What's Wrong with this Picture?
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Junior User
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From: South Norfolk/Chesapeake
What's Wrong with this Picture?
Got a quick question for you guys and gals. As we all know, the Carter YFA is one of the simplest carbs out there (barring all the emissions junk). That being said, I just can't seem to keep this one working correctly. Before I bought my rig, the PO had replaced the carb and had the truck running (sorta). Since I bought it, I fixed all the emissions stuff and got the old girl running right, but something about this carb just doesn't seem correct. I can't seem to tune it in properly, and it doesn't like to stay running if you shift from 4th to neutral to stop. Here's a few pics of the carb as it stands:
Apart from the bolt sticking out of the choke housing, which is obviously wrong, any thoughts?
Apart from the bolt sticking out of the choke housing, which is obviously wrong, any thoughts?
FTE Legend
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From: Northeast, OK
Posting Guru
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From: Orlando area
I think I see a major twist in the fuel line (how bad is fuel line being restricted?). EGR gone.
Is that a vacuum port uncovered between the fuel line bowl vent?
Have you checked the ignition timing? May be in "limp mode" with fixed timing.
How does it run other than problem you posted about?
Is that a vacuum port uncovered between the fuel line bowl vent?
Have you checked the ignition timing? May be in "limp mode" with fixed timing.
How does it run other than problem you posted about?
Lead Driver
Joined: Jul 2009
Posts: 6,477
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From: Sheffield, AL
1984? The heated air for the choke is missing [bolt], so the choke will open sluggishly, depending only on the electric assist heat [wire from the alternator to the choke]. The stepper motor is missing [helps control idle speed]. The EGR valve is blocked off [mentioned previously by CountryBumkin]. The idle fuel mixture screw "appears" to be way out, which might indicate adjusting to overcome a lean mixture [vacuum leak?]. The open port on the valve cover near the oil fill cap... is it closed when the air filter is on? You still have the MAP sensor for the feedback system,... do you still have the O2 sensor? Does the distributor have a vacuum line going to a diaphragm or a bunch of wires to the base?
Cargo Master
Joined: Oct 2005
Posts: 2,298
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From: NJ
I would check the float level and be sure there's no sediment in the bowl.
What's that electronic thing on the side of the carb? How is the carb bowl vented? Could that solenoid be blocking the fuel bowl vent if the brass tube is not a vent?
Idle mixture set for max RPM or vacuum, maybe a tad rich of that point if it runs smoother that way?
Base timing set to 10* or so? Consistently returns to same timing you set it at?
What's that electronic thing on the side of the carb? How is the carb bowl vented? Could that solenoid be blocking the fuel bowl vent if the brass tube is not a vent?
Idle mixture set for max RPM or vacuum, maybe a tad rich of that point if it runs smoother that way?
Base timing set to 10* or so? Consistently returns to same timing you set it at?
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Cargo Master
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From: Washington
On the 1986 carb, the electric choke only works (heats up) when it above ~60 deg F, give or take a little on the temp. So as is, the choke won't work if its cold outside. The primary choke is the "hot air choke". The electric choke is an emissions thing, it pulls the choke off faster in warm weather.
Jim
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From: Virginia
Got a quick question for you guys and gals. As we all know, the Carter YFA is one of the simplest carbs out there (barring all the emissions junk). That being said, I just can't seem to keep this one working correctly. Before I bought my rig, the PO had replaced the carb and had the truck running (sorta). Since I bought it, I fixed all the emissions stuff and got the old girl running right, but something about this carb just doesn't seem correct. I can't seem to tune it in properly, and it doesn't like to stay running if you shift from 4th to neutral to stop. Here's a few pics of the carb as it stands:
Attachment 181612
Attachment 181613
Attachment 181614
Apart from the bolt sticking out of the choke housing, which is obviously wrong, any thoughts?
Attachment 181612
Attachment 181613
Attachment 181614
Apart from the bolt sticking out of the choke housing, which is obviously wrong, any thoughts?
Electronic Engine Control - ???Gary's Garagemahal
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Joined: Jul 2010
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From: Northeast, OK
I will summarize the previous posts; You have the classic 300 six cylinder mess. You have a computer controlled engine, but there are too many things not working and not plugged in. This is not your ordinary simple carb and simple engine like you thought it was. You can make it so by converting to a older type distributor, or you can keep going with what you have and try to figure out what you need. Here's a schematic of your engine on page 56. See that long bar at the bottom? Look to the left, it says "Electronic Control Assembly".
Electronic Engine Control - ???Gary's Garagemahal
Electronic Engine Control - ???Gary's Garagemahal
Were it mine, I'd go research DS-II conversions and start stockpiling the parts. You'll need the right distributor, ignition module, and wiring harness. The current carb will probably work, but really should be replaced.
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Junior User
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From: South Norfolk/Chesapeake
Thanks for all the info, guys. As it sits, the truck is in AZ being driven most every day by my mom, while I'm in VA. The truck will be shipped out here at the end of next month, so I figured I gotta figure this crap out now, since I'm planning on making it my daily driver. On that note, are there any advantages with keeping the EEC setup that are better than the DSII and vice versa? I'm only really looking for reliability, at the moment (get it running before getting it just right).
FTE Legend
Joined: Jul 2010
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From: Northeast, OK
The EEC setup gives better emissions, but DS-II gives better reliability. With EEC the computer is adjusting for many things, sampling the exhaust, etc. However, it depends on many hoses, valves, relays, wiring, and sensors that are now 30+ years old. And if any one of those things goes wonky the computer throws its hands in the air and cries foul, and locks the timing and air/fuel ratio into a basic value that should get you home. But, it also absolutely kills power and economy.
If you have been around these trucks quite a bit or really understand the early years of emissions equipment then putting one right initially and keeping it there is said to be fairly easy, although I've not done it. But there's no OBD-II port into which to plug your scanner. You put a jumper on a port under the hood and the computer flashes the Emissions light to give you codes. From that you can figure out what the computer thinks the problem is.
If you have been around these trucks quite a bit or really understand the early years of emissions equipment then putting one right initially and keeping it there is said to be fairly easy, although I've not done it. But there's no OBD-II port into which to plug your scanner. You put a jumper on a port under the hood and the computer flashes the Emissions light to give you codes. From that you can figure out what the computer thinks the problem is.
Thread Starter
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Junior User
Joined: Nov 2012
Posts: 77
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From: South Norfolk/Chesapeake
The EEC setup gives better emissions, but DS-II gives better reliability. With EEC the computer is adjusting for many things, sampling the exhaust, etc. However, it depends on many hoses, valves, relays, wiring, and sensors that are now 30+ years old. And if any one of those things goes wonky the computer throws its hands in the air and cries foul, and locks the timing and air/fuel ratio into a basic value that should get you home. But, it also absolutely kills power and economy.
If you have been around these trucks quite a bit or really understand the early years of emissions equipment then putting one right initially and keeping it there is said to be fairly easy, although I've not done it. But there's no OBD-II port into which to plug your scanner. You put a jumper on a port under the hood and the computer flashes the Emissions light to give you codes. From that you can figure out what the computer thinks the problem is.
If you have been around these trucks quite a bit or really understand the early years of emissions equipment then putting one right initially and keeping it there is said to be fairly easy, although I've not done it. But there's no OBD-II port into which to plug your scanner. You put a jumper on a port under the hood and the computer flashes the Emissions light to give you codes. From that you can figure out what the computer thinks the problem is.
FTE Legend
Joined: Jul 2010
Posts: 32,875
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From: Northeast, OK
Yes, you could. And, if this is an EEC system, without an O2 sensor the computer will have its knickers in a twist and have the ignition in limp-home mode. But show us pics of the distributor so we can make sure it is computer-controlled.
Lead Driver
Joined: Jul 2009
Posts: 6,477
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From: Sheffield, AL
For future clarification sake, though, the 1984 [my son's original 4.9L engine] also has a Throttle Position Sensor. Can we assume that the 1985 does, as well?