engine won't idle-HELP!!

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brucepinpoint

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1993 240 Sea Ray with a 454 mercruiser bravo 1 Carbureted with 1300 hours.If the motor sits for a week it won't start without starting fluid. Just tuned it up and it runs 4800 RPM.Shut it down and is still hard to start and sometimes will stall at idle. I think it is a fuel problem-possibly anti siphon in the tank not working. The fitting on tank won't turn and I'm afraid of breaking it. Is it possible to add a anti siphon valve somewhere else?Any other ideas what might cause the engine to be hard starting? Thanks!!
 
I'm asuuming it is a 4 barrel Weber with mechanical choke. Why is starting fluid usage bad?
 
It could be your IAC valve sticking, a carb float problem, an internal leak in the carb, or a host of other possibilities. You need to check out the entire fuel system. If you've never done that, you should get a reliable technician to check it out for you.
 
If it is a Quadrajet carb like I have on my 454 Crusaders, they are notorious for the fuel bowls to leak down over a few days due to the plugs in the carb allowing the bowls to drain. I too had to use starting fluid if it sat for a week. The trick I learned, after many cans of ether, was to crank the engine for 7-10 seconds, pump the throttle a few times...then close the throttle down and crank for periods of 10 seconds or so...after 2-3 repetitions it would finally catch fire. Try varying your start up routine and see if that solves the problem.
 
I have the 4V Weber/Carters on my boat. After sitting a week the float bowls drain and it won't kick right over. I leave the throttles closed and crank for about 5 seconds to fill the bowls. Advance the throttle and crank again. They'll usually catch after 5 seconds or so of cranking.

First thing to check is that the the choke plate closes when your motor is cold, and opens when it's warm. If it's stuck open you'll crank for a long time before it fires. To your knowledge, has the carb ever been rebuilt? It's probably time.

A quick squirt of starting fluid won't hurt a 4-stroke engine, but you shouldn't need it. I'd consider the anti-siphon valve a long shot, cause the engine starts and runs.
 
Thanks for all the suggestions! I think a rebuild is in order.Will report back with results.
 
I have had the IAC valve stick issue repeatedly.
Can overcome this issue by putting neutral and advancing the throttle slightly above idle, then starting.
 
Just pulled the fuel pick up out of tank. There is no anti syphon valve. Going to add one and see if the problem improves.
 
The anti-siphon valve is just a safety thing, doesn't help anything. It's a small check valve so if your fuel line is cut or pops loose it will stop the gas flow so your bilge doesn't fill up with gas due to the siphon effect. It will cause problems but isn't going to help with anything. It looks like a normal barbed fitting that your gas line attaches to.
 
Brucepinpoint noted it is a carbed engine, so no IAC.

Mcarrigan pointed out the A/S valve is a check valve.
It normally takes fuel pump suction "cracking" pressure to open flow to the engine.
If the engine is not running , and the float valve has a slight debris leak ( or a leaky injector on injected engines) or a fuel filter is opened to replace it , the A/S valve can prevent drain-back to the tank.

And of course prevent the contents of the tank siphoning out into the bilge if a fuel distribution hose falls off or rots/chafes/splits below tank-contents level. In that respect especially it can be an extremely valuable safety device , ...not to mention it is required where fuel lines dip below tank top (except on O/B's I believe).
 
It's a good thing that your engine won't turn over right away. give it full throttle to release the choke. Crank it over 6-8 revolutions and pause. Do it again and pause. Do it a third time...what you're doing is pre oiling and getting oil into the oil galleys for the lifters. The pausing is just to save the starting motor from getting too hot. You are also filling the float bowl in the carb. NOW, give the throttle a full advance and pull back. She should start. If not, report back and we can go from there.
 
Replaced anti siphon valve and fuel P/U. I think the problem is the manifold choke. When I hold the choke closed it will start.If it is open even a 1/4 inch it will not start. The bimetal spring is not holding the choke closed. Do I have to remove carborator to replace spring?
 
Not generally. You can usually take the 3 screws loose that cover the spring. I would begin by loosening the screws and rotating the housing to close the choke. You should see the choke plate pulling closed. Feel your linkage to see if it is actually attached to something. If the choke plate just flops around either the spring has broken or the linkage has come apart. If the choke plate closes when you turn the housing (richer) you want to rotate until the plate just does close. Now as you use your finger to push the plate open it should snap back closed on its own. Don't make it too tight or is will never open.
 
Its a divorced choke with a bimetal spring that the intake manifold heats up then it closes.There is no adjustment other then bending the connecting rod-which I already tried to bend to make shorter
 
Ah... I was thinking the other style. IIRC there is just a single Phillips head screw that I removed and it came right off. Didn't have to remove the carb to get it off.

Sorry for my confusion.
 
quote:
Originally posted by brucepinpoint

Its a divorced choke with a bimetal spring that the intake manifold heats up then it closes.There is no adjustment other then bending the connecting rod-which I already tried to bend to make shorter

Click to expand...


On my old carbed Crusaders that employed the bi-metal coil on the intake manifold , I kept spares onboard and had to replace them about every 1-2 yrs.

But make sure a quick pump of the throttle lever makes a strong squirt of gas down the carb throat before cranking. If not , but it runs well & accelerates normally after you do get it running, then the carb bowl was empty ( leaky float valve or Quadra-jet welch plugs. )
 
I think by '93, the welch plug problem has been solved. If not, you turn the carb over and add JB weld to the screws/plugs on the ends of the tubes.

Two things can be happening, either tha float bowl is empting into the intake manifold making a VERY rich mixture, in which case you open the throttle all the way to 'air out' the cylinders.

The other possibility is the engine is extremely lean(not getting any gas) in which case you have to pump the throttle a couple times. First you have to check that the accelerator pump is working. Look down the carb as you open the choke and have someone pump the throttle you should see two thin streams of gas squirting out. If no streams of gas, you have to replace the accelerator pump. There are two basic types. One is just a rod with a cup in a cylinder and the other is a diaphram in a square housing.
 
Thanks for all the great responses. The engine will not start without the choke being closed completely.The bimetal spring has to be replaced but I can't get to the bolt without removing carburetor.I realy didn't want to have to do that but I see no other alternative.Thanks again for the respones-I will report back when it is fixed.
 
When I had my Qjet I removed all the choke and accompanying components including the pivot rod that the choke screwed on to. I fish in SF bay and Pacific ocean so the temp is usually in the 40's-50's in the morning. Not really cold so the engine starts pretty easily with just a couple pumps of the throttle, just to richen the fuel/air mixture. That's all the choke is doing. The choke also sets the throttle up slightly but with boat type throttle system, the throttle is easily set to the desired RPM...900-1000 RPM. Don't bother with the choke, remove it. Wire it open or unscrew the two tiny screws holding it on. Use a magnet to catch the screws as the come loose.
 
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