stevieapollo Posted November 7, 2009 Report Share Posted November 7, 2009 when i turn off my starquest the engine does not shut off smooth. Its more of a ruff shut down if that makes sense...I dont know how to describe it other then the word clunk and bump. lol if i were to guess it seems like the fuel pump is continuing to pump gas in the engine after it shut off, or perhaps there are a few last minute sparks that are causing this to happen.... Sometime it is worse then other times, and sometimes it sounds rill bad and it takes a minute to start the car after. almost like the engine is flooded. I recently changed the fuel pump and distributer cap. I upgraded to the walbro 255 pump i wander if that has anything to do with it...... any ideas how i can go about correcting this problem? any help would be awesome!!! i am totally lost on this one. thanks *apollo* Link to comment Share on other sites More sharing options...
jettajody Posted November 7, 2009 Report Share Posted November 7, 2009 when i turn off my starquest the engine does not shut off smooth. Its more of a ruff shut down if that makes sense...I dont know how to describe it other then the word clunk and bump. lol if i were to guess it seems like the fuel pump is continuing to pump gas in the engine after it shut off, or perhaps there are a few last minute sparks that are causing this to happen.... Sometime it is worse then other times, and sometimes it sounds rill bad and it takes a minute to start the car after. almost like the engine is flooded. I recently changed the fuel pump and distributer cap. I upgraded to the walbro 255 pump i wander if that has anything to do with it...... any ideas how i can go about correcting this problem? any help would be awesome!!! i am totally lost on this one. thanks *apollo*Mine does it to. Lots of cars that are from these times will do it, it's called dieseling. Continues to run for a sec befroe shut down. Most of the time it is bad or wrong octane gas. This is not my problem though, as I think it has to do with my stock mounts. When you start motor and shut down the motor will flop from side to side. Orther wise you have a fuel issue or timing issue. Link to comment Share on other sites More sharing options...
mistapickles Posted November 7, 2009 Report Share Posted November 7, 2009 I'd bet motor mounts... Link to comment Share on other sites More sharing options...
Cobalt60 Posted November 7, 2009 Report Share Posted November 7, 2009 A buddy and I both had different Chevy 305s; they would "diesel" sometimes for over a minute. "Dieseling" is caused by hot spots in the engine being hot enough to ignite the fuel. You can try a higher octane and see if it stops. If it does, this may suggest that it is indeed dieseling. If it is, you should probably figure out why you have hot spots in your engine. Link to comment Share on other sites More sharing options...
mikec Posted November 7, 2009 Report Share Posted November 7, 2009 Dieseling or "run-on" is pretty hard on the motor. Basically one (or more) cylinder is trying to run with uncontrolled "ignition timing." There is no spark from the ignition system; instead the air:fuel mix is ignited by compression and/or a hot-spot on the piston or cylinder. Either way, the burn starts while the piston is still on its way UP, which tries to slam the piston back down... ergo heavy vibrations. Hot spots come from:* carbon deposits in the cylinder or on the piston, especially uneven deposits from a history of poor air:fuel mix.* incorrect "heat range" spark plug. A spark plug that is tool long can't get rid of combustion chamber heat it picks up as easily: spark plugs dump their heat into the cyl head. For an engine to diesel though it requires fuel. With they key OFF, the StarQuest ECU and ECI relay should be shut down so the injectors shouldn't have power at all. So if fuel is getting into the engine to make it diesel, odds are you have a fuel leak: injector leaking or fuel pressure regulator is leaking into the small "L" shaped vac hose coming from the bottom of it. Don't let the engine diesel. When turning the key OFF:* leave an auto tranny in PARK while you have your foot firmly on the brake* for a 5-speed car, put the tranny into 4th or 5th gear and leave the clutch pedal pressed. As you turn the key off, slowly release the pedal (other foot on the brake) so the tranny helps "stall" the engine. Once you find the source of the fuel leak, go for a long highway drive with some hard accel/decel cycles. That'll help clean out larger carbon deposits. mike c. Link to comment Share on other sites More sharing options...
stevieapollo Posted November 7, 2009 Author Report Share Posted November 7, 2009 how can i go about finding the fuel leak?? where is the most likely place it would be leaking from? Link to comment Share on other sites More sharing options...
mikec Posted November 8, 2009 Report Share Posted November 8, 2009 As I posted: either the injectors or the fuel pressure regulator. No other places where gas is present. To test:1: with the engine warmed up and shut back off, remove the "over the valve cover pipe (OVCP)." The "OVCP" is the metal pipe running over the top of the engine, into the injection mixer/throttle body assembly. Actually, just loosen the mounting bolts for it... THEN start the engine and go for a short drive. Don't boost, just putt-putt around town for ten minutes or so to completely warm things up. Come back and park. Loosen the hose clamps and pull the OVCP out. 2: Look at the wire bundle between the air filter canister and fender. You'll see a couple connectors hanging from it, or still taped to it, that go nowhere - they just have protective caps on them. Find the one that is a single black+white wire. Run a beefy wire from the battery "+" post to this black+white wire. You'll hear a whirring sound: that's the fuel pump running and the fuel actually going through the injection mixer & throttle body. 3: The fuel pressure regulator is the small round "beer keg" hanging from the top/front of the injection mixer assembly. It has a small vac hose coming from the bottom of it: remove that hose. Any signs of gas in the hose or in the regulator's hose nipple? If so, the fuel pressure regulator is garbage and must be replaced. 4: shine a flashlight into the throttle body. You'll see a vertical divider and the tips of the fuel injectors. Is either injector spraying or dribbling gas? If so, that injector is bad... it needs a good cleaning (if you're lucky) or more likely will need to be replaced. The injectors should flow NOTHING WHATSOEVER with the engine OFF even with the fuel pump running with that jumper wire. mike c. Link to comment Share on other sites More sharing options...
stevieapollo Posted November 8, 2009 Author Report Share Posted November 8, 2009 i have a 87 that i use as a parts car. it ran fine and didnt have the shutting down issue i have....I used that fuel pressure regulator and those injectors and found that i had the same problem... is it possible that the parts i interchanged could be bad as well even tho the car didnt have the same problems? Link to comment Share on other sites More sharing options...
mikec Posted November 9, 2009 Report Share Posted November 9, 2009 Injectors that have sat for a while often go bad. Without gas flowing through them regularly, they can start rusting internally. Of course, they could have been bad before too. Do the jumper wire test. Find where the gas is coming from rather than throwing parts at it. mike c. Link to comment Share on other sites More sharing options...
Shelby Posted November 11, 2009 Report Share Posted November 11, 2009 couple other things to look at AFTER you do the checks Mike sugest'd high idle rpms,, above 1000 rpms, improper throddle plate opening ( too much air )late ign timeing , over heat'd engine normaly you'l find several small things worng rather then ONE thing to cause this when you turn off the ign swt,,the ecu runs the ISC in to lower the rpms,, then after the engine has stop'd the ecu runs the ISC back out to high idle position , now if the ISC is non funtional,, it can not do it's job thus alowing the engine to see excessive air when shuting down, fix the problem with the ISC and the run on will be solve'd Link to comment Share on other sites More sharing options...
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