popping from carb
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=31397
Printed Date: October-08-2024 at 7:25pm
Topic: popping from carb
Posted By: mcfunnymoney
Subject: popping from carb
Date Posted: August-31-2013 at 11:47pm
| I'm a new member and a new owner. I just rescued a 1980 Ski Nautique that had not been off the trailer in 10 years. After washing the green off the entire boat I rebuilt the carb and cleaned the points. The boat runs but not well. I cant get it to idle under 2k and when it is loaded (in the water vs running on the trlr) it pops through the carb. I'm suspecting timing but I am at a loss. Ant ideas? I have cleaned and lubed the weights in the distributor and they don't seem to be stretched. I also posted this in the general section accidentally. Woops. Rookie mistake |
Replies:
Posted By: Dreaming
Date Posted: September-01-2013 at 1:36am
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First off, welcome to the forum, and congratulations on your purchase! two things generally cause a backfire: timing & plug wire placement. there are other things that can cause a backfire, but they don't sound like the issue you have. what I suspect is that you have your plug wires in the wrong firing order. Since the boat is new to you, check to see that you haven't got the wires reversed from the distributor rotation, and that the sequence that you have the plug wires in is the actual firing order for the engine. there are a couple of different ford firing orders, you may have the wrong one. If the order is not on the engine's data tag, you can figure it out the old fashioned way by checking the order that the cylinders come up on their compression stroke. timing could be your problem, when the spark plug fires too early in the stroke, and the intake valve is open, it will cause a backfire. try advancing the timing a bit if this is the case |
Posted By: mcfunnymoney
Date Posted: September-01-2013 at 1:48am
| I'll check the timing tomorrow. I found tdc #1 and followed the firing order listed on the tag on the intake and the cylinder numbers stamped on each runner. Where should the timing be? I will hit it with a light tomorrow. |
Posted By: Dreaming
Date Posted: September-01-2013 at 1:52am
I don't know the timing numbers, but you could probably find them in the reference section of this site. It would help anyone who is familiar with your boat if you listed which engine you have. Pics are always good too 
|
Posted By: SNobsessed
Date Posted: September-01-2013 at 2:50am
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Also could be vacuum leak. Spray carb cleaner around base of carb. If that changes RPM, you are onto something. ------------- “Beer is proof that God loves us and wants us to be happy.” Ben Franklin |
Posted By: oldcuda
Date Posted: September-01-2013 at 8:51am
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Cracked dist cap would be my first guess check for carbon trail and make sure all is dry |
Posted By: ArtCozier
Date Posted: September-01-2013 at 12:30pm
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The above suggestions are all good. I will add the following: Leaking exhaust manifold or riser gasket. Sticking intake valve or a burned valve. Broken timing advance spring in the distributor. Art ------------- "Art" |
Posted By: mcfunnymoney
Date Posted: September-10-2013 at 8:39pm
| ok, I finally had a minute to mess with the boat. I tested the plug wires when I checked the timing and found two ad ones. Today I installed new ones. The popping and backfiring is gone but I still cant get it to idle below 2k. It seems to run out of fuel when I idle it down. Looking down the carb the fuel stops spraying and sprays off and on. Fuel pump? When I give it gas it stutters (not like it was before with the popping) its a fuel stutter. The boat did sit for 5+ years. The fuel lines are new and there is a full tank of two week old gas and there is a see through filter in line and it is clean. I bypassed the separator and it made no difference. By the way art, I had the springs looked at by the dealer and he said they are ok. I wondered that too. |
Posted By: ArtCozier
Date Posted: September-10-2013 at 10:36pm
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The high idle and backfire are symptomatic of an intake system vacuum leak. One thing to check is the PCV valve to make sure it has the proper amount of restriction in it. You can simulate the high idle situation by removing the PCV hose at the base of the carburetor. Typically with that fitting open, it won't idle below 2000. Art ------------- "Art" |
Posted By: mcfunnymoney
Date Posted: September-10-2013 at 11:11pm
| The high idle is due to me raising the idle screw on the carb. if i drop it lower than 2k it dies. I should have specified that. I suspected the pcv hose and put a hoseclamp on the end where it meets the carb and no change. This is frustrating. It does seem to starve for fuel lower than the 2k idle setting. Im going to test the pump by taking the line off at the carb and seeing how much fuel it produces when I turn it over. Ill update after I test it. |
Posted By: ArtCozier
Date Posted: September-10-2013 at 11:31pm
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Were you able to idle it down enough to properly set the base timing? If you set the timing with the engine running at 2000, no wonder it does't run right! I believe, from memory, that a 1980 with Ford (PCM or Commander) should be set at 10 degrees. There will be a highlighted mark on the vibration damper indicating the proper base timing. Art ------------- "Art" |
Posted By: mcfunnymoney
Date Posted: September-10-2013 at 11:55pm
| i couldnt get it that low. it died. i advanced it a bit. The pcm sticker on the valve cover said 6 degrees so I went with 10 at 2000 rpms. That was the best I could do. It sounds healthy at that high idle though and starts without drama if i give it a quick shot of gas. |
Posted By: boardersdad
Date Posted: September-11-2013 at 1:28am
+1, Art. My other boat has an old Mercruiser 140. I suffered through a few years of high idling and lousy starts. I eventually found a vacuum leak due to an aged carb gasket. A new gasket helped a lot. Then I had the carb rebuilt (I'm not good with small parts), and for a decade now that 40 year old four-popper has been idling smoothly at spec.  Steve |
ArtCozier wrote:Posted By: ArtCozier
Date Posted: September-11-2013 at 10:17am
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OK, now I think we're making progress. Please help me think about this, because I'm in a hurry and wondering if I have this in my mind correctly. I think the timing is set too far retarded, because if you set it at 10 degrees at about 2000, you set it too far retarded. I don't have a distributor curve handy, but I think that at 2000 you are probably already advanced by about 15 to 20. Advance the timing and see what happens. Try setting it at about 20 at 2000 and then back off the throttle and see what happens. If you have to, put down the timing light and try playing with it by "timing by ear." Work the distributor with one hand and the throttle lever at the carburetor with the other. (disconnect the throttle cable) Move the timing, (distributor clockwise) and back down on the throttle as it will tolerate. If and when you get it down to a reasonable idle, put the light on it. I hope that a third party will read this and tell me whether I'm thinking straight. Art |
Posted By: backfoot100
Date Posted: September-11-2013 at 12:32pm
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You're absolutely right Art. At 2K RPM I'm guessing the timing should be at least 20 degrees, maybe even a bit more. Do just as Art recommends to set the timing with two hands as you get the idle lower and the timing decreases. Also, what did you set your point gap at? That will change your timing and therefore your idle too. Should be .019". ------------- When people run down to the lake to see what's making that noise, you've succeeded. Eddie |
Posted By: mcfunnymoney
Date Posted: September-11-2013 at 12:56pm
| Ill give that a shot. I replaced the points and the dealer said to set them at .018". I hope that is within tolerance. Ill get out there tomorrow and see if i can drop the timing and idle at the same time. |
Posted By: ArtCozier
Date Posted: September-11-2013 at 2:47pm
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Eddie Backfoot is spot-on about the points. I'll try to look in an old owner's manual and check the point gap recommdation. Actually, you should be able to find one on "Reference" on this site! Art |
Posted By: mcfunnymoney
Date Posted: September-11-2013 at 4:15pm
| I looked at the manual and it says .018" so that makes me feel ok about them. Thanks for the reference to the reference. Thats a great resource! Im reading all of the manuals for this boat |
Posted By: backfoot100
Date Posted: September-11-2013 at 6:27pm
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.018 or .019. That's splitting hairs. Either one will get you running so that you can time it properly. I was worried you had them set to .025 or .015 or something crazy like that. ------------- When people run down to the lake to see what's making that noise, you've succeeded. Eddie |
Posted By: Busted Knuckle
Date Posted: September-11-2013 at 8:19pm
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I'll add my 2cents since I'm lurking around right now - popping - sounds like you found it high idle = not enough fuel, which means either an air leak @ the carb base gasket(s) or blocked / restricted idle circuit, not the fuel lines or fuel pump they'll be suspect if you low power under load good luck Dan T @ the BKG ------------- Volante Barefoot Skier built by American Skier Boats - www.footngear.com |
Posted By: mcfunnymoney
Date Posted: September-14-2013 at 6:20pm
| i finally had a chance to mess with the boat... I removed the choke to look inside it for gunk. For fun I covered the hole where it gets vacuum and the engine idled like a champ. Huh? Where is the common area for a vacuum leak inside the choke housing? The gasket appeared good. |
Posted By: ArtCozier
Date Posted: September-15-2013 at 3:46pm
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That strikes me as being a bit weird. Does your carb have the electric choke? There will be two wires connected to the connectors on the black bakelite cover. I will have a look at one when I'm in the shop today. Art ------------- "Art" |
Posted By: mcfunnymoney
Date Posted: September-15-2013 at 4:46pm
| Sorry. I should have said that. Yes it is electric. The wires get a key on voltage. I haven't seen it work properly (move the butterfly) to date but it was lower on the nitpick list than the boat running so I had overlooked that. I took the cap off of the choke housing and it looked pretty clean inside there and the piston moves easily. I haven't messed with an electric choke before so any help would be great. I found a replacement cap at the parts store but they aren't as cheap as I was expecting so I hate to buy one if I possibly don't need to. |
Posted By: ArtCozier
Date Posted: September-15-2013 at 8:35pm
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OK, first let's make sure it is assembled correctly. The tang that operates the choke butterfly should go through the eye in the outer end of the thermostatic coil so that when the eye moves in either direction it takes the tang with it. Once it is assembled, set it so that the butterfly is just barely closed all the way when the cover is turned in that direction. Turn on the ignition switch, don't start the engine. In about 3 minutes you should see the butterfly start to open. While you are waiting, check for 12 volts at the connectors on the cover. If you have it and don't get any action on the butterfly after 5 minutes, the heater coil could be failed. It's rare, though. If you don't have the 12v, check the wire at the resistor at the rear of the engine. The wire that goes to the choke should be connected to the side of the distributor where the 12v comes from the ignition switch. If any questions, or if this is not clear to you, please get in touch with me again. Don't go buy a choke cover until we are sure you need one. ------------- "Art" |
Posted By: mcfunnymoney
Date Posted: September-16-2013 at 11:54am
| I did note that the tang was around the coil so thats step one... I will try the operation of it this afternoon. I checked the voltage the other day and it was only 9v. The battery might be low though due to cranking. (although it did turn the engine at a normal speed) I will charge it tonight and check again tomorrow. |
Posted By: ArtCozier
Date Posted: September-16-2013 at 2:30pm
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If you are only getting 9v there, the wire going from the resistor to the choke is likely on the wrong side of the resistor. Having the choke connected there will also reduce the voltage to the ignition coil. Does your distributor have a points-and-condenser system, or has it been retrofitted to an electronic module? If it's points, you might try putting the voltmeter on the choke wires and "bump" the engine over with the starter until the points open. You might see an increase in the voltage. Let me know. We might need to talk on the phone while you are in the boat. Art ------------- "Art" |
Posted By: mcfunnymoney
Date Posted: September-16-2013 at 7:57pm
| the choke is getting 9v with the points closed and 10 volts with them open. the coil is getting the same voltage. annoyingly the other side of the resister is only getting 4v. So it appears that the choke is hooked to the correct side of the resister. The batt has 12+ volts. Im wondering of the choke has not worked in awhile. The main issue I have is the vacuum loss mystery. Could a malfunctioning or low voltage choke cause a vacuum leak? Also unfortunately I messed up the gasket on the choke so I at least have to buy a cap. Where does the red wire originate that goes into the harness loom on the top of the engine? |
Posted By: mcfunnymoney
Date Posted: September-16-2013 at 8:26pm
| I looked again and I meant to ask where the purple wire originated. Sorry. It appears to be on the ignition switch. |
Posted By: ArtCozier
Date Posted: September-16-2013 at 9:40pm
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Is the 4v on the "other side" of the resistor with the points open, or closed? If it's points closed, it's probably OK. It should go to a bit under battery voltage when the points are open. A malfunctioning choke will have no effect whatsoever on engine vacuum. Once the engine warms up, the choke is out of the picture anyway. Of course the vacuum will still be applied to the housing. I guess they do that to keep the choke from overheating. I don't think there is any opening into the choke housing other than the vacuum port. If the gasket is good, there should be no airflow into the choke housing, and therefore the engine won't get extra air via the choke. Could it be that the housing gasket was failed to begin with? If there is a speed shop (hot-rod shop) in your town, you might be able to buy that gasket as a separate item there. Let's test the choke heating coil off the engine. Just run 12v and ground with small jumper wires to the terminals on the cover. Watch the "coil" in there for at least two minutes and see whether it starts to move. You might have to put a clear glass dish or something similar over the open side of the choke housing to retain the heat. If you leave it completely open it might lose enough heat to keep it from operating properly. The purple wire on the choke housing comes from the ignition switch, via the "high" side of the resistor. Here is what the circuit looks like: Starting from the terminal on the starter relay where the red battery cable connects, battery current flows from there to the ammeter, then through the ammeter. (<Your boat does have an ammeter in it as opposed to a voltmeter, right?>) From there, a red wire goes from the ammeter to the "hot" side of the ignition switch. When you turn the switch to "on," the red wire is connected to the purple wire coming out of the ignition switch. From there, it lands on the "high" side of the resistor, where the wire to the choke stove also is connnected. Now, all of the wire mentioned above will cause a certain amount of voltage loss. There are two occasions when ignition current has to pass through the 8-prong plug at the right rear corner of the engine where the engine harness plugs into the boat harness. Unplug that plug (it might be taped up. Take off the tape.) Get some fine sandpaper and clean up the prongs on the male side of the plug. Then roll up a little piece of sandpaper and clean the holes on the other side. Use an in-and-out motion to sand the inside of them. It is very common for those prongs and receptacles to have corrosion on them, resulting in a voltage loss. If voltage loss is causing your ignition system to have weak spark, you can try this: Run a small jumper wire from the "high" side of the resistor to a source of 12v. (the engine end of the + battery cable is good. It's on the starter relay, remember?) BE CAREFUL that you don't hit anything grounded with the jumper while is't connected! You don't want to be welding! Start the engine with that jumper in place. REMEMBER that with the jumper in place you won't be able to turn the engine off with the ignition switch. You will have to have the switch off AND the jumper disconnected. I didn't get a chance to have a look at a carburetor today. Hopefully tomorrow! ------------- "Art" |
Posted By: mcfunnymoney
Date Posted: September-16-2013 at 9:51pm
| I'll run to the speed shop tomorrow. I see a tiny stress crack in the cap. It could or couldn't go all the way through but I'm one to be proactive so I will get a cap tomorrow. I didn't look at the 4v side of the resister as far as open or closed points. I will check that tomorrow also. I will clean the contacts on that connector and get back with you. Thank you for all of the help! I'm hoping to get a run or two in before it gets chilly here. By the way it does have an ammeter. Also once i get her going I will post some pictures also. |
Posted By: cphase
Date Posted: September-16-2013 at 10:00pm
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Holley choke cap and gasket part# 45-258. http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_x_6122159-P_x_x?cm_mmc=ACQ-_-Google-_-enhancedRM-_-6122159&ci_src=17588969&ci_sku=6122159&ci_gpa=pla&ci_kw=&gclid=CN6UiMmg0bkCFS_ZQgoduFYA8A#utm_source=acq&utm_medium=google&utm_campaign=enhancedrm&utm_content=6122159" rel="nofollow - Advance Auto Parts ------------- Thanks, Jeff http://www.correctcraftfan.com/diaries/details.asp?ID=6549" rel="nofollow - 82 SN http://www.archlinux.org" rel="nofollow - Arch Linux |
Posted By: mcfunnymoney
Date Posted: September-20-2013 at 7:57pm
| Just figured I would give an update. I installed the new choke housing (I bought the whole thing), adjusted it properly which was easy, and no major change. It idled like a champ for about two minutes and then did the same thing. I sprayed carb cleaner around and where the venturi shaft goes into the primary under the choke it idled up a bit. But other than that no change. I checked the carb plate with a straightedge and it was fine as well as the gaskets. I have a friend who is a mechanic coming over tuesday to look at it with me. Hopefully this does the trick. My wife has named the boat the "SS Bad Decision" Im at a loss as to what to do next. |
Posted By: ArtCozier
Date Posted: September-20-2013 at 11:59pm
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Hope that your wife has her tongue planted firmly in her cheek when she says that. It's never good when they are serious about critisizing our boats! Ask your mechanic friend to go over the coil/resistor/choke wiring. If the choke is wired to the coil side of the resistor, it will pull the voltage so low that it might affect the performance of the coil. Art ------------- "Art" |
Posted By: mcfunnymoney
Date Posted: September-21-2013 at 8:38pm
| Haha. Yes, she is just joking. That name is just between us. Will do with the choke. It seemed to work fine when I turned the key. It slowly opened up the butterfly. One question though. The fast idle portion of the choke doesn't seem to be long enough to hit the fast idle cam. I have been idling it up a bit manually on cold starts. Would that affect anything other than it not idling itself up? |
Posted By: backfoot100
Date Posted: September-21-2013 at 11:12pm
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Marine carbs don't have a fast idle cam like auto carbs do. Fast idle is accomplished with the throttle. ------------- When people run down to the lake to see what's making that noise, you've succeeded. Eddie |
Posted By: ArtCozier
Date Posted: September-21-2013 at 11:23pm
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Backfoot is correct. (though not a Craft) I am assuming that you have the marine version of the Holley 4160, which is the original carb for a 351. If it isn't that, all bets are off. The fast idle is intentionally disabled on the marine version. They dont't want you putting it in gear on fast idle. It is easy to identify the marine version of this carb; the bowl vents are shaped like an inverted "U" with a squarish hole in the bottoms of them. The automotive version has straight vents cut at an angle. Art ------------- "Art" |
Posted By: mcfunnymoney
Date Posted: September-25-2013 at 12:20pm
| Well I have an admission. When I rebuilt the carb I used the wrong gasket between the base plate and the body. I will definitely never do that again. It stinks being wrong or making a mistake but it Im happy that I finally figured it out. Good sleep tonight. Thank you for all of the help and ideas. The boat idles great and starts great also. I hate to admit it but there is one more problem. It wont rev past 2k rpms. when I punch it the tack drops to 1k and it bogs. When loaded the carb secondaries dump as they should etc. My mechanic friend had to leave before much digging last night but he was fairly confident I had a weak spark or it was weakening with rpm's . I'm happy to start a new thread if necessary. I don't know the format here. Again, thank you guys so much for everything so far. The boat thanks you too! |
Posted By: phatsat67
Date Posted: September-25-2013 at 12:30pm
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Does it sound like its spinning more than 1000 rpms? The tach is hooked directly to the ignition system and usually shows problems if something happens to the signal or something shorts with RPM. ------------- |
Posted By: mcfunnymoney
Date Posted: September-25-2013 at 12:36pm
| It will spin up to 2k then bog and not go any further. It sounds like its running out of power (electricity) It seems to be advancing with a timing light. The springs are unbroken and recently have been cleaned and oiled. Weak coil? Bad resister? I set the points at .018 when they were new two weeks ago. New cap, rotor, condenser. |
Posted By: phatsat67
Date Posted: September-25-2013 at 12:40pm
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Possibly, Got a spare coil or know someone? ------------- |
Posted By: mcfunnymoney
Date Posted: September-25-2013 at 12:41pm
| I have a vw bug. I can steal that one and give it a shot |
Posted By: phatsat67
Date Posted: September-25-2013 at 12:43pm
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Fair enough. ------------- |
Posted By: JoeinNY
Date Posted: September-25-2013 at 12:55pm
If you changed all that you had the plug wires off.. check the firing order, then check it again. If you have low voltage to the coil (would need to check it under load) you could experience similar symtoms as well. A great big ignition wire bypassing the switch and going straight to the battery would be a decent test ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
Posted By: phatsat67
Date Posted: September-25-2013 at 12:58pm
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+1. Buy a multimeter and a test light. They will be your best friends when testing anything electrical. ------------- |
Posted By: ArtCozier
Date Posted: September-25-2013 at 1:12pm
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I'm still concerned that the choke heater might be hooked up to the wrong side of the resistor. Run the engine and after it's warmed up, unplug the positive wire off the choke housing and see whether the engine behaves normally. Unplugging the wire will take the choke's load off of the ignition system and raise the voltage some. Whatever coil you try needs to be a non-internal resistor type coil. Some have resistors in them. Don't know anything about VWs. Art ------------- "Art" |
Posted By: phatsat67
Date Posted: September-25-2013 at 1:32pm
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It probably has a bosh on it and the coil type is determined by the housing color. Blue, red, etc. ------------- |
Posted By: mcfunnymoney
Date Posted: September-25-2013 at 1:48pm
| The coil on the vw is red in color. I have a test light and voltmeter. What is a good bench test for a coil? Or is it ok the throw the vw one on it and try that? I will be able to run the boat tonight and unhook the choke wires. |
Posted By: phatsat67
Date Posted: September-25-2013 at 1:57pm
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Search bosh coil types and find out if its internally or externally resisted. I think the blue coil is the internally resisted but I could be wrong. ------------- |
Posted By: mcfunnymoney
Date Posted: September-26-2013 at 12:10am
| My mechanic friend came over again tonight and we took a look in the distributor. We compared the old points to the new ones. The spring on the old points was significantly stouter than the one on the new points. I checked the kit after searching the forum and seeing a similar post about the weaker spring floating the points above 2000rpm and did not find another spring or a helper spring. After re-installing the old points the boat purrs like a kitten and revs like it should. Thanks again for everything. Its such a beneficial tool to have advice from experience at my fingertips. Needless to say I have ordered a new set of points with a stronger spring. |
Posted By: phatsat67
Date Posted: September-26-2013 at 9:58am
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Cake! ------------- |
Posted By: ArtCozier
Date Posted: September-26-2013 at 10:46am
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Glad to hear that one is solved! Art ------------- "Art" |
Posted By: JoeinNY
Date Posted: September-26-2013 at 11:32am
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Always nice when we get the ending of the story - congrats. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |