454 hard starting

[paulrfrancisco]

I have Cruisers Inc. with twin 7.4L 300hp yr 1990, and each of them is quite hard starting. When they are cold, both of them have to be cranked and pumped significantly to get them started, and even when they are warm, they both are very tempermental.. One is less worse than the other when warm, but still tricky... The auto choke seems to be working as far as I can tell. However it seems that there is no gas when cold, and flood easily when warm... Any thoughts here?

 

[rodbolt]

Re: 454 hard starting

hello<br /> if theses motors have quadra jet 4bbl carbs there is a good chance the seconday meteringjet plugsare leaking. this will drain the float chamber while sitting. will also cause a richer idle. can be cured by epoxy on the plugs.

 

[Don S]

Re: 454 hard starting

You could also have bad accelerator pumps or plugged passages or stuck check balls in the accelerator pump system.<br />The engines may also just need a tuneup. When was the last time you had new plugs, cap, rotor, etc. installed????

 

[LubeDude]

Re: 454 hard starting

With all of todays cars being fuel injected, we tend to think everything should just start at the touch of the key. This just aint so with a carbed engine. Several factors could be the cause, and the most common ones have been addressed here allready. You might pull a plug or two out of each engine. If they are pretty black, then you probably need a tune-up or as stated allready, the carbs are draining when shut off. You do need to turn the engines over for a few seconds when cold to fill the carbs, then pump like heck before starting. The collector cars have the same problem I manage, when thry sit for a month, you have to crank for about 10-15 seconds before you even try and pump to start. If you troll a lot, you might try one step hotter plug, but dont go any more than that.

 

[Bondo]

Re: 454 hard starting

As Stated Above, It Could Be Anything ...!!!<br /><br />Depending on Your Reply to the Questions posted above,....<br /><br />It Might be time for a Full,+ Complete Tune-up.......And, While You or your Wrench is In there Anyway......<br />Do Full Diagnostic Tests on Everything..........<br />Compression test...<br />Leak-down test...<br />Fuel Pressure..<br />Is the Carb In Tune,+ Working Properly ???<br />Has All the Preventive Maintance Been Done ?? Filters ??<br /><br />The motor is 15 years old,.... Do a Full Survey of it,+ See How It's Doing........

 

[salty87]

Re: 454 hard starting

i pump my single 454 about 5 or 6 times before i touch the key. she'll catch pretty quick and then i have to give her some gas fast to get the idle up or she'll stall. then it might take a little while, but that's with a holley.<br /><br />have you tried starting with the throttle wide open, like an old car? be sure to throttle down fast but that works for me often.<br /><br />is it possible your starter is having trouble? loose connections, worn points, old distributor cap, old coil...all of these can add up.

 

[paulrfrancisco]

Re: 454 hard starting

I am no expert, but it sounds like the first response from rodbolt might be right on... I dont know when the last tuneup was but it really runs quite well once it starts.. no lag when punching it so accel pumps are probably ok... As Rodbolt stated.. with this type of leak, the floats will drain off, and that would cause long cranking to refil.. no amount of pumping would work after sitting over night if the float bowl are empty, Right?... However on the other hand, after running and warm and then restarting, it acts flooded.. WOT starts are the way to go here.. especially if it does not fire right up, which is about half the time.. I beleive I have the quadrajet carbs, how can I get information on these metering jet plugs?<br /><br />thanks, Paul

 

[Bondo]

Re: 454 hard starting

Well Paul,<br />After reading your reply,<br />I believe your Right,....Rodbolts post at the top Nailed it...........<br />Aanndd,...... Even though You're not an Expert, You've Already figgered out What's Wrong.........<br /><br />You've gotten some good mileage out of those Rochesters...... It's Time to give them the "Float Test"..............<br />Pull 'em off the motors,+ Toss'em Overboard.......... If they Float, They Might be Rebuildable................ <br /><br />Seriously,<br />For the price of 1 of those Merc./Rochester replacement Marine Carbs, <br />You can get 2 Eldebrock 750cfm Performer Marine Carbs.............<br />You'll end up with a Very User Friendly Carb, That Works Just Like It's Supposed Too...........<br /><br />Even though the Eldebrock is known as a Square bore carb, it has Both bolt patterns.....<br />The 600/625cfm Is Square bore, but the 750cfm is a Spread bore(Bigger 2ndaries)............<br /><br />And,.. I think you're going to Want to go with the 750cfms to Feed those Big Blocks.................

 

[rodbolt]

Re: 454 hard starting

paul<br /> when you remove the throttle plate from the main body turn the main body upside down. you will see 2 almost dime size steel plugs with a lead seal. that is the secondary main well metering plugs. mix some j&b weld and after a thoughrough cleaning of the casting with acetone then cover the plugs well. not to thick on the sides or you will have to trim the blob to fit. they make a gasket just for this but it does not work well or long. this problem has been around since about 1965.and when I went to carter carb school in 1978 that was how they told us to fix it.maybe some of the other oldtimers remember that carter built rochester carbs for years aint that a kick

 

[jimmythekid]

Re: 454 hard starting

Carter carbs must work well in boats, I ve read here that alot of people like them. Go figure, on cars and trucks they suck IMHO. Especially on trucks that go off roading Seem to not like the inclines that well.

 

[paulrfrancisco]

Re: 454 hard starting

Would it be worth just having the both of the existing carbs rebuit rather than buying a pair rebuilt or new? Would it be a DIY job?

 

[rodbolt]

Re: 454 hard starting

paul<br /> with some care and time spent reading about how the rochester q-jet works its a basic simple carb. its about the easiest on the market and one of the most infinatly adjustable. if you hear a mechanic refer to it as a quadra junk leave that establishment.<br /> the carb has been in production with no major design changes since about 1965. it uses tapered rods for all metering systems. the primary rods and jets have tons of combinations and the secondary rods can be changed and modified to allow more or less fuel with the same airvalve opening. if you have never done a carb this may not be the one to start on. if you do attempt it you will need a torx driver set. a 1" open end and a 5/8ths flare wrench. if you have a good carb shop it may be easiest to remove them and let a pro do it. but no its not difficult at all. I mean if I can do it anyone can . however some of the parts are delicate in assy and if you force it they will be destroyed.

 

[paulrfrancisco]

Re: 454 hard starting

Youve been a big help... thanks.