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318 stall issues

joe_l

joe_l

Contributing Member
"1981 318 engine BW 1.91:1 tur

"1981 318 engine BW 1.91:1 turning a 4 blade 18x17 prop. Edelbrock carb, OEM Prestolite ignition.
Engine would start and run for an hour or so.It would the stall at idle (no wake zone) It could not be restarted until it cooled off.It never overheated. fuel and ign would check OK and the engine would restartafter cool down.
I replaced the Ignition reluctor, pickup, module, ballast resistor and the wiring.
Now it will run for a couple of hours and then stall in a no wake zone. It can be immediately restarted runs a little rough unless accelerated and stalls if put in gear. let it sit for 15 minutes or so and all is normal.
Engine vacuum/compression/oil pressure are good.
Any one have any suggestions?
Thanks,
Joe"
 
Choke stuck partially closed?

Choke stuck partially closed? When engine is cold(ish) the mixtures are suffcient for the engine to idle and then mixtures become too rich for it to idle when warm.

Partially blocked idle circuit? Choke at least partially closed when cool/cold allowing enough fuel to be pulled through idle circuit of carb to keep engine running when cold and then when the engine is warm and choke is off there is not enough fuel to idle.

Cheers
Jamie
 
"I see you are "up" on

"I see you are "up" on automotive carbs as well, Graham. Not that I'm surprised!

Jeff"
 
"Jamie/ Jeff
Engine has a new

"Jamie/ Jeff
Engine has a new edelbrock 1409 installed with electric choke.
The choke is wide open when the engine is warm.
carb set up and adjustments are per spec. engine will idle and run fine for several hours then stall.
Boat is in South FL,never gets cold, lots of no wake/ ship channels. This requires lots of running at low speeds.
Thanks,
Joe"
 
Black smoke from exhaust??? Co

Black smoke from exhaust??? Color of spark plug tips???? Remove air cleaner and check for any visible fuel leaking into carburetor throat at idle...There should be no fuel visible at idle speeds
 
"here's my 2 cents worth..

"here's my 2 cents worth...what about the coil? is it mounted east/west or flat, or north/south or upright? , it might be breaking down as it heats up,"
 
"Possibly, but I'll bet th

"Possibly, but I'll bet the carb is not adjusted correctly. You said it's adjusted to "spec", but that's just an approximation. Marine carbs are surprisingly hard to get the idle right since they don't rock back and forth like car engines (rigid mounts). I suggest you adjust it with a vacuum gage to get the mixture right--shoot for the setting that give you maximum vacuum, then add 1/4 turn rich.

Jeff

Note: Be sure the motor is fully warmed up and that you don't use the PCV hose for your vacuum source. That would trick you."
 
"I had the same problem with o

"I had the same problem with one of my Chrysler 440's. I replaced the coil and it helped,but the problem returned. The electronic control module was the culprit. It looks like a 4" square box with a 5 pin plug going to it. Be careful to cut off your 12V. power at the perko switch and bolt it into place before putting the plug back on and turning on the power.

Good Luck!"
 
"If so, that's a cheap fix

"If so, that's a cheap fix: $30 at NAPA (and the automotive units are the same, despite BS from the sellers).

Jeff

PS: They sell 4 and 5 prong units, which are fully interchangable. I have one of each on my boat."
 
"I'm having the same probl

"I'm having the same problem with my '72 LM318's. I installed new Edelbrock 1409's after drilling for PCV. Port engine started right up, no smoke, idled fine for 10 min. Put it in gear and it stalled. It would restart and run for a few seconds and then stall.

The starboard engine did the same thing but only ran for about 5 seconds then stalled. It restarts then stalls immediately.

Did either of the above suggestions fix joe_l's problem?"
 
"Soon as it warms up and the c

"Soon as it warms up and the choke opens it dies, That says to me tour idle speed/ mixture settings are off.

Adjusting the idle correctly on a marine engine--that is ridgidly mounted and doesn't rock when it's idling roughly--is more difficult than most people realize. The best way to do it is with a vacuum gage, but you need a good vacuum location for the gage. DON'T use the PCV line or it'll be off a mile. (Ah-hem.)

Jeff"
 
"Goin back to the original pos

"Goin back to the original post.
the engine will stall after several hours of running fine. The problem occurs during return to dock, running through a six mile no wake zone.
It will restart but stall when put in gear
1- choke is wide open
2- plug tips clean
3 idle mixture and speed was set with a vacuum guage hooked up to intake manifold not PVC port
4- coil is mounted port / stbd on intake manifold with one inch spacers to give it a air circulation.
5- all ign parts are new
6- ECU is a new 4 pin type.
Joe"
 
Shessh! Looks like everything

Shessh! Looks like everything is set perfectly. I'm stumped. Sorry.

Jeff

PS: Is the carb sitting level when running slow?
 
"Wrong or defective PCV??? Vac

"Wrong or defective PCV??? Vacuum leaks...Broken vacuum line???use wd 40 to spray where a leak might occur(Manifold, carb gasket, etc."
 
"Jeff/ Bob
engine vacuum at i

"Jeff/ Bob
engine vacuum at idle is 18.5hg and steady, so I doubt vacuum leak.
engine is at a very low installation angle,as low as possible with straight drive due to a 7 ft. shaft. probably less than 5 degrees.
I was thinking fuel tank vent restricted but they are free and clear.
I am going to put the vacuum guage on it and run it for a couple hours and see what guage reads when problem occurs.
It will be awhile but I will let you know out come
thanks,
Joe"
 
I don't believe you answer

I don't believe you answered the question about whether or not there was any gasoline leakage visible above the throttle plates as the engine starts running rough. A defective float or float needle and seat would cause an overflow out of the float chamber into the carburetor above the throttle plates resulting in a rich condition. I don't think it is ignition because the ignition demands are usually lowest at idle and highest at increased RPM's.
 
"Finally got my new Edelbrock

"Finally got my new Edelbrock 1409's up and running. I found that the stalling was caused by my electric fuel pumps. I had mounted them sideways so they would fit where I wanted to mount them. Turns out that they needed to be mounted with the ports down and the cannister up. I also had to prime them. Both engines start right up, no smoke, idle real smooth and no stalling when they go into gear."
 
"PSI is 4-6, flow 72 gph. Min

"PSI is 4-6, flow 72 gph. Mine are installed approx 8' from the tank and push the fuel another 10' through a primary fuel/water separator and then a small fuel filter at the carb. The hose is 3/8" dia. They seem to be working fine but I haven't used them on the water yet."
 
"My son, Sully117, has similar

"My son, Sully117, has similar problem as Joe L: Just put the boat in the water, Engine started & ran for 45 mins or so, stalled at idle, could'nt restart until it cooled off (next day), replaced Ignition Control Module, ceramic resistor & coil. (Note: ICM had melted spots & drips of bakelite below it.) After long cool down, Still stalls at idle & it blows puff of white smoke out of the Edelbrock carb just at stall (in mariner slip). Mechanic friend (who suggested replacements) spoke to his boss & wants the Voltage regulator checked for "HighVoltage". It does run only at 2000 rpm. Please help with some suggestions (they are having a baby this June & would like to have boat running before then.)"
 
"Some feed back on an old post

"Some feed back on an old post:
I installed a fitting on the intake manifold, ran a hose to a remote vacuum guage in order to read vacuum under way.
1- Started at the slip, engine warm vacuum guage reading of 18.5 "hg.at idle and 14.5 in gear.
2- after traveling one hour at 1000 RPM (no wake zone)vacuum guage reading suddenly dropped to 10 "hg.
with wide fluctuations. Engine stalled.
3- shifted into neutral and restarted, engine ran rough and vacuum reading now 14 "hg. with 2"hg. flucuations.Stalled when put in gear.
4- engine would start and run at 2000 RPM in Neutral with a 19 "hg but would not idle.
5- fortunate that current took boat back in direction of slip and allowed time for engine to cool down. No help....This is First time cool down did not fix problem.
6- replaced distributor, coil and ballast resistor. no help, adjusting mixture screws (edelbrock 1409)have minimal effect. the intake manifold is not leaking, checked with WD40 along all parting surfaces.
I am thinking valve train problems, but there is no lifter clatter and timing chain does not indicate excessive stretch.
I will have to do another compression check.


Any thoughts?


Joe"
 
Disconnect and reconnect one s

Disconnect and reconnect one spark plug wire at a time while the engine is running to see if one of the cylinders is not contributing when the low vacuum occurs. This may help to isolate the problem to a particular cylinder or cylinders.
 
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