Turn off key, fuel drops to ZERO psi instantly. HELP!

[gcomfx.com]

I had a full w/e and decided the price was cheap enough for the fancy little hose shutoff so I can check it about anywhere there is a rubber hose and not worry about damaging the hose. It will be here Tues. Hopefully I'll be able to work on it this w/e. I just can't seem to find "time". Anyone have extra they could email to me?

 

[gcomfx.com]

Hose crimper is here.... now to track down the problem. You should have seen the look on the Oreilly's guys face when I told him what I was checking for.

Everyone one of them was a little shocked at my car symptoms and possibly resolutions, but all agreed it sounded like it would definately do that. I told them the power of the internet is a wonderful tool to find those of knowledge.

 

[FORCED2DV8]

I had the same issue, fuel pump valve was staying open. Do exactly what HISSIN said the best way to test if its the FPR or the pump.

 

[wytstang]

The little rubber baffle/nipple is not really important. It does slow fuel down coming off the return line. I lost mine when chasing a fuel problem (255 fixed mine) but since I'm good friend with some ford techs they had a spare off a focus. The driveabilty tech said there would be zero problems running the car with or without it. It doesn't help hold pressure or anything. Think of the rubber baffle as a gutter drain on a house, rain falling off the house can dig a hole into the ground....same difference except metal will take a lot more to dig as hole through, you'll change fuel pumps before you even scratch the metal.

 

[gcomfx.com]

I had the same issue, fuel pump valve was staying open. Do exactly what HISSIN said the best way to test if its the FPR or the pump.

So is the fuel pump "valve" part of the pump or part of the assembly you bolt the pump too?

In case it's too much to read through, I've already changed my pump and regulator, thus my confusion.

 

[gcomfx.com]

Okay, finally got an evening to check a few things. The car has sat in the garage for a week.

Just turning the key to accessories (turning on fuel pump) will yield little to nothing on the fuel rail guage. Key off, then back to acces. will show roughly 15 psi. Key off, then back to acces. fuel pressure will jump to 40 psi then drop to 15 suddenly... then to 10psi, and take aprox. 45 seconds to drop down to Zero.

I wasn't 100% which was the return fuel line, so I crimped off the top line (on strut tower) first. Really not much difference than before. It took three key turns to get the psi up to 40 with the same weird drop in pressure.

I switched to the other fuel line going to the front end of the rail. Didn't see any difference.

I can hear the fuel dumping back into the tank each time. I looked under the car for any sign of gas leaking on the floor. Didn't see anything.

I then decided to start the car. Turn key twice to get some fuel pressure reading and quickly went on to start the car. Fuel pressure that was falling like before jumped back up to 40psi and stayed there while the car was running.

The car had to warm up a bit before it started the poor idle syndrom. I let it run for 8-10 minutes.

This time I shut off the engine and instead of holding at 10psi for 45 seconds. It's back to instant 0 pressure.

 

[Jack's95gt]

I had a same problem twice. The first time it was the pump's check valve and the next time it was the hose right off the fuel pump blew a hole in it. You most likely change both of these a few times already.

 

[gcomfx.com]

So is the check valve IN the pump... or NEXT to it... or where exactly?

 

[BlackVert]

HISSIN50 says that the valve is in the pump.

There is a check valve in the pump to keep fuel from backflowing. The regulator can pass fuel and the injectors can dump fuel.
...

 

[gcomfx.com]

But I just changed the pump and was having the problems before, thus the reason I changed the pump yet again. This is my 3rd fuel pump in the car total. Stock - 190 - 255. There was absolutely no change between the 190 and the 255 in the idling or dieing situation.

 

[HISSIN50]

The check valve is integral to the pump. I will note that in all my reading of threads (I hate to post info like that, but how many pumps do we go through individually, except Paul, that is. ), that some folks on the Corral have reported that they thought their new Walbro pumps did not have a check valve since their pressure bled off almost immediately. Now per the factory manual, FP should not bleed off quickly (this is for quicker/easier start ups) but we know this depends more on the aftermarket FPR's than anything else (when a new pump has been installed).

A new pump should hold pressure though (those Corral folks might have had a FPR issue - that is just my conjecture).

Paul, have you rigged up your last pump on a bench, to see if it will hold pressure? The thing that would concern me (though I dont know how you tested it exactly) is that I think you said you crimped the supply line and noted no real difference. Unless your FPR and pump are both not holding pressure, you should see pressure maintain when one or the other line is crimped (sound right to you too?).

 

[gcomfx.com]

When I get more time, I'll test the old pump. I would guess I could just get it to pump some gas with a hose attached. Then put my finger over the hose and cut the power. Then check and see if it runs back through the pump.

My recent test of crimping the lines to me shows one of two thing possible, not mentioned thus far. One I have didn't get them fully crimped. I tightened the clamp down with plyers and couldn't turn the wing nut any further. Or two, I could have a tiny leak in the fuel rails or where the injectors are seated. I really don't see it being the injector seating as I've replaced the bottom intake gaskets thinking it might be a problem there. So the seating has changed and o-rings checked during all of this.

I don't actually smell gas anywhere in the engine bay when I cycle the pump over and over. But even a pin hole leak will relieve the pressure fairly quickly, I would think.

I think my next step will be to crimp off BOTH lines at once and see where that gets me. If I can tighten the last one down while I have the pump priming I had BETTER be able to hold pressure then correct?

 

[BlackVert]

a while back i had an extremely small leak in my fpr, but it was still very easy to smell the gas when i would open the hood.

if you had a leak somewhere, you would definately smell it, especially if it was large enough to cause the fp to go to zero immediately.

would it be possible to put in an in-line check valve somewhere after the pump to see if it changes things?

 

[gcomfx.com]

What gets me is the fact the FP didn't drop immediately when the car was cold. But then did after it had run for a little while. Kinda strange....

 

[chickendreamer]

I would doubt that it's the fuel pump since you already replaced it twice now. Can you think of any other modifications you've done since you started having troubles with the car idling rough? Also, tell me a bit about the tune you have, the mass air, the type of chip you have and if you've done any performance modifications after you got the custom chip.

 

[gcomfx.com]

I feel bad, I have time for the net while at work, but no time for my car when I'm at home.

The chip is just a stock superchip. It has been in the car since I've owned it and before I ever started modding the car. I pulled the chip out once and also tried a different computer during this mess without the chip to see if the car ran any different, and the only real difference I could find was my stock rev limiter is too low for the higher power band of the cobra intake and stall converter.

My tune is currently a little rich off the bottle and lean on the bottle according to the last dyno runs (before the 255 pump and second adjustable regulator). I'm either done with the dry kit or need bigger injectors.

My M/A and injectors were used when I bought them. While I was told they only had 5,000 miles on them - they very well could have more.

I guess I could spend an evening and swap the stock M/A and stock injectors back in.

 

[chickendreamer]

I guess I could spend an evening and swap the stock M/A and stock injectors back in.

You could try this, it of course won't be fun but at least you could eliminate the problem from the mass air and the injectors. You've already replaced the fuel pump twice, when you went from the 190lph to the 255lph there was no change so it really seems unlikely it was the fuel pump unless you damaged something while installing the fuel pump or you hooked something up wrong?

 

[gcomfx.com]

The more I think about this, the more I lean towards the injectors. On occassion the car would have a hard time starting like it was flooded like my carbed blazer will do on occassion. Could that be from a stuck injector?

I drove the car to work today, as I have to get it inspected and the tags renewed this month. I turned the key a couple of times before going ahead and starting it. It fired right up. I still have the surging going down hills when it's idling. I really didn't have many stops to test a dead idle though. I was doing 20mph in first and hammered on it, and it roared to life and spun and got sideways going into second. Injectors definately are not stuck closed.

 

[chickendreamer]

The more I think about this, the more I lean towards the injectors. On occassion the car would have a hard time starting like it was flooded like my carbed blazer will do on occassion. Could that be from a stuck injector?

I drove the car to work today, as I have to get it inspected and the tags renewed this month. I turned the key a couple of times before going ahead and starting it. It fired right up. I still have the surging going down hills when it's idling. I really didn't have many stops to test a dead idle though. I was doing 20mph in first and hammered on it, and it roared to life and spun and got sideways going into second. Injectors definately are not stuck closed.

Swap out the injectors and MAF for the stock one, at the same time pull the chip. It's not recommended to run an aftermarket chip if you have a nitrous kit installed, unless it's a chip with a custom tune on it. If you keep running that off the shelf chip it's just a matter of time before the engine takes too much detonation and you'll be building up a new engine. Keep us posted.

 

[gcomfx.com]

May not be recommended, but it's worked for 5+ years and a LOT of juice ran through it for 2 of those years. Ran 2 bottles a w/e for longer than I care to admit (threw away a lot of money).

My stock rev limiter is way too low to get the full potential out of my car. As a matter of fact I don't think I could race the car with the juice on. I'll hit the limiter in each gear which is MUCH more dangerous.

The car doesn't detonate with the timing dropped down as long as the plug gap is closer and the fuel pressure is up.

As far as building a new engine... that's been the plan all along anyway. The stock engine is close to 200,000 miles and I've never had the valve covers off.

I need to figure out the idling issue as putting a new engine in will most likely have the same results. I would rather find the problem BEFORE I have to swap engines.