Found lots of sludge during 2bbl carb rebuild - why???

[Fords4Us]

Good morning all, and thanks for such a great forum. This is my first post.

We have a 1983 Ford Ranger, 2.8L engine with the 2bbl Motorcraft carb, standard shift, 100% stock as far as I know. She's a hard worker as a farm truck, and we try to keep up with typical maintenance needs. But lately she's been struggling. Rough cold idle, so rough that she stalls out if I don't keep the gas pedal slightly down. Then the idle runs super-high during warmup, even after goosing the gas pedal. Super-thick exhaust also during cold start, and fuel efficiency went into the toilet. When we first had these issues a few years back, the shop replaced the choke thermostat. That helped for awhile but the problems came back pretty quickly, and fuel efficiency went from never-that-great down to terrible. Everything pointed to a carb that needed a good cleaning and possibly some adjustments for the idling.

During the carb teardown, we found something interesting. Towards the end of the teardown, after we'd taken all the topside stuff off and flipped it over, we removed the spacer plate and found sludge caked into one of the carb's compartments. This is the lower half of the carb, at the back of the engine compartment, the corner aiming towards the driver's side. Everything in that corner was chock full of sludge. The vacuum line going out to the passenger side valve cover was open and clear, but the point where that vacuum line came into the carb was completely blocked by that sludge.

We also saw signs that a lot of oil had been blowing through the PCV valve. Our theory is that somehow that vacuum line coming off the carb to the passenger side valve cover got blocked somehow, either at the valve cover end or the carb end, creating a blockage in that carb compartment and creating an air dam in the line. Question is, WHY? I have the sinking feeling that we're going to have to pull the valve cover and see what's going on within that half of the engine. Does anyone have any ideas why this is happening?
Kathryn Kerby
frogchorusfarm.com
Snohomish, WA

 

[509lifted]

all i can say is during warm up it is suppose to idle high. sorry i can't help on the other stuff as idk what causes that.

 

[85broncduece]

Off the top of my head burning lots of oil would gunk everything up. how often are you adding a quart of oil to the system?

 

[PanamaExpat]

What kind of oil are you using? How often is it changed? Your idle problem sounds like gunk or varnish in the idle circuit on the carb. Your sludge problem could be due to old age and just an all around loose motor. Run a compression test and check your EGR system. Let us know what you uncover.

 

[Tedybear]

Good morning all, and thanks for such a great forum. This is my first post.

We have a 1983 Ford Ranger, 2.8L engine with the 2bbl Motorcraft carb, standard shift, 100% stock as far as I know. She's a hard worker as a farm truck, and we try to keep up with typical maintenance needs. But lately she's been struggling. Rough cold idle, so rough that she stalls out if I don't keep the gas pedal slightly down. Then the idle runs super-high during warmup, even after goosing the gas pedal. Super-thick exhaust also during cold start, and fuel efficiency went into the toilet. When we first had these issues a few years back, the shop replaced the choke thermostat. That helped for awhile but the problems came back pretty quickly, and fuel efficiency went from never-that-great down to terrible. Everything pointed to a carb that needed a good cleaning and possibly some adjustments for the idling.

During the carb teardown, we found something interesting. Towards the end of the teardown, after we'd taken all the topside stuff off and flipped it over, we removed the spacer plate and found sludge caked into one of the carb's compartments. This is the lower half of the carb, at the back of the engine compartment, the corner aiming towards the driver's side. Everything in that corner was chock full of sludge. The vacuum line going out to the passenger side valve cover was open and clear, but the point where that vacuum line came into the carb was completely blocked by that sludge.

We also saw signs that a lot of oil had been blowing through the PCV valve. Our theory is that somehow that vacuum line coming off the carb to the passenger side valve cover got blocked somehow, either at the valve cover end or the carb end, creating a blockage in that carb compartment and creating an air dam in the line. Question is, WHY? I have the sinking feeling that we're going to have to pull the valve cover and see what's going on within that half of the engine. Does anyone have any ideas why this is happening?
Kathryn Kerby
frogchorusfarm.com
Snohomish, WA

Is it wet sludge..or does it kinda look like soot and baked black crud? It's (sadly) common for the EGR system to get bunged up with carbon crud and that can pretty much plug up the carb spacer. Need slightly more to go on. First guess? If it's wet sludge? Clean it out with carb spray...replace the pcv hose and the valve. And I'd have look the engine over for some heavy blow-by.

If it's just hard carbon crusty? Clean out the system/ports...test the egr valve and make sure it works...and reinstall. Over time it can build up some nasty black carbon.


As for the idle issues and running poorly? I think you're making a good call with having it rebuilt. Add a new float to the replace list...as the black "Rubberish" type float? Can actually soak up fuel over time and it will cause your fuel level in the float bowl to run high. I've seen 'em so bad it actually starts to flood out the engine.

Super High idle after the engine warms up..and goosing it fails to help? Possible linkage issue or choke out of adjustment. Could just have some binding from crud.

S-

 

[Andy D]

Give this truck an Italian tuneup to burn out the carbon. Are you sure the junk in the carb is sludge? Could it be bits of 30 yr old fuel line insides?

 

[tmcalavy]

Pull the valve covers and have a look, could be carbon and crap in an old ford engine that got sucked into the carb but I'm leaning towards the melted insides of 30 year old fuel lines...unless you are running it on real gasoline...modern ethanol dissolves the inside layer of older fuel lines and you get ethanol manure in your carb...see this all the time in outboard motors running old pre-ethanol fuel lines. Clean and reinstall the carb, give it new, fresh fuel lines and filter, check the choke set up, and then sea foam the engine or flush the engine with a 50:50 mix of oil and tranny fluid next time you change the oil...to clean the insides out. Caution: Seafoam will clean all the funk out of the engine but that's not always a good thing on old engines, if I wanted to keep it as a reliable farm truck for many more moons, I would do the oil/tranny fluid flush instead.
If you can, can that auto choke and install a manual choke cable on it...it's a farm truck, right?

 

[RustedRanger]

+1 on blow-by if it has a bunch of miles or sits long enough for the valve seals to dry out. My 2.9 was getting a bunch of oil in the intake so I made a "catch can" for the PCV line. I started using Lucas in my oil and it almost stopped using oil and the catch can stopped collecting oil so I took it off.

 

[Fords4Us]

Hey everyone, thanks for the replies. I'll keep in mind the potential sources of the "gunk" I reported, but I do want to provide an update. When we re-installed the carb, we set the electric choke thermostat to what it had been prior. But the idle mixture screws were set VERY far off from what factory spec said - instead of 1.5 turns from bottoming out, they were quite a bit further out - 2.5 turns on one side, and 3.75 turns on the other side. We tried to get new needles as part of the rebuild but none of the shops in town had them in stock, so we put the old ones back in, at the factory spec settings.

When we went to fire up the engine, she ran really nice and smooth on the cold (high) idle, and came up to temp a lot faster than usual - 5min vs 10min. But the moment that butterfly came open, she stalled and died. From that point on, we can't keep her running. We'll restart, she'll run smoothly for about 10 seconds, then the RPMs will just tank and she'll die. We backed out the idle mixture screws another 1/4 turn each, so that now we're 1.75 turns to the bottom instead of factory-spec 1.5 turns to the bottom. No change. Do we continue to back those out, or is this the choke setting?

PS -while this is a farm truck, it's more accurate to say it's my daily driver. I deliver product in this truck and run all my in-town errands. So we need her running strong. Thankfully she's old enough that I don't have to worry about emissions testing. Interesting idea on the manual choke - I might just do that. Thanks all.

 

[Tedybear]

The needles will almost never be the problem. It's the seat they screw into...that's where the issues can kick in if they are over tightened.

If the engine is 'at temp' the choke should be wide open and the base idle RPM set. Once done I normally will back each needle valve screw out 1/4 turn equally until it has a smooth idle. Factory spec is just the starting point, you'll need to tweak it in/out until you find the butter zone.

S-

sidebar note: This is just how I do things. There are other opinions on how to set the needle valves for correct air/fuel mixture at base idle. I'm also known for removing the screws during a rebuild and hosing the batcrap out of them to get rid of crud in the ports and passageways.

 

[enginepaul]

If the truck is stock, you need to set your base idle. I think instructions are in the tech section.

Mileage note: I get 20 to 21+ MPG with stock tires; mostly highway miles at 65 to 70MPH. I think, nor sure, about 3.40 rear end.

 

[96fordranger]

hook a vaccum gauge up to manifold vaccuum warm it up,back the screws out til you get the highest reading then advance the timing to get the highest reading then repeat the carb this will compensate for wear.

 

[kimcrwbr1]

Do not mess with the timing it never goes out on these engines. You probably have more than one issue here the one causing the sludge is probably valve guide seals. You probably get a big puff of black smoke when you start it especially after it sits for about 20 minutes after you turn it off. When I did my valve seals none of them were even touching the valves. If you dont have to pass emissions ditch the computer and duraspark it. As long as your getting good oil pressure you can change the valve guide seals without pulling the heads, pull the egr and put a block off plate with a new gasket. For around 120 bucks you can buy a new distributor cap rotor adaptor and module from autozone. I`m pretty sure it`s over 25 years old it dont need to pass smog anymore. But for now you can try put on a new PCV valve, Pull the egr and see if it can be cleaned to where it seals allways use a new gasket when mounting, on the drivers side pull the foam breather filter out of the air filter housing its probably totally plugged also. disconnect the battery while your cleaning/changing those three items. Get a can of seafoam and bring the engine all the way up to temp and then while running it around 2000 rpm quickly pour about half the can of seafoam into the carb and quickly shut it down. Wait half an hour and start it up and run it around 3000 rpm until the smoke show stops. Never start these motors with a sensor disconnected even the one in the air filter housing if you do you need to reset the computer by disconnecting the battery for at least 20 minutes. Adjusting the choke can be a biotch make sure it is getting power when the engine is running if not just turn it where it stays open full time if it stays half closed let the engine full warm up and adjust it where it pulls the choke fully open. The motor is pretty much bullet proof It took me about four times but what I do is about 100 miles before a oil change I add half a quart or so ATF into the engine and change the filter. run it for a bit and then do a complete oil change. You can nurse it along just dont put alot of time or money into the computer it will never work correct.

 

[Fords4Us]

Update on Sludge in Carb (long)

Well, I have an update on the 2150 Motorcraft carb rebuild project for our 2.8L Ranger. In short, we're running even more poorly now than before. We are being vexed by something (or a combo of somethings) which is suddenly driving down the RPMs and making the engine stall. Here's the testing/results we've done so far:

Prior to rebuild: suddenly worsening fuel efficiency, lots of gray smoke during cold startup, SLOW cold start warmup (5-10min between turning the key and having high enough RPMs to drive away), and then the truck died at normal operating temps as I was driving home, and put in the clutch. That was the last straw, at which point we pulled and rebuilt the carb.

After rebuild:
Test #1: with electric choke at pre-rebuild condition, and idle mixture jets at 1.5 turns from the bottom, we were able to start the truck, and warm it up to normal operating temps. As the butterfly valve opened, suddenly the RPMs tanked and the truck died. Could restart but couldn't keep her running afterwards. End of Test #1.

Test #2: backed out the idle mixture jets to what they had been at time of rebuild (LEFT: 2.25 turns from bottom, RIGHT: 3.75 turns from bottom). The left jet was bent, which might explain why there was such a difference in adjustment. Left the choke alone. After making the idle mixture adjustments, the truck still started up fine, ran a little rich, came up to temp normally, but still tanked right as the engine temp gauge hit the bottom of the "M" for the "NORM" range. Could restart but couldn't keep it running. End of Test #2.

Test #3: Butterfly valve didn't seem to be opening as it should, so left the idle mixture valves alone and worked to adjust the choke. As the engine came up to temp, butterfly never opened. As engine hit the bottom of the "M", died again while the butterfly was still closed. Could restart but couldn't keep it running. End of Test #3.

Test #4: Strongly suspected the electric choke wasn't operating properly. Marked the position of the tang and room temp, then put the bimetallic in the fridge. Marked the cold temp. Put the bimetallic on the radiator. Marked the hot temp. The full range of hot to cold corresponded nicely to what the full range of motion should be to fully operate the butterfly valve from full open to full closed.

Test #5: tried to start the truck without the bimetallic, so that we could control the butterfly valve manually. Couldn't keep it running even long enough to start to bring it up to temp. Put the choke back on, tried again. Still couldn't keep it running long enough to bring it up to temp. The only way we could keep it running, was to continually work the gas pedal to keep the RPM's moving up and down. Even if I left the gas pedal depressed A LOT, which would send the engine revving quite high, if I held it in one place the RPMs would almost immediately wind down and it would stall. End of Test #5.

OK, this has been long but I wanted to be clear what we've tried. My hunch is that something other than the carb is misbehaving - some solenoid or computer widget. I was intrigued by the earlier statement that if the sensors are disconnected that could cause a computer somewhere to misbehave. My next test tomorrow will be to pull the cables off the battery for the recommended 20min, then try again. BUT, what else might be so dramatically affecting the RPMs and forcing them down such that the truck stalls? This just feels like something electrical to me, rather than either the choke and/or the idle mixture valves. Any guesses/suggestions? Thanks in advance......

 

[drgrcr]

Sounds like a fairly large vacuum leak. Check the vacuum tree that is behind the carb toward the passenger side. It has the majority of the vacuum line connected to it. Make sure the large line that goes to the brake booster is connected and is not cracked/rotten somewhere between the vacuum tree connection and the booster check valve.

Check the PCV hose for cracks or rotten pieces, you are looking for a fairly obvious leak of probably 1/2".

If you still have the old base gasket for the carb, compare that to the replacement part, I have been the victim of the wrong gasket that did what you are describing, it did not seal on the back side of the carb base and the engine would not idle.

This carb is a feed back carb that has a computer controlled vacuum leak on the back of the carb. It has a 2 wire electrical connection that the computer dithers voltage too. It only works when the engine is at cruise and the computer is monitoring oxygen content of the exhaust through the oxy sensor. If this valve is leaking, stuck open, it will cause idle problems. Check for obvious leaks first

The best thing, convert it too a non feed back carb, and a Dura Spark ignition system, When this system is set up right, it is a nice working piece. I have this system on my 83 Ranger and cold starts @ 32" weather are great. Mileage improved from 13-14 mpg around town to 18-22 mpg.'