and was told it had been sitting so long I assumed the battery was dead but little did I know the PO had tried to get it going and had dropped a new battery in it and guess what. As soon as I turned the key.... no fuel pump. So we found a good place to start. That and draining the tank.

Its a decent car if we can get it up and running. Thanks for the help!

Douge · #7 05-27-2009, 07:23 PM

OK we swapped the fuel pump out with a salvage unit and got nothing. Next we got a fuel pump relay and now still no power to the pump.

What is next?

I don't know if it is related, but there is a control unit, part #000 820 39 26 that is cycling/clicking for about ten seconds when the key is first turned on and cycles every so often if the key is left in the on position.

I have no voltage at the pump. Salvage pump has 3.8ohm resist. replaced pump has .9

And for what it is worth, if there is fuel present, the car fires right up.

ctaylor738 · #8 05-27-2009, 07:40 PM

Remember that you will only have power at the pump with the starter cranking or the engine running.

Douge · #9 05-27-2009, 08:09 PM

Quote:

Originally Posted by ctaylor738

Remember that you will only have power at the pump with the starter cranking or the engine running.

It doesn't prime itself when the key is turned on, never had a Merc that didn't do that. Maybe that brief whirring noise when the key is turned on is something else.

Douge · #10 05-27-2009, 08:53 PM

I checked the pump with the starter engaged and it is getting 9v. I am not getting gas up to the motor however.

Little frustrated now.

Mike D · #11 05-27-2009, 09:04 PM

The brief whirring noise you hear is probably the pump. Have you drained the tank and removed the strainer?

Have you removed the fuel line at the distributor (remember the 3/8" line fuel flow test I mentioned earlier?)? Don't jump over the test procedure steps or you will just be shooting in the dark.

ctaylor738 · #12 05-27-2009, 09:14 PM

TTBOMK, there's no priming.

9V is really pretty low and might not produce enough pressure to open the injectors. In addition to Mike D's suggestions, you might want to check for a wiring problem like corrosion.

Did you charge the battery?

Mike D · #13 05-27-2009, 09:45 PM

Dang it! Will you guys quit doing that! I just spent 5 minutes trying to decipher TTBOMK!

9 volts is probably about right with the starter cranking. A little low but it should be enough.

I thought the '84 was the first year of the K-jet? Do you have electrical connections going to the injectors?

Douge · #14 05-28-2009, 12:20 AM

Mike, we drained the tank and refilled with about 5 gal of seafoam treated gas. I checked the flow from the tank to the pump and its fine.

I have a schematic of the fuel system but its pretty rudimentary and I cannot tell what the incoming fuel first hits. I did not jump the relay connnections but I will do that tomorrow in lieu of turning the car over, however, I have checked that inlet and there is no flow with the engine turning over. At this point, I do not believe that gas is reaching the engine bay.

Schematic diagram of KE-Jetronic
1. Fuel tank
2. Electric fuel pump
3. Fuel accumulator
4. Fuel filter
5. Primary-pressure regulator
6. Fuel injection valves (injectors)
7. Intake manifold
8. Cold-start valve
9. Fuel distributor
10. Air-flow sensor
11. Electrohydraulic pressure actuator
12. Lambda sensor
13. Thermo-time switch
14. Engine-temperature sensor
15. Ignition distributor
16. Auxiliary-air device
17. Throttle-valve switch
18. ECU
19. Ignition and starting switch
20. Battery

I have all of these components to the best of my knowledge, obviously its an eight cylinder.

Components of the KE-Jetronic.
1. Air-flow sensor
2. Mixture-control unit
3. Fuel distributor
4. Pressure actuator
5. ECU
6. Fuel filter
7. Fuel accumulator
8. Electric fuel pump
9. Fuel injection valves (injectors)
10. Throttle-calve switch 11. Thermo-time switch
12. Cold start valve
13. Engine-temperature sensor
14. Auxiliary-air device
15. Primate-pressure refulator

Douge · #15 05-28-2009, 12:35 AM

If the primary pressure regulator were defective, could that be a potential blocking point?

Also FWIW (for what its worth) if you drop gas down the pipe (air flow sensor) it fires right up. Not the lumpy bad gas, fouled injectors, crap plugs kind of a mine field, but the firing on all eight ignition that tells me that this car will run well if it gets some fuel.