73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Fuel Systems and Drivability => Topic started by: Burgersquatch on November 28, 2012, 12:23:26 pm
-
So this 73 K10 I picked up.... the carb is flooding randomly. Well, the other day it ran out of gas. Should have had plenty but stalled rolling into the gas pump. Since pretty much this entire truck is original, I'm gonna go ahead and assume there's some crap in the tank. Going with that, something got past the one little fuel filter at the carb and got stuck in the float or needle somewhere. I'm thinking it flooded out what gas I had left because my gauge dropped out of nowhere (unless the gauges are bad - have dual tanks). A friend told me to tap it with a hammer or something and knock it loose. It worked and ran fine all day yesterday until the last trip home.
It started to idle funny while waiting for a left-turn. Shortly after that I could smell gas and knew it was stuck again. I argued with it through the neighborhood before it stalled as I rolled into the driveway. Checked under the hood and yeah, it was wet. Since it was dark outside, I left it til this morning. Tapped on the carb around the fuel inlet and float bowl like I did the other day and it started up fairly ok - not like when the block is warm, but it cooperated. It sputtered a little gas out of the pump rod hole (where it was straight spewing the other day at the gas station).
Supposedly, someone at an off-road shop took the carb apart, cleaned this and that, adjusted the float and replaced some secondary rod. I'm not trying to doubt that this work was in fact, not done... but seeing as I wasn't charged for it (bought a battery tho), it's possible they did nothing.
The carb is a Rochester 4bbl, rebuilt by Holley (I don't know the model #). It was put on this truck about 9-10 months ago. The guy I bought it from said it would stick on occasion but not frequently. He also stopped driving this truck after he got a newer Toyota 4Runner. He said it only happened a couple times but I don't know the time frame. This is the 3rd time it's happened to me.
I'm considering splicing a secondary fuel filter in the line between the tank selector valve and the engine-mounted pump. I have not yet checked the fuel filter I have now, I should, I need to, just don't have any tools or time right now. Oh man, do I need tools. I really can't afford a new carburetor right now, or probably for quite a while. There's no way to even try to warranty the carb I have, so I'm kinda just stuck messing with it. Really just looking for some advice on how to deal with this issue...
-
Welcome form California.
Install the in-line fuel filter between the pump and the carburetor - not on the suction side of the pump. The inlet needle may be sticking because of the way it's installed, if it "hooks" onto the float. You may also have a float that is heavy with fuel if it's composed of closed cell composite material. There are other possibilities, as well, but all should be correctable at low cost if you can do the work yourself.
-
With a small set of screw drivers and wrenches, a rebuild kit, and some patience, for around $100.00 you can rebuild it yourself.
If you can not afford that right now, get on the Internet and copy off instructions on how to take it apart and clean it. Find a friend with a basic set of tools and you will be set.
If you keep messing around with it you will probably only frustrate yourself and possible end up doing more harm in the long run.
It is not hard to take one apart if you follow instructions and take your time.
Good luck in whatever you decide.
-
Thanks for the reply and tips. I was thinking an in-line filter before the pump would help keep the pump clean but I'll do some more research for I go and do anything.
I haven't gotten into this carb for myself and since I need this truck for daily transportation, it's difficult to find the time to dig into it and get it back on without causing a problem myself. I realize it's probably easier than I'm thinking, and call me a noob or whatever, but I'm a little apprehensive to take my only ride "off the road". I have one friend here who knows old vehicles but we work at the same place, which makes it a bit tricky for both of us to have the same day off and we can't really mess with it at work. It's also been pretty cold and windy here (Tahoe). Rained all day today and will probably have snow by the weekend. There is a garage at the house here that I could probably have access to on occasion (housemates park in it). Not many tools here, I'll have to hit up a thrift store or something.
Didn't make the parts store so I don't have a replacement fuel filter yet.
Earlier today, I went to work and it acted up around the corner from the house and stalled. Got out, tapped the carb a bunch and managed to get it going before too long. Ran fine on the 20min drive to work. When I got there my boss needed a ride down the road, started and ran fine, I waited in the truck with it running and it was again fine. Left work ok, stopped for groceries and dropped off a friend and was fine the whole way home. Then, as I pulled into my neighborhood, downshifting from 4 to 3 (4spd manual) with not really revving high at all, as I gave it a little gas to continue moving along, it chugged and acted like it was gonna get stuck and stall. I kinda "pushed" through it, argued at the stop sign but got it into the driveway without stalling. After the stop sign/left turn it seemed fine and didn't sputter in the driveway when I pulled in.
-
Here's a thought. First pay attention to what bd said. Do not put the filter on the suction side.
You got any junk yards up there ? I have been to Tahoe a lot but don't get around to everywhere. If you can get a carb off a junker and rebuild, then it is only 4 bolts and hoses to put on, 1 hour tops with the fine tuning.
I am not going to presume your situation for a second with money and what, but take it from us who have 30 plus yrs working on vehicles, sometimes it is better to get a second one and replace the first one if you can not afford your vehicle to be down.
You might have to save and look around for awhile but it would be worth it. If you have absolutely no access to another carb, I am not too far away, I bet I could find a used one around and send to you.
-
Good call on the spare carb, pretty smart thinking. I'm a tattoo apprentice (Cosmic Creations) and on a pretty tight budget. I'm pretty busy between keeping the shop happy and trying to pick up side jobs for whatever money I can get. So far, so good... but I'm gonna have to do some crunching and see what I can come with that will work with my situation. I haven't had time to get into anything yet and the weather has been pretty miserable so I can't even tinker during downtime at the shop.
Thanks so much for the info guys, really helps my stress levels knowing there's someone who knows what they're doing.
-
I'm wondering if the idle is set too low, if that would cause this problem? I seem to be having daily issues with this thing.
I'm pretty much in the habit of tapping the carb before I start the truck, before I hit the road, or both.
It's been starting ok, sounds like the auto-choke runs a bit high so I push the pedal a little and the rpm's drop to normal idle. Although it seems the idle is a bit low because this is when it'll chug and stall if I don't hold the pedal slightly. After it warms up a bit, it usually idles fine. Add the heater or defrost and you can hear/feel the system work a bit more. Turn on headlights and the power drops a little more, to the point where I feel it somewhat necessary to put my foot back on the pedal. Should I try increasing the idle speed?
It seems that somewhere, roughly half-way, on my 20 minute drive to/from work, that if I have to stop at a red light, it starts to sputter and wants to stall. I put my foot into it and "argue" with it through 2nd, which is pretty much my starting gear since 1st is granny gear. Once it's got some rpm's and is cruising down the road it's fine. At about 40-45mph in 4th (4spd), the motor/exhaust note seems to oscilate (kinda go up and down rhythmically). With all this sticking/flooding going on, it would make sense that the plugs/points got fouled. Still being tool-less, I haven't checked anything. The distributor cap seems to be a little noisy, kinda rattly at times... think it's got issues?
When I first got this truck and started with the carb, there was a cable hand-tied around the linkage for the vacuum side. It was tied in a way to keep the front flapper open and a rod pressed into the vacuum diaphragm. It was removed a while ago, after the first time I got stuck in a parking lot, should I put it back?
-
It sounds like you may have several issues going on. You shouldn't need to adjust the carburetor idle (screw on driver's side of carb) if it is idling fine when the engine is warm.
I'm not certain, but when referring to the cable and "front flapper" it sounds like someone tried to disable the choke mechanism by tying the vacuum choke pulloff closed. It also sounds like you may have a partially working fast idle mechanism and/or other issues. There should be a fast idle and intermediate idle with the choke operating correctly. The idle settings on the choke can be adjusted. One common issue with the choke is the choke thermostat isn't working properly.
If you still have the factory Q-jet on your truck there should be a little metal box (thin sheet metal) attached to the intake manifold beside the carb on the passenger side. It should have a metal a rod coming out of it that attaches to the choke mechanism on the carb. That metal box has the choke thermostat spring inside. If it is not as above, take a photo of the passenger side of the carb. Other models of Q-jets had electric or hot air thermostats.
If the thermostat is not working properly the choke mechanism isn't going to open or close as it should. Same thing goes with the vacuum pulloff.
-
It sounds like you may have several issues going on. You shouldn't need to adjust the carburetor idle (screw on driver's side of carb) if it is idling fine when the engine is warm.
I'm not certain, but when referring to the cable and "front flapper" it sounds like someone tried to disable the choke mechanism by tying the vacuum choke pulloff closed. It also sounds like you may have a partially working fast idle mechanism and/or other issues. There should be a fast idle and intermediate idle with the choke operating correctly. The idle settings on the choke can be adjusted. One common issue with the choke is the choke thermostat isn't working properly.
If you still have the factory Q-jet on your truck there should be a little metal box (thin sheet metal) attached to the intake manifold beside the carb on the passenger side. It should have a metal a rod coming out of it that attaches to the choke mechanism on the carb. That metal box has the choke thermostat spring inside. If it is not as above, take a photo of the passenger side of the carb. Other models of Q-jets had electric or hot air thermostats.
If the thermostat is not working properly the choke mechanism isn't going to open or close as it should. Same thing goes with the vacuum pulloff.
This carb was rebuilt by Holley, purchased and installed by the previous owner. I'll see what I can do to upload a picture.
Thanks for the info.
-
I'm on my android phone, let's see If these pics work...
(https://picasaweb.google.com/101713312645093748273/5818986961441990625/5818986970470968114)
(https://picasaweb.google.com/viewer#photo/101713312645093748273/5818986961441990625/5818987572543528898)
(https://picasaweb.google.com/viewer#photo/101713312645093748273/5818986961441990625/5818988122497619890)
(https://picasaweb.google.com/viewer#photo/101713312645093748273/5818986961441990625/5819023886887143490)
(https://picasaweb.google.com/m/viewer#photo/101713312645093748273/5818986961441990625/5819019617331159186)
-
I'm on my phone, let's see If these pics work... again
(https://lh3.googleusercontent.com/-mFm-MFZfK58/UMEx0b-MazI/AAAAAAAAAHE/vUVxVnU9G6M/s400/2012-12-06%25252011.08.21.jpg)
(https://lh5.googleusercontent.com/-PMkGLi1UWIg/UMEyXe3en8I/AAAAAAAAAHM/QR_kRFwE0Us/s400/2012-12-06%25252011.05.41.jpg)
(https://lh3.googleusercontent.com/-Hnpwu2yNT80/UMEy3fmwF7I/AAAAAAAAAHU/E7G3p-jk2DI/s400/2012-12-06%25252011.05.49.jpg)
(https://lh6.googleusercontent.com/-HmHE54zezKI/UMFTZQVryEI/AAAAAAAAAH8/Fnt9OFT85dg/s400/2012-12-06%25252011.06.00.jpg)
(https://picasaweb.google.com/m/viewer#photo/101713312645093748273/5818986961441990625/5819019617331159186)
-
Your missing the choke mechanism from the side of the carb. The flap set-up is there, but you need either an electric coil unit or a hot-air set-up on the intake (the Blackish pad on the intake under the carb in your last picture with the 2 holes in it) to control the top flap. It would explain the wire tie holding the pull-off...it would keep the flap from going shut.
I'm guessing this is much of your problem, flap flops shut, floods out engine, ect. Lorne
-
The images show what Lorne is saying.
Image number...
- The choke parts you're missing...
- The flat rectangular manifold surface inside the red circle is the choke thermostat mounting pad. The thin purple line points to the slot in the choke linkage for the "clip" end of the metal rod. (Ignore the red arrow).
- An approximation of how the missing parts should be installed - the choke thermostat is screwed onto the mounting pad; the end of the rod with the long 90° bend hooks to the choke thermostat coil; the end of the rod with the short 90° bend hooks through the 'slot' in the choke linkage and is held with the 'clip;' and the 'stove' snaps down over the choke thermostat to hold the rod in place and help trap heat around the coil, so the choke will open properly.
-
Anyone happen to know part #'s ?
1973 Chevy K10 350 V8, Rochester Quadrajet - unsure of model, here's a photo of some numbers i found:
(https://lh5.googleusercontent.com/-0WGIxajY708/UMFPgvANoJI/AAAAAAAAAHk/ukpBHIgoqBw/s1024/2012-12-06%252011.10.29.jpg)
-
The model should be a Rochester Quadrajet. I don't have any books right on hand at this moment, however according to http://www.recarbco.com/technical/rochester/qjet.html (http://www.recarbco.com/technical/rochester/qjet.html), http://www.cliffshighperformance.com/tech_carb_ID_2.html (http://www.cliffshighperformance.com/tech_carb_ID_2.html) and http://www.carburetion.com/quadnumber.htm (http://www.carburetion.com/quadnumber.htm) your carb is a 1973 Chevrolet Q-jet, 49-states emission (i.e., non-California) with an automatic transmission produced on the 306th day of 1972 (i.e., 3062). The QM should be a production code.
-
The model should be a Rochester Quadrajet. I don't have any books right on hand at this moment, however according to http://www.recarbco.com/technical/rochester/qjet.html (http://www.recarbco.com/technical/rochester/qjet.html), http://www.cliffshighperformance.com/tech_carb_ID_2.html (http://www.cliffshighperformance.com/tech_carb_ID_2.html) and http://www.carburetion.com/quadnumber.htm (http://www.carburetion.com/quadnumber.htm) your carb is a 1973 Chevrolet Q-jet, 49-states emission (i.e., non-California) with an automatic transmission produced on the 306th day of 1972 (i.e., 3062). The QM should be a production code.
Yeah, I found this out recently looking up info about this carb. I kinda doubt it makes a difference, but I'm curious about the automatic transmission part. Like if it matters that my truck is manual.
Anyway, I'm taking it to a mechanic today to have it looked at. I cant really get it done myself and im having trouble finding help. I described what's going on over the phone and mentioned y'all helped me find out I'm missing parts to the choke. The dude said he could put a manual choke on it no problem. I'm gonna have him look over the rest of it to see if its got any other problems... the distributor is a little noisy/rattly/buzzy ... and there may be an exhaust leak or bad PCV valve - its like a flappy/tick sound on the passenger side. I hear it more from inside the cab and it increases with the acceleration. And while driving there's an oscillating hum, thinking it might just be the exhaust note.
-
Mechanic didn't touch much, I took off the air cleaner and you see where gas was spitting up through the pump rod hole and a couple other spots from starting it up this morning. He also mentioned a heat riser gasket or something like that. Said there should be a larger (gasket) space between the Carb and intake manifold. Bringing it back tomorrow morning.
-
Mechanic didn't touch much, I took off the air cleaner and you see where gas was spitting up through the pump rod hole and a couple other spots from starting it up this morning. He also mentioned a heat riser gasket or something like that. Said there should be a larger (gasket) space between the Carb and intake manifold. Bringing it back tomorrow morning.
I thought you took it to him to do something with the choke ?
-
He saw other things that needed attention?
Brought it in this morning, actually ran OK after a cold cold start (tied the linkage to the flap). Called at 2:30 and parts still hadn't arrived. Whatever he's doing he says its under $100. But for taking 3 days I could have done that. I'm not excited about the situation but if gets it running good then ill be satisfied.
-
The fuel pump was over pressurizing and blew the needle off the valve, new pump, new needle valve, new fuel filter. Installed a 'heat riser' gasket thing that wasn't there (between the carb and manifold) and a manual choke cable. I'm not 100% on the choke cable, seems a bit finicky whether it actually pulls the flapper closed and operates the fast idle properly. I moved the throttle spring to a tighter position cuz the linkage seemed a bit sticky. Now the gas pedal seems a bit sticky, like it takes a little extra to move it and when I take my foot off the pedal, it returns kinda snappy. I'm going to move that spring back to it's original position and see if that helps but the linkage on the carb could use some lube/grease or something.
I kinda like the thermostat coil / auto / divorced choke seems like a better idea. I don't really notice a difference with how the manual choke is set up. It was a bit warmer this morning and I didn't use the choke to start, just sat in the cab and held the pedal until it warmed up to idle fine. It runs a lot better now (after it warms up). The choke cable does move the linkage but not as well as I would like / feel comfortable with. Maybe I just need to get accustomed to this setup.
It's pretty nasty out right now, wet, snowy and very windy, I'll post some pics when I can.
I also think the choke cable has some slack under the dash and when I pushed it in last night, the fuse for the tail/courtesy/dash popped. It blew Saturday night and I ended up leaving my truck at work and crashing with some friends who live nearby. Found the blown fuse yesterday, got a puller tool and replaced it. Then it popped again later when I went to leave. Luckily there was another spare in the glovebox, although it was a 30amp instead of a 20 that used to replace it the first time. I read somewhere that there are some grounds under the dash on that side (might have been a different year or GMC) but when I pushed the choke in, the tab it's mounted to flexed a little. Maybe it moved the connection and shorted a ground? The choke cable has a metal sleeve which is why I'm thinking with the pressure from pushing the choke in, the slack moved and touched the fuse box, which doesn't have a cover.
The directions the mechanic gave me to operate the choke are as follows:
Turn ignition on but don't start, push the gas pedal to release the flapper and pull choke.
Feather the gas while starting and it should fire up, then adjust the choke as it warms up.
With the linkage sticking (maybe the cold?) this process doesn't seem to really work. Maybe I'm not doing it right? I've had to take the air cleaner off and adjust things on the carb. That was the cold-cold morning the day after I got the truck back. My roommates were needing to leave in a hurry and rushing me to start my truck. We ended up pushing it to a point where they could move around me. After they left and a few more minutes of trying, it started and ran fine. Unfortunately, I do not have any covered parking and my truck is exposed to cold, snowy, icy elements of South Lake Tahoe.
I also have and aftermarket Barden bumper that one of the previous owners put on and the mechanic said to check the wiring there.
-
The directions the mechanic gave me to operate the choke are as follows:
Turn ignition on but don't start, push the gas pedal to release the flapper and pull choke.
Feather the gas while starting and it should fire up, then adjust the choke as it warms up.
I've had quite a few manual chokes. The way I always start them is this:
Get in and pump the gas pedal 1 or 2 times.
The last time you pump the pedal hold it down to the floor and pull the choke cable.
Release your gas pedal and turn the key with your hand on the choke cable.
As soon as it starts push the cable in partially.
Let it run like that until the motor is comfortable with less choke.'
Let it run like that until the motor is comfortable with no choke.
You will get used to it and it will be second nature before you know it.
-
Ran fine for some time, then the choke linkage started sticking to where I had to pull the linkage to get the carb to fully open. Pretty sure there's some sediment in my tank(s) as well, when it gets low it'll act up and flood/stall when I come to a stop. Might only happen once then clear out but it still happens. Filled up the other day and it's behaved since.
Just put new plugs in, 3 looked good while the rest were a bit white and all gapped much larger than the .035 the sticker on my truck says to gap at (which is where they currently are). Then my friend adjusted the air/fuel screws and it's feeling a lot better. Throttle/power response is quicker and generally feels a bit better. I need to install secondary fuel filters, I'm thinking between the tanks and the tank selector valve.... but I'm pretty sure someone around here said to put it between the pump (which is on the motor) and the carb.
Truck's going to the mechanic Thursday afternoon to have him go over the steering and see what's going on there. In another thread I created on the topic, after I posted pics someone mentioned that it's likely needed to replace the ball joints.
-
Question:
Why wouldn't you place the filter on the suction side of the pump?
-
Most fuel pumps are more effective at pushing fuel than they are pulling fuel.
Although, symptoms of filter placement don't generally appear until fuel filters begin to restrict, to prevent the fuel pump from starving for fuel, a filter installed in the suction line of the pump requires more frequent maintenance compared to a filter installed on the pressure side. For electric pumps, it can actually mean death to the pump if starved of 'cooling' fuel flow. Mechanical pumps are less susceptible to damage, but are still susceptible - especially the diaphragms.
The 'sock' on the fuel pickup in the tank functions as a coarse, self-rinsing pre-filter/water separator that has a significantly higher micron rating than the in-line filters routinely serviced during tune-ups, so 'socks' aren't generally a problem unless excessive sediment or rust accumulates in the tank.
-
I figured that is what you would say, and it is not incorrect, but I prefer to put the fuel filter before the pump, and here is why. Actually I should state that I prefer to install the filter before the regulator.
Most mechanical pumps have the fuel pressure regulator built into them. I want nothing in between my regulator and the float valve. As a fuel filter becomes plugged the pump/regulator only sees a restriction. The regulator doesn't know if this is the float valve, or a chunk of dirt in the fuel line. With the filter between the regulator and the float you can see an inadequate supply of fuel as it starts to plug.
One other reason I like the filter on the tank side of the pump is simple physics. If your standard pump is regulated at 4 psi there will not be as much force available to push through a similarly restricted filter as there would be if you had 29.4" of vacuum drawing (14.7 psi pushing from the outside) through the filter on the suction side.
Ideally you would want tank>pump>filter>regulator>fuel distribution device in a similar fashion to the way GM has all fuel injection systems. GM's approach to putting the filter in the inlet of the q-jet carb was bad, just bad.
One other reason I like the filter on the tank side of the pump is because it traps any crud that may settle in the low parts of the pump.
-
My truck has a mechanical pump on the motor and a dinky little filter right at the carb.
To me, it makes sense to filter sediment before it goes through other parts. However, it also makes sense to put it on the push side of a pump with 'weak' suction. Added restriction on the weak side could/would cause the pump to wear or burn out. With the age of this truck, I'd be tempted to put filters everywhere. Like, high-flow/low-resistance filters off the tanks before the selector valve and better/regular filter after the pump. And probably toss a regulator in there somewhere to help keep things in check.
Pretty sure there's some sediment in the tanks, at least the default (pass side) tank that I've been using while the tank selector valve wasn't switching. I have one to replace it, just too dang busy. Since I have my bike now, I can afford to take my truck apart and work on stuff when I do have time, and can leave it apart longer than a day. So sometime this summer (if time/money allows) I would like to drop my tanks, clean them out and if they're not too trashed, seal them and put them back in.