Rookiedyn

Hi a few of you know from my earlier posts that back in July I had a problem with my fuel pressure dropping at random intervals and the car nearly stalling. I took my car to the tuners where he was unable to duplicate the problem. (I drove it there 70 miles without a problem as well.. go figure).

Anyway they tested all the grounds and looked for all obvious electrical problems etc. Finaly we decided it wouldn't hurt to upgrade the fuel pump. I opted for the Racetronix pump as we would be eliminating all the stock wiring in between as well. I also bought a new fuel filter (even though the car only has 6k on the odo.). After waiting a while to get the parts and time for my tuner to get to it everything was installed and looked good 66 pounds of pressure etc.

Now the saga continues. As my tuner was backing the car on the Dyno to fine tune to take account the higher fuel pressure the car did the same thing. Dropped pressure to the point of almost stalling then after cycling through that a few times is running fine.

My tuner is now suspecting the siphon pump or check valve in the right tank as a possible culprit but is not sure because he hasn't seen this problem before. I don't blame him because the last time I posted here no one seemed to have heard about it either. GM says check the emergency brake. :skep:

Heck at this point I am willing to give a reward to the person that can narrow down the problem so I can have my tuner correct it before the snow flys up here :lol: Its getting frustrating. Should I just go ahead and have them replace the siphon pump (jet pump)?

Help!




[Modified by Rookiedyn, 9:33 AM 8/27/2003]

AC54ME

:lurk:

Rookiedyn

Ok I found my original thread in the archives. I will post the link here if anyone cares to give an opinion. I really hope one of the tech sleuths on the board can give me some good advice.
http://forums.corvetteforum.com/zerothread?id=608963

thanks!

luvinc5

I wish you well in your quest for a solution.

This may sound futile but check all grounds are tight. A slightly loose ground can cause intermittent problems.

I had a problem with the car hesitating, initially. The cause was a broken ground wire connecting the left fuel rail to the back of the head.

Buckmaster

Damn :( ttt for ya

Rookiedyn

thanks guys..

::Bump::

Anyone?

SFVetteman

I don't believe it's the siphon pump because it's mechanical amd mechanical pumps either work or don't work or don't work very well. They don't act sporadically. More importantly since you've had this problem with a full or nearly full tank it wouldn't matter if didn't work as the fuel level would equalize and there would still be a lot of fuel in the left tank.

The check valve might be worth looking into but I would also check the fuel strainer in the left tank. Perhaps it is becoming blocked at times from something in the tank.

Bugster57

Just some fodder for thought, sorry but I don't have enough time to search the boards this minute but wanted to lend some encouragement for your problem.

Can you mount a remote fuel pressure guage between the fuel tanks and the filter? The 2000 and above have a regulator in the filter I believe, has that been replaced?

I'd probably drain and drop the fuel tanks and do a little exploratory. I've heard stories of siphon lines/screens being obstructed. The tank arrangement is far too complicated on these cars.

I'll dig more later when I have time.

Also search this and other boards for fuel tank issues,

0vetteshop

The siphon jet pump in the right tank simply transfers fuel to the left tank and would have no effect on performance.If fuel wasnt being transfered from the right tank to the left tank (the one that feeds the motor),you would have a fuel gauge issue :yesnod:

If you are sure that it is fuel pressure related,and you have replaced the pump and wiring,I would suspect the PCM...You need to hook up a scanner so you can monitor PCM fuel pump voltage :yesnod:

tomdcarguy

Had a very similar case a couple years back.... took a good hour to norrow it down... But try this..... runn the car at idle... open the hood and remove the fuse box cover.... wiggle the box a bit and tap on it as well... In my case the customer had a slight open intermitantly caused by frequent relay swaps to keep the fans running at the track. The fuel pump relay is right next to it...Not saying this is your cause, but try it..Its free!!! GOOD LUCK :thumbs:

Rookiedyn

Thanks a lot guys. I forwarded every bit of advice to my tuner. This is getting to be a real pain but we have to be close to the solution.

C-5 Tech. thanks for checking in I appreciate it. I read a ton of your posts and you know your stuff thats why I figured I would give you a shout. My tuner tells me "We have a volt meter hooked to the pump to check voltage but the problem has not reoccurred." Is that what you are refering to?

thanks!

Racetronix

The Racetronix harness is triggered off of the factory harness that is in turn controlled via the PCM and a relay. Perhaps the PCM or factory relay is acting up? Contact support@racetronix.com as we have some harness interface test adapters that will allow you to monitor the fuel pump voltage while you are driving provided you have a DVM. This will allow you to rule out voltage / control issues.

sffish

I've got a similar problem and replied to your previous thread as is. I had the fuel pump replaced at a shop and the car ran well after that. I picked it up Tuesday and drove it home. Took it for an hour long shake down run that night. Yesterday (Wednesday) same problem, no fuel pressure and the alarm goes off when I hit the lock button on my key fob. I'm pretty sure it's eletrical. I guess I'll have to get it towed again if I can't get it started. I will let you know what we find out. I have been without my car for over a month as well so I know how you feel. It's probably gonna be another 1-2 weeks before it's fixed.

Rookiedyn

Hi Sffish I wish you luck with your problem. It seems some related components are involved with both our problems but the problem is most likely different.

Where you are not able to start your car. My car starts and runs great. Perfect fuel pressure (stock and new pump), no misses, etc. It just drops fuel pressure (not to the point of stalling but close) once in a great while (which of course if I ignored the problem would result in it occuring while I was getting on it and grenading the motor because thats just my luck).

Going without the car for so long is terrible but what can you do? I have already accepted the fact that this summer is a wash for me. Perhaps I can get it back in time for a few nice dry fall cruises but we shall see. Let me know how it works out for you.

Racetronix: thanks for the input they are watching the voltage on the pump now but the problem hasn't reoccured (which makes this a royal pain). With all the new wiring if it was the PCM wouldn't the PCM just shut the pump down all the way? Correct me if I am wrong but the voltage to the pump does not vary does it? The PCM just tells the pump to turn on or off. Not drop voltage just a bit. The car never stalls and sometimes the pump just drops 10-20 pounds then jumps back up.

thanks guys

Rookiedyn

Update: 9/10

Still nothing :( The car is still at the tuners and now they can't get the problem to recreate. They want to take a "snap shot" of the system when the pump drops pressure in an effort to narrow down the problem.

This is the list of the main things that have been done over the past 7 weeks.

-Fuel Pump Replaced (Racetronix with full harness)
-Fuel Filter Replaced (perhaps two faulty regulators? Doubtful but may have to replace this again)
-All grounds checked over many times.
-Fuel tank internals inspected thoroughly.

Currently waiting on a call from a C5 engineer for his input. I am in no way mad at my tuner. I could come and get the car at anytime as it runs great and only drops the pressure once in a great while. The problem is if it decides to do that while I am getting on it. I will obviously lean the motor out and blow it up.

I am updating this hoping I can gain any additional insite from any of you. Summer is gone this truly sux.

thanks

EDIT:

TEN MINUTES after I posted this I got an email from my tuner.


"I have good news and better news. The Vette is fixed. We found a pin in the computer wiring harness that was not seated properly and when the body moved just the right way it would partially break contact when the engine would shake (ready to stall).
I tested it on the dyno and after reprogramming the computer it makes 551.1 at the rear wheels. It drives very well and wants to come home."

What a coincidence!





[Modified by Rookiedyn, 11:58 AM 9/10/2003]

sffish

Okay my car is now fixed (well for the past 5 days atleast). I took it to Tony's Corvette shop and they found a bad ground connector. I don't know which one, but they said there was nothing visually wrong with the connector, but they were able to find it with a computer. So that was the problem.

Rookiedyn

Great news sffish. It looks like both our issues are finaly resolved. :thumbs: