Hesitant on acceleration and nothing when you mash the throttle

[Vette73]

Originally Posted by XfireZ51

Is this something new or has it been like this since mod?

This just happened yesterday....The car was modded over 3 years ago.....Swapped my fuel pumps 2 years ago .....

[Paul Workman]

FUEL-AIR-SPARK What's missing?

I think I'd start with checking the fuel pumps (current draw) first, and then fuel pressure under WOT load.

With the ignition switch OFF you can measure 4-5 amps/ pump for a total of 8-10 amps) current between the positive battery post and the diagnostic connector (poking out of the big wire loom between the wiper motor and the brake booster - a red wire with a black connector.

For a dynamic pressure test, you can tape a pressure gauge to the windshield and monitor pressure at cruise and WOT. (Cruise = 45ish psi and 55 psi at WOT).

[Vette73]

Originally Posted by Paul Workman

FUEL-AIR-SPARK What's missing?

I think I'd start with checking the fuel pumps (current draw) first, and then fuel pressure under WOT load.

With the ignition switch OFF you can measure 4-5 amps/ pump for a total of 8-10 amps) current between the positive battery post and the diagnostic connector (poking out of the big wire loom between the wiper motor and the brake booster - a red wire with a black connector.

For a dynamic pressure test, you can tape a pressure gauge to the windshield and monitor pressure at cruise and WOT. (Cruise = 45ish psi and 55 psi at WOT).

Ok Paul thanks....What sucks now is we are getting hit with a monster snow storm....I guess for now I can check at idle....Idle is fine BTW......

[Paul Workman]

Originally Posted by Vette73

Ok Paul thanks....What sucks now is we are getting hit with a monster snow storm....I guess for now I can check at idle....Idle is fine BTW......

Well, you CAN check to see (at least) if both pumps are working.

Buy powering the pump's at the diagnostic connector, you can observe the current draw of both pumps combined. And, by pulling either pump 1 or pump 2 fuses (eliminating one or the other pumps), you can ascertain if one of the pumps is failing: my guess would be the secondary pump is 'kaput' since the car runs until you mash on the "go pedal"!

One other thing: The "accordion" air tube between the air filter box and the throttle body may be collapsing (mine was) causing it to fall on its face at WOT. If your car has the stock air tube, you might want to install the wire hoops that Mark Haibeck makes to support that tube, OR fab up a metal sleeve to insert in the tube to prevent it from collapsing, OR Jerry's Gaskets can fix you up with a stiff, aftermarket replacement. (Your issue doesn't sound like the air hose collapsing, however. But, if you have the stock hose, taking one of these steps to ward off future issues is worth considering!

[Vette73]

Originally Posted by Paul Workman

Well, you CAN check to see (at least) if both pumps are working.

Buy powering the pump's at the diagnostic connector, you can observe the current draw of both pumps combined. And, by pulling either pump 1 or pump 2 fuses (eliminating one or the other pumps), you can ascertain if one of the pumps is failing: my guess would be the secondary pump is 'kaput' since the car runs until you mash on the "go pedal"!

One other thing: The "accordion" air tube between the air filter box and the throttle body may be collapsing (mine was) causing it to fall on its face at WOT. If your car has the stock air tube, you might want to install the wire hoops that Mark Haibeck makes to support that tube, OR fab up a metal sleeve to insert in the tube to prevent it from collapsing, OR Jerry's Gaskets can fix you up with a stiff, aftermarket replacement. (Your issue doesn't sound like the air hose collapsing, however. But, if you have the stock hose, taking one of these steps to ward off future issues is worth considering!

I actually went out tonight in the garage to start it.....Took about 5 times before she finally turned over....The idle is good ...When you rev the car its not smooth...You can feel it breaking up when you give it gas...Could only go back and forth about ten feet since there's still so much snow here....

The accordion is in great shape....Just waiting on the tool from my friend...Checked around the fuel regulator to see maybe if there were any leaks and its dry at least...

[Paul Workman]

Originally Posted by Vette73

I actually went out tonight in the garage to start it.....Took about 5 times before she finally turned over....The idle is good ...When you rev the car its not smooth...You can feel it breaking up when you give it gas...Could only go back and forth about ten feet since there's still so much snow here....

The accordion is in great shape....Just waiting on the tool from my friend...Checked around the fuel regulator to see maybe if there were any leaks and its dry at least...

I think we're all dying to hear what the fuel pressure is doing! But, as for the accordion hose, what issue you describe, I agree @ this moment it doesn't sound like the hose is the issue here...BUT..."great shape" doesn't tell us much, i.e., is it reinforced (with Marc's wires) or what?

Anywayz...back to fuel pressure questions: did you check the pressure, and what is it? What happens when you "mash the gas"?? Did you measure the current to the pumps diagnostic connector (w/ ignition OFF)? Just out of curiosity, does the fuel rail hold pressure to wi/in one PSI for 15 minutes or so with the switch turned off? And, the "granddaddy question" of all: Have you scanned it (OBD-I) to see what clues reside within?

[XfireZ51]

Originally Posted by Vette73

I actually went out tonight in the garage to start it.....Took about 5 times before she finally turned over....The idle is good ...When you rev the car its not smooth...You can feel it breaking up when you give it gas...Could only go back and forth about ten feet since there's still so much snow here....

The accordion is in great shape....Just waiting on the tool from my friend...Checked around the fuel regulator to see maybe if there were any leaks and its dry at least...

You?ve pulled the regulator hose to see if there?s fuel in it?

[Vette73]

Originally Posted by XfireZ51

You?ve pulled the regulator hose to see if there?s fuel in it?

I'm just still waiting on the diagnostic tool....This is my first vette with an ECM so not too familiar with scanning and such...Will check the regulator hose over the weekend...

Quick question....Which pump is responsible for starting the car ?

[A26B]

Originally Posted by Vette73

I'm just still waiting on the diagnostic tool....This is my first vette with an ECM so not too familiar with scanning and such...Will check the regulator hose over the weekend...

Quick question....Which pump is responsible for starting the car ?

Both primary & secondary pumps are enabled for cold start only, until coolant temp reaches 172F. Primary pump for starting when coolant temp is >172F.

[secondchance]

Originally Posted by Vette73

I'm just still waiting on the diagnostic tool....This is my first vette with an ECM so not too familiar with scanning and such...Will check the regulator hose over the weekend...

Quick question....Which pump is responsible for starting the car ?

Also, pull the vacuum hose to fuel pressure regulator and see if gas is dripping. You can tell if the diaphragm in the regulator has failed. There should be no gas in the vacuum line.