1977 280 SE Won't Start

Hello group,

I need some help on this old bird. It's a 116 024 with the O;d 110 double overhead cam engine in it.

Vehicle was towed in since the engine would not start anymore after Engine had been steam cleaned by some car salesman. I was told that they tried for hours to get it started but to no avail.

Below I will list the repair steps I have done in a sequential manner:


Upon arrival I pulled the plugs and they were soaking wet.


I disconnected the fuel pump relay to make sure that I don't flood the engine even further.

Next I cranked the engine for some time to make sure that all the "possibly" remaining fuel in the intake manifold would be "pumped out.

Thereafter a compression check was done and I noticed that I had about 125 psi on every cylinder.

The spark looked somewhat weak to me so I replaced the spark plug wires and and both ballast resistors on the coil. The "blue" resistor was beyond bad. I now have a health 30 KV spark.

I now tried to start the engine but to no avail. I sprayed staring fluid into the intake system but the engine would not even react to it.

Next I pulled the plugs out (not wet) and put a new set of Bosch plugs in, still no start.

I began to think that I may have a timing/camshaft/crankshaft problem. After pulling the valve cover, everything was ok in that area.

Next I checked the fuel pressure and it is up to 5.2 bar and drops to about 2 bar after the pump stops.

Again at this point I tried to start the engine but it would not start.

Next I jumpered the fuel pump relay and disconnected one injector line to see what the delivery amount of the system was. Sure enough someone had adjusted the the setting so rich that there was just to much fuel going into the intake system. After this I retraced my steps, drying plugs and such, but I was still not able to get this engine to run.

I did look for large vacuum leaks but there is so much vacuum generated when I crank the engine over that practically there is no leak.

Last but not least I did disconnect the cold start valve to make sure it was not blindly injecting..

What am I overlooking group ???

Best regards

Gary Hoffmann

Sounds like you are on the right track. However, did it run before they "steam cleaned" the engine ?

This problems sound very similar to the problem I am having with my 71 250CE. Which injection system does this have ? DJetronic or Kjetronic ? If you have adequate spark, and fuel and it's still not firing, then that sounds pretty strange. Did you make sure the timing is on? I once had a 4.5 280SE that someone had loosened the distributor on and accidently turned it around, it was getting spark alright just in the wrong order !

You are on the right track using Bosch or NGK plugs, I once bought a 280SE 4.5 because the owner was told the ECU was bad and it was going to cost her $2000 to fix it. In the end someone had put champion plugs in the car! $18 worth the plug solved a $2000 problem.

Make sure your Ignition control unit didn't get blasted also. It's a square box with fins on it. Usually under the battery or mounted to the firewall near the coil.

Also try changing your gas filters, perhaps somehow water found it's way into your fuel system. Does the pump run when you turn the key on? It should pump for like two seconds then stop.

125PSI sounds terribly low for this engine. My 250CE runs around 165PSI or so and I think the minimum was 145psi. You might want to check into that.

Remove your cold start valve and make sure it's only spraying for a few seconds when the car is first cranked and not continuously.

Start checking cold start components like the temp feelers, thermo time switch etc.

Contact me off board and I might be able to help a bit.


Cheers
Chris M
71 250CE
Starts but runs super rich

[ctaylor738]

I vote for checking the timing - turn the engine to TDC by the timing marks, make sure #1 is up on compression, check that the rotor is pointing to #1 - I am sure you know the drill.

You might also try cranking the engine and "tapping" the cold start valve with a 12V lead to give it a little fuel and see if it fires.

Is it possible that the return valve is stuck and thus allowing too much fuel to the cylinders?

Good luck and do keep us posted.