Mikelly Posted June 6, 2000 Share Posted June 6, 2000 We are now into the third month of lack of stable fuel pressure in the Z. Here is the problem: Motor holds 7.5 psi of pressure until about the 10 minute mark, then starts to slowly drop off... at the 30 minute mark the pressure drops off ot about 4-3.5 psi. This is when I shut it down... Here is what I have done so far to correct it: Replaced the Mallory 3 port regulator with a BG two port unit, with the proper BG fitting. No luck.. Replaced the pump and regulator with the Holley blue pump and regulator... No luck. Re-routed all the fuel lines so there is no heat issues... all lines are cold to the touch.. No Luck Added 10 guage wire to the whole system, including the pump, oil pressure switch, toggle switch... No luck. Added a painless wiring relay... No Luck. Reduced the line after the regulator from 8AN to 6AN... No luck. The only two areas we haven't touched yet are the fuel cell, an RCI aluminum unit, and the carb, a BG 750 double pumper... Could either be causing the pressure drop? I cannot seem to get the pressure to hold at idle. And obviously I can't drive the car, 383 stroker.. without the stable pressure... the few times I did.. the motor was starved. Mike ------------------ "I will not be a spectator in the sport of life!" mjk Quote Link to comment Share on other sites More sharing options...
Mike kZ Posted June 6, 2000 Share Posted June 6, 2000 Why don't you try calling B&G's tech line, maybe they can figure it out. Quote Link to comment Share on other sites More sharing options...
Guest RyalC Posted June 6, 2000 Share Posted June 6, 2000 Mike - have you checked your vent valve on the fuel cell to see if it is working? I could envision a scenario where the fuel pump would have problems if the vent valve was not "venting" and a psuedo-vacuum was being created. Just a wild thought. Quote Link to comment Share on other sites More sharing options...
Mikelly Posted June 6, 2000 Author Share Posted June 6, 2000 I'm gonna investigate that again this evening. Spoke with the president of AED Carbs and he advised me to do just that. I'm gonna get the car running for about 15 minutes, just enought time to allow the pressure to start to fall off, and then I'm gonna open the bail on the cell. I'm gona see what happens when I do that. If it rises, then I'll know that the cell roll over valve will allow fumes to vent, but not allow sufficient air back into the cell... I'll be doing away with the vent roll over valve and plumbing in a try vent. Mike ------------------ "I will not be a spectator in the sport of life!" mjk Quote Link to comment Share on other sites More sharing options...
MYRON Posted June 6, 2000 Share Posted June 6, 2000 Mike, I am using the stock tank and vent system. I do have a sump with the #8 AN fitting coming out of the tank... No problems here... I was messing around with it the other night and was revving the engine to 6500 and the pressure never dropped below 6.25 psi Quote Link to comment Share on other sites More sharing options...
John Scott Posted June 6, 2000 Share Posted June 6, 2000 A last shot in the dark. Kenne Bell makes a cockpit controlled pump voltage stabilizer. Says it will keep pump voltage within 1%, eliminates fule pressure drop off, adjustable between 1-50%. Never heard of the thing 'till I ran across it in a turbo mag. 909 941 0985 (tech) JS Quote Link to comment Share on other sites More sharing options...
Mikelly Posted June 7, 2000 Author Share Posted June 7, 2000 Chris C. came over last night and we checked a few things out. Opened the filler on the fuel system after the car was running for 10 minutes and the pressure had fallen to about 6 psi, a drop from 7.5psi. It didn't recouperate. So Chris is in the middle of searching for a carb for me to try. We now think that it might be the carb... We'll see. I'm also gonna grab a can of gas, run a line form the inlet of the pump to the can, open the vent on the can and see what happens. At this point I have narrowed it to the carb or the cell. I checked the volts at all connections after 30 minutes of running and the readings at all electrical points were 13.78, more than enough to keep any pump running at max volume. Mike ------------------ "I will not be a spectator in the sport of life!" mjk Quote Link to comment Share on other sites More sharing options...
DennisK Posted June 7, 2000 Share Posted June 7, 2000 Mike-I'm impressed! You seem to work well UNDER pressure!!! Quote Link to comment Share on other sites More sharing options...
Mikelly Posted June 7, 2000 Author Share Posted June 7, 2000 I'm just running out of clues at this point... hopefully we have narrowed it down... Mike ------------------ "I will not be a spectator in the sport of life!" mjk Quote Link to comment Share on other sites More sharing options...
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