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1985 Ford F150 4.9L 6cyl 300 cid truck not idling/won’t stay running… help needed!
Hello everybody, this is my first post here so please bear with the length (I'll try to keep it much shorter next time). I own a 1985 Ford F150 Lariat XLT pickup truck with a straight 6 cylinder 4.9L automatic 300 cid engine (long bed, dual gas tanks). This truck is a plow truck and is only used to plow my ˝ mile long dirt driveway. It sits a lot and doesn’t get driven as much as I know it should (bad on me).
Anyway I've had the truck several years (it’s never run superb, but it always started and ran) and of late I've had a terrible time keeping it idling/running. Basically the only way to keep it running now for just a few seconds/minutes it to spray starting fluid into the carb and have someone start the truck with the accelerator to the floor and hold it there as it struggles and chugs. I have to hold the choke plate wide open to keep it idling/running for a minute or two.
Some important notes:
<>The exhaust is black and sooty (can be seen on the ground).
<>The spark plugs are about 2 weeks old. They are black and sooty when I inspect them after trying to start the vehicle.
<>The truck has a single barrel Carter YFA carburetor… I rebuilt this, but was concerned that I might have muffed it up so I bought a cheap Kipa brand carb off of Amazon that is temporarily on the truck now. I mainly wanted to see if the Kipa produced any better results. It did not.
<>At times the fuel mixture is misting up out of the carb when I’m holding the choke plate open. Also on the Carter lately when it was trying to run the choke plate was flopping (opening and closing) violently.
<>I connected fresh gas from a gas can directly to the fuel pump and checked the pressure at the filter right before the carb connection and got a steady 6psi. It wouldn’t even idle or run any better with gas pumping straight from the gas can to the carb.
<>When I disconnected the fuel line from the fuel pump there was just a dribble of gas. I lightly blew compressed air back to the tanks and they gurgled a bit and then gas flowed up to the line. The fuel sending units may be failing (definitely need to investigate this further – probably will need new tanks and sending units).
<>When it sits overnight and I start it up it starts right up and idles for about 45 seconds and then will just start struggling and die. (This happens with either carburetor installed).
<>This truck has the TFI unit mounted on the side of the distributor (have not removed it yet but cleaned up the connections).
<>All the vacuum lines are old/original and have not been replaced yet (and need more thorough inspecting).
New parts:
Fuel filter, air cleaner, mechanical fuel pump, spark plugs + plug wires, distributor cap & rotor, coil, battery, starter solenoid, starter motor, oil catch can (the air filter was getting oily), Kipa carburetor
Recent things I’ve checked:
<>The rotor rotates when the engine is turned over by hand.
<>The rotor is pointing at #1 spark plug location when the timing marks line up on the engine. Rotated it to the ZERO (0) mark and the (---) straight scratch line on the engine.
<>The spark plug wires are wired to 1-5-3-6-2-4 firing order.
<>Used a spark tester and each spark plug had spark that appeared fairly strong and consistent.
<>Did a dry compression test and the cylinders (#1-6) were respectively: 110, 118,116,110,110,112
<>Attempted to do a vacuum test but could not get a reading (the truck won’t stay running or idling very long).
<>Tried to use my OBD2 scanner, but the plug didn’t match up so I guess I need the Ford adapter for OBD1... if that will even work.
I need someone who knows these trucks inside and out to point me in the right direction. We are expecting a huge snow storm and I’m going to be in big trouble if I can’t get the truck running. I am a novice mechanic at best and just try to listen and learn and fix things when I am able to. I plan to put the original Carter YFA carb back on the truck after I clean it and check it over again. I'm not sure if the vacuum lines are correct because the original owner capped off a lot of the ports. I’ll try to post some pictures so you guys can tell me what’s right and wrong. Anyway thanks in advance for your help I greatly appreciate it!
Carter YFA on vehicle prior to rebuild Carter YFA carb side view inspection prior to rebuild Rear of Carter YFA carb Old plug wires,coil,dist cap... have since been replaced with new
Not sure if you got this answered but I had this same problem with my buddy's truck... Make sure you're using the right timing marks, check out the third post here: https://www.ford-trucks.com/forums/1...nline-6-a.html
Here's his post:
Hi, Ok here goes. Ford in all its infinate wisdom put two sets of timing marks on the 300. There is one set on the right hand side near the top of the timing cover, these marks are cast in the cover. These naturally are the WRONG marks. On the left side of the timing cover where you can't see them are the right marks. They are on a metal plate bolted to the cover using the cover bolts. The vibration damper also has two sets of marks, wouldn't you know it! There is a large square notch , nope not the right one . There is also a very thin scribed line on the damper, yep that is the right one. . To do this right, slide under the engine and clean off the thin scribe line and paint it white and while you are under there you can see the bolted on timing mark on the cover there is a large triangle cut in the plate , that is 10 degrees before TDC the correct setting .Pull your distributor cap and crank the engine untill the rotor points at number one cyl on the cap.Then see if you can see the alignment of the timing mark on the damper some how and the mark on the bolt on plate, its easier when the engine isn't running and you can stick your head in there without loosing half of it. Your timing marks should be some where near each other. Crank the engine to align the 0 degree mark and the mark on the damper, don't worry about the distributor position. Just line up the marks. Then go to the right side of the cover with the cast in marks( that you can see) and mark the damper with white somthing, paint even whiteout works.Now you have a new timing mark that you can see. Pull the spout, yes it is in the same harness as the distributor connector, its a gray jumper.Put the cap back on. Start the engine and use your new marks to set the timing at 10Degrees before TDC. Of course this only works if your cover has the cast in marks, I have a 90 and it has the marks. I have just finished assembling the engine and found out that the engine was set using the damper line and the cast in marks. I figure the engine was running 40 degrees retarded, but MAN did ever start quick in any weather with any oil at any temp. There are other way to do this but it takes too long to describe them here.Sorry I almost forgot. When you mark the damper with the new mark it should be marked the same as the left side original, i.e.-- if the original marks are aligned at 0 you should paint your new mark to align at 0 also, if the original is at say 6 your new mark should be painted to be in line with 6 on the cast marks and so on.
Buddy's truck fired right up, required some slight adjustment but was running and idling on its own.
Hello. I am new to all of this but it looks like the hot air line that goes from your exhaust to the side of your choke has a bolt plugging it. From what I have learned it helps the engine idle properly.
Those Motorcraft / Autolite / Carter YF-1A carbs need a working power piston diaphragm
That piston raises and lowers the metering rod, and the little hose attached is the accelerator pump
Do you understand?
Replace only that out of a carb kit and it'll probably run fine
Bitchy to replace that for a non-expert, good luck,, you will become an instant expert
Those Motorcraft / Autolite / Carter YF-1A carbs need a working power piston diaphragm
That piston raises and lowers the metering rod, and the little hose attached is the accelerator pump
Do you understand?
Replace only that out of a carb kit and it'll probably run fine
Bitchy to replace that for a non-expert, good luck,, you will become an instant expert
truth here. This is a huge part of the issue I was having with my truck
Those Motorcraft / Autolite / Carter YF-1A carbs need a working power piston diaphragm
That piston raises and lowers the metering rod, and the little hose attached is the accelerator pump
Do you understand?
Replace only that out of a carb kit and it'll probably run fine
Bitchy to replace that for a non-expert, good luck,, you will become an instant expert
lll
this guy is right on. I rebuilt my carb ? 10 times? I avoided the piston pump because it looked fine to me. After the last time I pulled it out diaphragm was dry rot with tiny slits it it……yea it’s kind of a bitch but really it’s not rocket science any of you can do it and yes immediate difference
WOW !!! This says a lot about this forum. There's been nearly 20 thousand people look at you post and only 5 people have replied !!!!! GOOD GRIEF !!!!! I hope you get some good advice.
Nobody knows anything about carbs anymore
Last class I went to about carburetors was 1984 when our I/M program came out in Davis County Utah
They sent a bunch of us to get schooled up to prove their worth down at the I/M board
They are still trying to justify their existence
1985 Ford F150 4.9L 6cyl 300 cid truck not idling/won’t stay running… help needed!
