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78merc
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May 28, 2012, 3:07 PM
Post #1 of 28
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Mercury carb problems
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Hello,
I have a 1978 Mercury Grand Marquis that has the 460 V8 with 122,000 K miles. It has been my weekend driver for about 4 years. I recently had the carb rebuilt because I figured it had never been done and it had gasoline leaking from it. After the rebuild, vacuum leak repair, tune-up, and $470, it ran terrific, with one exception. The high idle screamed like a bat out of hell. I returned the car, and they fixed the problem, only now, the engine took about 2 minutes of cranking to start when cold. I returned, and they told me that the problems were the result of "a bad batch of choke pull offs" and fixed the problem. After that, it took about 20 seconds to start when cold, but sputtered a while before starting. Thinking the timing was off, I went back, but now am being told that the problem has to do with the gasoline. He said that he let the car idle for an hour, turned it off, and attempted to start it. He said the gasoline in the carb had disappeared, and that the starting problem was caused by summer gasoline with lots of ethanol that evaporated, causing the gasoline to disappear. His idea was to put a spacer between the manifold and the carb, as well as install a colder thermostat. I did not go for this. Now the car hesitates when driving, as well as coming close to stalling when going around corners (float level?). It has been very hot lately here in Indiana, so I'll give him that.
Does his idea about evaporating gasoline make sense to anyone, or does it sound like this car probably needs the timing, idle speed, and float readjusted? (or maybe even more). I apologize for the long winded post, and ANY help would be greatly appreciated.
Thanks!
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Hammer Time
Ultimate Carjunky
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May 28, 2012, 3:20 PM
Post #2 of 28
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Re: Mercury carb problems
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He said that he let the car idle for an hour, turned it off, and attempted to start it. He said the gasoline in the carb had disappeared, and that the starting problem was caused by summer gasoline with lots of ethanol that evaporated, causing the gasoline to disappear. His idea was to put a spacer between the manifold and the carb, as well as install a colder thermostat.
That's about the wildest idea I ever heard. It sounds more like this guy doesn't know how to rebuild and set up a carb. If he lost a bowl full of fuel that fast, it leak either onto the engine or into the engine, probably the latter if the car go flooded. I've seen some carbs hold fuel for a year.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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78merc
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May 28, 2012, 3:56 PM
Post #3 of 28
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Re: Mercury carb problems
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I'm no mechanic, but that's what I was thinking too. I think that was his way of saying that he can't or won't tune my carb properly.
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Hammer Time
Ultimate Carjunky
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May 28, 2012, 4:00 PM
Post #4 of 28
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Re: Mercury carb problems
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If it's leaking fuel, then it's more than a "tuning" problem and there is an internal issue with assembly that was missed or done wrong. Rebuilding carbs is an art that very very current day mechanics are experienced in. You are sometimes better off buying a reman from a carb rebuilder online.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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nickwarner
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May 28, 2012, 4:08 PM
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Re: Mercury carb problems
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If the man doing the work is less than 40 years old, buy a new carb.
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Hammer Time
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May 28, 2012, 4:10 PM
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Re: Mercury carb problems
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Better make that 50...................LOL
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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78merc
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May 28, 2012, 4:21 PM
Post #7 of 28
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Re: Mercury carb problems
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Yep! The shop was referred to me by several friends who had good luck having carb rebuilds there. As far as i can see, the guy who rebuilds the carbs is an old timer and the guy who installs them is in his thirties. The guy who installed the carb when I first went there is nowhere to be found! For all I know, he quit or was fired.
The younger guy said that gas has ethanol which burns off in a carb sitting on top of a manifold. He even compared it to Jim Beam burning off! Looks like I have a long road to getting this resolved. 
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nickwarner
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May 28, 2012, 4:31 PM
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Re: Mercury carb problems
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For perspective, I'm 30 and don't touch carbs because I was raised in EFI and only know enough with carbs to get in over my head. I leave them to the guys before my that grew up with them. I'm sure the next batch of techs will look at me the same way when its time to work on a pre-95 car.
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Hammer Time
Ultimate Carjunky
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May 28, 2012, 4:31 PM
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Re: Mercury carb problems
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That's a load of crap. Nothing is going to evaporate in less that a few days.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Discretesignals
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May 28, 2012, 4:46 PM
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Re: Mercury carb problems
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You guys make it sound like some type of mysterious lost art voodo BS that only the grand elders of the automotive community can do. Motorcraft carbs are one of the easier ones to overhaul, esp a 2150.
One of the main things with a carb is that it is affected by the manifold vacuum in the intake. If the engine is worn slap out or you have some type of problem affecting manifold vacuum, no amount of carb work is going to make it run right.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on May 28, 2012, 4:46 PM)
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Discretesignals
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May 28, 2012, 5:00 PM
Post #12 of 28
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Re: Mercury carb problems
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You probably right, but there isn't a need to know anymore. We rarely get any vehicles in the shop that are carbed. One of the worst is the older Honda VV carbs or the Toyota emissions carbs of the late 80's If you really wanted to know, it's not that hard to figure out if your mechanically inclined. They still sell carb and parts cleaner.
Of course, thanks to Ethanol, the alcohol will keep the inside of the carb clean as long as it doesn't eat up the gaskets or you let it sit around too long.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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78merc
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May 28, 2012, 5:10 PM
Post #14 of 28
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Re: Mercury carb problems
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Its a Motorcraft 4350 4 barrel.
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Discretesignals
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May 28, 2012, 5:19 PM
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Re: Mercury carb problems
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See it's not that bad...there aren't very many parts....LOL
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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nickwarner
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May 28, 2012, 7:32 PM
Post #17 of 28
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Re: Mercury carb problems
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I stay away from them myself because my knowledge base isn't to the extent that I would charge for my work. I like to be confident in my ability before I touch it. I applaude those who know these systems, but I want it to be my own vehicle that I learn this on.
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re-tired
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May 28, 2012, 8:15 PM
Post #18 of 28
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Re: Mercury carb problems
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Heres my 2 cents. Yes rebuikling a carb is an art ,either you have a "feel" for it or you dont , putting a "kit" in one and squirting a little carb cleaner around is not a rebuild.. Years , decades , of hands on and knowledge of a host of rules of science's will will make someone a carb man . Ethanol blended with gas will not evaporate as you watch. If so the tanker truck and the underground storage tanks woul have to be hermetically sealed, least it would disappear before they could sell the stuff. What is disappearing is the 50+ yr old techs . THe young guns are good at what the were raised on , EFI , Direct Injection, multiple ecms to control everything. SO i also agree that you may be better to buy a reman from a REPUTABLE firm. After you have a competent tech confirm the need.
LIFE'S SHORT GO FISH
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Tom Greenleaf
Ultimate Carjunky
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May 29, 2012, 3:10 AM
Post #19 of 28
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Re: Mercury carb problems
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My 4 cents (inflation continues) there was nothing but carbs when I started except some exotic vehicles with mechanical FI and never even saw one they were so rare.
Got good at carbs. Had all the measuring tools, hand held vacuum pump, weigh floats (some would sink if heavy) then the last ones became a problem to meet emission spec so car makers gave up. A good carb can start in a couple revs. From brand new some weren't set quite right and some would evap out fuel in bowl requiring more cranks but not excessive.
Same carbs some lost their fuel and some didn't but took some time. Ex: Had a Chev 350 w Quadrajet in a boat set wrong and easy for me to set right. Bought new. If that boat was out for a long run the engine heat would boil off fuel in bowl over the week and would crank longer as I chiefly only had weekends with the thing. If I Just was at the marina till engine was cold again, just cranked it a few turns after a day out there it would start right up and fuel didn't evap out of the cold engine for weeks.
Ethanol: I'm near sure it killed all but two gas yard care machines! Nice.
Who just said over 50 years old? That # is fading in the rear view - smile. You know you are getting old when that seems young.
Mechanics do many times just "burn out" from doing this stuff, getting cuts, burns smell like an exhaust pipe after working all day and so on.
Still own a now 64 year old mostly GM engine (tractor) with an "up-draft carb! Now who remembers those? I know re-tired does
That idea allowed for placing gas tank higher than carb so you didn't need a fuel pump at all!
My guess is a good newly redone carb would be tolerant of the ethanol.
OK if designed for it but gets less MPG on older stuff anyway and to make it is showing up in food prices if you didn't notice. Can't fight with stupid ideas/people as the beat you with experience every time!
Tom
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chickenhouse
Enthusiast
May 29, 2012, 10:53 AM
Post #20 of 28
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Re: Mercury carb problems
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My Model "A" had the same updraft. Remember backing a Model "T" up a hill because the gastank was under the seat and no fuel pump! Wanna talk old? Bet I got ya beat Tom. Worst carb I ever attempted was a Ford variable venturi. He was happy when finished but never again!
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Tom Greenleaf
Ultimate Carjunky
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May 29, 2012, 11:05 AM
Post #21 of 28
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Re: Mercury carb problems
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Yup - Ford put VV carbs on I think '79 + '80 (maybe) Crown Vics almost none would work right no matter what! Funny but not is most police cars here are Crown Vics and at the time a new fleet with those caused all hell. Vaguely recall they had to remove them for another something or always in trouble.
Every car maker has done some fool thing over the years that made it to market!
Tom
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78merc
User
Jun 4, 2012, 7:20 PM
Post #22 of 28
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Re: Mercury carb problems
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Just thought I would update you guys on my car. I went in again, they had the car for 3 days, and told me that they "drove it down the street", and it ran fine. I went back in to pick it up, explained that is was running rough, and they are holding firm to the boiling gasoline explanation. I asked them to at least make sure the timing was set properly, and in the process he noticed that a diaphragm attached to the distributor was malfunctioning. I can't remember what the part was called, but it was attached to a vacuum line that he plugged to adjust the timing. Of course it would cost another $130 to replace. I drove the car a while, and after about a half an hour, it started running rough again. It sounds like a fish gasping for air, and occasionally stalls. I am so mad I can't think strait!  If I can ever afford to get the car fixed, I'll let you all know. Thanks for the input.
Dave
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Tom Greenleaf
Ultimate Carjunky
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Jun 5, 2012, 5:25 AM
Post #23 of 28
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Re: Mercury carb problems
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That "vacuum advance" should not cause if plugged off the problem you are having. I think you are having fuel problems and dinky OE filter can't take much.
Quite possible a brand new Ford vacuum diaphragm is available. One place I know that only deals with Lincolns (many only used the 460 for years) and near certain same engine and parts.
Baker's Auto, Putnam, CT. Owner = Steve O. Ph: 860-928-7614 or websites www.bakersauto.com or email sales@bakersauto.com . Probably the world's largest stock of new (NOS = New Old Stock) parts that would fit the engine in this and of course the Lincolns 1961-2002 only. You could have Googled that anyway and links not allowed but this isn't competing IMO with any paid advertisers here. Use the PM system if you have your own links. We spend (regular techs) hours here for free so I'm breaking the rule for myself,
Tom
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78merc
User
Jun 12, 2012, 8:18 PM
Post #24 of 28
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Re: Mercury carb problems
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I went to a mechanic that a friend of mine recommended. My friend has several old cars, all made in the 60's, and has been going to this mechanic for well over 20 years. These guys were in the age range to know a little about carburetors! The new mechanic told me that the previous place had frozen one of the idle screws in place for some reason, as well as mis-gapped some of the spark plugs. He also said that the vacuum advance was fine. They re-adjusted the carb and the spark plugs, and the car is running great. It idles a tad rough at times before it has warmed up, but at this point I'm not being to choosy! (also, I'm flat broke). Thanks for the great advice as well as the link to Baker's Auto, I'm sure it will come in handy some time.
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Tom Greenleaf
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Jun 13, 2012, 4:28 AM
Post #25 of 28
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Re: Mercury carb problems
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Rough when cold issue: Even to spec it may want some judgment adjustments slightly off spec. Post #14 with diagram shows me that idle mixture screws had limiters when new and we managed to defeat that if only to clean them out and put back.
Choke may be either too tight or too loose on choke plate making slightly richer or leaner only while cold. All that should just be out of play when warm. The black plastic choke spring held in place by probably just screws now (some riveted those and you drilled those out for screws) probably has marks and arrows for richer or leaner for just cold operation. Can be adjusted for choke spring TMK but mark with removable paint or a silver sharpie where you started so you can go back. Same with any adjustments - know where you started if changed so you can put it back on any adjustments to tweak it out.
Sorry if a repeat but have you compression checked this engine? Unless worn (not so common on a tough heavy and huge motor like this) may be so under taxed that carbon build up, unseen can make compression go UP! Could show up as higher manifold actual vacuum being on the high side. Hard to say exactly what # to look for and would have to factor you altitude. Quite the calculation that I don't have. Live at 232 above sea level so not an issue here but is in some places,
T
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