I'm really getting tired of this. I've had this tank out more times than I fill it. Anyway. I changed the pump...again....last summer. Car maybe has 500 Kilometers on that pump. Yesterday I was out and about, and the car sputtered for a couple of seconds, then stalled. By the way its EFI, not carb. 1987 5.7 GTA. I had a look under the hood at the fuel rail pressure gauge and it was reading about 5 to 10 psi with the engine barely running and stalling out. I removed the gas cap and a lot of pressure released from the tank. Not sure if thats normal. I Let it sit for 10 minutes and tried again. It started and pressure was back to 45psi. I drove for about a minute and it stalled again, no pressure on the rail again. Let it sit for about 5 minutes started again and drove for about a minute then the whole process repeated itself until I finally limped it home. The whole time this was happening I could here the pump prime, even though there was no pressure on the gauge until I let it sit for a few mins. Have I gone through another pump again? I did use a cheap ebay pump because I was sick of spending a lot of money on them and not having them last. I did think of vapor lock, however not likely under a fuel injected engine, and this has never happened in the 14 years I've owned the car. I should add that I'm just under half a tank, so there is enough fuel in there for the pump to operate.

 

Try replacing your gas cap. If it doesn't vent properly, that fits your symptoms.

 

It's not a vented gas cap on this car. Would tank pressure not actually help the fuel pump? As far as I know the EVAP system is working. I believe that system is supposed to deal with pressure release so as not to release to atmosphere. I've had this burst of pressure for as long as I can remember. It's never seemed to be a problem in the past. Thats why I'm thinking a bum pump is at fault.

 

im experiencing the same problem. if i let it sit over night im right at 43psi. the walbro 255 has about a few thousand miles on it. new filter relay afpr...

 

It's killing me. I've been through 4 pumps. Now I'm scared to drive it anywhere. It's not the lightest car to push around. I did some reading and have determined the oil press switch will not cause this problem. Yesterday I watched it happen. I got it started up and had 40 some odd psi. Then it dropped to 10psi instantly. Stalled seconds after that. Pump primes and no pressure. Two things come to mind. Pump is leaking in the tank, or pump is failing do to heat build up. Leaking in the tank would be chronic, and would never, ever build pressure. Cheap offshore fuel pump made in the same chinese factory that builds toasters? Also will lead to a pressure problem.

 

Did some troubleshooting and heres what I found. Warmed up the car. 30 mins at idle and sure enough it stalled. Lost all fuel pressure quickly. I let it sit a couple of minutes, no more than 5. Pressure returned so I pinched the pressure line, and pressure bled off. Primed the pump again and pinched return, pressure bled off. Primed it again and pinched both pressure and return at the same time locking the fuel in the fuel rail and pressure bled off again. Only place for that to go is injectors. Can and injector(s) leak to that degree? When the car is running I lose all pressure. Thats a massive leak. If thats the case, why only after 30 mins or a hot engine? For that matter, when pressure does return, it's only after 5 minutes, and thats certainly not enough time to make a difference in temperature.

 

i know your looking in to your fuel leaking or bleeding off somewhere, but for the heck of it did you ever replace the fuel filter.

also i never had this problem with my car. it was around the same time when i relocated my coolant over flow tank, made a homemade cai, and i had the charcoal canister out of the car for a few days. dont know much about these things but maybe i pissed it off?

 

I disconnected the fuel pressure line and gave it two shots of prime. I came up with 6oz of fuel. I then reconnected and the problem has not returned. I notice some crap in the fuel so I went and changed the filter. As for the old filter, I could barely blow through it at all and that required straining. The new filter has free flowing air both dry and wet with fuel. I went and disconnected the fuel pressure line again and did another two shots of prime with the key on. This time I flowed 9oz of fuel. Thats pretty significant. Performance was up substantially. I still have a leak down somewhere. I'm thinking injectors but I dont think thats why I had the stall condition. I'm wondering if the filter was so plugged that it choked off supply? I just cant figure out why it took 30 to 40 minutes to occur. Also the fuel in the container I was using was quite warm. I think I may have to wrap the mufffler.

 

this makes me want to change my filter again. just to see if it has a restriction like you've experience. its not all that unlikely that if theres crap in the system one filter might not be able to trap it all. might take a few filter changes. i went to see my car today primed it and guage reads 50psi. had no time to start it up.
btw did you drive it yet, or still want to wait and see what else turns up?

 

I idled it for over an hour without fail. Drove locally and its running very good. Im pulling and testing the injectors tomorrow

 

im changing my filter tomorrow, should i prime and flush too? i became a caa member this week because im expecting the car to die in a bad place.

 

You could see what you get out of it. First I ran two primes worth of fuel into a container, then poured it into a measuring cup. I had 6oz. After the filter I split the line again and did two primes into the container, poured into the measuring cup and got 9oz. Pressure is up as well. I think I'm going to go with CAA as well.

 

I see that a lot has happened since my last post. Your more recent information led me to suspect a bad fuel filter, and the fact that you can't blow through the old one tells me that the filter was the problem. Your injectors MAY be leaking down, but I am certain your pressure issue was the result of a clogged filter.

 

I did some more testing this morning. According to the Pontiac service manual minimum pump flow over 15 seconds is 0.25 Quarts. I'm flowing 1 full Quart in 15 seconds. Thats 4 times the minimum speck. However I still have a leak down problem.

I pulled the injector rail and not a single drip from any of them. But yesterday on a hot engine I had a very fast leak down with both return and pressure lines pinched off, leaving only the injector as a leak source. Can these injectors have a leak when they are hot? On initial prime I see over 60PSI at the rail, then that drops off to 22PSI quickly. Yesterday it fell right to zero. So the pump is allowing bleed back at the higher pressure, that Im not concerned with. I am concerned with the total loss of pressure on a hot engine.

 

Did you check that little tank vent thingy back at the gas tank? If its working, you shouldnt be getting pressure release when you open your cap......

 

I thought that let air into the tank? Is the EVAP system not responsible for tank venting so as not to vent to atmosphere?

 

You may be right on that.....i was just trying to think of some more possibilities....

 

this morning i backed up on some ramps changed the fuel filter, primed it to flush alittle and there was a few little grains of black crap in the fuel. fired it up. ran normal fixed a vacuum leak from and injector. decided to take a trip around the city. drove for about 25min doing about 120kms. started to feel the car wanting to die. pulled over:

-as soon as the car sits at idle when this problem is occuring it usually dies within under 1min

-primed it again... get out of the car to check the fuel rail pressure 10-psi

-wait 10min 43psi

-drive for 5min pull over to let it die... before it died i was under the hood and reving the throttle the pressure guage would increase as i rev it up more than it should! but still i was lucky to be at 30psi at this point

-sat for 10min fired it up 40psi drove home (2min away) pulled it in the driveway as it died.

now every time i would prime the pump i would listen for it. it sounds quiet and sick. this is the walbro unit. my old one i remember it to be much louder. most likely the design not trying to compair apples to oranges.

if i have crap in the tank can this destroy the pump?

this sucks!

 

It shouldn't. That's what the strainer is for on the pump unless it's fallen off or so severly clogged fuel can't get through, although I can't see how that much dirt would get in there. Do a flow test. Unscrew the fuel pressure line up front. Put the line in a container. Attach a wire from battery 12 volt to G terminal on the test connector under the dash. That will run the pump. Run it for 15 seconds. You should have a minimum of 1/2 pint of fuel in that container.

 

where do i find the test connector/ what does it look like?

 

No test connector. Disconnect the fuel feed line at the front of the engine by the left wheel well

 

im good with the fuel line but to feed the 12v so i can prime the pump for 15seconds. its under the dash and im looking for a test connector? ill have to check next time im i work it. sounds easy

 

By the drivers right knee. G terminal is bottom left corner when looking at it

 

at the moment im working on my car, i connected the g terminal to the positive terminal on the batt. this is the same as turning the key forward so did not have the benifit of running for more that a few seconds at a time. but there was no crap in the fuel. so i re attached the line. and ran the car in the driveway for 20 min. the temp increased, eventually the car lost fuel pressure. so i started to bleed the line at the fuel rail. noticed that the pressure guage would not drop past 10psi as it seemed to almost have air in the system or boiling from my exhaust. this must be a clue! what do you guys think?

 

I believe if the black vent by the charcoal canister and the plastic white vent by the gas tank are not working properly then EFI fuel pumps die prematurely because they have to work harder. Also letting the fuel level drop below 1/4 tank in-between fill-ups isn't good for it either because the gas keeps the fuel pump cool. If the charcoal canister vent isn't working properly then there may be a very long hissing sound after the gas cap is open.

 

how do i test this canister or know if its working correctly? i had the thing out of the car and may have connected it wrong. before this it was running fine!

 

I don't know about the canister itself, never had trouble with that. I have a haynes manual for 93-02 f-bodies and it says that fuel odor in the engine bay is a symptom but does not say anyway to test.

The small black vent by the charcoal canister or its more formal name, the evap pressure control valve, usually gives the symptom of the hissing from the opening of the gas cap for a few seconds. It runs about $25 off of ebay but can also be bypassed. Just put a hose in place of it and see if the hissing stops on a very warm day. A lot of people do bypass it or remove/bypass it when they do an engine swap. If its installed and working properly it only opens when pressure gets too high and maintains the right amount of tank pressure.

 

pressure is a measure of RESISTANCE TO FLOW
your symptoms sound like a defective fuel pressure regulator, or vacuum line to it to me, but a few tests will tell you the source of the problem so test don,t guess



http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf


http://forum.grumpysperformance.com/...hp?f=55&t=1241

 

I had a problem with the pulsator on my car, I never knew to remove it and replace it with that short hose u get with a new fuel pump. I took it back out and never had a problem again.

 

where do i find the pulsator valve?

 

Its connects the fuel pump to the sending unit.

 

Pulsator, if leaking should cause the problem all the time. At least I think it would. I took mine out when I did the fuel pump change. I'm going to run checks on the EVAP. My gas tanl almost blows the gas cap across the gas station if Im not ready for it when I open it. That cant be good

 

My car acted the same way as yours.

 

i called aeromotive support today, they said i should try driving my car with the gas cap off. worth a try

 

I drive mine all the time it a little loose.

 

My EVAP checked out perfectly, however I did find a vacuum tube burned right through underneath the plenum. It was resting against the EGR valve. This line is tee'd into the line thats connected underneath the Thottle Body. That tee'd line goes right to the gas tank pressure control valve. It applies vacuum to the valve in order to allow the vent hose from the tank to vent to the EVAP can. With no vacuum the line stays closed, and the pressure builds in the tank. Took it for a drive. It no longer sounds like an angry freight train when I take my cap off. There's a little pressure release but it's not blowing my har back like before

 

Just an update on the pressure problem. The 10+ PSI drop when the car warmed up was due to the oil filled fuel rail gauge. They are garbage. This was a problem on the Mustang, Audi, Toyota, and Jeep forums. All of them were experiencing the same issues with the oil filled gauges. I drained mine this morning and its holding set pressure hot or cold. Its dead steady now. I was chasing ghost problems as far as pressure was concerned due to that damn gauge.

As for the original problem; I believe that was a fuel filter. I have changed injectors and fixed the vacuum leak to the EVAP. So far everything is running great. Best it's ever been

 

glad to hear about the car edge! as for mine ive driven it with out the gas cap on and it has no effect on the system. im going to change the filter again and ensure theres no crap in the line. then drop the tank and see what happens.