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| | | | Joined: Apr 2006 Posts: 172 Wrench Fetcher | | Wrench Fetcher Joined: Apr 2006 Posts: 172 | hey guys im having a little bit of a problem here. the truck still idles fine but as i acclerate, it seems to only accelerate in increments like its short on fuel for a second and then it gets it and then repeats that process. eventually it levels out and is ok once it gets up around 2,000-2,500 rpm but its just strange. ive asked around and msot people seem to think it has to do with fuel delivery and more specifically a fuel pump on its way out or possibly a clogged fuel filter. any suggestions on where to start? | | | | | Joined: Feb 2004 Posts: 29,747 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,747 | Start with a fuel pump volume test. Disconnect the fuel line at the carburetor, slip a piece of rubber hose on, and put the hose into a container. Start the engine and let it idle. There should be enough fuel in the float bowl to idle for some time. The pump should deliver at least a pint in 30 seconds, if it's in good shape and the inlet line isn't restricted.
If the volume is low, connect a pressure/vacuum gauge to the outlet. It should produce about 4 lbs. of pressure, and hold it for a few seconds after the engine is shut off. Then check the inlet. There should be about 10-15 inches of vacuum, and that should stay put for a short time after stopping the engine. Low vacuum or pressure, or an immediate drop to zero is cause to replace the pump. Good results on pressure/vacuum tests but low volume- - - -look for restrictions in the tank-to-pump line, or a blockage inside the tank. Also check any filters or strainers for restrictions.
Jerry
Last edited by Hotrod Lincoln; 09/07/2008 1:28 AM.
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Feb 2004 Posts: 29,747 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,747 | I've seen this symptom repeatedly on engines with carburetors and mechanical fuel pumps- - - - -surging on acceleration due to low fuel pump output or a clogged fuel filter, and just barely able to maintain steady RPM on a light-throttle cruise. A slight increase in fuel demand drops the float level, and a lean surge develops. The float bowl doesn't have to get empty, just a drop from the normal level of the fuel in the bowl in relationship to the venturi makes the mixture go lean.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Apr 2006 Posts: 172 Wrench Fetcher | | Wrench Fetcher Joined: Apr 2006 Posts: 172 | well actually, i didnt want to say anything at first cause i got chewed out for it last time but this is on a 95 suburban with a fuel injected 350. i just really needed advice and figured this was the best place to get it. any changes in advice because of the fuel injection? | | | | | Joined: Feb 2004 Posts: 29,747 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,747 | Send me an IM, and we can talk about troubleshooting techniques off the main board. There is an entirely different diagnosis process on a computerized fuel injected engine. What you're describing does not sound like fuel problems on that one.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
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