BIG fuel pressure drop at WOT?
BIG fuel pressure drop at WOT? I have read a **** ton of threads in searching that have had small pressure drops at WOT but nothing like this. I recently had my car go very lean at wot and found out that the fuel pressure is dropping from ~53psi at idle to as low as 30 under wot in the higher rpms. I don't think it was a gradual change either since I went from a steady afr on one pass to a VERY lean afr on the next. I have a racetronix pump in my car that has about 3k miles on it. I never put in a hot wire kit so I was going to try that but I don't think that's going to help at this point. I just changed the filter also but no change in pressure. It seems to me like the pump just took a **** but I want to make sure before I get a new one. What do yall think?
I checked all the lines I could see without pulling anything apart, didn't see any damage. I'll be pulling the pump when I get my work truck back and checking things a little more in depth. I guess if I don't find any visual damage I'll have to order a new pump and hotwire kit 
I replaced the pump a while back and just now got a chance to test it out and it's still dropping. I'm going to try to get the hotwire kit on tonight and see if that does anything.
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Mine was dropping with the stock pump and even after I installed the racetronix pump along with the hotwire kit. I ended up getting rid of the reg in the tank and went to a front mounted regulator to resolve the issue.
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Got the hot wire kit in a few days ago and it didn't help anything. Just got a new pressure regulator put in and the pressure is much better than it was. It now idles at 58 and stays above 55 while driving normally but it still drops down to as low as 44 psi at wot. I'm not sure what's going on with that but it's much better than the 30 or lower it was at and it's good enough now that I'm able to tune it to get the afr spot on.
You are risking tuning with low pressure as the tune is masking your pump problems. If the fuel pressure gets worse due to your current problem, you can hurt the engine. I suggest you try to fix the fuel delivery before doing any tuning.
I always have a wideband and fuel pressure gauge in the car so I'll know if it gets any worse. But I know I still need to find the problem so if anyone has anymore ideas I'm all ears. I'm going to pull the pump out again and check the regulator housing for cracks, I know I'm missing something.
Not yet, I'll try tonight. I did check it at idle though and it shows a little over 13 but it's only idling at 54-55 psi???
I also checked the pressure at the pump with a mech. gauge and it's only going to 65 psi when I prime it, shouldn't it be higher than that with this pump and a hotwire kit?
I'm thinking at this point there may be a problem in the connector at the top of the sending unit since it's getting good voltage up to that clip but the pump still isn't producing enough pressure. Any thoughts?
I also checked the pressure at the pump with a mech. gauge and it's only going to 65 psi when I prime it, shouldn't it be higher than that with this pump and a hotwire kit?
I'm thinking at this point there may be a problem in the connector at the top of the sending unit since it's getting good voltage up to that clip but the pump still isn't producing enough pressure. Any thoughts?
Found the problem... kinda. Tonight I capped the return line and hooked up a mech. gauge to the T fitting where the return was. This way I can start the car and check actual pump pressure at the same time.
Both gauges showed a steady 82 psi at idle so the problem is somewhere in the stock regulator housing or the return tubing inside the sending unit. Luckily I ordered a complete fuel system with new feed/return lines and an adjustable regulator last night so my fuel issues should be solved once and for all!
I want to thank everyone for their help and advice through all this, it was without a doubt the most frustrating problem I've dealt with so far.
Both gauges showed a steady 82 psi at idle so the problem is somewhere in the stock regulator housing or the return tubing inside the sending unit. Luckily I ordered a complete fuel system with new feed/return lines and an adjustable regulator last night so my fuel issues should be solved once and for all!
I want to thank everyone for their help and advice through all this, it was without a doubt the most frustrating problem I've dealt with so far.
Update:
I ended up testing it using the stock rails with a return coming from the test port into an adjustable regulator and back to the tank from there. After running it the pressure is still dropping at wot. So now it's pretty much narrowed down to the rails/pulse damper, feed side of the sending unit, or it's possible that the power to the pump is dropping at wot. I'm done messing with the stock stuff so I'm putting the rails and the rest of the lines on tonight, I'll post up if that fixes it.
I ended up testing it using the stock rails with a return coming from the test port into an adjustable regulator and back to the tank from there. After running it the pressure is still dropping at wot. So now it's pretty much narrowed down to the rails/pulse damper, feed side of the sending unit, or it's possible that the power to the pump is dropping at wot. I'm done messing with the stock stuff so I'm putting the rails and the rest of the lines on tonight, I'll post up if that fixes it.