300 E Backfire at 3200 RPM

[BENZ TEK]

In need of help!!!!!!

Have a 90 300E in the bay that will not rev past 3000-3200 RPM. Backfires through the exhaust if you try to push it pass that point. The harder you push the accelerator the more it misfires. Sounds like the ignition coil, EZL, OR Crank sensor is breaking up.

Any help would be appreciated.

[pmckechnie]

I had this problem on an 87 300E one time and it was the fuel pump relay. It has a rev limiter in it. The customer, thinking he was fixing a no start problem put in a fuel pump relay from a 4 cylinder 190 or something. It fixed the no start problem but he later found this problem. Replaced the FP relay and fixed the problem. By the way, most of these relays have are marked as 4 , 6, or 8 zyl. Could also just be a defective relay.

[BENZ TEK]

Thanks alot for the reply. I will check the relay and let you know how it turns out. I noticed that this model has a MAS relay instead of just the single fuel pump relay. I will straight wire pins 1&2 to see if that will allow the car to rev pass 3200RPM. I'll keep you posted.