Weldon 600-A PLEASE HELP!!!!!!!
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On The Tree
Joined: Jun 2002
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From: Jacksonville,FL
Weldon 600-A PLEASE HELP!!!!!!! O.k. i posted a while back about the pump not holding pressure when it initially did. Well today i was driving the car, trying to get in some break-in miles on the new set-up and my fuel pump started freaking out. (the pump only has like 100 miles on it) the pressure started going up and down from like 60psi to 20 to 40 to 0 and all over the place and also it got really freakin loud, then I pulled over and waited like 15 minutes and started it back up and everything seemed like it was going to be fine and two miles down the road it started acting up again the same way. Luckily i was able to make it home and I siphoned the tank and i am going to take apart the fuel system tomorrow but what in the hell!!!! I really think the pump is bad, I got it in the setup from Nasty performance,. I don't know of anything else it could be, the wiring is the same from the aeromotive a1000 i was using before, the tank was full of gas. Any comments or suggestions? Please? I am trying to finish this thing compleatly before G10 in atlanta but this type of thing keeps putting me behind. thanks, -Andy
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I think its your gas, not the pump. What you mentioned are the symptoms of cavitation brought on by heat, a high inlet vacuum performance pump and high volatility fuel (winter blend normally). Shuttingg it off allowed the fuel to cool down to a point where it stopped vaporizing in the inlet of the pump. You're in Florida and I'm sure the weather is pretty nice. Your fuel station might have got a deal on winter blend fuel. Times are tough all over. Call the gas station and see if they have received any complaints. Most people wouldn't have this problem with an intank pump and stock volume. The other issue may be if you're drawing through stock line, or pump into the weldon pump.
Look and see if your fuel lines run near anything the gets hot, like the exhaust and insulate if possible. This will help if your car has a return system.
Look and see if your fuel lines run near anything the gets hot, like the exhaust and insulate if possible. This will help if your car has a return system.
Thread Starter
On The Tree
Joined: Jun 2002
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From: Jacksonville,FL
I was thinking about it after posting today and there is something else that happened too that concerns me. the vapor tube on Nasty's tank is level with the filler. when I filled up, the vapor tube started throwing fuel all over the place. If the vapor tube was blocked, would that also cause these type of symptoms? the car does have a full -6 return and I did notice that when I siphoned the tank that the fuel was pretty warm. I have been driving like this for about a hundred miles and never had this problem. This was the first time I filled it all the way up though.
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If the tank ventilation is blocked a vacuum could be created in the tank as fuel is used. This would amplify the inlet vacuum situation created by the high volume pump. When pressure drops from vacuum the fuel will start to turn into vapor sooner. This is why people run pump speed controllers to reduce the amount of recirculated fuel that picks up heat from primarily the fuel rails. The speed controller will also lower the vacuum at the inlet as the pump isn't drawing as hard. Change fuel stations first.
Thread Starter
On The Tree
Joined: Jun 2002
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From: Jacksonville,FL
I always use BP for gas but i guess I could try another BP. Well i put 5 gallons in and road around today and everything was fine, i think it was the vapor tube being blocked by fuel that started all the problems. I guess i just can't fill the Nasty Performance tank up all the way. I know this tank is a quality piece but between the sending unit not registering until i have 5+ gallons in the tank and the whole vapor tube location thing, it is not as functional as I had first hoped. I do have a fuel system controller from aeromotive also. Thanks for the help andereck, i appreciate it
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Is the controller hooked up? If not I'd hook it up to rpm and set it so it doesn't go 100% until you're over your cruise rpm. The controller should really help. Also, what filter do you have on the inlet side? Do you know what the micron rating is?
BP is usually good fuel but these days you just can't be sure.
BP is usually good fuel but these days you just can't be sure.
Thread Starter
On The Tree
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From: Jacksonville,FL
Yeah, the controller is hooked up and it doesn't come on until around 3500 rpm. I had the 60 micron pre and 10 post. I switched the internals of the 60 with a 100 micron aeromotive due to weldons recommendation (phone conversation). You see, I kinda think the vapor tube location is a design flaw since it is level or below a little with the filler inlet. the vapor should be above the filler that way when the tank is full at the filler, it's not choking the vapor tube. If it wasn't so much trouble, i would rip the tank back out and find someone to weld a vapor tube bung higher on the tank.
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Well I am having problems with mine being able to maintain pressure also. 
But I will never fill mine to the top either. Because of that. But I ran the vent into the drivers side panel with a roll over vent valve and a k&n filter. But this fuel pressure **** is driving me crazy!
But I will never fill mine to the top either. Because of that. But I ran the vent into the drivers side panel with a roll over vent valve and a k&n filter. But this fuel pressure **** is driving me crazy! LS1 Tech Stories
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Originally Posted by andyws6
Do you have a picture as to how you ran your vapor tube with the vent and everything? What kind of pressure issues are you having?
Before I take it apart this sunday,I will take a pic for you
I think my weldon is bad. Cannot maintain 60 psi by 5200 rpms. 
Nate thinks its the pump and Im going with his reconmendation. 
Thread Starter
On The Tree
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From: Jacksonville,FL
Originally Posted by JMBLOWNWS6
Before I take it apart this sunday,I will take a pic for you I think my weldon is bad. Cannot maintain 60 psi by 5200 rpms. Nate thinks its the pump and Im going with his reconmendation.
I think my weldon is bad. Cannot maintain 60 psi by 5200 rpms. Nate thinks its the pump and Im going with his reconmendation. As of last night I am pretty sure it is that pump. Its starting to make a bleeding down noise and the more you drive the car and as soon as you hit it the pressure will drop flat on its face. The only reason I noticed it is because my buddie Shawn and I were doing some logging,tuning and when I hit it the fuel pressure was rock solid. The car was totally cold and as soon as she got warm fuel pressure falls. I drove the car 1 hr striaght just being really nice to it. Should not have a problem.
Last edited by JMBLOWNWS6; May 11, 2006 at 07:06 AM.
Thread Starter
On The Tree
Joined: Jun 2002
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From: Jacksonville,FL
It Happened again O.k. I was out today driving and everything was fine. I got to where I was going and then went to drive home and a mile from home the fuel pump started going crazy again. The tank is only half full so it's not the vapor tube this time. The engine temp was fine, I don't know what to do. Is it possible something is wrong with the pump? My aeromotive never once acted like this. I am really kicking myself in the *** for changing my fuel setup. Nothing is going right. I need this to be reliable!! What can I do?
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Loosen, but don't remove your gas cap and take a long cruise. If the problem doesn't reappear then the problem is with tank ventilation. Depending on the car this might set a check engine light but don't worry about that. Some vehicles run an emmisions test where a vacuum is drawn on the tank during a long drive to check the integrity of the tank seal and read a tank mounted differential pressure sensor.
