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Unread 10-11-2013, 09:41 PM   #1
Gante
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Help! Difficult to start and shuts off when shift

Guys,

I need your infinite expertise. I have a 1991 Grand Wagoner with a 360 and auto transmission.
Recently I had my carb rebuilt and thereafter it was "adjusted" to lower idle and adjust the timing for smog check purposes. It passed smog check but now the truck is difficult to get started on a cold engine (after sitting off for a while). I have to pump the gas quite a few times and crank the ignition at least three times. Then once it is started for a few seconds, it idles just fine until I shift it into Drive or Reverse. If I let it warm up for a several minutes the issue is not too bad. I don't seem to have the same issues to restart after it has been running for a while.

Any idea what my problem could be?

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Unread 10-12-2013, 09:37 PM   #2
Gante
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Anyone ?

I've had some embarrassing moments when the trucks shuts off just from waiting at a street light.
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Unread 10-14-2013, 03:47 PM   #3
SIUADOG
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Ill take a guess that in order to pass emissions, the mechanic leaned out the carb by adjusting the mixture. The two idle screws were probably turned in a little too far. If I'm not mistaken, they should be turned out only 1 1/8 turns.
Hppefully this helps.
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Unread 10-14-2013, 04:20 PM   #4
Gante
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Quote:
Originally Posted by SIUADOG
Ill take a guess that in order to pass emissions, the mechanic leaned out the carb by adjusting the mixture. The two idle screws were probably turned in a little too far. If I'm not mistaken, they should be turned out only 1 1/8 turns. Hppefully this helps.
Yes, I am sure they messed around with the idle on the carb. You mentioned two screws? I only noticed the one in the driver side (on the carb of course). I tried to increase the idle by adjusting this screw. The funny thing is that the car idles fine when in park or neutral, once I put it on drive the idle speed seems to reduce a bit...
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Unread 10-14-2013, 05:32 PM   #5
jeeper54
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Have you checked the choke operation/adjustment?
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Unread 10-14-2013, 06:03 PM   #6
SIUADOG
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Two screws, (held in place with springs) located at the front, near the base of the carb. Check the recommended settings, I'm not sure.

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Unread 10-14-2013, 08:55 PM   #7
Gante
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Quote:
Originally Posted by jeeper54
Have you checked the choke operation/adjustment?
Excuse my ignorance but I am not familiar with the choke adjustment. Would you have any pictures of what this looks like? What does this do? And when I adjust it what am I looking for?
Thanks for the help!
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Unread 10-14-2013, 08:58 PM   #8
Gante
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The only screw I was messing around with is the screw towards the back on the driver side that helps increase or decrease the idle rpms. Honestly I am not very familiar with Carburators adjustments. At times it feels that gas flow may be limited to the carb... Is there a way to adjust the gas flow and where do I do this?
Thank you!
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Unread 10-15-2013, 01:17 PM   #9
jeeper54
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Don't feel bad. Carburators are an extinct species & I've run across younger people that have never heard of them. With eng. cold, check the flap on the top of the carb and it should be closed. When working, it will slowly open as the coil spring (round, black on right side of carb with wire attached hopefully) heats up from supplied voltage. This will cause an enriched mixture slowly leaning out allowing the engine to run more smoothly until warmed up. There is also a fast idle cam & adjustment screw that works in conjunction with the linkage for the choke flap. This gives the engine a higher idle to help prevent it from dying. I'm sure you will find a better explanation & maybe pictures if you look up "choke" in the search function. Good luck.
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Unread 10-15-2013, 02:38 PM   #10
Gante
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Thank you, I will need to inspect this.
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Unread 10-17-2013, 09:45 PM   #11
Gante
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I just noticed that none of the vacuum motors on the original air filter housing are operating. I think this would be due to lack of vacuum. Both flaps are closed which means that they are blocking any air flow into the carb. This may be one of the thousand reasons why my truck is so hard to get started. Would you agree?
Now I would need to figure out how to get those vacuum motors to work. I believe that this may be a lack of vacuum at the motor lines since a while back a mechanic did "something" to disconnect/ block vacuum to resolve an annoying vacuum leak I had associated with the 4x4 switch. He did "something" around the back of the carburetor... Any idea what he may have done? He didn't have any tools, so I am sure it would be something simple.
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Unread 10-18-2013, 09:00 AM   #12
super98lsc
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Air Cleaner Heater Doors:
The flaps will open only when the THERMAC which is a thermally actuated switch that opens to allow vac to flow when the engine fully warmed up. So with the aircleaner in place drive it until its warm then re-check them. They are supposed to be closed when cold. This allows heated air off the exhaust manifold on the passenger side to pre-warm the air going into the carburetor. Kinda like carb-heat on planes. Carburetors do not atomize fuel well when they are cold thus the faster they warm up the more easy the car will drive in cold start conditions and the faster the emissions will reduce.

Timing:
I would check the ignition timing before you tune on the carb. These trucks run better with a bit more timing in them especially with age as the timing chains stretch out internally. For emissions they may have retarded the timing back a few degrees and thus you will feel a lower idle speed, stalling, lack of power, stumbling and all sorts of driveability issues. Once the timing is properly set and verified then you can set the carb mixtures and idle speeds to where its happy. This is most easily done with a vacuum gauge connected to a manifold vac source. Allow the engine to fully warm and adjust the screws slowly for the best vac signal. Then if she runs rough or stumbles when cold you would adjust the choke to compensate for that until the engine is warmed, so you will have to wait overnight to test it.
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Unread 10-18-2013, 02:18 PM   #13
Gante
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Quote:
Originally Posted by super98lsc
Air Cleaner Heater Doors: This allows heated air off the exhaust manifold on the passenger side to pre-warm the air going into the carburetor. Kinda like carb-heat on planes.
.
Yes, one of the flaps I was dicribing is the one that opens to allow air from the exhaust into the carb. But the way things look right now both "flaps/doors" at the air filter housing are blocking air any air flow to the carb. I would assume that at least one of these should be "open" to allow air in.
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Unread 10-18-2013, 02:49 PM   #14
CSP
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It sounds like a vacuum leak to me, given the fact that it will idle fine but dies under any kind of load. I'd start by inspecting and/or replacing all of the vaccum lines, which I'm sure that year has a ton of them.
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Unread 10-18-2013, 03:01 PM   #15
Gante
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Quote:
Originally Posted by CSP
It sounds like a vacuum leak to me, given the fact that it will idle fine but dies under any kind of load. I'd start by inspecting and/or replacing all of the vaccum lines, which I'm sure that year has a ton of them.
Yes, it does have a lot of them. I am not looking forward to this work but I guess it will be best to start working on that.
Thank you for the input.
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