vaporlock

[Lucas van Altena]

Hi all,
I look daily at this great forum, so i'm wondering if you can help off with this problem.
When i have driven with a cold engine for a couple of mls than after a stop the engine will start badly: coffing in the webers (2 times the carbs went on fire) and the startermotor has a hard time to turn the engine.
Have change the plugs (gap 10 mm, gives beter throttle repons in low revs), but no changes.
Cold start is oke.
Regards, Luc

 

[Andy Besic]

Regarding starter motor diffculty....If your static timing is too far advanced, the starter motor will have a difficult time. This may also be the cause of the backfire.
Check your static and fully advanced timing and post your results.

 

[Lucas van Altena]

Thanks Andy,
I will look to it.The car has bin driven for 5.000 mls without starting trouble only the last days it gives with a warm start trouble.
regards , Luc

 

[Eric A.]

I think that Andy is right on this one. I have had the same thing happen to me and it only takes a couple of degrees of too much advance to cause this to happen.

 

[emiel]

you can also check all connections to the starter motor.Even the starter itself can go bad so the engine doesn't turn fast enough to get a good a starting condition when warm !!

 

[Phil]

Luc
This used to be a big problem here in the states with small and big block engines. Mostly it was the timing being too far advanced initially as Andy and Eric have said. Also we had a problem in the 60's & 70's with GM engines doing the same thing, the bushing in the front of the starter would become worn excessively, and when the starter pinion hit the ring gear it would bind the armature and effectively stop the starter. You would get a partial turn, and draw so much current that the battery couldn't turn the starter. Hopefully your problem is timing and an easy fix. We solved our problem eventually by going to gear reduction starters, and even with a lot of initial advance they crank the motor just fine.
Good Luck
Phil

 

[Ian Clark]

Hi Luc,

Timing certainly is an issue although there are others factors when the cold start is easier than the hot start.

You questioned vapourlock. If the carbs are getting above 160f then boiling fuel could become a problem. http://www.gt40s.com/ubbthreads/showflat.php/Cat/0/Number/62711/an/0/page/0#62711 This is where the heat sheild around the carbs really hepls.

Also check your fuel pressure, Webers like 2lbs, more is not required and may flood the float chambers.

If you've had carb fires you need to know the causes are not from leaks.

Backfiring through the exhaust is rich and popping in the carbs is lean. Idle adjustments and syncronizing carbs alone will not cure this.

More to think about... What model of carbs do you have by the way? IDAs have no cold start provision so are harder to get going cold than warmed up.

Hope this helps

 

[Lucas van Altena]

Hi Andy, Emiel, Phil and Ian,
Just checked several times a warm start, all went normal.
We checked the connections on the startmotor and the bendix they were tide fit and masured the voltage 11,2 volt and 180 amp went starting without ignition.
maybe the startmotor is taking to much current?
Ian, the engine is a 302 5 ltr.with edelbrock performer, rollercam, webers 48 idf and msd6al.-+400 hp.
the problem is: warm start, flames( 2 inches) comes out of the trompets and the same time the startmotor starts to turn likes the battery is going to die, we checked also the battery, which is oke.
I thank you all for helping me with this problem, you know a fire in the back of your car and you cannot get very quick under the rear bonnet scare my pants down.
Regard, Luc

 

[Pete McCluskey.]

I'm no expert but it sure sounds like a timing issue to me.

 

[Ian Clark]

Hi Pete,

I'm inclined to go with you on timing. If the engine pulls strong with no detonation then the timing can't be too far advanced however the Webers like advance. So if it's fighting the starter and still fires (bad choice of words) starts and idles smooth you're ok too.

What's got me going is 2" high flames on hot restart. There's way too much fuel going in on hot restart. Also it helps the cranking speed if the throttle is held partially open during cranking.

Luc, take a look at the fuel pressure, some how you're way to rich on restart. Hmmmmmm...

 

[Howard Jones]

Set static timing at 10 degrees BTDC. Try again. You may also have a new problem with the electronic's. MSD's are very good units but they can fail. Check the coil also. You might want to try another one of each if you can. By the way the 10 degree number is just to get you to a point that the engine should start well. I have no idea how your motor is tuned and therefor I can't tell you what the best settings are. My motor is similar except for the carbs, I have a holly, and I have my timing set to be all in, 34 degrees BTDC, at 2500RPM's. I also think you problem is timing, or weak spark.

The very slow chanking when warm is a good and bad thing. Good because your motor seals well, valves and ring maintain a good seal. When shut down, one or more of the cylinder's will have both valves completely closed. The air in the cylinder(s) warms up, builds pressure and makes the engine hard to turn over. As the motor begins to turn the presurized cylinder(s) opens a valve, relieves pressure and the engine cranks normally. The bad news is many of the starters used with these conversions are marginal and when there is a little resistance they can't quite handle the job. The above mentioned gear reduction starter will solve this problem.

Good luck.

 

[flatchat(Chris)]

FWIW Had a similar mystery (302w single plane/600dp holley,accel elect. distributor and remote ign. module)after some time of faultless performance suddenly it seemed as if it would go to full advance when trying to start therefore backfiring etc, if it did start --would run fine. The result finally from much cursing a swearing (bloody electronics) was the ignition module-- swapped the two middle wires over and everything went back to normal--happily
Note:- I don't know, it just worked /ubbthreads/images/graemlins/confused.gif /ubbthreads/images/graemlins/grin.gif

 

[Steve Toner]

[ QUOTE ]
There's way too much fuel going in on hot restart.

[/ QUOTE ]

I had this problem on my car. Try shutting off the fuel pump a few seconds before shutting down the engine (thus depressurising the fuel lines) & see if that helps.

 

[Ian Clark]

Hi Steve,

Great tip, also reduces the standing vapour smells off the Webers and takes some load off the float valves.

 

[Lucas van Altena]

Hi all, thanks for the reponses.
Steve i will put the pump off before shutting down the engine.
The tining will i check later, i'am very busy with my firm the coming weeks.
Have a trayday to let pass, but that's live.
regards, Luc