M10 help plz

[Thizzy]

I recently purchased a 1985 318i that had sat for 22years…..long story short I flushed everything and have replaced fuel pump, fuel pressure regulator, fuel filter as well as tons of the fuel lines. It has new spark plugs and oil filter as well as new fluids. The car will only start and stay running if I pinch the fuel supply line to the fuel rail. Once you do that the car will start and run Just fine until it gets to temp then the fuel pump starts to heat up and the car shuts off. I’m pretty new to e30s and the m10 any help would be greatly appreciated.

[reelizmpro]

What about the tank? was the tank in good condition internally? Which fuel pump did you buy? Did you pinch the supply or did you mean return line?

[Thizzy]

Yessir tank was fine nothing internally maybe I will pull the push pump from inside but I replaced the in line fuel pump it was the one that was making a ton of noise when It did run.

[82eye]

check or replace your fpr

[Thizzy]

Already replaced that as well I’m boiling it down to possibly an injector issue atm? But the car I’ve seen it run and don’t show any signs of something major

[Sunnyledge]

I would consider checking the fuel pressure at the fuel rail. It should be 3 atm or 42 psi +/- since that is what the M10 pressure regulator is rated for. It doesn’t sound like you’re getting too little fuel. If the fuel pressure regulator is bad (I know you said it’s new, but that doesn’t guarantee it’s functional) or there is an obstruction in the return line that could cause your in line pump to overheat.

[TobyB]

...yeah, +1 for fuel pressure,
and not running without the line pinched (how the heck did you discover THAT worked?) makes it sound like it's
a regulator issue- possibly the new one has different inlets and outlets, and it's bypassing the regulator entirely.

Last I looked the in- tank pump was expensive- but any low- pressure generic pump will work. This probably isn't your
problem here, but the pressure test will help diagnose that.
t

[packratbimmer]

Any chance that you reversed the fuel lines at the rail? I would test fuel pressure, fuel delivery and the regulator as stated above. Also, there was a similar thread recently and the culprit was the fuel pump relay. Good luck!

[Thizzy]

Thank you guys update on the car is I got the pressure tester at the rail I’m instantly climbing over 50psi car runs just fine at 40…my question is would the fuel pump relay control on and off function as well as voltage!? I feel like the pump is getting over volted and it’s causing it to overheat and also over work!

[Sunnyledge]

The pump should be running continuously, as long as the engine is running. The fuel pump relay will not power the pump if there is no ignition signal or if the starter motor is not powered. The pressure regulator allows “excess” fuel to flow back to the fuel tank. Engine vacuum helps to regulate how the pressure regulator works.

[Thizzy]

Thank you the pump is running continuously and turning on every time there it is over pressuring it hits 50psi instantly and dies. I’ve cleaned and checked every line and the tank. It has to be that the pump is being over powered and producing more than the 40psi it’s rated for. The pressure regulator is working fine it’s dumping excess fuel back into the tank but the issue is the pressure is reaching 50psi instantly and it should not be the pump is brand new also the oem pump is doing the same. There has to be a voltage problem and I was just wondering if the relay would play a party there.

[Sunnyledge]

The pump will receive battery voltage at start up, which should be 12.6 V for a healthy battery. When the car is running you should see approximately 13.5 - 14 V if the alternator charging. So you may want to check the output of the alternator. If you’re getting much above 14 V then you may have a bad alternator voltage regulator.

[Thizzy]

Thank you I will go play with the voltage meter now and post an update

[Sunnyledge]

Another thing is to be sure the correct pump for your car is installed. Is is OEM (Bosch) or aftermarket. They all pretty much look alike, but you may have a pump that is producing a much higher gph flow. There are high performance pumps that can produce 2x the required flow. I still would suspect the fuel pressure regulator if you’re getting high pressures and the return line is clear. Could the vacuum line attached to the FPR obstructed?

[82eye]

you may have a pump that is producing a much higher gph flow. I still would suspect the fuel pressure regulator if you’re getting high pressures and the return line is clear. Could the vacuum line attached to the FPR obstructed?

agree with this.