Fuel Pressure Regulator - PeachParts Mercedes-Benz Forum

usaf 1 · #1 08-12-2015, 03:54 PM

I have a 95 R129 SL320 I found that the Fuel Pressure Regulator was bad, replaced it and everything was working fine for a few months then the same symptoms showed up and the engine would conk out and die in the middle of the street. If I would wait for aprox 3 to 5 minutes then try to start it up again, I could get it started and going no problem. Then it would go for another few days or weeks and then bam, would be driving along and all of a sudden it would die again.

I have Replaced the Fuel Pump, replaced the Fuel Filter and replaced the fuel pressure regulator twice and the same problem is back.

I've even ran a diagnostic test and no codes show.

Thanks for any Help, this is really becoming a nightmare. I can be reached at david_reeder@sbcglobal.net

Elektri · #2 08-12-2015, 08:20 PM

Is the fuel pump getting electricity when this happens?

I would connect wires and a voltmeter to the wires AT the fuel pump so I could see if it is getting power or not.

If it is getting electricity when this happens, then I would connect a fuel pressure gauge to be sure it is in fact losing fuel pressure when this happens.

The trick to troubleshooting intermittent problems is to be able to "see" what is going on by connecting monitoring test equipment.

optimusprime · #3 08-13-2015, 04:27 AM

Try the fuel pump relay ,swop it out for a new one.Allways come in as spare if its not that in the end .I am thinking its trial and error ,dizzy cap can do it ,the plug wires can do it.

Benz Mondi · #4 08-13-2015, 10:28 AM

Are you sure that your problem is not actually heat related? Perhaps a prolonged idle while still at your home is worth trying. I'm talking idling for 15-20 mins or more. A higher rpm would be a better test, but noise will be a factor. If you can get it to die in your driveway, then you can quickly test for what went wrong.

I will tell you that I had a similar symptom with my 91 300SL, thought it didn't die while driving down the road. It just would not start after having parked it for even just a few minutes. It turned out to be a loose crank shaft position sensor. If you do replace this sensor, replace it with the real Bosch part. I've had bad luck with the much cheaper versions from China for this car and my other cars.

Good luck.