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Question on engine starting, cranks good runs good but after everything is warmed up I can shut it off let it set bout 20 or 30 mins it don't want to start to good I have to turn it over quite a bit to get it started. what could be the problem here.:cool:
My guess timing a bit advanced, but are we talking lawn mower or car???
With the info you've given the options are wide. Timing like Charlie says, weak spark, marginal plugs, choke setting, accelerator pump not giving a good "shot" to prime, etc, etc. Tell us a bit more about the engine we're looking at, how it's built, knowns on the internals, ignition system, for starters.
Ok sorry bout that 383 Stroker timting set Elgin # SS-3145, E-Tec 200 heads,powermaster starter,edel manifold,edel 650 carb elec choke, Allstar ignition system
I'm not familiar with Allstar ignition, but looking on Google I find a lot of brackets, supports, pieces & parts including a coil. What distributor are you running? Was it doing OK and then started doing this, or has it never really started hot well?Quote:
Originally Posted by 39 Chevy
Left out 2 words MSD ignition Allstar distribuator reason for that is I killed 2 MSD before i figured out I had a bad alternator. Allstar is just about the same as MSD $100.00 cheaper you can also change out parts an not have to buy the whole unit.
Hmmmm, my '62 Fairlane is doing that sometimes and I have a MSD also. However, I'm thinking the after market electric choke setting may be my problem. Anyhow, I'm gonna keep an eye on this thread for sure.
So was it doing OK on the heat soak starts, but recently started this action or is this a long term problem?
The first thing I'd do is get it warmed up as normal and then give it the 20 to 30 minute resting time. Before trying to start it pull the air cleaner, get up where you can see down the carb venturis and give the throttle a couple of full pumps to prove that you've got gas in the bowls. I'm thinking that you might be leaking down the fuel, or boiling it away with the heat soak. If you don't get a fuel shot consider a thick phenolic gasket to isolate the carb base from the intake. It could be that you're leaking all of the bowl fuel into the intake and it's flooded? Maybe try hard WOT during crank to see if it comes to life quicker with more air?
If the carb seems to have gas, given recent experiences with spark plug QA/QC I'd invest in a new set of quality plugs to rule out the possibility of them breaking down with heat. I like NGK's, and I now avoid AC's like a plague after watching the video of the China sweat shop making them.
If the plugs don't change anything then go through the warm up & heat soak again, pull a plug and with the plug well grounded have someone crank the engine and observe the spark at the plug for a strong blue/white spark and a distinct "pop" from the MSD. If the spark is weak I'd probably spring for a new hot coil, like an MSD Blaster.
It's one of those trial & error things, trying not to simply replace a bunch of parts helter skelter. Let is know what you find, or what you've done to date that might change the approach.
Ok, I will give it a try let you know what going on. Thanks
Unless it is severe, it is not unusual for a carb to act like this. It will help it start if you give it just a little gas on a warm start, slightly press the accelerator down and hold it there till it starts. It's hard to get use to giving it a little gas at start up, as most of us are used to not having to give it gas with our modern fuel injected motors.Quote:
Originally Posted by 39 Chevy
X2 on the heat soak issue. Get the engine to operating temp, shut it off, and remove the air cleaner. I'll bet you'll see fuel vapor rising from the carb, as the gas boils out and drips into the plenum and vaporizes.
MSD (and others I would assume) is very sensitive to poor ground connections. I chased a problem for a quite awhile before I found it. Be sure yours is perfectly clean and solid. The factory recommends a direct connection to the battery.
If you check out the MSD and everything is ok.
I would think your losing prime, take the gas cap off the tank while it is running after the engine is warm, shut down and leave cap off 20 min, then restart, If the engine fires right up than you need a vented gas cap.
Where are the floats in the carb set? you can raise them a little to keep more fuel in the carb bowls.
I'm thinking you may be causing a vacuum in the tank, when you shut it down this vacuum sucks the fuel back into the tank.
this was the first thing to come to mind, both easy to check and rule out fuel delivery.
Godspeed
MrC.
any updates?, I'm interested to hear what the fix was.
Good luck
Godspeed
MrC.
Mr. C
I thought all fuel pumps have a check valve. Wouldn't that prevent vacuum induced back flow?
If the O.P. is using the stock engine driven pump, it indeed would have check valves.
not necessarily, the diaphragm may have a hole/tear in it.
Godspeed
MrC.
then the gas above the diaphragm would drool into the motor. but the line above (going to the carb) would remain full. The inlet side check valve would prevent drainback.
no update yet proly be this weekend before I get a chance to look at again. Lot of overtime right now
One more thing I have a electric fuel pump in the tank.
JMHO;
The float bowl is vented and needle valve (fuel inlet) is above float level and will not allow the fuel to siphon from the float bowls. The fuel line could siphon back, but there should still be enough fuel in the bowls to start and run until the fuel line is re-charged. If the float bowls are empty it is either heat soak or a cracked float bowl.
If it is heat soak, the car will also start hard when it is cold as there will be no fuel in the bowl to prime the accelerator pump charge that's needed for the cold start until it cranks enough to fill the bowls. If the float bowl is cracked or damaged fuel will leak all the time, again hard to start when cold and most likely fuel on the motor.
Unlike EFI, carburetors are not self priming. If you're not giving it a little gas at a warm start, you will have to crank it until the venturies pass enough gas to prime the motor.
Again, JMHO, but sometimes we overlook the simple.
What fuel pump?
If its carbed you need to set pressure to 5 - 6 lbs & use a return style regulator
He can also use a deadhead regulator and set to the 5 pounds. Then he won't need a return line.Quote:
Originally Posted by t-top havoc
But until he verifys that he's lost fuel after sitting there hot, it's all a guess.
.
Erased post.
are you people making this up as you go along? What float bowl check valve (needle and seat) is so low it would empty the bowl? and what diaphragm leaks in the motor instead of on the motor? which would be easy to spot from the flames.
What is his timing set at? where is the coil mounted and most important if you wait til it cools down a little more does it start?
Actually, I've seen fuel pump diaphragm failure result in fuel in the crankcase. Oil pressure really gets bad. And no, the motor didn't blow up. More often, the fuel will vent out the weep hole; that's what it's there for. Of course I'm talking about mechanical pumps mounted on the side of the motor.
Way more common that fuel goes into the motor in my experience. So common that whenever we checked oil in the service stations I worked for, we automatically sniffed the oil on the stick. Probably saved dozens of folks their engines.Quote:
Originally Posted by MalibuChevelle
As for the rest of the questions.. we're all standing by waiting to ask the O.P. once he has time to investigate and come back with findings. Sometimes it's a slow process as daily life still happens...;)
Update, I done a couple checks opened up the gas cap as someone asked while it was running shut it off bout 20mins made no differance. I also took the breather off to see if there were any vapor coming up didn't see anything or any gas dripping down. I do have a regulator that is set between 5 an 6 also with a return line to the tank. I'll keep looking.
I read it as an accelerator pump diaphragm which leak to the outside of the carburetor on to the engine and could result in fire. Either way there should be an obvious gas smell.
sure on AFB style or Quadrajets can leak from plugs into the engine, but they don't have diaphragms they have plungers that can only leak back into the bowls . Do we even know what kind of carb 39 chevy has?
Edelbrock Thunder Series 650
Have you tried letting it cool longer before restarting it? If that works then just use a thicker carb gasket or synthetic spacer if the following items check out ok. Verify your thermostat is the correct temp, if you have a clutch or elec fan make sure it is functioning proper and make sure you timing isn't too retarded and raising engine temp. Also you might check your radiator return to make sure it's not just sucking air as it cools. hope that helps
Well it took a while but problem solved. I wound up putting a 1 inch thick phenolic spacer under the carb that done the trick.