Pressure dropping under acccel.
Pressure dropping under acccel. Ok have a cammed 2001 SS. When I did the cam I also threw in a hot wire kit and 255 walbro. When I had it tuned the tuner Jeremy said that he had to put in some large values to get the a/f right. At the time I didnt think it was a pump issue but I just installed a fuel pressure gauge and it takes a serious dip after 3000. Idle it shows a touch over 50 psi I would say 52. After 3 it drops quick its down to around 30psi by 5500.
I have no idea where to start. So some input would be well recieved here just need to know what to eliminate first. New hot wire and new pump so go from there.
Ground
Pump
Filter- New filter so not the problem
Voltage
Regulator
Thanks for your input, Eric
I have no idea where to start. So some input would be well recieved here just need to know what to eliminate first. New hot wire and new pump so go from there.
Ground
Pump
Filter- New filter so not the problem
Voltage
Regulator
Thanks for your input, Eric
My car has been doing this exact same thing for the last few months. Even posted a thread on it a while back https://ls1tech.com/forums/fueling-i...-drop-wot.html
I've checked and replaced everything but the FPR and that should get here tomorrow so I'll know by tomorrow night if that's the issue. I'll let you know what I find.
I've checked and replaced everything but the FPR and that should get here tomorrow so I'll know by tomorrow night if that's the issue. I'll let you know what I find.
Even your base pressure is too low (it should be around 58 psi) - you'll need to get in the tank sooner or later. I'd check the internal connections first - the regulator is a pretty low tech piece of equipment in the tank, so the chances of it failing I'd say aren't quite as good.
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Even your base pressure is too low (it should be around 58 psi) - you'll need to get in the tank sooner or later. I'd check the internal connections first - the regulator is a pretty low tech piece of equipment in the tank, so the chances of it failing I'd say aren't quite as good.
Both have new filters.
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Your symptoms indicate (one of a few reasons) too small a fuel pump -- as engine's consumption (and possibly fuel pressure, if boosted) rise there is not enough fuel in the system and this causes the fuel pressure to drop. The pump in its present configuration cannot keep up with the demand of the engine.
Your symptoms indicate (one of a few reasons) too small a fuel pump -- as engine's consumption (and possibly fuel pressure, if boosted) rise there is not enough fuel in the system and this causes the fuel pressure to drop. The pump in its present configuration cannot keep up with the demand of the engine.
Yes, a single 255 will support way more than a typical heads/cam car will require. Typically in excess of 550rwhp at a 58psi delivery pressure.
If you have a serious pressure drop at 3000rpm, there is no way your engine needs this much fuel at this rpm/power level.
If you have 50-52 at idle you have a problem. Stock pump should have about 58psi, a good 255 should show approx 62psi at idle.
Typical problems are:
An internal fuel line leak (rubber lines are often the cause)
A bad regulator or a piece of dirt in it caused during pump replacement.
A loose connection at the hose connection in the tank.
A bad pump usually just stops working, but also can be the cause of this problem. I would look at the other items first.
The lack of pressure at idle is a very good indication of another problem as the car consumes almost no fuel at idle.. like 5hp worth of fuel. It is likely bleeding fuel off somewhere.
If you have a serious pressure drop at 3000rpm, there is no way your engine needs this much fuel at this rpm/power level.
If you have 50-52 at idle you have a problem. Stock pump should have about 58psi, a good 255 should show approx 62psi at idle.
Typical problems are:
An internal fuel line leak (rubber lines are often the cause)
A bad regulator or a piece of dirt in it caused during pump replacement.
A loose connection at the hose connection in the tank.
A bad pump usually just stops working, but also can be the cause of this problem. I would look at the other items first.
The lack of pressure at idle is a very good indication of another problem as the car consumes almost no fuel at idle.. like 5hp worth of fuel. It is likely bleeding fuel off somewhere.
Last edited by Lonnies Performance; Feb 5, 2010 at 06:00 PM.
Just got the regulator 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.
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i got a 2002 silverado doing the same. mine was idling@30 psi and dropping as low as 20. i put new fuel pressure regulator and was idling at 45psi then dropped after like 3 min to 20. while driving, it wont let me rev to 3000rpm. idling i can rev to 5500 but pressure drops to like 15. im going to pull out old pump and install new one. this should eliminate problem??
GOT IT! (post from my thread)-
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.
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.