jonjonbear

Good morning,
I have had nothing but trouble with the carburetor/fuel system on this car since we bought it. When we first bought it, it had a surge that happened during light cruising. Felt like it was running out of gas or had a plugged filter, but if you stomped it, it would clear up and run fine for a long time. Changed the fuel lines, filter, rebuilt the carb (filter element was pristine so the tank must be clean), tune up, Pertronix, still did it. Someone suggested changing the fuel pump. The one on the car was I am pretty sure the original. #40030 two line pump (no ac), that is bolted together. The replacements are all the newer, sealed units. Got the new one put in, and the surge went away. Soon afterwards I noticed that when I would shut the car off, gas would leak out the top of the carb. Both into the carb and down the sides and sometimes pool in the manifold. The garage reeked of gas. Also sometimes driving in traffic it would start to act up and stall. My first discovery was that the heat riser was wired shut. I fixed that thinking it was overheating the carb, and it works as it should now but had no effect. I worked on the floats and nothing fixed it so ordered a rebuilt carb from Rockauto. Seemed to be better but then started doing the same dang thing. I was talking to one of the Oldsmobile guys in our local car club and he told me he had a 442 that had a similar issue, and it turned out to be the fuel pump was bad. He said the new pump had a faulty pressure regulator and over-pressured the needle valves. So we ordered a Holley fuel pressure regulator and gauge and plumbed it in. When I started the car, the pressure was between 7-8 psi so I backed it down to 4.5 psi. Car seemed to run better in traffic but the gas would still come when I turned the car off. I then did a warranty exchange on the carb and the second carb arrived cracked so it went back. I contacted Rockauto and they basically told me to send the first one back, that they didn't feel comfortable sending me another (the first one arrived broken too. Choke housing nipple broke off but the rebuilder sent me a new one) I told Rockauto and Autoline that they both had problems with packing and shipping.

So, the original carb that I rebuilt is back on the car. Runs perfect, starts on the first crank but drive it and bring it home, pretty soon the garage reeks, and the inside venturies are wet as is the gasket around the top of the carb/airhorn. What i've noticed, when I run the car the fuel pressure sits right at 4.5-5psi. I turn it off and in a few minutes, the pressure rises to about 7psi (as if the pressure regulator doesn't hold the pressure when the engine is not running). It is as if the fuel pump will not allow any pressure back down the fuel line and heat expands the gas and the carb is trying to hold the pressure but finally it leaks past the needle and fills the carb. Is the fuel pump supposed to allow the pressure to bleed back down the fuel line? It will eventually leak the pressure down to zero but it takes quite a while. I have the old pump, I'm tempted to put it back on to see if it stops this issue but my original problem will likely come back. I've been looking for one of the old, original style pumps and found some on Ebay but who knows how old they are and if they are still good. I've thought about taking mine apart to see if I can clean it up, or see if the rubber diaphragm is bad but have not found any illustrations on how they come apart. There are a series of screws around the perimeter and one large bolt in the center cap.
Anyone else seen this? I've talked to Sparky (carb specialist) and he too thinks it is something in my fuel pump system and not so much the carb. In all the many cars I've had, I've never had this problem before. I really don't want to put an electric fuel pump on it. I've used them in the past and have not had good luck with them, plus it looks like it would be a pain to put on on this car and mount it correctly.
Any insight would be greatly appreciated. Happy New Year!

Thanks everyone,
John

joe_padavano

There is nothing in the fuel system that can cause fuel to flow into the carb after the engine is shut off. The only way for this to happen is if the needle and seat are leaking or if the float is low or heavy. The outlet check valve keeps 5 PSI in the line from the pump to the carb, but the carb needle and seat are designed to resist this. Any leakage of this fuel into the carb is caused by the needle and seat, period. Changing the pump won't change this, though a different pump with a lower outlet pressure might just mask the underlying problem with the needle and seat.

76olds

I had the same problem on my quad years ago. Shut the engine off and you could hear the fuel purging into the Carb. I used a piece of brass and hit the top of the carb several times. It settled the needle and seat back down and worked for a while, I eventually gave up on the quad due to other issues.
Hope this helps
Eric

Don R.

Wild guess - make sure you have a vented gas cap on the filler pipe.

shiftbyear

John is it possible to post a couple of pictures of your engine/carb and fuel lines with the air cleaner off, thanks.

D. Yaros

The same thought crossed my mind while reading the original post.

jonjonbear

Hi Joe,
My line pressure was much higher than that. We took off the steel line and put a rubber line in place for testing purposes. We put a Holley pressure regulator on it, and straight off the shelf it was putting out 7-8psi. I adjusted it down to about 4.5 like I mentioned but when I turn it off, it slowly creeps up to 7-8 psi as if the pressure regulator only really regulates the pressure while the engine is running.
I too suspect the needle and seat. I've contacted the people at Daytona to see about getting some Daytona valves. I talked to Sparky who has a great reputation with carbs, told me the first thing I should do is to get rid of that "chinese" Airtex pump and try to find an original. We tried putting the original one back on and it spewed gas everywhere. I then adjusted the pressure down again to about 3.5 and it seems to have helped but I'm hoping for the needle valves being week. The floats looked good. They are brass and were intact when I rebuilt the carb.

jonjonbear

Hi Don,
I think this car doesn't use a vented cap because the gas cap is behind the license plate. It has a vent hose attached to the tank that comes down near the rear axle. I just checked the cap, it's an aftermarket locking cap and it says clearly "NON VENTED" If you're sure it should be vented I'll see if I can locata a new one. I hate the locking one anyway, I didn't put it on there.

Thanks so much,

John

jonjonbear

The fuel lines on there are a temporary setup while I am troubleshooting. The car originally had a solid steel line from the fuel pump to the carb. Everyone wanted me to check fuel pressure which is impossible with the solid line so we bought rubber line and put inline the Holley fuel pressure regulator and installed the pressure gauge in it. I can get pics but not sure if that would be helpful being this is all a temporary setup.

shiftbyear

John, this could be a heat problem. Try starting the car from dead cold for 5 min then shut off and check pressures. If pressures check normal increase run times by 5 min each day or when engine is completely cold. If pressure increases after a certain elapsed time you may need some type of heat shield between the intake and carb. Apparently the problem is new fuel related and has stumped quite a few other classic car owners. I hope you get the problem fixed soon, good luck. Also consider stainless fuel line, it deflects heat better than regular steel.

jonjonbear

Hi Shiftybear, that was actually my first suspect. I ordered a phenolic spacer for the carb, thinking it was exactly that. Didn't make any difference so took it back off. I then discovered that the second owner had tied the heat riser shut. Bingo I thought. So I did the opposite, and tied it open. All that did was cause a cold hesitation. So now the heat riser is functioning as it should. Seems the car has a flat spot until it gets very warm and seems to be controlled by that heat riser, as if the manifold has to be hot enough to atomize the fuel. I lowered the fuel pressure again yesterday to just under 4 psi. Drove the car and it didn't seem to starve for gas. Got home and it seemed that the leaking was less. Nothing on the outside of the carb and a smaller amount inside causing the venturis to be wet. Garage didn't reek of gas as it usually does. Left the car sit for half hour and the pressure didn't rise this time. Car fired off on the first crank. So maybe it is weak needle and seats so hopefully those guys at Daytona will reply to my email so I can order a pair and put them in. Thanks for the tip on the fuel line. I bet that would be hard to make, the steel one was a bear to bend.

OLDSter Ralph

I think Joe P was correct. The needles have a rubber tip that is probably leaking OR the plastic float has started being saturated and lacks the buoyancy needed to close the needle into the seat.
......Just my two cents worth

jonjonbear

Hey Ralph!
This one has the brass floats which checked out good when I overhauled the carb. I too suspect sub-par quality needles and seats. Keeping my fingers crossed that I can get the daytona style and that it fixes it so I can take off all that rubber fuel line and put it back as it should be with the steel line.

OLDSter Ralph

Ok, I know you checked the float, but It missed that it was a BRASS float in earlier posts. Where did you get the brass float ? You may still have to lower the float level. What is this "Daytona style" thing ? .

joe_padavano

4GCs all have brass floats.

OLDSter Ralph

Thanks Joe, I stand corrected

sysmg

Go through a cycle and shut the car off, when you see the pressure rise on the gauge, go to the back of the car and remove the gas cap. Walk back to the front and check the pressure on the gauge. I'll bet it will drop to near zero.

classicmuscle442

Good thought and a very easy check. Thinking the problem is the needle/seat, maybe the rubber is not ethanol resistant. Second thought is after all of the fuel got into the engine, probably need to change oil.

jonjonbear

Ralph, here's the Daytona valves:

https://daytonaparts.com/daytona-car...oat-valve.html

I ordered a pair today.

joe_padavano

I'm sorry, but this BS is pure snake oil. First, it this design is so superior to that of normal needles and seats, do you think that SOME carb manufacturer, SOMEWHERE, would have used it at some time in the last century or so? The claim that their flat seal isn't susceptible to "wear groove" is hilarious. It that were true, why do we have to change the washer in faucets periodically? And I really don't understand this diagram. The float level is the same in both cases.




I'll also point out that the original 1965-66 iterations of the Qjet used a similar "flat seal" concept. Not only did that design not catch on, but it's been so expunged from history that I can't even find a photo on the web!

jonjonbear

Hi Joe,
Mine does, but they are shaped differently. More pointy and trapezoid shaped. The two rebuilt carbs I got from RA, both had black plastic floats like I'd seen in Qjets. Yesterday I took the carb apart for the umpteenmillionth time and discovered I did have one float that had gas in it. Just a tiny amount. I put it in a cup of hot water and found the leak. I was able to get the gas out by melting the plug on the side with a soldering iron, then fixed the leak and resealed it. Got all excited that I found and fixed my problem. Put it all together and took it for a short drive. Runs great, leaks gas when I turn it off. I think I must have raised the float level a bit because now it leaks outside the carb more than it did. When I set the floats at the levels the specs say to set them at, the car will stall when you step on the brakes so I had to take the airhorn off and lower them. This thing is literally driving me nuts. If all this still happens after the new pump, and the Daytona valves, I'm going to get back with Sparky again but he didn't think it sounded like the carb is the issue.
My floats look a bit different also, the primary float has a fork that goes under a cup/spring on the power valve. I've looked online for a float like the ones I have, was going to replace the one I fixed in case my repair didn't hold but I can only find these round ones.

I did get a nice email from a guy at Daytona Parts. He said my car is experiencing classic case of heat soak which is what we thought originally but it will do it without the engine being hot. I talked to Sparky the carb guy. He ran all this past his engine buddies and they told me the first thing I need to do is to get that chinese junk Airtex fuel pump off of it and get an original style pump. I found one on Ebay, it's an Airtex, but US made and is the screw together type that looks exactly like the old one. Thenks for your input! John

joe_padavano

Yes, the round ones are early 4GC, the trapezoid are later. I just grabbed the first photo I found on Google Images.

jonjonbear

Both of the rebuilt carbs I got had them so Autoline is using them. Read some reviews that people like them so thought it was worth a try. Can't hurt anything at this point. I've seen them before in my past but can't remember what they were on. Not sure I believe all that lean/rich stuff they claim but will be interesting to see if they seal well. Read somewhere when googling that this fixed similar issues for people. For 8.00/each, not an expensive try given I've tried so much already.

jonjonbear

I'll give it a try. I doubt that is it because i've never experienced any pressure when removing the cap to put in gas. This tank is vented at the top with a piece of rubber hose that comes down by the frame. I'll give it a try though, can't hurt to try it. Thanks for the tip!

OLDSter Ralph

I'll have to go with Joe on this. Maybe I am overthinking this, but that inverted flare could cause cavitation and reduce fuel flow. You have to assume the flat disc contacts the inverted flare straight everytime. Every synthetic (plastic, rubber, elastomer, etc.) develops a contact area over time. The tapered needle and seat works.
.......Just my two cents worth

jonjonbear

Hey guys, Ron at Daytona asked me to send him pictures of my fuel lines. He's been really helpful, said he didn't think the Daytona valves would fix my issue. He thinks it is heat soak but this morning I think I ruled that out. It is 50 degrees in my garage. This am I started the car and it ran for about 30 seconds. I opened the choke and just as I suspected, the gas was leaking. I then decided to make a video and send him rather than just photos, so I'll share that here. In the video you see the gas at the bottom of the carb. Normally you don't see the gas leak until the engine is shut off, but I had already started the car a few minutes before. In the video you will see the fuel pressure gauge on the regulator which hovers around 4psi when it's running. Regardless of rpm, it pretty much stays right there. As soon as I turn off the car, the pressure slowly rises to about 6.5psi. During this entire test, the gas cap was off the car. I even suspected that heat was causing the fuel pressure to rise, but this engine is stone cold so heat cannot be the issue here. I suspect the pressure regulator loses it's effectiveness when the engine is turned off and slowly allows the pressure behind it through.
Sparky suspects the fuel pump. I have one coming from Ebay and will be here Friday. I figure the first thing I'll do is put the new (new pump but old stock) pump on it and hopefully it's still good. If it still leaks gas, then we'll try the valves which I hope come this weekend. Here's the video:


Thanks again guys for all your wisdom and help..This is really frustrating me. This should not be this complicated or difficult to fix. Other than the leaking, the car runs nearly perfect. Starts on the first crank every time when cold and runs like a scalded dog. You can see in the video how smooth it runs and that's a cold engine. Another thing, I stopped by Auto Zone yesterday and picked up one of those "aftermarket" glass fuel filters. Ron mentioned air in the gas causing cavitation to the pump. He said you can't regulate foamy gas. I told him that we have already changed all the rubber hoses but thought if there is any air in the fuel we'll see it in that glass fuel filter (and yes I know they suck and will come back off along with the rubber lines and regulator when this is all figured out)

jonjonbear

Here's a video I shot this morning. Posted below but wanted to reply to your post so you'd see it (hopefully, I'm not getting update notifications from this forum)

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jonjonbear

Joe, are they interchangeable? You can find these all day long but I cannot find any of the ones like mine. I'm hoping my repair is good. I'll check it when I pull it back off again. I posted a video, hopefully maybe you can see something in that. You had mentioned that the fuel pump should be at 5psi. Mine was much higher than that before I put the regulator on. it was between 7-8 before I cranked the regulator down. The regulator holds it at 4psi but when I shut off the engine, the pressure slowly sneaks through and eventually goes up to about 6.5-7psi. I guess the regulator loses its ability when the engine is not running. I'm wondering if that is enough pressure to push past the needle and seat?

joe_padavano

The brass floats don't usually go bad, unless there is a bad solder joint or corrosion from sitting with water in the fuel bowl. I don't know if the round ones have exactly the same buoyancy properties as the trapezoidal ones. Obviously any difference would require a different float setting. The regulator should maintain pressure after the engine stops. If it is not, then it's leaking. Apparently the leak rate is low enough that you don't see it when the engine is running. Note that you can set the float lower than spec to increase closing force on the needle and seat. Note that "lower" means that the float sits lower in the fuel bowl when the needle is closed, so the float would actually be higher if the air horn is flipped upside down on the bench and you are measuring it. Also, be sure that you don't have any debris or damage in the needle and seat. I recently had the fresh Qjet on my wife's D88 start leaking. Turned out that a piece of plastic gasket from the inlet fitting had been sliced off by the treads and found it's way RIGHT into the needle and seat, holding it open.

Lonnies Performance

I would say you are correct.
The fuel pump has a check valve that holds pressure at the outlet of the pump... presumably about 7lb.

Your regulator is set lower & typically functions fine with the car running as it is slowly consuming fuel. Once you shut the engine off, the regulator allows some pressure creep, which drives it up towards the pressure at the pump.
The typical AFB & Quadrajets do not like high fuel pressure & that can overcome the needle/seat assembly. Holleys are typically fine with 7psi.

You could make a small bypass arrangement with 2 tees that would send fuel back to the pump inlet, from the pump outlet. A small orifice in this line, about .020" would allow the pressure to bleed off, but not cause a significant reduction in pump capacity.

joe_padavano

Or, simply install a fuel pump from a car with fuel return, which already has the extra port and the orifice.

sysmg

I don't know much about 4GCs. But should the fuel level be higher than the gasket between the airhorn and the carburetor body? It would have to be that high to be leaking as shown in the video. My guess is that now the float level is too high.

-Stew

joe_padavano

Debris holding the needle open can cause that. Excessively high fuel pressure can cause that. A leaking float that isn't buoyant anymore can cause that. All will look the same from the outside.

shiftbyear

John, since we're kinda shotgun troubleshooting at this point, just for the heck of it try removing the fuel filter and doing your test. Sometimes answers defy logic. Also here's a video to test brass floats. Best of luck.

jonjonbear

Lonnie, I had actually thought about that bypass idea but couldn't figure out how to do it. I see how it would work with an orifice. I know this car had a different fuel pump on it if it had AC, but nobody lists it. This number is the only one I've found. I guess those with AC have a hell of a time finding a fuel pump.

jonjonbear

That's exactly what I did. when I heard the liquid in my float, I put it in a hot cup of water and it blew the tiny bubbles. I then found instructions online how to fix it by melting the plug on the side with a soldering iron, getting the liquid out and repairing the seam, then resoldering the plug. Seemed to work. I was all excited thinking that was my problem but when I put it back together the problem still existed.
I did scrub the net for all the information I could find on the 4GC and found some good illustrations and see that at least one of my adjustments was wrong. The float drop with the vacuum assist compressed (and finally an explanation as to what that is for). I didn't do that correctly. The biggest problem I've had with trying to do this is the illustrations are TERRIBLE in most cases so you really can't see what they are referring to but now that I found some better ones, I'm going to redo some things after the new fuel pump gets put on. Thanks for the video! His videos are very helpful.

Lonnies Performance

If your car had a factory return line to the tank, it would be much easier... then you could get a 3 port pump, a filter with a vapor return port or a return style regulator.
All allow fuel to bleed back to the tank instead of deadheading the fuel at the carb.

My method prevents buying another pump, but is a little crude by comparison to a pump designed this way.

jonjonbear

I know this is an old post but I found it googling 4GC carbs with jet plugs. As does the OP, I have a 1965 Starfire with carb issues. Carb does not have a tag. I rebuilt it and the car runs fine but leaks gas from the airhorn gasket when you turn it off. Both inside and sometimes down the outside. I've adjusted the floats at least a dozen times. I did find one of the secondary floats had a small amount of gas in one pontoon. I found the leak, purged the gas and repaired it but that didn't fix the problem. Replaced the fuel pump (suggested by other Olds guys, that the "cheap new pump" I put on might be the issue so found an oe style rebuilt pump and put it on), put on a pressure regulator, still does it. I ordered a set of Daytona float valves, still did it. I finally gave up and this week boxed it up and sent it to Daytona Parts Co. The owner has been really helpful and knows his carbs. He said that because mine does not have the baffles on the airhorn, it is not a 65 carb (he sent me pics of what it should look like). But, something I just realized (looking at an ebay listing because the guy mentioned it) my carb has those two brass plugs in the front. I've looked everywhere on the net for a picture of another on and this is the first one i've seen. So my carb must be from a 442? I see by your note, it should work well but I saw a comment above (it can also be "identified" by its poor part-throttle response) What would cause this? I did have a hesitation, worse when cold but discovered I didn't get the Accelerator pump back together right. Car runs great, just leaks gas. They have not gotten the carb yet so not sure what they will say about it. just wanted to ask since I saw this post, even though it's old but I see Aliensaitmybuick is still active.
Thanks,
John

joe_padavano

You already have this lengthy post detailing your problem. Resurrecting an ancient, unrelated thread and asking the same question is NOT the way to get a useful response. You'd have to repeat everything from this thread to bring everyone up to speed. I moved your post into this thread.

For what it's worth, I eventually threw in the towel on the 4GC that came on my 62 F-85. I rebuild and adjust all my own carbs, and have mastered the finicky CCC carbs, but this 4GC just kicked my ***. I chalked it up to rust in one of the drilled passages in the cast iron throttle body that I could not access because the ends of the passages are plugged after drilling from the outside. I installed an E-brock instead. I'm not saying this is your problem exactly, but I don't know wat else to tell you. Fuel leaking from the seam between the fuel bowl and air horn can only come from one source - the level inside the float bowl it too high. There is no other way for this to happen. Figure out why and you'll solve your problem. There are only so many possible causes - floats set too high, floats not buoyant enough, leaking needle and seat, or excessive fuel pressure. There are no other possible causes.

jonjonbear

Hi Joe,
Sorry, my question there was more about the fact it appears mine is from a 442, since it has those two brass plugs in the front to access the jets. I have searched high and low on Google trying to find another one like it and the only one, was the thread I commented on. Specifically where he said this (it can also be "identified" by its poor part-throttle response) whereas his comment left me to believe that would be one way to tell if you had this 442 carb on your 425. Given the closeness of power ratings between the two engines, I'm going to assume that both engines should have similar CFM carbs so this one shouldn't be too small. The car doesn't seem to lack for power. Is there even any way to look up CFM specs on Rochester carbs?

I agree what you say. But I tell you I have adjusted those damn floats so many times I can't even remember. When I pull the top off the carb, the level of the gas in the bowls actually looks low, something like 1/2 to 3/4" from the bottom. I realize the floats will cause a bit of a rise but the level is nowhere near the top of the carb body and this is literally taking the carb right off the engine after running it. We've ruled out the fuel pressure and pump. The exact model that came off just went back on and made no difference. Heck someone even recommended putting a second air horn gasket on in case it is warped. No difference.

I've thought about an E-Brock. That's what I put on our Avanti and never had an issue. Only thing is, I really don't want an aftermarket air cleaner on the car. This car is so original (literally almost a survivor) I'd like to keep it that way and I know my air cleaner opening is too small for the E-Brock. Yes they make an adapter for the air cleaner, but from what I understand that first, the E-Brock would need an adapter to fit on the manifold. Then, another adapter to fit the air cleaner on..At this point my hood won't close. Already the air cleaner hits the fiberglass.

So as you read in that post, I've finally given up. I took it back off, took the air horn back off, took off the second gasket and dumped the gas and put it back together, packed it up and shipped it to Daytona Parts Co in Florida. Ron, the owner has been very helpful and knew very specific things about the 65 carb so I feel they are competent and if anyone can fix it, they can and likely have backup parts if needed. They also get excellent reviews. Maybe he can figure out what the heck i've got. Odd too, on the bottom of the throttle plate is a stamp. "DPC" and I'm wondering if perhaps they might have worked on this carb somewhere in it's past. So now I sit and wait..I sure do appreciate all the guidance and help. This has been very frustrating and has made my dream car unreliable and not enjoyable to drive. I'm actually two shakes from considering EFI, but then again we're back to the air cleaner and the return line I don't have. I wish it had a quadrajet, I've never had a problem rebuilding those.

Something else I thought of after shipping it off. The fuel runs through that airhorn..Maybe there is a hairline crack in it:? Who knows, I too am out of ideas! It arrives at their shop tomorrow. He sent me a picture of the correct 1965 airhorn, maybe he'll put that one back on! :-)
I'll surely keep this updated with the findings. By moving my comment on that other post, will the other posters get a notification of my comment? Maybe my carb is "rare" and they'll want to trade me! :-)

This will give me a few weeks to work on the power window. The motor in the pass side door is wonky and I'm going to have to figure out how to get that out. No Youtube videos on that and the shop manual isn't very clear! Only thing I've learned that you better drill a hole and put a bolt through the regulator lest you lose a finger!

Thanks guys,
John