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CarburetorsCarb discussion and questions. Upgrading your Third Gen's carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.
your carb and dist look to be the correct original parts.
timing is set by disconnecting the four wire connector to the dist for base timing at 0-4 degrees advanced.
Had another look at this tonight while i was in the garage, so i thought it was this connector going into the back of the dizzy you were saying to unplug, on further inspection, this isnt a plug, its just a wiring harness that goes into the dizzy and is bolted in place ?
So im not sure what i unplug to set the timing correctly. its been running fine by just turning the dizzy by hand to where it sounds right but it would be nice to know how to do it properly for peace of mind.
the four wires that go into the base of the distributor attach to the wiring harness with a black connector. should be about a foot, or a little less, of wire from dist to plug. attached pic from web.
Right then. Timing set. Fixed the power problem with my choke so it actually works. The light goes off on the dash when the engine starts and the flap opens more and more as the car warms up.
This morning I looked at the carb and the flap was totally closed. And it started on the key. Absolutely perfect. As it cranked it fired and the pull off opened the choke flap a bit and the car ran great.
Just tried to start it again earlier, nothing had changed but it just kept cranking over. So I fiddled on and opened the choke flap manually again like I have been and it eventually sputtered into life.
Does the choke flap need to be a little bit open all the time ??? I don't get how it started with it fully closed one minute but wouldn't the next unless I opened it.
Thats what i assume is happening, or if there just isnt enough air on initial start up to fire the engine ? it just always starts up if i open the choke flap slightly.
its weird how this morning it was fully closed and started perfectly on the key.
Another item relating to the distributor. Can't wait to get the new one in. I ran the car quite a few times yesterday and it starts when hot as the choke flap is fully open still but I have to hold the key and it cranks for a while then you can hear it try and try and try faster then it will fire, idle low for a few seconds then the rpms sort themselves out and it's ok
I've been doing the rear suspension lately but back to this carb now.
I'm thinking fuel delivery problem. I've done the timing etc and it idles the same all the time now and starts pretty easily too. The car will sit and idle fine.
However, if I rev the engine the car wants to cut out. But if I slowly rev the engine up its fine and I can rev the engine in the high rpms range and it feels great.
I've also noticed that fuel doesn't squirt into the carb if I pump the gas like it used to while looking in the choke flap ? But it's obviously getting fuel...
Hot start problem = leaking fuel well plugs in the bottom of the carb
No fuel squirting out when moving the accelerator = bad accelerator pump, or all the fuel has already drained out of the carb due to the above
Sounds like carb rebuild time, including epoxying up the plugs. Whether it has already been "rebuilt" or not. Either it works or it doesn't... if it doesn't, which is clearly the case, then its history of "rebuilt"ness, or not, is irrelevant.
it starts when hot as the choke flap is fully open still but I have to hold the key and it cranks for a while then you can hear it try and try and try faster then it will fire, idle low for a few seconds then the rpms sort themselves out and it's ok
That is the ABSOLUTE CLASSIC DESCRIPTION of the Q-Jet Hot Start Problem. I couldn't have described it better myself if I tried. The only thing you didn't mention was the fact that it also blows out a bunch of smoke until it smooths out, due to the excess fuel and the rings being all washed down such that it may also burn oil as well as all the fuel.
It's caused by the plugs in the bottom of the fuel bowl casting leaking and allowing the fuel in the bowl to drain into the intake manifold.
The root cause is, the casting is some kind of chinesium, and the plugs are some other metal. Over time, with exposure to moisture especially, a dissimilar-metal electrolysis situation develops, which destroys the casting by EATING the metal. That is, the plugs stay intact, but the casting (the more "base" metal of the 2) corrodes and erodes where it touches the other metal. It's as inevitable as night following day. The whole casting is subject to it, actually; the threaded screw holes are another site where it occurs, which causes them to strip out. If there's ANY SIGN of a white powder ANYWHERE on the fuel bowl or air horn castings (the throttle plate is aluminum and thus not near as prone to it) then the carb has this issue and CANNOT be successfully made to work right until it is addressed.
The particular plugs in question are the smaller ones that are spun into the casting after certain passages are drilled during manufacture. There are 4 of them under the primary main jets and 2 more under the accelerator pump. They are about 5mm diameter. The larger ones under the secondary metering wells, about 1cm dia, do it too but don't cause The Problem unless the throttle plate gasket has failed... they're inside their own little "chamber" isolated by the gasket, and fuel can't just drip into the intake like it can from the little ones.
The cure is, take the carb apart, wire-brush and sand the area around the plugs down to clean unoxidized metal, sterilize the area with a NON-RESIDUE solvent such as lacquer thinner or MEK (NOT brake parts cleaner, gasoline, mineral spirits, "paint thinner", etc.), allow the solvent to dry completely, cover them with epoxy, and bake the fuel bowl in the oven at a low temp (80 - 100°C) for an hour or so to set the epoxy before exposing it to gasoline.
Of course, the carb must be disassembled to do this, must be cleaned up, and must be reassembled afterwards with new gaskets and other soft parts. The common name for this procedure is "rebuild".
Once again, IT DOES NOT MATTER whether the carb has already been "rebuilt" or not. You can "rebuild" it every single day of the week, and twice on Sundays just for good measure, and NEVER fix the Hot Start Problem. Which of course sounds like EXACTLY what has happened to yours: somebody "rebuilt" it without fixing the plugs, and now you've got a nice clean shiny new-looking "rebuilt" carb, that is still just as defective as it was before it was "rebuilt".
Likewise, failure of the accelerator pump to work is indicative of ... failure. The cure is a "rebuild".
At this point, you either want your car to work and will do what it needs to make it so, or you don't. Pretty clear choice it would seem. I'm telling you what your car needs, having experienced it countless times in my own cars and others, and LEARNED what the true cause and repair methods are, which I am now GENEROUSLY sharing with you in spite of the fact that I don't have to. If you'd rather argue with me than do it, that's fine with me, after all it's not my car that isn't working.
Plugs #3, 4, & 5 are the main culprits in this photo I ganked off of some other forum. #1 & 2 look tempting to mess with but don't cause the problem. #6 is in the front of the carb near where the fuel line hooks up, and leaks all over the front of the carb rather than into the intake. The photo is of a non-computer carb, which is slightly different from yours but similar enough to use as a guide.
Last edited by sofakingdom; 03-26-2017 at 10:35 AM.
I'm not arguing with you lol. Thanks for the lengthy reply. Right screw it then I will take the carb off the car and have a look at these plugs then I guess.
The car seems to have a mind of its own really. I can leave it for a week and it will start on the key pretty much straight away which it did on Friday after not starting it since last weekend.
Other times it will attempt to fire straight away but won't so keeps cranking until it slowly starts and ides low for a few seconds then it sorts itself out
slow rev fine, but quick rev-cuts out and lack of fuel squirt are consistent with a failed booster pump.
first ensure that the lever arm for it hasn't become disconnected from the throttle linkage.
The booster pump is ok, goes up and down fully with the throttle.
Before i take the carb off i disconnected the fuel line to the filter housing and it was surprisingly dry. not even a little fuel dripped out when i pulled the pipe out. the inside of the pipe seemed a bit wet but i really thought some fuel would of come out, i had been pumping the throttle a few times before hand too.
Is this the fuel pump perhaps ? or is it all related to these plug things.
when i disconnected that pipe to take the old carb off fuel came out and dripped all over the intake manifold, and ive had the fuel pipes off my 87 a few times and fuel always dribbles out of them even when the car had been sat idle for weeks.
fill the carb bowls and start the engine with the fuel line disconnected and into a catch can. the motor should idle for about a minute with the fuel in the bowls and you should observe fuel going into the catch can.
fill the carb bowls and start the engine with the fuel line disconnected and into a catch can. the motor should idle for about a minute with the fuel in the bowls and you should observe fuel going into the catch can.
Where exactly do you pour the fuel into the carb? Really don't want a fire.
Last edited by gta_knight; 03-27-2017 at 01:00 PM.
Not there. He's suggesting filling the bowls through the vents.
The vents are the 2 holes just to the front of and on either side of the idle air bleed valve, which is the thing that looks like an enormous screw with a brass pin in it in the center.
Sometimes (usually) the fuel leakage problem is so bad that the carb completely empties after a time, say, overnight; but then, if it sits long enough that all that fuel evaporates, it won't start up cold either. When that happens you have to crank it long enough for the pump to refill the bowl but then when it does start it's normal, as if nothing was ever wrong.
fill the carb bowls and start the engine with the fuel line disconnected and into a catch can. the motor should idle for about a minute with the fuel in the bowls and you should observe fuel going into the catch can.
Tried that, i put a syringe of fuel in each hole just to see if it worked and it fired straight up but obviously died after a couple of seconds with it being just a tiny amount, i directed the fuel feed line into a can and it fired out fuel so i know the pump is good.
i had my friend take a look and on my fuel feed pipe someone has cut it for whatever reason then rejoined it with a piece of rubber fuel pipe, i took that off and it looks like the rubber is coming away on the inside, however there wasnt any black bits on the fuel filter when i checked that so im not sure if it was a problem or not.
Ive put 3 syringe fulls of fuel in the holes and left it, see if it fires up tomorrow or not, providing it doesnt evaporate over night !
sofakingdom, so are you still pretty sure my problem is with these plugs inside the carb ?
Besides a probable distributor problem, I think your electric choke and choke pull-off
are not properly adjusted, thus closing the choke too far after a five to fifteen minute run, and flooding the engine upon warm restart.
The choke has the rivets in so hasn't been adjusted. I'm not sure what the adjustment on the pull off is exactly I know you can turn a screw on it. However it seems to work as it should. It's fully closed when cold then opens slightly upon startup then opens gradually the longer I leave the car running.
I hadn't considered a dizzy problem since I found it was a tooth out so I fixed that and set the timing and it always starts and idles fine
Not there. He's suggesting filling the bowls through the vents.
The vents are the 2 holes just to the front of and on either side of the idle air bleed valve, which is the thing that looks like an enormous screw with a brass pin in it in the center.
Sometimes (usually) the fuel leakage problem is so bad that the carb completely empties after a time, say, overnight; but then, if it sits long enough that all that fuel evaporates, it won't start up cold either. When that happens you have to crank it long enough for the pump to refill the bowl but then when it does start it's normal, as if nothing was ever wrong.
All symptoms of the same syndrome.
Tried the car just now after leaving it overnight and it started straight away and ran for a few seconds like it did last night with the same amount of fuel from the syringe.
Do you still think it's the plugs inside the carb or perhaps a blockage somewhere between the fuel line and the bowls. Although I would of thought the filter would prevent that and it looks clean when I took it out.
fuel goes through the filter from the inside out, no way to tell if it's clogged without cutting it open or maybe blowing air through it.
if the needle/seat assembly was replaced with one that has the slots in the side AND the one-way check valve within the filter is missing, only a small amount of fuel need leak out to lift the seat and allow more fuel to flow back through the line. don't worry about that yet though.
best test of the well plugs is to place the carb over something overnight that will show whether fuel is leaking out. a dry paper towel maybe. ensure the bowls are filled, as above, first.
Ok so following my little test last night with the fuel feed disconnected and aimed into a fuel can, then putting fuel into the bowls via the vent holes everything worked fine. The car started immediatley and fuel shot into the can.
So I reconnected the fuel feed line, put a little fuel down the vents again and started the car. It ran for a few seconds then cut out. I tried starting it and nothing...sputtered a few times then just kept cranking.
FFS !!
So where the hell is the fuel stopping exactly. Tried pumping the throttle on the side of the carb and still no fuel squirting out. So what's blocked ?
Sounds now, like debris inside carb fuel inlet blocking gas flow. Or bad needle and seat(needle stuck closed on seat).Are you sure the small filter(with spring behind it) inside carb isn't bad or plugged?
I'm not even sure what the needle / seat is so that's another thing to look up. As for a spring?? There is no spring inside where the filter is. The filter was just inside the threaded part that screws into the front of the carb.
So ive been at it again today, i removed the fuel filter and connected the line back up, put the air cleaner on and after a bit of cranking the car started and idled really high, backed the idle screw down where it was normal-ish, maybe 1krpm and reved it up a bit and it felt great, no hesitation or anything.
Ignore the thumbs up at the end, that was short lived... lol
So after that while looking at the engine i could hear a weird noise, so i took the air cleaner back off and coming from down in the carb is a sort of pressurised hiss / leak noise, you know when something is leaking slightly under pressure, you can hear it really clearly in this other video, it comes and goes, and this was about 20 minutes after i had shut the car off too.
Sounds like a tiny person is taking a whizz inside the carb ! what the hell is that....
I also noticed a fuel leak coming from somewhere under the choke too and dripping onto the intake manifold, urgh.
one thing pointed out to me was this carb was bought to go on a 350 goodwrench crate motor, and it may have 350 jets on it, but mines a 305 ?
So im not sure where to go from here other than removing the carb, getting a new gasket set and replacing the gaskets to hopefully stop that drip from around the choke area.
Ok guys, i think this is the problem. its not spraying fuel at all on the drivers side of the carb. It just squirts a little bit out under throttle from a different hole. heres a vid
I tried blasting air through the fuel filter port when i had the line disconnected but that obviously hasnt helped. So im wondering how that jet is blocked and how easy is it to sort out.
Im guessing the carb has to come off and be opened up to access that part, hopefully there is something just blocking it and can easily be sorted out
Im also wondering if that weird pressuried leak noise in my previous post is the fuel trying to force its way through this blockage perhaps ???
It appears the carb has leaky well plugs ( the hissing sound).The fuel is leaking and dripping onto hot intake manifold and vaporizing.....making the noise.With all the issues seen in the videos....the carb should be removed and gone through by an experienced rebuilder as you have multiple issues with this carb.My first guess is the fuel float level is too low when running...... because of a possible blockage internally. You should also have a spring behind the filter to keep it sealed against incoming fuel/pressure.That may have caused particles to block fuel flow internally and/or contaminate fuel bowl. With no spring ....you will definitely have to at least open carb.clean.adjust float level or replace if necessary, install spring behind filter (check with left hand pinky finger inside fuel inlet for stuck spring), etc.Also ...make sure accelerator ball check valve is in place.Some tips to look for with carb. Good Luck.
Last edited by hockeyman48; 03-30-2017 at 06:23 PM.
You can take this carb apart yourself, that's the easier part.
Getting it back together, the tough part. Being inexperienced with carbs,
you are almost certainly guaranteed to break the TPS plunger, at the very least.
I've took the carb off the car now. I know there is definitely not a spring inside the fuel filter port so I will have to get one.
I think I'm going to have to find someone locally that can sort it out for me then. I'm kind of being put off doing it myself with some of the comments here saying I'm going to break something when trying to put it back together
It appears the carb has leaky well plugs ( the hissing sound).The fuel is leaking and dripping onto hot intake manifold and vaporizing.....making the noise.With all the issues seen in the videos....the carb should be removed and gone through by an experienced rebuilder as you have multiple issues with this carb.My first guess is the fuel float level is too low when running...... because of a possible blockage internally. You should also have a spring behind the filter to keep it sealed against incoming fuel/pressure.That may have caused particles to block fuel flow internally and/or contaminate fuel bowl. With no spring ....you will definitely have to at least open carb.clean.adjust float level or replace if necessary, install spring behind filter (check with left hand pinky finger inside fuel inlet for stuck spring), etc.Also ...make sure accelerator ball check valve is in place.Some tips to look for with carb. Good Luck.
I took the carb off the car yesterday and set it to one side, and i brought it out of the garage just earlier for a look, started turning it upside to look at the underside and petrol spilled out. So i guess its not leaking completely ?
As for checking the float level etc ive got no idea where im looking, a few people have told me to see how much fuel is in the float bowls but how can you tell ?
I thought these things were the well plugs you were talking about that could be leaking but after a search these arent what i was looking for, im not sure if thats how they should look as they to have been modified.
Yes, those are the well plugs. Is there epoxy on them? Looks like there might be.
But the lower left one in the pic is shiny, compared to the others.
Did the epoxy come off of that one?
No I don't see epoxy... the one that's in shadow is just that, in shadow. Can't tell if they're leaking.
These carbs are definitely tricky to put back together right. Not "hard", not something I would tell you not to try; just, tedious, and lots of opportunity to get something wrong along the way, and hard to fix a mistake other than by a teardown and starting over. So you have to be careful and meticulous, and make sure you get each step right before moving on to the next.
you can remove the base plate without opening up the carb, three screws on the bottom and the two longer screws top-rear. I'd still leak check it first to check but epoxy on the plugs is a good idea anyway.
I had to swap this base plate onto this new carb as it was set up for a manual transmission car instead so that's no problem. I'm going to try blowing out anything that's blocking that jet then put some fuel in the carb and leave it overnight and take it from there
Right then..... leak test. put the carb outside on my storage box with the intent of putting fuel into the vent holes then finding a big clear plastic box to sit the carb in overnight.
No sooner had i put about 30ml of fuel in each vent hole it started running out the bottom of the carb, argh ! I took the base plate off for a closer look, and the well plugs appear to have been epoxied over anyway.
the gasket felt very firm, im not sure how firm this gasket should be ?
I dried the bottom off and done it again to see if i could see where it was coming from and it looks as if its seeping through those slots and holes here, that pill shaped one possibly as it still looks wet inside in this picture.
It's kinda weird about the epoxy on there... there are 4 plugs on the primary side that can leak; they only covered ONE. Of course you can take ONE LOOK at those big ones on the sec side, and see OBVIOUSLY that they CANNOT POSSIBLY leak into the intake as long as the gasket is good, because they are COMPETELY enclosed in the throttle plate casting. Total waste of perfectly good epoxy that they SHOULD HAVE put where it can actually DO SOMETHING.
Butt yeah,,, if you put fuel into the bowls and it comes out those passages, it's bad news for that casting.
And yes, the throttle plate gasket is supposed to be pretty hard.
before giving up on that carb, remove the airhorn and give us a pic of the airhorn and its gasket along with the main body. we may have a mismatch somewhere that's allowing an overfill of fuel to flow into the air bleeds. I'd also like to see the condition of that main body.
overfilling the bowl 'might' let fuel come out those passages-I'd have to look at one to refresh my memory though.
before giving up on that carb, remove the airhorn and give us a pic of the airhorn and its gasket along with the main body. we may have a mismatch somewhere that's allowing an overfill of fuel to flow into the air bleeds. I'd also like to see the condition of that main body.
overfilling the bowl 'might' let fuel come out those passages-I'd have to look at one to refresh my memory though.
Well ive gone over all the plugs with some new ethanol / petrol resistant JB weld, ive sprayed the accelerator pump with carb cleaner and started working it and it free'd up real nicely. Put fuel into the vents again and nothing came out of the bottom at first which was great. I then moved the carb and tipped it at angle, and fuel came out again. After a few more experiments with putting more fuel in and tipping it toward me slightly its coming from where i thought it was in the first place, that kidney bean shaped hole
I dont know how much the fuel bowl can hold so is it possible ive put too much fuel in and its running out when the carb is at an angle. at least it didnt pour out immediatley like it did before i put the epoxy stuff on !
also when operating the accelerator pump it blasts fuel in on both sides again which is promising, obviousy i wont know if it sprays out of the jet until i run the car but there is only one way to find out.
If you have not changed the accelerator pump cup, then before you put it back together you can massage the cup to a larger diameter using your fingers. The additives in the fuel shrink the cup over time. This also happens from non-use when the fuel evaporates from the well it resides in. If you have ethanol in the fuel in England, then you should really install an ethanol resistant accelerator pump.
Ive already put the carb back on the car and tried it, the hesitation is gone as in it revs up no problem and is smooth, its spraying fuel in on both sides now too which i guess was that problem with the accelerator pump sticking.
its still making that leaking noise after shutting the car off though, like a tiny guy is taking a whizz inside the carb !
and theres a leak from under the choke still, drips out now and then. ive been speaking to Quadrajet Power in Texas and they can supply me with a fully redone carb ready to just bolt straight on, i honestly think i might do that as im getting sick of taking this one and off and on and off now.
02-14-2017, 03:45 PM
Of course you can take ONE LOOK at those big ones on the sec side, and see OBVIOUSLY that they CANNOT POSSIBLY leak into the intake as long as the gasket is good, because they are COMPETELY enclosed in the throttle plate casting. Total waste of perfectly good epoxy that they SHOULD HAVE put where it can actually DO SOMETHING.