Fuel starving?? |
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78sport
Member Joined: 24-September-2009 Location: syracuse Status: Offline Points: 77 |
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Posted: 10-July-2010 at 4:19AM |
Been drivin the 78 LTD II sport with 351 windsor lately and notice a hesitation off the line if I ease into the gas. Being stiffer into the pedal makes it's not noticable. At highway speeds I notice a rhythmic pulsation in the car's pull down the road as if it is staving for fuel. The other night after vince neil concert, I pulled up to a stop sign to make a left and the car just shut off like fuel supply was cut. Turned the key and it started right back up and was fine rest of the way home.
Has anybody else experienced these symptoms with mechanical fuel delivery systems? I already replaced the fuel filter on the front of the 2 barrel carb. Lines are all nice but I'm starting to suspect the mechanical fuel pump. There are no leaks anywhere. Anybody have any guesses what to look at? Thanks for some insight other than my own.
P.S. Carb is stock but has an aftermarket air cleaner without all the extra vacuum hook-ups and I can hear lots of air getting drawn into the carb at various RPMs(too lean?) Edited by 78sport - 11-July-2010 at 11:39AM |
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78 LTD II sport touring edition
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Skinnys Garage
Senior Member Joined: 26-February-2010 Location: South Dakota Status: Offline Points: 277 |
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Check to see if the needle valve has the small screen cage still in place in the carb. My '77 T-Bird gave me fits even after changing the pump, cleaning lines and fuel filter. Finally I pulled the cab top off, removed the needle valve, found the small screen, removed it and all is well.
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Scott -'73 Gran Torino Brougham
Past Torino's -'73 Q-code GTS, '76 Original PS-122 S&H, '73 H-code GTS, '73 Ranchero '71 Cobra 351 Auto, '70 351C Brougham 2dr HT, '71 351C Ranchero |
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78sport
Member Joined: 24-September-2009 Location: syracuse Status: Offline Points: 77 |
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OK thanks, I will remove the carb top plate and check the needle valve for that screen. Where abouts should I see that valve?? I hope I don't drop anything down below the carb ZOINKS
Also when it's cold it likes to die during the first minute of operation unless I push on the gas slightly. Choke seems to work well and idles down after letting it warm a bit and blip the gas pedal. Edited by 78sport - 10-July-2010 at 11:01AM |
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78 LTD II sport touring edition
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torkair
Senior Member Joined: 01-May-2010 Location: Tucson, Az Status: Offline Points: 430 |
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Could be time to replace the rubber fuel lines, they might be sucking flat due to age. Also a new fuel pump isn't very expensive and easy to replace.
Good luck! |
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72 Gran Torino "sport"- in progress
73 Ranchero GT- Q code-460/C6/3.25 open rear |
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Skinnys Garage
Senior Member Joined: 26-February-2010 Location: South Dakota Status: Offline Points: 277 |
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Not saying the needle valve screen is causing all your symptoms, but is one place to check just to rule it out. Usually if the screen is plugged, it takes a little more than just firing it back up after it quits.
Anyway, the screen is under the needle valve. After removing the top, you need to remove the float. The actual needle part of the valve will be hooked over a tab on the float - be careful. The brass seat portion of the valve can then be removed with a socket. The small cylinder shaped screen (if yours still has it) will be pushed into the bottom of the seat. It's suppose to catch anything that gets by the filter and if it plugs - no more fuel gets into the carb. Sometimes after it shuts off, the small particles fall back away from the screen and you can get it going again - for a while. The same thing can happen in the fuel tank if the "sock" gets plugged up on the end of the fuel pickup. These are just a couple suggestions for a fuel delivery problem. The running problems may be something unrelated. Good luck with the diagnosis. |
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78sport
Member Joined: 24-September-2009 Location: syracuse Status: Offline Points: 77 |
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Yeah, I'll try the screen first. If it looks clean then I'll move onto others. I was thinking new fuel pump also since pretty cheap and heard the arm wears down some over time from riding the lobe. Hmmm new rubbers, ok I'll check em out for rigidness. I hate to re-use them
The tank sock did cross my mind but wasn't sure what's all in there.
At least I got my huge rocker mouldings back on under the doors. Now I can tinker with the fuel system. Thanks for the ideas
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78 LTD II sport touring edition
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78sport
Member Joined: 24-September-2009 Location: syracuse Status: Offline Points: 77 |
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OK so I decided to start at the top and work my way backward thru the fuel system. I pulled the top plate off the carb and saw the float n needle valve. My needle valve had slots for big flathead versus having hex for socket removal. I took it out and no screen. I did clean a bunch of brown fine granular sediment from the two bottom caverns in the fuel bowl but I bet that's what that low area is for to keep it all. Pulled the filter on the front of carb and it was very clean and free. I replaced the rubber section from that filter to the steel line curving around the front of the engine. Was only about a 4 inch section. I squeezed the rubber sections under the fuel pump and they were stiff(I max out the "test your grip" machine at the state fair)
Next I will pull the larger filter just before the fuel pump on the supply line from the tank. I'm narrowing it down to maybe a plugged tank sock or worn out fuel pump. Maybe too lean tho for that huge air cleaner??
Does anybody know the proper float adjustment or angle when it's sitting atop a closed needle?
Here's a pic of my carb, what's the electric hook-up on the vapor line(far left in the picture) used for? Thanks again
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78 LTD II sport touring edition
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78sport
Member Joined: 24-September-2009 Location: syracuse Status: Offline Points: 77 |
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UPDATE: Fired up after carb put back together and noticed gas dribbling out a small hole near the top of the fuel pump. It's kinda on the side where the arm pivots inside the pump. It looks like one of those holes where if it leaks, that means it needs replacement. I've seen some water pumps with those holes telling you the seal is bad as an indicator. I've been smelling gas smells sometimes at traffic lights or after short trips so that must be where it was coming from. I'll pick one up tomorrow. Kinda looks original with some blue paint in spots. I can't wait to see how bad the arm is worn down where it rides the lobe Edited by 78sport - 11-July-2010 at 5:38PM |
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78 LTD II sport touring edition
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Turbo301
Senior Member Joined: 11-March-2007 Location: London, Ontario Status: Offline Points: 331 |
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My car does the exact same thing; did you ever find a solution?
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1977 Cougar XR7
1980 turbo Trans Am 2009 Pontiac G8 GT |
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Psquare75
Admin Group Member of the Stroker Club Joined: 26-November-2005 Location: United States Status: Offline Points: 4591 |
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Did you guys try raising the fast idle speed? I have no idea. My 2 bbl answers are always "remove, replace with 4 bbl".
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Paul
77 XR7 460/C6/3.00:1 *SOLD* 78 XR7 523/C6/3.5:1 79 F100 460/TKO500/3.25:1 'I also have some left over potatoes-I understand you can generate electricity from them'- Foote500 |
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78sport
Member Joined: 24-September-2009 Location: syracuse Status: Offline Points: 77 |
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So far all I did is turn the idle speed screw in slightly but maybe it will run better with that new fuel pump. I couldn't believe it was spitting out the top and spraying onto the oil filter. Right behind the oil filter and slightly above is the driver side exhaust manifold and gas getting on there can't be a good thing.
My pump comes in tuesday so I can pull the old one off today Edited by 78sport - 12-July-2010 at 4:58PM |
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78 LTD II sport touring edition
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78sport
Member Joined: 24-September-2009 Location: syracuse Status: Offline Points: 77 |
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Kind of a let-down. I thought I was gonna see the arm worn pretty bad but just a slight wear mark from friction. Looks to be lubricated ok so I'll take it. Took all of 5 minutes to remove. HA!, try that with an in-tank modern fuel pump. Makes these cars a pleasure to work on.
New one arrives at the parts store tomorrow. I'll grab a new lower filter(holding up the pump in the pic) and install all new rubbers(hoses) down there too.
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78 LTD II sport touring edition
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Psquare75
Admin Group Member of the Stroker Club Joined: 26-November-2005 Location: United States Status: Offline Points: 4591 |
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You should never do a filter like that before a pump, only "after".
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Paul
77 XR7 460/C6/3.00:1 *SOLD* 78 XR7 523/C6/3.5:1 79 F100 460/TKO500/3.25:1 'I also have some left over potatoes-I understand you can generate electricity from them'- Foote500 |
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Turbo301
Senior Member Joined: 11-March-2007 Location: London, Ontario Status: Offline Points: 331 |
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It's high idle is high enough, but it just doesn't like going to high idle most of the time. It starts and slips right into low idle 90% of the time.
I'm trying to keep my car as original as possible, so I'm stuck with my pooey 2 bbl :D
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1977 Cougar XR7
1980 turbo Trans Am 2009 Pontiac G8 GT |
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78sport
Member Joined: 24-September-2009 Location: syracuse Status: Offline Points: 77 |
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Really, what is the reasoning? I'm curious about that.
The pump has one fitting for a push on rubber hose and this filter has been on the car since god knows when. It still flows free as can be. The purpose from what I see is to keep any sediment that gets past the tank sock from getting into the pump and messing with the diaphram in there.
Does anybody else have this filter just before the pump on their car?
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78 LTD II sport touring edition
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torkair
Senior Member Joined: 01-May-2010 Location: Tucson, Az Status: Offline Points: 430 |
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mothball the 2bbl intake and carb, then step up to the 4bbl. I know it kinda goes against the grain but if you ever get a wild hair up your hindquarters then you've still got the original parts. Life and fuel economy is better with a good 600 cfm 4bbl.
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72 Gran Torino "sport"- in progress
73 Ranchero GT- Q code-460/C6/3.25 open rear |
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78sport
Member Joined: 24-September-2009 Location: syracuse Status: Offline Points: 77 |
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OK got the new pump on and new rubber lines down there. I had the parts guy pull a new "lower" fuel filter and I blew thru his and my old one. My old one flows much more than the new one so it went back on. When I first removed it, I blew the gas back out the inlet end and it was clear as water(no rusty tint or grit)
Damn it picks up RPM much better now with my hand working the throttle arm under the hood. Better yet NO LEAKS. I can't wait to get it on the road and see any change in acceleration.
If it ain't broke, don't fix it so I'm not wasting money I don't have on trying to fit a 4 barrel with all the necessary hook-ups
UPDATE:
Much more lively where the rubber meets the road now. No more gas smells and she's ready to finish out the summer cruises. Edited by 78sport - 13-July-2010 at 5:44PM |
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78 LTD II sport touring edition
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Psquare75
Admin Group Member of the Stroker Club Joined: 26-November-2005 Location: United States Status: Offline Points: 4591 |
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Mechanical pumps are great at 'pushing' fuel, not so good at 'pulling' fuel. A filter before adds a restriction that causes the pump to work that much harder. Should only put one after the pump, like OEM. Someone added that your car.
Make that " Lower" an "Upper". Also, the OEM fuel tank sender has a screen to stop the very sediment you are worried about. |
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Paul
77 XR7 460/C6/3.00:1 *SOLD* 78 XR7 523/C6/3.5:1 79 F100 460/TKO500/3.25:1 'I also have some left over potatoes-I understand you can generate electricity from them'- Foote500 |
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78sport
Member Joined: 24-September-2009 Location: syracuse Status: Offline Points: 77 |
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Naw, it's all good. Been on there for years and years. The pump was also very old and had been pumping good for years until a couple days ago. As I was sayin, the NEW filter the parts store had was harder to pull air thru and mine was flowing very nicely and still clean(probably cuz the sock in the tank has been catching for years) Runs great so I'm leaving it as-is.
I understand what your saying about pumps pushing more than they can pull. Same with electric pumps but I believe this filter has an internal screen and not paper.
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78 LTD II sport touring edition
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