Fueling Issue
Last edited by 1970gsx; May 15, 2019 at 12:30 PM.






When was your fuel filter replaced?
So after leaning towards an electrical issue since I would hear the relay click off and the car would stall after 5 seconds and the car ran with a jumper wire albeit without the supercharger functioning, I put a fuel pressure gauge on the rail. (yes I know should have started there probably). Anyhow, the pressure would go to about 30psi on the prime, when started jump to 70psi and slowly fall until the relay would kick off at about 20-30 psi and the car would stall. So since I had a little fuel on top of the sender, I put the jumper wire back on and drove to Mercedes and complained about the fuel smell. They replaced the fuel tank assembly at no charge under the extended warranty. When I left the dealer it still had the jumper wire on it, and it still had no supercharger function. I pulled over and popped in the relay, and prayed it would stay running for more than 5 seconds which it did. Took of and everything was back to normal with supercharger working again
So all along it was either the fuel filter was clogged or the pumps were on the way out. But, I would think if you had a small jumper wire in the glove box, and you break down due to a fueling issue, the jumper wire trick will probably get you home without a tow if you put it between the 86 and 87 pin in the relay socket. So I guess the fuel pump relay circuit is tied into the supercharger circuit also, so when things aren't correct it will cut the power down. Hopefully this will help others in the future with the same symptoms I had.


So after leaning towards an electrical issue since I would hear the relay click off and the car would stall after 5 seconds and the car ran with a jumper wire albeit without the supercharger functioning, I put a fuel pressure gauge on the rail. (yes I know should have started there probably). Anyhow, the pressure would go to about 30psi on the prime, when started jump to 70psi and slowly fall until the relay would kick off at about 20-30 psi and the car would stall. So since I had a little fuel on top of the sender, I put the jumper wire back on and drove to Mercedes and complained about the fuel smell. They replaced the fuel tank assembly at no charge under the extended warranty. When I left the dealer it still had the jumper wire on it, and it still had no supercharger function. I pulled over and popped in the relay, and prayed it would stay running for more than 5 seconds which it did. Took of and everything was back to normal with supercharger working again
So all along it was either the fuel filter was clogged or the pumps were on the way out. But, I would think if you had a small jumper wire in the glove box, and you break down due to a fueling issue, the jumper wire trick will probably get you home without a tow if you put it between the 86 and 87 pin in the relay socket. So I guess the fuel pump relay circuit is tied into the supercharger circuit also, so when things aren't correct it will cut the power down. Hopefully this will help others in the future with the same symptoms I had.
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