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8/9/10 3:59pm - Original Message: 'Lost of Fuel, at wits end now'
Almond81Vette
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Stanley, NC - USA

Vette(s):
1981, dark blue w/carmel interior. 350 stock, auto tranny, Q-jet carb, ECM box

Joined: 8/9/2010
Posts: 91

     Any help will be great for I am at wits end now on this fuel or lack of fuel problem. Sorry for long post but want to give as much info as can.

1981 Corvette – stock 350 engine, auto trans, Q-jet carb, ECM and all parts in place and working

    Problem: Sunday drove home 15 miles in about 90 degree temps, got to garage, stopped engine while got out to open garage, cranked engine drove in and stopped engine again. Open hood and waited a few minutes and then proceeded to crank engine again and made a slight idle adjustment, to increase RPM just a tab. While doing this the engine just stopped. I checked the fuel flow into the carb thru the jets as I moved the throttle level and no fuel.

   With assistance from the wife I unconnected the fuel line to the carb and had her spin the engine, no fuel came out (but as later discovered may not have spun the engine long enough).

  With no fuel from line I jacked up the vette and went underneath. I first unplugged line from fuel tank to fuel pump and had fuel. I then disconnected the outlet fuel line from the fuel pump and she spun the engine and I had fuel there. I then blew out the fuel line from the pump to the carb, good air flow, no restrictions.

   I connected everything back underneath and went back engine side. Before reconnecting line to carb I had her to spin the engine again. Still no fuel but then I told her to spin engine until I told her to stop, she was only doing it maybe 2 seconds at a time and even this short of time initially.

   The last time I had her spin the engine I got fuel out in about 3 to 4 seconds so I had fuel to carb now. One of my thoughts is now I may have had fuel initially just didn’t spin it long enough, don’t know for sure.

   Reconnected line to carb, spun engine, checked fuel thru jets, no fuel. Re-spun engine and pump gas pedal a few times and re-checked the gas thru jets, had fuel now. Started engine up, she ran fine.

   Past work that has been done:

New rebuilt Q-jet carb from Ecklers; new manual fuel pump; gas tank cleaned out and new sock on fuel pick up line; lines from tank to fuel pump blown out; fuel line from fuel pump to carb replaced with new line and line wrapped with 500 degree heat cover. New ECM box installed, new power chip prom in ECM. New ERG valve installed; New fuel filter (goes inside carb, replaced 1 month ago).

  Again I wanted to give as much info as possible to seek the best advice on where to go next.

  Could it be the plunger inside the fuel filter sticking? If so can I remove that and still operate normally?
  Could it be the fuel inlet needle sticking? If so what would make it just do it every now and then?
   I had this problem twice before hence all the other work done on the engine (once before carb swapped). Luckily yesterday it happened once in my garage where I could check items, before both times while on the road and had to get hauled back home, and once back she cranked up but had to pump gas pedal several times so was hard to ID where the problem was then.


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Tommy
 
   
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8/9/10 4:51pm - Reply: 'Lost of Fuel, at wits end now'
Louiecr
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yardley, PA - USA

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1968 Corvette Convertable L71

Joined: 9/13/2009
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You can have fuel after the pump in the line if the pump stops pumping, the carb will not suck up the fuel in the line, it has to be presureized. You should put an inline fuel presure gauge or just change out the fuel pump from a local parts store. Cost is about 18-20. You should have about 4lbs of presure runing. Do you know if you have a three or two line pump? 
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8/9/10 5:13pm - Reply: 'Lost of Fuel, at wits end now'
Almond81Vette
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Stanley, NC - USA

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1981, dark blue w/carmel interior. 350 stock, auto tranny, Q-jet carb, ECM box

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Posts: 91
I have a 3 line fuel pump and this one was put on a month ago. Do not know what pressure I havem need to get a gauge.

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8/9/10 6:28pm - Reply: 'Lost of Fuel, at wits end now'
danascar
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Germansville, PA - USA

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1974 Coupe 358ci 4 speed Black w/Medium Saddle interior w/79 custom leather seats. 1999 Covertible, 6 speed, Atomic orange, Oak interior

Joined: 1/28/2010
Posts: 763
If it only does it when its hot, vapor lock may be the problem.

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Dan T
 

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8/9/10 6:51pm - Reply: 'Lost of Fuel, at wits end now'
Almond81Vette
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Stanley, NC - USA

Vette(s):
1981, dark blue w/carmel interior. 350 stock, auto tranny, Q-jet carb, ECM box

Joined: 8/9/2010
Posts: 91

I have run the vette when hotter, even with AC on and not have it to lose fuel to carb. This really is getting me since it does not seem to be a definite cycle, timing or use that will create the problem. When we did the other work to address possible vapor lock on the fuel line from pump to carb we installed the 500 degree heat sleeve over it since before just a naked steel line running up the front of the block.

  What else do you propose could be vapor locking? The fuel pump? I had fuel from the outlet of the pump when I tested it about 10 minutes after loss fuel to carb's throat.



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Tommy
 
   
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8/9/10 7:00pm - Reply: 'Lost of Fuel, at wits end now'
yostusota
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York, PA - USA

Vette(s):
1969 daytona conv. all original 350 350 380 4 sp w/air..and hard top

Joined: 5/18/2010
Posts: 1518
? I don't know for sure but do you have a vented gas cap??  I am not extremely familiar with the 81 set up but I know that may cause no fuel to the carb when running for a while if you don't..if the evap system is that tight and not allowing air to got back to the tank..try to run it with the gas cap loose..simple but may work..get the clear filter or pressure gauge on it too..that will help if it happens again..
Rich


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8/9/10 7:08pm - Reply: 'Lost of Fuel, at wits end now'
danascar
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Germansville, PA - USA

Vette(s):
1974 Coupe 358ci 4 speed Black w/Medium Saddle interior w/79 custom leather seats. 1999 Covertible, 6 speed, Atomic orange, Oak interior

Joined: 1/28/2010
Posts: 763
That is strange. Just guessing but maybe vapor locking right in the carb....if gas is everywhere but the carb it may be boiling fuel out of bowl. Does it start and run ok after sitting and cooling down?

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8/9/10 8:15pm - Reply: 'Lost of Fuel, at wits end now'
Almond81Vette
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Stanley, NC - USA

Vette(s):
1981, dark blue w/carmel interior. 350 stock, auto tranny, Q-jet carb, ECM box

Joined: 8/9/2010
Posts: 91
Yes it has run fine once cooled. In Corvette Forum one guys mentioned carb vapor locking and mentioned adding another spacer under the carb. When I changed the carb it did have 2 spacers under it but I only added one back so thoughts on that? I can add the other spacer back, still have both I took off old carb.
  But thinking more the lost of fuel did occur once with old carb on it but was told by Chevy dealer that plates inside was worn and they recommended a new carb, so that is why the change.


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8/9/10 9:56pm - Reply: 'Lost of Fuel, at wits end now'
dskopp
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Oak Creek, WI - USA

Vette(s):
1981 Great White Shark. Red Interior, 350/190hp. PS, PB (SS), A/C CC, T-Tops, Going to remain as Stock as possible. Served three years in Active Duty Army, then Retired Air Force after 34 years! Badger State Vetts Car Club. 175,000 Original miles!!

Joined: 5/21/2008
Posts: 1956
I'm gonna take this post to my Corvette Mechanic.  I got an idea why its doing that but not sure.  I will have an answer for you in a couple of days.
DanGeek


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8/9/10 10:04pm - Reply: 'Lost of Fuel, at wits end now'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

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[QUOTE=Almond81Vette]

made a slight idle adjustment, to increase RPM just a tab. While doing this the engine just stopped. I checked the fuel flow into the carb thru the jets as I moved the throttle level and no fuel.[/QUOTE]


If you're moving the throttle by hand, a Quadrajet requires a pretty quick movement to actually push much fuel thru the squirters. If you were just slowly working the throttle, it may not have pumped any fuel like that.


"The engine just stopped"....as in just shut off like you turned the key off? If it just shut down like that, then chances are the ignition module in the distributor is about to take a doo-doo. That is one of the most common failure modes for them....they'll just shut off. It may start right back up after a few minutes of cooling off, or it may take an hour or so to cool enough to start back up. You've done a ton of work on the fuel system....I kinda think the problem is somewhere else. The fuels today will RARELY create a vapor lock....the stuff is just not volatile enough. Of course, if you get any metal carb or fuel line hot enough, it will certainly boil the fuel, which is what a vapor lock is. You'd prolly have other problems too if it was running that hot, imho.Wink

I'd be checking the ignition system.


The electronics on your car(ECM) really only controls the idle fuel mixture, and the timing.

hth



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Joel Adams
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8/10/10 7:20pm - Reply: 'Lost of Fuel, at wits end now'
Almond81Vette
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Stanley, NC - USA

Vette(s):
1981, dark blue w/carmel interior. 350 stock, auto tranny, Q-jet carb, ECM box

Joined: 8/9/2010
Posts: 91
Joel thanks for the insight on the ignition module. I understand what you are saying but would that stop fuel flow thru the throttle body's jets when moving the throttle level? I may not have been moving the throttle level fast enough to squit fuel but a few others have been around the vette when it did this once before so we may all have moved the level slower, but again not sure.

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8/10/10 9:17pm - Reply: 'Lost of Fuel, at wits end now'
ranger3 Lifetime Member
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North Charleston, SC - USA

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1975 L48 AT AC T-top

Joined: 3/20/2004
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I agree that it sounds like the module. That's exactly what mine did and a new module cleared the problem. It would just shutoff and would not restart until it cooled down.

Scott


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8/10/10 10:04pm - Reply: 'Lost of Fuel, at wits end now'
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Duncanville, TX - USA

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#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

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It may well be a fuel problem...I'm not totally discounting that at all...it just sounds more like an ignition failure. IF the carb was running out of fuel while idling, it wouldn't just shut off quickly...it would stumble for a little bit then die.
You could maybe carry a small bottle of fuel with you...something with a top that would allow you to pull the top of the air cleaner off, and squirt just a bit of fuel into the vent of the carb, then see if it would start right up. If it does, then you need to determine what the heck else in the fuel system needs attention. If it still won't fire off like that, then it points more to the ignition area. BE extremely careful if pouring any fuel into the carb when the engine is hot!!! Don't try to use a soda can or such!



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Joel Adams
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8/10/10 10:18pm - Reply: 'Lost of Fuel, at wits end now'
yostusota
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York, PA - USA

Vette(s):
1969 daytona conv. all original 350 350 380 4 sp w/air..and hard top

Joined: 5/18/2010
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A can of starter fluid in a spray can might be a little bit easier and a lot safer! A fire extinguisher might be needed also! I do like fire though..I had a few take off on me and it was no fun explaining that one..the module does make perfect sense and is very easy and cheap to pop in..
Rich


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8/10/10 10:43pm - Reply: 'Lost of Fuel, at wits end now'
Almond81Vette
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Stanley, NC - USA

Vette(s):
1981, dark blue w/carmel interior. 350 stock, auto tranny, Q-jet carb, ECM box

Joined: 8/9/2010
Posts: 91
Joel when it stopped it was not just like the switch being turned off but did sorta just idle down. Before when it happened on the road I had just stopped and fueled up, started and drove off and about 100-200 feet she just die out and I coasted to a safe spot. And had no fuel coming thru jets in the carb then either and had 3 other vette's owner and one of them a good mechanic stop to assist. They felt the fuel pump so I did swap that out as well as doing all the other work to the fuel system to hopefully remove and other problems.
    One major light that has come from the replys is that I did have 2 thick fabric spacers between the carb and maniford before but when placed the new carb on I only used 1 spacer so gonna go back and add the second one anyway, can't hurt and at least maybe reduce heat to the carb.
     I need to address upgrading the ignition system and dist as well to know all parts are at least newer than now so will probably be swapping out cap, module etc soon anyway.


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Tommy
 
   
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8/10/10 10:44pm - Reply: 'Lost of Fuel, at wits end now'
Almond81Vette
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Stanley, NC - USA

Vette(s):
1981, dark blue w/carmel interior. 350 stock, auto tranny, Q-jet carb, ECM box

Joined: 8/9/2010
Posts: 91
Dan thanks for your offer to have the corvette mechanic see this post, I look forward to hearing his thoughts.

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8/11/10 7:18am - Reply: 'Lost of Fuel, at wits end now'
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Duncanville, TX - USA

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#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
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It is entirely possible that the float in the carb has swollen up, and is sticking to the sides of the bowl. The float is made of a resin type material, and they will soak up fuel and expand. New or not, it can happen. You've done so much to the fuel system, that the carb is really the only other thing that could cause a fuel starving issue.
The check valve in the filter can be removed, but I doubt it is the problem...its only purpose is to keep fuel from draining back out of the carb.
Adding the second spacer/insulator under the carb might help, I s'pose, if it is heat related. The Q-jet should have a thick gasket under it. You might want to check and see if your heat riser(on the pass side exhaust) is working properly. If it is stuck closed, it can certainly push more heat thru the bottom of the intake, and thus transfering the heat to the carb...


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Joel Adams
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8/11/10 12:16pm - Reply: 'Lost of Fuel, at wits end now'
yostusota
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York, PA - USA

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1969 daytona conv. all original 350 350 380 4 sp w/air..and hard top

Joined: 5/18/2010
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  I like the heat riser idea..

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8/11/10 1:35pm - Reply: 'Lost of Fuel, at wits end now'
Almond81Vette
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Stanley, NC - USA

Vette(s):
1981, dark blue w/carmel interior. 350 stock, auto tranny, Q-jet carb, ECM box

Joined: 8/9/2010
Posts: 91
Well installed second thick spacer today and she ran okay, a couple of short road runs. Then when got back in the garage and shut it down.........antifreeze started out from under engine...but found clamp lose on line from radiatior neck to overflow jug so tigthen it up and hopefully fixed that.
  On the heat riser on r/s air cleaner will check that too to see if opening properly. I checked the l/s a week or so back it it was doing okay, but will recheck the r/s.
   Thanks to one and all for the  comments, Chip told me this was a great group of folks and you are. This beautiful vette is not going to whip me, I will get her right.


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8/11/10 9:57pm - Reply: 'Lost of Fuel, at wits end now'
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19457
The heat riser I was referring to is in the exhaust, right where the head pipe bolts up to the manifold. On your '81, the heat riser will be vacuum operated, so you should see a small metal tube going down to the riser valve itself. There will only be the one on the pass side exhaust.

 I think what you are describing that you checked is the valves on the bottom of the air cleaner wings/inlets? While those being stuck OPEN would also contribute to excess heat to the carb, I can't see them causing your problem.  

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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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