Desperate, can't figure out fuel issue!

[graphite9]

History...

So, I will try to make this sweet and short. My car is a 98 m3. I purchased it from a guy who mis-shifted and smacked the valves. Car is completely stock minus the conforti intake. I had the head rebuilt, new DrVanos stg1, H20 pump, therm, housing, belts, etc..etc.. Car runs amazing, smooth idle, no smoke, no cel's

Problem...

Takes 3 attempts to get it to fire after is sits for more than 3-4 hours. If I just try it once, and just keep it cranking, it will try to fire once, then just nothing, just cranks over. Second time, it does the same thing. Third attempt it fires right up. I did notice however, if I sit in the car and turn the key to prime the pump, 3-5x, it will start on the 2nd attempt.


When I checked pressure on the schrader valve, its 3.2bar, running, and with ign off, just primed. If I go out in the morning to head off for work, and bleed off the schrader valve, there's absolutely no pressure, no fuel. The pressure slowly goes away. about .75 bar/hr.

Parts replaced/checked

FPR (new)
Fuel filter (new)
(checked for leaky injectors, with pressure on the rail, they were all dry)

Clues?
When I bleed the pressure off the rail within the 4 hours of running the car, I get massive amounts of air coming out, along with fuel. But honestly its more air Sometimes I also hear what sounds like air being sucked in the tank when I prime it. Almost like a straw in the drink when your running out of water. Im seriously stuck here. Also, I don't throw any codes with my gas cap off (normal?) I don't know what else to check?

[markdas]

I'm assuming you have a single high volume/high pressure pump in your fuel tank. Have you removed this yet and inspected both the pump and intake screen or sock. Also have a good look at the tank and fuel condition?

It could be that you have an air leak somewhere in the fuel or vent flexy pipes....Im just trying to think if by some sort of venturi effect, the fuel could drag air in.....

I also assume your FPR is downstream of the fuel rail, hence controlling the fuel at the 3.2barg (about 46psi). Have you done a volume check.....see what the pump is deliveing in 30 seconds, I usually estimate about 1 quart (0.94 litres) in 30 seconds. Then see if you get the same volume after the FPR?

Check online and see how long you should be maintaining pressure in the fuel system......even if the pressure falls off, unless the fuel is draining or leaking out of the system, the pump will re-prime it instantly.

Have you done any other checks to ensure this is not an electrical or signal type issue?

Not sure if that helps much

Mark

[graphite9]

thanks for the reply! Seems near impossible to get help. Im on M3forum, but its extremely hard, people aren't as willing to lend a hand for some reason. Anyways, I tried two different fuel pumps in my car. I talked to a bmw shop today, and he said its completely normal to bleed off that fast. He said it he would have done exactly what I did, to diagnose the problem. He also thought I need to look into electrical. I just dont know what could NOT throw a code, and NOT affect the cars driveability. Its only when Its cold. MAF? o2? cts? I have a buddy with a couple $7k scan tools, but he doesn't know how to use them, and I don't know if he's willing to let me use them. Im computer and car saavy, but thats another realm.

[graphite9]

gonna clean my ICV, and look into how to test my cts.....Just did it, I cleaned it, but the ICV was spotless. My car has been sitting for about 3 hours. Unplugged my cts, and it fired right up, along with a CEL. I dont know id it was sitting long enough though. Im going to repeat the test in the morning, and if it fires up, Im gonna put in a new sensor.

Update. I unplugged the cts, and started the car. Fired up first attempt. So, I ran down to the store, picked up a new one. Put it in the car, plugged it in, and it took 3 tries again! I dont get it. With the sensor unplugged, it fires right up. With it plugged it, its hard to start!!

[graphite9]

Ok well I did a vacuum check. When I fire it up, and it stumbling around, I get 11-12hg. When the Idle levels out, It jumps up to 19hg. Does anyone know if this is normal?

[bemmer]

the vacuum jump think would be normal as the motor speeds up or quits stumbling try the carb spray test thinks this is best for checking leaks GL

[markdas]

Hmmm, not sure if the cts is causing or helping the situation? Do you have a cold start injector on your fuel rail?

Its' sounding like its not fuel related though?

Not sure about the vacuum figures? Just keep double checking you have no leaks though?

Can you do a compression test?

[bemmer]

had a problem with air also in fuel lines had gas but was low add gas no more air as with the pressure bleeding off seem that you might have a pin hole leak or something going on had a leak ta the T where the gas split off the rails and ICV not leaking till moved around and stopped when yet go open up many of there fuel line at auto wreckers where they have to remove all fuel / fluids and always still have pressure and fuel to injectors so losing some pressure might be normal but they hold pressure seems like forever or a long time back. to a leak problem I would think trace the line move or wiggle everything that will move look for build up or clean spot ? and best of luck maybe call a different dealer or go in and talk with the mechanic the sound in the tank sound like fuels to low or worst then that a leak or hole in the pickup line in tank