Fuel Pressure issues
Thread Starter
On The Tree
Joined: Jun 2006
Posts: 126
Likes: 0
From: Novi, MI
Fuel Pressure issues I did some extensive forum seaching, but have not found exactly what Im looking for.
I have a 1996 Firebird Formula with about 67,000 miles on it.
The optispark is a 1 year old, wires are about two years old, plugs are about a month old.
What happened was, I was driving normally and then my RPM's dropped and it felt as if my engine lost all its power, I managed to limp my car about a mile, the engine ran when i was coasting with the clutch disengade , but when i engade the clutch and applied power it just bogged down and just barely pulled.
I have ruled out ignition because i do have spark.
However fuel pressure is another story.
I hooked up a fuel pressure gauge got the car running and ideling very steadly at 1k rpm. The reading I got (with the vacuum line attached to the regulator) was a whoping 10 PSI. When I removed the vacuum line it held 10 PSI. The fuel pressure does not fluctuate at all it is locked at 10 PSI.
Now the question is, is the FPR diaphram stuck or is something wrong with the fuel pump?
I have a 1996 Firebird Formula with about 67,000 miles on it.
The optispark is a 1 year old, wires are about two years old, plugs are about a month old.
What happened was, I was driving normally and then my RPM's dropped and it felt as if my engine lost all its power, I managed to limp my car about a mile, the engine ran when i was coasting with the clutch disengade , but when i engade the clutch and applied power it just bogged down and just barely pulled.
I have ruled out ignition because i do have spark.
However fuel pressure is another story.
I hooked up a fuel pressure gauge got the car running and ideling very steadly at 1k rpm. The reading I got (with the vacuum line attached to the regulator) was a whoping 10 PSI. When I removed the vacuum line it held 10 PSI. The fuel pressure does not fluctuate at all it is locked at 10 PSI.
Now the question is, is the FPR diaphram stuck or is something wrong with the fuel pump?
Launching!
Joined: Jun 2004
Posts: 274
Likes: 0
From: nowhere
fuel preasure should be around 50 psi. my car did this exact same thing. good luck fuel pump is in gas tank. you have to drop it or you can do the gay cut a door in your hatch area. I did it all by myself for less than 120 bucks. good luck. ask if you have any questions i might be able to answer
Thread Starter
On The Tree
Joined: Jun 2006
Posts: 126
Likes: 0
From: Novi, MI
Now if the fuel pump died should the fuel pressure gauge read zero? Like I said, I do have fuel pressure just not much of it. Thats why i was leaning more towards the regulator.
BTW. When you drop the tank do you have to remove the rear axle? And would i need a lift or will i be fine with jack stands.
Thanks for the reply
BTW. When you drop the tank do you have to remove the rear axle? And would i need a lift or will i be fine with jack stands.
Thanks for the reply
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Staging Lane
Joined: Jun 2006
Posts: 53
Likes: 0
From: Queens, NY
well if you are gonna change the pump urself i would recommend the "trap door method". I just did it like a month ago and it was quick and easy. i got a nice stainless steel plate to cover the whole and closed it up with some insulation and zip screws. Now i have a trap door for the fuel pump just like every other car in the world.
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Verdad Gallardo Thread Starter
On The Tree
Joined: Jun 2006
Posts: 126
Likes: 0
From: Novi, MI
It was the Fuel Pump. I got a Walbro 255 lph from Detroit Speed Shop. I did the "trap door method"; work smarter not harder... plus its under insulation plus carpet so unless you tell someone no one is gonna notice. As far as Butchering the car, I used dremel with a reenforced cutting wheel, nice clean access hole. <3 hour job.
Thread Starter
On The Tree
Joined: Jun 2006
Posts: 126
Likes: 0
From: Novi, MI
o yea i used this as my guide and thats exactly how it looked when i got the door cut out.
http://www.geocities.com/formulapower2/fuelpump.html
http://www.geocities.com/formulapower2/fuelpump.html
Fuel pressure should be 45/47 psi (not 50), engine running with the vacuum hose off. If you clamp the return line shut and the pressure does not come way up, the pump is dead. If the fuel presusre spikes, the regulator probably has a broken spring.
If you have a fairly stock engine, I would just replace it with a new stock GM pump. More pump than you need will only heat up the fuel due to returning an excessive amount of un-needed fuel through the regulator and back to the tank. Absolutley no sense in pumping an excessive amount fuel in circles.
Btw, I would also think twice about cutting a hole that size in the floor of a uni-body car. I did it to mine, realized what I had done, and welded it back up. It's not that hard to drop the tank.
Good luck, Ed
If you have a fairly stock engine, I would just replace it with a new stock GM pump. More pump than you need will only heat up the fuel due to returning an excessive amount of un-needed fuel through the regulator and back to the tank. Absolutley no sense in pumping an excessive amount fuel in circles.
Btw, I would also think twice about cutting a hole that size in the floor of a uni-body car. I did it to mine, realized what I had done, and welded it back up. It's not that hard to drop the tank.
Good luck, Ed
While a little OT, how long should the fuel system hold pressure for after being pressurized with just turning the key on and allowing the fuel pump to prime and then shut the car off?
Originally Posted by buffman
While a little OT, how long should the fuel system hold pressure for after being pressurized with just turning the key on and allowing the fuel pump to prime and then shut the car off?
Many cars will hold pressure for hours after shutdown.
Originally Posted by Ed Wright
Many cars will hold pressure for hours after shutdown.
is it typical to loose some pressure Ed? Im trying to track down this weird problem I seem to only have in open loop after car has sat for a while. I threw the gauge on there today when I had some free time. Started at 42psi with key on, and 1hr 45 mins later I lost 8lbs (Looking for a leaking injector right now. They're practically brand new SVOS. I suppose I should pull the rail to check)
Last edited by buffman; Sep 21, 2006 at 07:18 PM.
Thread Starter
On The Tree
Joined: Jun 2006
Posts: 126
Likes: 0
From: Novi, MI
Im pretty sure that specific area (the rectangle above the tank) is not subjected to any significant load. I'm also pretty sure that, that specific area is subject to more load from groceries than car dynamics.
ANYWAY! as I have learned from this ordeal; this entire hole or no hole argument is like saying which catback exhaust better. Its all personal prefrence. I do not have a lift and did not feel like laying on my back all day so I picked the "trap door method".
Thanks for all the advice
ANYWAY! as I have learned from this ordeal; this entire hole or no hole argument is like saying which catback exhaust better. Its all personal prefrence. I do not have a lift and did not feel like laying on my back all day so I picked the "trap door method".
Thanks for all the advice
TECH Apprentice
Joined: May 2005
Posts: 349
Likes: 0
From: Mount Sterling KY
Hell with my aftermarket Aeromotive AFPR if I let the car sit for more than a half an hour my fuel pressure drops to 0. I have to turn on the ignition key, let the Racetronix pump prime and start it like a carbirated car by pumping the the gas peddle. Really sucks. 
HVY SS
HVY SS
Originally Posted by buffman
is it typical to loose some pressure Ed? Im trying to track down this weird problem I seem to only have in open loop after car has sat for a while. I threw the gauge on there today when I had some free time. Started at 42psi with key on, and 1hr 45 mins later I lost 8lbs (Looking for a leaking injector right now. They're practically brand new SVOS. I suppose I should pull the rail to check)
I wouldn't think that was excessive.
Originally Posted by hvyss
Hell with my aftermarket Aeromotive AFPR if I let the car sit for more than a half an hour my fuel pressure drops to 0. I have to turn on the ignition key, let the Racetronix pump prime and start it like a carbirated car by pumping the the gas peddle. Really sucks.
HVY SS
HVY SS
No more than you have there, you have no need for an aftermarket pump and regulator. I still have a stock fuel system on mine. Only the injectors are different.
Originally Posted by ws6chicken
Im pretty sure that specific area (the rectangle above the tank) is not subjected to any significant load. I'm also pretty sure that, that specific area is subject to more load from groceries than car dynamics.
ANYWAY! as I have learned from this ordeal; this entire hole or no hole argument is like saying which catback exhaust better. Its all personal prefrence. I do not have a lift and did not feel like laying on my back all day so I picked the "trap door method".
Thanks for all the advice
ANYWAY! as I have learned from this ordeal; this entire hole or no hole argument is like saying which catback exhaust better. Its all personal prefrence. I do not have a lift and did not feel like laying on my back all day so I picked the "trap door method".
Thanks for all the advice
Originally Posted by Ed Wright
I wouldn't think that was excessive.
thanks ed
The only reason I have a walbro fuel pump in my car was because I got a killer GP going for them on ISSF. It was such a good deal the vendor we went through was not allowed to discuss the purchase price on the forum!!
