Gone through 3 fuel pumps in 5 years... Need help diagnosing the problem. :(

[RenaissanceMan]

car is an e30 318is with an M50 vanos swap. still using the original 318 tank and in-tank pump setup. it is a track-only car and sees hard use on a regular basis. the problem always begins with the same symptoms... first, as an intermittent hard start issue (car cranks a long time before finally firing). this seems to happen more right after cool down after a hot track session. eventually, the car displays hard start symptoms every time. then, the car will next start to show loss of power symptoms at WOT. it acts like i have a failing fuel pump on the track (at WOT car will barely accelerate over 5000 rpms, if at all). this will begin as intermittent, and then will ultimately get to the point where it happens constantly if driven hard for extended periods of time. (by the way, i regularly have fuel starvation issues on the track if i let the fuel drop below 1/2 tank, so i try to avoid letting it get that low thinking starvation might be contributing to early fuel pump death...) i am getting ready to replace my fuel pump for the 3rd time, but have to believe that the problem starts elsewhere and ultimately destroys the pump. i have been trying to do some tests to figure out what the heck is going on. at my last track event, i had to bail on my last 2 sessions because i had absolutely no power past 4000 rpm and didn't want to risk burning up the motor. this last fuel pump (if it is indeed bad) only lasted me 18 months.

i connected a fuel pressure tester yesterday, and the readings appear normal. with the car off and the fuel pump running (by bypassing the fuel pump relay), i'm showing 51 psi. when i start the car, the pressure lowers to an indicated 41.5 psi. the bentley says 43.5 +- .9psi is normal, so i'm assuming my pressure is at least right now in the proper zone. also, fwiw, the car has not run since my last track event and is not currently exhibiting the hard start symptoms mentioned earlier.

another observation: as soon as i turn the car or the pump off, the pressure drops to zero immediately. i'm assuming that either the check valve in the pump is toast, or that i have some issue with the fuel pressure regulator.

-i don't see any leaks coming from the fuel rail or injectors. also, i'm assuming i don't have a vacuum leak, as the car idles perfectly and runs perfectly on a good fuel pump.

yet another observation: new fuel pumps make all of these problems disappear for at least a year and a half or so...???

so, i have questions, of course:

-if my fuel pressure regulator was bad, wouldn't it exhibit these symptoms regardless of how new the fuel pump was? the chain of events always seems to have the same order here, with the new fuel pump temporarily curing the problems?

-could fuel starvation on the track lead to this premature a fuel pump failure? that seems kind of hard to believe for me, considering the pump would only be in a state of 'dryness' for only a few seconds at a time in a single corner on most of the tracks i drive on.

-are there any other components i should be testing?

sorry for the very long post, but i'm pulling my hair out here... any advice and insight would be greatly appreciated!

[SamE30e]

Do you run the tank below 1/3 tank fairly often. The fuel actually cools the pump down, so when it's not submerged it tends to get hot and wear out quicker.

[Adrian_Visser]

paging jlevie...

(rust in fuel tank)

[Fidhle007]

Idiot check: How is your fuel filter?

Just for cheapness sake I'd throw a filter and regulator on there and just see where that leaves you. If it doesn't solve your problem, it should at least prevent others down the road. After that I'd start looking at something aftermarket perhaps, if you don't have any contaminants or rust in your tank that are causing the issues.

[BMW_TUNER]

How do you have the evap setup configured for the tank breather? This is a real issue that I have seen. If connected without a canister it will build a vacum in the tank and cause the pump to have to work harder and harder to pump the fuel thus killing the pump. Next time you drive the car take the gas cap off and see if you have built a vacum.