After refuel, start up pulsing/ hiccuping

[stormtrouper7]

After i refueled the car(2001 540i) turned over and started but instantly it was pulsing/ hiccuping and the accelerator was also pulsing without any pressure on the gas, I turned it off within 5 sec of this going on and then i was never able to get it to start again. It was just under 1/4 of a tank when i filled up. I have been having problems with trying to fill it up all the way without the gas pump shutting off before it was full, i think its a siphon problem not transferring the fuel from one side to the other properly. Fuel pump seems to be working and battery is fine and the fuel pump fuses are good. I'm thinking maybe a fuel filter problem? Anyone else run into this before?

[Dave Sal]

Any thought that the fuel pump may have died? Have you checked for fuel pressure at the fuel rail? Any CEL or have you had the codes read? Also wonder if the fuel truck just refilled the storage tanks at the gas station and stirred up the sediment on the bottom of the tank and you got a tankful of debris which clogged your fuel filter.

[sleuth255]

... or a tank full of water. I think you may need to drain the fueltank.

[JimLev]

... or a tank full of water. I think you may need to drain the fueltank.

There should have been enough good fuel in the filter and lines for it to run for a few minutes.
Check the fuel pressure like Dave suggested.

[geargrinder]

Third assplanation: If the evap system is borked up it can suck a little extra raw gas through the evap plumbing. This usually manifests as runability problems like this only when the gas tank is totally max-filled.

Frankly sounds like you also may be an "over topper" which is not good on modern cars, as it can result in the evap cannister getting flooded w/ raw gas which can cause/exacerbate this problem.

Naturally theres all systems in place that in theory should prevent any of these problems and prevent you from messing things up too badly... but with the cars getting old... they can go bad.

The way to check that would be check the evap plumbing in the engine bay and see if it smells extremely like raw gas. I will say this though, seems like that happens more on I6's than V8's but still throwing it out there.

The suction pump side/side thing isn't an answer because that would be the opposite - when the tank is totally full it floods over both sides and can self level. That manifests usually as weird gas tank readings and running out with still something on the needle, or, sputtering here or there around corners as one side goes dry for a second.

I poo-poo the fuel filter idea myself. People (mostly old-timers who are thinking of how it used to happen all the time with metal gas tanks and rust BITD...) throw that out all the time but they are NEVER really clogged these days and its almost impossible for it to occur. The FF's on these motors are big enough to suck a dead cat through and not clog, and there's screens in the gas tank on the pump itself that prevent anything major from even getting that far, and anyway, gas pumps have big ass filters on them so the idea that particulate can be sucked out of the tank and put in the car anyway is impossible, and and.... OK I guess there's always the crazy outlier event so theoretically it could happen (it doesn't... but i guess it could...)

I'd be more likely to look for dead pump, which is more likely to happen "out of the blue on startup". Easy enough to test for fuel pressure at any rate.

Also... reading codes of course is always a good idea.

[edjack]

+1 on the evap system (having trouble filling the tank; that's part of the evap system, to vent the tank whilst filling), and jacking the nozzle to overfill.

[stormtrouper7]

I think your on the right track with my problem.

I probably did fill it up to max. When filling up if i had the gas pump handle all the way compressed it would click off about every half gal but, if i had it 1/4 of the way compressed and added fuel slowly it wouldn't click off as fast and i would be able to fill up very slow with maybe it clicking off a few times vs every half gal added.

Looks like i was wrong thinking my refuel problems were siphon, gas tank related. I had been adding some fuel injector cleaner in hopes of it cleaning up some gunk that might have been giving me the problems but it seems to be relating to an evap problem.

I connected 2 different code readers and both read error before finishing the diagnostic. One was an obd2 reader. I took the battery out to charge and will re try tomorrow, i thought it might have something to do with a low battery from the attempts to get the car started. tips on this one?

I am curious to think if the evap system did get fuel in it, if after sitting a few days it would reside and be able to turn over again? Does anyone know what part in the evap system to look at replacing first with this problem?

[JimLev]

What were the Pxxxx codes?
If it was an Evap problem you could pinch off the Evap line that connects to the pass side of the intake manifold. It's just behind the throttle body. That would prevent raw fuel from being sucked into the manifold if that was the problem.

[stormtrouper7]

I wasn't getting any codes, it read error/ unable to finish diagnostic. i think i may have a problem with the ecu in addition to a problem in the vapor system. I will be troubleshooting and looking for bad fuses/relays tomorrow so any tips/ advice is appreciated

[geargrinder]

Agree first order of business would be voltage. Is the car up in high 12 to 13 volts while you're scanning or did the battery droop while you had it turned on tryin to diagnose? Any rate you are on the right track there.

Per your description of fueling up - yes these cars for some reason at least IME can be fussy about the filler pipe and gas pumps - I think the filler pipe has bad flow or there's inadequate evap vapor flow or something for a high volume gas pump with a sensitive shut-off. I have to sometimes fuss at a real 'high volume' gas pump like you say to keep it from turning off but you don't want to turn that into over-topping.

Now while that would explain your issues with weird running after fueling up, I'm not sure a complete no-start now after sitting at rest is explained by that. So one possibility is there's 2 things going on - 1. either a flooded or broken evap system, and 2. some other no-start problem (i.e. indeed a dead fuel pump or something). Cars like to do that kind of effed up stuff to us just to keep us confused.

[stormtrouper7]

Turns out i had a blown fuse in the ecu relay. replaced it and the car turned over and ran like normal.