fuel pressure drops when I give it gas and it builds boost - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 11 Old 07-15-2012, 10:17 PM Thread Starter
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fuel pressure drops when I give it gas and it builds boost

fuel pressure is dropping off when I get into the gas . Pressure is set at 42 and is fine at idle . Then I give it some gas and the pressure drops right down to like 20 which leans the motor out . I put a new 255 fuel pump and new sending unit and fuel filter . I unpluged the tps and there is no difference. Could that be the problem ? Or something else ??? PLEASE HELP ME

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post #2 of 11 Old 07-15-2012, 10:21 PM
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What kind of car/fuel system? You have a rising rate fuel pressure regulator with a vacuum/boost line connected to it right? Did it just start doing this or is it a fresh build/new combo?

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post #3 of 11 Old 07-16-2012, 03:13 AM Thread Starter
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95 svt cobra with a 60 mm turbo stock motor kirban regulator . Has stock computer no dyno yet

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post #4 of 11 Old 07-16-2012, 11:02 AM
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If you have the stock regulator laying around, I'd throw that back on it to eliminate that possibility.

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post #5 of 11 Old 07-16-2012, 12:25 PM
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Ok, you didn't answer a question above that is very important, do you have a vacuum line hooked between your intake plenum and fuel pressure regulator? If not, put it on immediately. Next, you say the pressure is set at 42, is that vacuum line connected or removed?
You said you put a 255 lph pump in, all 255's are not created equal. A GSS340 walbro is a high pressure pump designed to provide increased volume for power adder cars. Other 255's are not designed with power adders in mind and will allow pressure to fall off as demand rises. What part number pump did you put in?
Read this, respond with answers, and your car will get fixed quickly.

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post #6 of 11 Old 07-16-2012, 12:37 PM
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Originally Posted by meastang80 View Post
fuel pressure is dropping off when I get into the gas . Pressure is set at 42 and is fine at idle . Then I give it some gas and the pressure drops right down to like 20 which leans the motor out . I put a new 255 fuel pump and new sending unit and fuel filter . I unpluged the tps and there is no difference. Could that be the problem ? Or something else ??? PLEASE HELP ME
Sounds like a kinked fuel line. Recheck the fuel pump install
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post #7 of 11 Old 07-17-2012, 01:11 AM Thread Starter
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Originally Posted by Mustangmichael View Post
Ok, you didn't answer a question above that is very important, do you have a vacuum line hooked between your intake plenum and fuel pressure regulator? If not, put it on immediately. Next, you say the pressure is set at 42, is that vacuum line connected or removed?
You said you put a 255 lph pump in, all 255's are not created equal. A GSS340 walbro is a high pressure pump designed to provide increased volume for power adder cars. Other 255's are not designed with power adders in mind and will allow pressure to fall off as demand rises. What part number pump did you put in?
Read this, respond with answers, and your car will get fixed quickly.
Yea the vacuum line between the intake plenum and pressure regulator is hooked up . The tps checked out ok I did some voltage checks on it , and it was died on with the correct voltage numbers . As for the fuel pump its a new knock off ebay one . My buddy give it to me it failed on him in his turbo coupe after like a month I think . And he send it back and got a new one which is the one he gave me . I blew air in all the lines seem like there all cleand out now . The first air I put in the lines alot of rust came out , so I did it again . Seems cleaned out now . I am so lost with this this is my first turbo car and there is very few people that know anything about them where I am from .
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post #8 of 11 Old 07-17-2012, 02:06 AM Thread Starter
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Originally Posted by Mustangmichael View Post
Ok, you didn't answer a question above that is very important, do you have a vacuum line hooked between your intake plenum and fuel pressure regulator? If not, put it on immediately. Next, you say the pressure is set at 42, is that vacuum line connected or removed?
You said you put a 255 lph pump in, all 255's are not created equal. A GSS340 walbro is a high pressure pump designed to provide increased volume for power adder cars. Other 255's are not designed with power adders in mind and will allow pressure to fall off as demand rises. What part number pump did you put in?
Read this, respond with answers, and your car will get fixed quickly.
Could it be a voltage problem at the pump ? bad ground at pump ? how do i check voltage at the pump and what voltage should it be ? bad fuel pump relay ? Or could the regulator be cloged up cause there was alot of rust coming out . On the first start of the car it ran fine but had a fuel leak on the return at the tank . line had a rust hole in it . Changed the pump housing sending unit . In which I mixed up the neg and positive wiring on the pump . Could that have screwed up the relay ? or wiring ?
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post #9 of 11 Old 07-18-2012, 07:22 AM
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Sounds like maybe the replacement 'Ebay knockoff' pump is no good. Can you borrow a known-good pump to try out?
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post #10 of 11 Old 07-23-2012, 11:13 AM
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Could it be a voltage problem at the pump ? bad ground at pump ? how do i check voltage at the pump and what voltage should it be ? bad fuel pump relay ? Or could the regulator be cloged up cause there was alot of rust coming out . On the first start of the car it ran fine but had a fuel leak on the return at the tank . line had a rust hole in it . Changed the pump housing sending unit . In which I mixed up the neg and positive wiring on the pump . Could that have screwed up the relay ? or wiring ?
Doubtful it's a voltage problem, the pump is working. It's a pos pump. You've spent thousands on a turbo setup and a nice car, and you skimp on one of the things that can destroy it all. Order a GSS340 Walbro pump off line, install it, and replace your fuel filter, make sure you didn't kink any of the plastic lines(peel back the rubber tubing that covers it to verify no kinks). do this, and your issue will be gone.


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post #11 of 11 Old 07-23-2012, 12:38 PM
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Fuel Filter??

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