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1998 C230 Fuel Pressure Leak

3K views 3 replies 2 participants last post by  Patman1 
#1 ·
Hello all, I have recently (past 2 weeks) developed a problem on my C230 (not supercharged). When the car sits for a long time, like 6 or more hours, it acts like all the fuel pressure is gone. It will start, but immediately stall, within a second. It wouldn't start until I have it full throttle while starting the car, then it will cough into life. Once its running, there are no issues, no chugging or jerking, drives just fine, no loss of power. It used to stumble and almost not start for a couple of weeks now, but it would start. Today was the first time it wouldn't start.

Is this a Fuel pressure regulator issue? I took off the vacuum line going to it and there was no fuel in it, if thats how you tell if its good or not, I dont know. What else could this be? Thanks.
 
#2 ·
run a fuel pressure test. Connect a pressure gauge to the fuel rail. Start the engine. Fuel pressure should be between 46 and 52 psi. Disconnect the vacuum line to the fuel pressure regulator, the fuel pressure should jump up by 6 to 10 psi. Turn the engine off, after 1/2 an hour, the residual pressure should be at least 36 psi.

Do you hear the fuel pump run when you turn the key to on? It should "buzz" for a few seconds as it builds pressure in the rail.
 
#3 ·
Whoops, I should have mentioned that I did do a pressure test already. It started at 48 PSI right after I shut the engine off, and dropped to about 30 PSI over 2 hours. The car started fine with that 30 PSI. I noticed that the pressure would drop 2 or 3 psi, then wait 10 or so minutes, then all of the sudden drop a few more psi. In the first 20~ minutes of the test, it had dropped to about 40 psi. I have not heard the fuel pump "buzz", although I haven't been looking for it. It appears that when I put the key in the run position, the throttle body will buzz, and wont stop till you start the car or shut the key off. I've let it go for several minutes and all that happens is that the back of the throttle body, nearest the firewall, gets hot. I disconnected the vacuum line with the car idling and it made no difference to how the car ran.
 
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