1975 911 3.6L swap (964) backfire through intake

[mryan318]

Started the car up in the morning outside (37 degrees). Ran for about 2 minutes and killed. Tried restarting car and was having hard time idling and backfire through the intake and popped the left side intake off, Reinstalled intake and tried starting again backfire again and popped apart by the Mass Air flow sensor. Car got towing home. Have not try restarting.

Started out by moving engine to top dead center and check to making sure the timing was on the distributor belt (dual Distributor) everything looks good.

Next thing is checking fuel pressure, Car is a 1975 so what I read on here, looking at pictures of where the relay is on later cars, there is no Relay and it turns on when starting the engine, Car has a no fuel pump relay to jump to run the fuel pump to check fuel pressure. Fuel pump is the driver rear wheel area. Wondering how people are doing this?

[Walter_Middie]

Mryan318,

My 1975 is stock, and the fuel pump runs with the key on ( like yours). When I check fuel pressure, I just turn the key to the run position. It doesn’t take too long to make the pressure checks, so I don’t bother disabling the ignition.

[mryan318]

Walter_Middle,

Thank you, I was hoping someone would confirm this that with the key in the accessory/on position the fuel pump should run make fuel pressure as long as everything with the system is stock. You can hear the pump run correct?

[3rd_gear_Ted]

Suck on the vacuum line to your fuel regulator.
Do you taste gasoline?
If so, failed fuel pressure regulator

[mryan318]

3rd_gear_Ted,

I will check that later today when I get home. Thank you

[uwanna]

Fuel pump relay is part of the DME relay for your 3.6. Do some research on the DME
relay unit, it has two sets of contacts, one set to power the DME box and the other
set to power the fuel pump. You could remove the DME relay and use a jumper
for the relay contacts to turn on the fuel pump. Just do a search for DME jumper.
Perhaps someone will post the relay socket numbers to jumper to turn on the pump.
Good luck.

[mryan318]

Got it figure out guys, removed the DME relay and banged on it a few times, and the car fired right up. Common thing i guess and I ordered two. Thanks your for the help!!