BOSS 357

iTrader: (1)

1989 Firebird Formula TPI

Four years ago I replaced the stock fuel pump due to a faulty pulsator (which I eliminated) with an Edelbrock/Warlboro 67 gph unit, which has run flawlessly until I replaced the stock engine harness & ECM with the EZ-EFI system.

That pump is the subject of my issue and question. In short, it will run between 40-85 minutes and then the pressure, almost abruptly, falls off and the car dies. For the time the car is running, it will start at cold idle w/ 36psi (44 WOT) and eek it's way down to 32psi at it's hottest point, shortly before totally giving up, which takes about 15 seconds to go from 32 to 10 or less.

Let me give some background as nothing here is stock. I did make the switch from the stock ECM to the EZ-EFI system, which works great. The wideband O2 really helped me diagnose the fuel pump quickly. With that, the EGR is gone and the charcoal canister was eliminated. The tank used the stock gas cap and the former canister purge line now runs from the sending unit through a rubber line, into the pressure release valve (formerly beside the canister) and out through a small length of hose by the filler neck. Kind of venting where a true vented gas cap would. My exhaust is true dual and dumps before the axle.

The conditions surrounding the issue have been documented pretty thoroughly. After driving in 95*+ heat for a couple days, the car would die after about an hour of spirited driving, once leaving me to find a tow home. I tightened up the headers which seemed to help part of the problem. I took it out and twice more the car died after the same time frame. While it idled, I hooked a pressure gauge up to the rail and noted the pressure decline, the shut-down interval was the same. However, with the hood open, I couldn't get it to stall. I closed the hood and moved it out in the sun and it died w/in 50 minutes. Water was about 215 each time the car died.

I called Edelbrock (pump dealer) and apparently I stumped every tech in the room. Eventually the fella said that heat is not an issue for these pumps and that my tank may not be breathing properly and to try using the stock gas cap (was using a pre-vent style Stant cap). I tried, it stalled again (warm restart) after 40 minutes. The vent line is letting vapors out, I can smell them and they are warm. When I remove the cap, I get the woosh of warm smelly vapors exiting the tank. I do not hear any liquid burbling nor do I hear the tank itself expanding or contracting. I have tried running the car without any gas cap and get the same results

What I've noticed is after letting the car cool, I will get successively more line pressure at prime. 5 minutes of cool down will get me 20 psi, 2 hours 30psi, overnight and I get the full hour (wow!) of run time. The low-pressure prime exhibits a higher pump whine sound note than normal. Full pressure and it sounds normal. With the car off, any pressure in the tank begins to decline almost immediately. With KOEO and prime, it will hold pressure for about a minute and then slowly begin to decline.

I'm concerned and may well be wrong, but please set me straight.
-w/o EGR, is it getting so hot that exhaust is heating the pump or vaporizing the fuel in the rail?
-could my pump be getting too hot?
-is my ventilation setup correct?
-please don't tell me I need to replace the pump again!

Jordan87TA

I was having this same problem!! I replaced my ignition module, and now my car runs like a champ in 90+ degree weather for hours!