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Engine shuts off when accelerating

Tiny
TOSMITH
  • MEMBER
  • CHEVROLET NOVA
I have the car listed above with a 250 straight 6. The motor will idle fine but when I accelerate it shuts off. It acts like it's starving for gas. I've changed the fuel pump and installed an electric fuel pump. I mounted it right next to the tank, as I read it was better closer to the tank. I replaced the fuel filter as well and still no change. If I put it in neutral it will rev just fine but as soon as I put it under a load it stalls. I tried to make adjustments on the carb but it doesn't solve the problem only make other things like idling worst. Does anyone have any answers? I'm pulling my hair out over here. Thanks
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Thursday, March 8th, 2007 AT 6:56 AM

11 Replies

Tiny
MIKE H R
  • MECHANIC
  • 3,094 POSTS
The carb could be the problem, check to make sure the fuel pump pressure is ok, check the timing, leaks in any of the vacuum lines, the carb could also be clogged or the float sticking.
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Thursday, March 8th, 2007 AT 9:54 AM
Tiny
TOSMITH
  • MEMBER
  • 4 POSTS
Ok do I just stick a pressure gauge on the discharge of the fuel pump. What pressure should I read? How many vaccum lines should I see coming off the carb if any? Thanks for the help
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Thursday, March 8th, 2007 AT 10:15 AM
Tiny
MIKE H R
  • MECHANIC
  • 3,094 POSTS
The fuel pressure for the 19997 250 is 4 to 5 psi. Check the pressure going into the carb. There is only one vacuum line. If the gaspressure is out ok then the carb would be the problem. Let me check on some things in reference to the carb, the carb sound like it is a holley 5210c. Let me know what you find with the fuel pressure.
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Thursday, March 8th, 2007 AT 11:06 AM
Tiny
TOSMITH
  • MEMBER
  • 4 POSTS
Hey thanks I'll check this afternoon the fuel pressure. I had a mechnic rebuild the carb last year but I have a feeling he may have done a half way job. He said it was really gummed up but he got it cleaned best he could. Thanks again for all the help.
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Thursday, March 8th, 2007 AT 11:59 AM
Tiny
MIKE H R
  • MECHANIC
  • 3,094 POSTS
Try spraying carb cleaner in the air adjusting screw hole. Note: record the number of turns it takes to screw it in, but do it until it is just touching. Over tightenening the adjusting screw will burr it up. Then after using the cleaner re insert the screw, then back off until it is set the same as before you did it. It might have to be readjusted but it gives you a starting point on the adjustment
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Thursday, March 8th, 2007 AT 10:52 PM
Tiny
TOSMITH
  • MEMBER
  • 4 POSTS
Ok guys thanks for the info so far. Last night I tried putting a guage on the fuel pump. Well I have about 5 lbs going to the carb. Atleast I elminated one problem. Next I wanted to say the carb is a rochestor, I think quadrajet makes it. I guess I'll try moving up to the carb now and pull the jets as someone suggested. Does anyone know about how many turns it should be out so I can compare to where I'm currently at. Thanks again.
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Friday, March 9th, 2007 AT 7:25 AM
Tiny
MIKE H R
  • MECHANIC
  • 3,094 POSTS
Here are a couple of reference pages to look at. if you are going to rebuilt the carb get a rebuilding kit. it will come with what you need and instructions and guages for the float level

let me know how you make out


https://www.2carpros.com/forum/automotive_pictures/54223_rochester_carb_1977_1.jpg


https://www.2carpros.com/forum/automotive_pictures/54223_rochester_carb_1977_1_1.jpg

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Friday, March 9th, 2007 AT 9:54 AM
Tiny
BURRBRIAN
  • MECHANIC
  • 158 POSTS
Probably too late but have seen the condenser in the dist. Do this, also. It will act like the carb is messing up, a cheap thing to check out before you dump the $$$ for a carb.
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Monday, May 7th, 2007 AT 8:42 PM
Tiny
ED ARMES
  • MECHANIC
  • 129 POSTS
Carb accelerator pump bad or linkage disconnected to accelerastor pump. Bad vacumn advance on distributor. Points adjusted wrong. All the above are possible. :D
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Friday, February 29th, 2008 AT 9:32 PM
Tiny
JOHNNYBLU
  • MEMBER
  • 1 POST
Hey guys. Just read this thread. I had the same problem as Tosmith recently. I tried tuning up my old '77 250 l6 nova, but that didn't solve the problem. I finally checked the fuel pump, and it registered 5 psi while running (ok), but the pressure fell off at a rather quick rate after shutting off the engine. When I checked for leaks after reattaching the outlet line, I finally saw it. The rubber inlet line running from the metal fuel line that runs to the gas tank was leaking at the fuel pump inlet. It wasn't that visible when I checked the fuel pump earlier, but there it was. Cracking ! A leaky fuel line would undoubtedly cause a rough idle and bad acceleration while in gear. I replaced the rubber fuel line and that was the end of the problem !

John
Northern Cali
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Friday, November 20th, 2020 AT 7:37 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,772 POSTS
Hi, John, and thanks for that information. I'm sure it will help someone in the future. Interestingly, when the vehicles get older, that is something a lot of people fail to check. Hopefully, your post will help others.

Take care and thanks again.

Joe
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Friday, November 20th, 2020 AT 8:28 PM

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