fuel pump question ........again
08-28-2011, 01:49 PM
#1
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fuel pump question ........again ok so last week i had a fuel pump that was giving me hell (only 30 psi at WOT) so i was told it was a walbro 255 and what do ya know the previous owner lied once again, so i have the walbro in and the car still wont start after its hot, takes 2 or 3 times of cranking and it still barley starts, then this morning tried to start it and nothing just cranked and cranked.
Then went back later and fired right up,has 55psi pressure. So what am i missing, ive noticed that when i take the gas cap off a rush of fumes come out but its always done that
Then went back later and fired right up,has 55psi pressure. So what am i missing, ive noticed that when i take the gas cap off a rush of fumes come out but its always done that
08-28-2011, 09:09 PM
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i wonder what fuel sender is in it, since the LT1 factory has the fuel regualtor at the fuel rail while a 98 has a regulator in the sender assm, while the newer 99+ have the new style plastic pump and bucket,
sounds like you need an access door cut into the back so you can see what you have and we can go from there
sounds like you need an access door cut into the back so you can see what you have and we can go from there
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08-31-2011, 11:11 AM
#9
Did it have fuel PSI when it didn't start? You only specified that it did have pressure when it did start.
When a car does not want to start when hot it is generally due to fuel metering (metering not supply) as in a improper signal from a temp sensor, MAF or MAP sensor, or maybe something in the tune. Engine sensors like cam and crank sensors are a fairly common problem on vehicles that have a hot start issue as well. I haven't heard of it really on LS1 cars but I wouldn't rule it out either.
When a car does not want to start when hot it is generally due to fuel metering (metering not supply) as in a improper signal from a temp sensor, MAF or MAP sensor, or maybe something in the tune. Engine sensors like cam and crank sensors are a fairly common problem on vehicles that have a hot start issue as well. I haven't heard of it really on LS1 cars but I wouldn't rule it out either.
08-31-2011, 11:15 AM
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This... 
ok so last week i had a fuel pump that was giving me hell (only 30 psi at WOT) so i was told it was a walbro 255 and what do ya know the previous owner lied once again, so i have the walbro in and the car still wont start after its hot, takes 2 or 3 times of cranking and it still barley starts, then this morning tried to start it and nothing just cranked and cranked.
Then went back later and fired right up,has 55psi pressure. So what am i missing, ive noticed that when i take the gas cap off a rush of fumes come out but its always done that
Then went back later and fired right up,has 55psi pressure. So what am i missing, ive noticed that when i take the gas cap off a rush of fumes come out but its always done that
08-31-2011, 01:32 PM
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well im trying to find someone to tune the car right now, but yeah has fuel pressure at start up but like i said when its how it cranks and cranks forever. but when its cold it fires right up with no problem
08-31-2011, 03:15 PM
#12
Not sure if that answered what I was asking but another idea is that now you have nearly double the fuel pressure you did before, so you are dumping a lot more fuel. It may have been tuned before with low fuel pressure. So its very likely it is dumping way to much fuel now. The way fuel metering works is to dump more fuel when cold to aid with cold start. Try holding the gas pedal down about 10-20% while cranking it, this will allow more air in to mix with the fuel and it will probably fire right up. Basically it is flooding so it needs more air.
09-01-2011, 07:56 AM
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so last night i hooked up mt pressure gauge and at idle i have 60 psi and at wot i have 55, not when i killed it and tried to start it back up it wouldn't start and it has 60 psi, so then i was just gonna unhook the pressure gauge so i bled off the pressure and the car fires right up after that ? I tried it a few more times and every time i bleed off a little pressure it fires right up ? could the injectors be locking up ?
09-01-2011, 09:10 AM
#15
so last night i hooked up mt pressure gauge and at idle i have 60 psi and at wot i have 55, not when i killed it and tried to start it back up it wouldn't start and it has 60 psi, so then i was just gonna unhook the pressure gauge so i bled off the pressure and the car fires right up after that ? I tried it a few more times and every time i bleed off a little pressure it fires right up ? could the injectors be locking up ?
Try holding the pedal to the floor and cranking it, get all the air you can in to mix with the fuel and let us know how that works. It's starting to sound like a possible tune issue. Which you need to have it tuned anyway if you now are running more fuel pressure.
09-01-2011, 08:28 PM
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well tried the pedal to the floor and it doesnt start at all, the car runs strong as hell for what it has and then one day it started to lean out, so thats when i discovered that the fuel pressure was dropping off and right around the same time i started having starting issues with the car. im working on the tune but trying to figure out why all of the sudden it doesnt want to start first
09-01-2011, 09:08 PM
#18
well tried the pedal to the floor and it doesnt start at all, the car runs strong as hell for what it has and then one day it started to lean out, so thats when i discovered that the fuel pressure was dropping off and right around the same time i started having starting issues with the car. im working on the tune but trying to figure out why all of the sudden it doesnt want to start first
