tips on starting l20b on cold day to set timing?

[DanielC]

Make sure then plugs are good, maybe follow the suggestion to get new ones. You may need to run more ignition timing advance that the stock engine, because your engine is not stock. Make sure the ignition system is in good shape. A good hot spark will help a lot with cold start problems.

 

Unfortunately, all the changes that give an engine more power, without increasing the displacement, do so by shifting the RPM the engine makes peak torque higher up in the RPM range. This unfortunately robs torque from the lower RPM range.

To get the engine to run with more torque higher, the most influential change is the intake valve is left open longer, into the compression stroke. This works fine at high RPM, because the inertia of the air rushing into the cylinder just keeps flowing into the cylinder, even after the piston is past BDC, and actually going back up.

However, at low rpm, it is easy for the air going in the cylinder to reverse, and flow back out the cylinder. So the cylinder sucks in 500 CC of air, and then pumps out 200 CC. it is like trying to start an engine with low compression.

Additionally, this in some cases causes the air to flow back and forth through the carburetor, screwing up the ability of the carburetor to meter the gas to air ratio correctly.

Add in the fact the engine is cold.

 

Sometimes you can help beat the bad compromises of a high RPM cam at low RPM, by increasing the compression. I do not think you want to tear into your truck engine again, at least until the weather is warmer.

Your engine might start easier with more initial ignition timing. However, too much timing advance will cause the engine to try to kick back, or run backwards. You also have to be careful to not to add so much timing advance, the engine knocks. You might have to add more initial advance, and limit the amount of mechanical (centrifugal) advance, to keep the the total ignition advance acceptable. If you are not using vacuum advance, hook it up. IF you are, you may have it hooked up to ported vacuum, off the carb. Try hooking it up to direct manifold vacuum.

 

Mechanical chokes can be tricky to get right, and even electric chokes may need a little adjustment to get adjusted correctly.

 

If all else fails, you might have to run a more conservative cam until it warm up a bit.

[.sunlover]

Well, I figured it out. Head gasket. :( good I know what to do, bad I gotta do that in the cold. I miss the fucking shop. Goddamn landslide :( It got hot when it blew the alt/water pump belt, just didn't think it got that hot, only drove it for a minute. My temp gauge had just quit working........ Now: pull head, fix compressor, buff surfaces, install head, Drive. (sigh)

[.sunlover]

well, Head gasket changed, all back together, and still no starty. guess I'll pull the top off my carb, and make sure nothings stuck, or goobered up, but I just dipped it, cleaned the fuel tank, the fuel system is newish. plugs were fouled, but I cleaned the 2500 mile new plugs, cooked them and installed them preheated and no start. got spark, fuel at proper pressure, compression. Timings close, so, yeah, i'll just make sure the carbs working right, because there is nothing else. (singing) "all I want for christmas is my truck to run...... .......then I could have a merry christmas" Hour and a half, and I got to leave for work, pray to the datsun gods for me that I can leave in my 521 :)

[.sunlover]

carb is working right..... ummmm.......... adjusted the choke too.

[datzenmike]

Generally adjust/set the choke when completely cold. Set adjuster in the middle of the scale. Work throttle and it should snap shut with the fast idle on the first step of the fast idle cam. Engine should rev 1,800- 2,300. This adjustment should work for the full range of temperatures in the winter and will self adjust for colder or warmer days.

 

Not recommended by the book but you can increase the choke enrichment to suit your needs. Engine won't warm up faster but it may be more drive-able when really cold.

[banzai510(hainz)]

distributor timmed?

valve lash set

Got spark at coil(center coil wire out from coil)?

 

If gas is shooting in the carb when you cycle the linkage it should fire the vapors. STARING FLUID!!!!!!!!

[ggzilla]

Preheating the spark plugs doesn't help -- they fire just as easily when cold. You might be thinking of diesel, which requires heating via glow plugs.

[mike]

Do you have a remote start "tool" basically a push button switch with a couple of alligator clips to hook from the batt to the starter? Turn the key to the "on" position and use the push button to start the car from under the hood... Either that or a friend to turn the key for a few minutes?

 

Youve messed with damn near everything on that engine so its best to start from square one...

 

Make sure your dizzy is in the right position and make sure that your rotor is pointing towards your no 1 spark plug when it is at TDC.

 

Make sure that youve got all vac lines and fuel lines hooked up and make sure that youre getting gas to the carb.

 

check to make sure that youre getting a good strong spark.

 

leave the timing adjust screws on your distributor loose enough to turn by hand but tight enough to hold the dizzy in place while running.

 

When starting something like this Ive noticed that its a bit easier to use carb cleaner or starting fluid for the initial firing just to keep from wanting to pump the shit out of the throttle and flood the engine...

 

Spray a little carb cleaner down the carb then turn the dizzy all the way to one direction. Then while trying to start it (either with the key or the start button) turn it SLOWLY in the other direction (either to advance it or retard it depending on which way youre starting from) and if everything is good it should fire, adjust the dizzy till it smooths out and it isnt racing... if youre outside and its cold just get it running and do what you need to do to keep it running till the motor gets a little heat in it and do your final adjustments with it all warmed up.

 

As for timing on most engines Ive worked on, if you dont have access to a timing light, once its running adjust the dizzy just to the point that the engine starts to race and then back it off a hair till it idles down and runs smooth and you will probably be within 1 degree of the timing being right where you want it.

 

If youve got good spark, fuel, and no major vac leaks it will fire and run without a working choke, even if it is really friggin cold outside, it will just take a bit longer to warm up to operating temp.

 

My brothers beater 620 (weber and matchbox)doesnt have a choke and it still starts right up with one pump to the pedal, he has to feather the throttle for a couple seconds and hes good to drive after about two minutes of warming up.

 

As for all that RTV... Id just about bet money that youve got that shit in your heater core and radiator and oil passages in your block... seriously, less is more :) Pull your valve cover and look down the front of your timing cover where it mates to the block and see if youve got a bead of RTV squished out... if you do THATS A BAD THING... for sealing an L series front cover, just make sure that it is spotless clean and as oil free as you can get it, replace the front oil seal if it looks bad at all (theyre cheap and usually come with the timing cover kits anyways...) Put a small dab of RTV behind the timing cover gasket between the block on the top by the head and on the bottom by the oilpan and do the same on the front between the gasket and the timing cover. Do the same on top and bottom of your oil pan gasket (spray it with carb cleaner and get it as oil free as possible) Make sure all your pins are lined up and install the bolts finger tight/snug but dont torque them to spec. Check inside your timing cover and see if youve got any RTV squished through, if you do wipe it out with a rag as well as you can... you dont want it in there. Let the RTV cure and torque them all evenly to spec. The waiting to torque isnt absolutely necessary but Ive had good results and if youve got the time, it cant hurt. After that check and make sure that your timing inspection plate on the head is clean with a good gasket and not overtorqued (it will distort the cover and let it "bow out" and cause leaks. After this you *should* have a leak free L series that doesnt look like a preschoolers attempt at finger painting... No offense :P Seriously though, if that were mine Id tear it apart and start over just to get all that shit out of there... its a hell of a lot cheaper than replacing oil starved bearings and clogged heater cores.

 

Oh yeah... youre comment on using the RTV on your head gasket... I hope that was a joke. Install it dry and just have everything as clean as possible, also dont forget to clean/chase all of your head bolt holes in the block. Taking your time and doing it right the first time is a hell of a lot faster and cheaper than redoing everything wrong a couple times over...

 

Good luck man

[.sunlover]

Preheating the spark plugs doesn't help -- they fire just as easily when cold. You might be thinking of diesel, which requires heating via glow plugs.

 

The preheating was to thoroughly dry them, installing them hot is to slow future flooding.

[.sunlover]

distributor timmed?

valve lash set

Got spark at coil(center coil wire out from coil)?

 

If gas is shooting in the carb when you cycle the linkage it should fire the vapors. STARING FLUID!!!!!!!!

 

dizzy is loosely timed, valves were set hot, spark is firing my timing gun to watch where it is timed when it's turning over, good cap and rotor, occasional carb fire with the starting fluid.

[.sunlover]

I ask the other mechanics at work, and they say i've got all the bases covered, scratch their heads, and say "good luck man" If my truck keeps defying all logic and reason, I'm gonna' have to start calling it "her" What's left to do? buy it roses, write it poems, talk to it in that slow low voice? maybe a little soft touching before I get into her guts and quit going so fast? I hear ya on the rtv, it's lined to the outside to avoid the inside puckering. I did follow the head gasket comment with a lol jk right? That would make me a terrible mechanic, so really bad at my job. I appreciate each and every comment trying to help me out people, and thank you all :)

[Laecaon]

I say switch the plug wires at the dizzy just for fun. Switch 1&4 and 3&2.

[DanielC]

Check the compression. Do not assume it is good. I know you just replaced the headgasket, but check the compression anyway.

[yello620]

I ask the other mechanics at work, and they say i've got all the bases covered, scratch their heads, and say "good luck man" If my truck keeps defying all logic and reason, I'm gonna' have to start calling it "her" What's left to do? buy it roses, write it poems, talk to it in that slow low voice? maybe a little soft touching before I get into her guts and quit going so fast? I hear ya on the rtv, it's lined to the outside to avoid the inside puckering. I did follow the head gasket comment with a lol jk right? That would make me a terrible mechanic, so really bad at my job. I appreciate each and every comment trying to help me out people, and thank you all :)

 

 

Hold on here, are you claiming to be a mechanic, yet cant make an L motor fire? And all that RTV?? Lined to outside or not, there is NO need for that. Four little dots of RTV is all that is needed to seal the front cover, one dot in each cover.

[.sunlover]

Hold on here, are you claiming to be a mechanic, yet cant make an L motor fire? And all that RTV?? Lined to outside or not, there is NO need for that. Four little dots of RTV is all that is needed to seal the front cover, one dot in each cover.

 

Sorry, did I miss the part where you had an idea of anything else I could do that I hadn't done yet? The purpose of this thread is to start my l20b with imperfect timing in the cold, not justify my career to you, but since this isn't the first time someone has jumped in to insult and not add anything positive to one of my threads, i'll quickly explain myself. Yeah, Mechanic, not senior mechanic, but the fleet I help maintain I don't think has even one truck with less then a million miles on it, and the shop insists on silicone on almost everything, lots. As I mentioned earlier, my timing cover in every l20b I've had has always had just enough leak to make the dirt stick, and I want mine to stay shiny aluminum for once instead of black. RTV mostly rubbed on the outside does NO harm. This is the part where I'd thank you for your help, but..... have a nice day anyway :)

[ggzilla]

Starting with imperfect timing should be no problem. As long as it is 5 degree plus or minus, it should fire right up.

 

Starting in the cold is largely a function of the choke. If the choke plate closes ALL the way (no gap) then with a few pumps of the gas pedal it should fire right up at below freezing temps. Just make sure there is gas in the float bowl as seen through the site glass.

 

Those are the general guidelines. Now back to your specific scenerio ...

[JWJohnson]

nvm