Timing issue

[Mark]

There is no painted mark on the crankshaft pulley, at least there wasn't. I used a white paint marker to highlight the small notch on the pulley. It's the only notch or marking around the pulley. I didn't verify that it aligns with zero degrees when the actual piston is at TDC. A couple of times I had the #1 spark plug out and could see the piston moving up and stopping at the top, but I didn't look closely down the hole with a light or feel to see if it was exactly tdc. I'm still wondering what the three close-together holes are on one side of the pulley. -Maybe for some kind of puller?Yesterday I manually checked the timing and it was at about 8 degrees BTDC. I'll just leave it there and not worry about it.

[dlb]

Yesterday I manually checked the timing and it was at about 8 degrees BTDC. I'll just leave it there and not worry about it.

what do you mean by manually check the timing? do you mean without a timing light? how would you do that?

It's probably not the best practice, but what I do is put in $20 of gas at a time and wait until the low fuel light comes on before adding another $20. This time when the low fuel light came on, I put in $20 in Duncan (that's the name of the town, not my car) at $1.34/liter. That gives me 14.93 liters. This lasted me 200 kilometers until the low fuel light came on again. I plugged the numbers in to the following online mpg conversion calculator: http://www.accommodationz.co.nz/economycalculator.html

That is not a reliable way to check economy, the best is to record and gallons (or liters) in, and mileage each time you get fuel, and than average it. the other way is to fill it to the top each time. than you know exact miles and gallons used between fill ups. You are likely averaging about 30 mpg which is normal.

actually, mark's method for calculating mileage is more precise than filling until the pump stops since the level at which each pump automatically stops is not standardized—some leave tons of space and some do not, which makes the point at which a gas tank is 'full' vary to some degree. by standardizing the point at which the pump stops, mark's method allows for less variation between pumps. of course, you still have to question the accuracy of the liters/gallons the pump is measuring out, and i have seen exposes showing pumps ripping off patrons. and mark may get slightly better mileage by never driving with a full tank—gas is heavy so a half full tank will cut some overall weight from the vehicle.

my only question regarding your mileage is how you wound up at 38 mpg. 200 km/14.93 L = 13.4 km/L, or 31.5 mpg. i have used several km/L to mpg calculators to verify that. it's still good (especially for a 4wd automatic!) and it sounds more realistic, but not quite 38 mpg. i think the site you linked to uses UK gallons, which are smaller than US gallons.

i'm afraid i have no idea what the 3 holes on the pulley are for.

[Petros]

if you are talking about 3 holes in the side of the heavy metal rim on the pulley, those are likely balancing holes. they are just drilled, not threaded.

it is easy to check TDC, pull the number one spark plug and turn the engine until you can see the piston top, use something soft like a wood Popsicle stick and put it in the spark plug hole so it touches the piston top and slowly turn the crank by hand until the piston is all the way to the top (the tool in the hole makes it easier to feel when TDC occurs). than inspect the notch on the front pulley, it should line up with the "0" mark. It has happened sometimes that the metal key in the pulley gets sheared and the pulley is off, not very often, but there has been at least one forum member that found his front key sheared and it gave him bad timing readings.

[Mark]

That's a bummer about the US vs UK gallons. You're right, my mileage isn't as good as I thought, but still much better than the US EPA ratings (24 mpg on the highway and 22 in the city). For manually checking the timing, what I did was turn the crankshaft until the mark on it and the camshaft pulley were at TDC (zero degrees). Then I took the cover off the distributor and made sure the rotor was pointing to the #1 wire. I then removed the rotor and checked where the "signal rotor" was in relation to the ignitor. There are 4 "points" on the signal rotor. One of them was very close to the center of the ignitor. I slightly moved the crankshaft until the point on the signal rotor was pointing exactly at the center of the ignitor. In my mind, this is when the spark is being sent to 1 plug. I checked where the crankshaft timing mark was pointing and it showed about 8 degrees BTDC on the lower timing cover. I may be wrong, but I assumed that this meant that my base timing was at 8 degrees BTDC (without having any centrifugal or vacuum advance applied to it).
I checked my other '83 Tercel and it also has the 3 smaller, close-together holes in the crankshaft pulley. The FSM doesn't show these. Instead of taking a picture, I lifted the attached picture off the internet. The holes in the picture don't go all the way through like mine do.

[rer233]

Balancing holes.

[Mark]

I assume the holes (for balancing, like you and Petros mentioned) are to offset the key and keyway. I just pulled out my #1 spark plug and I verified that it is at the top of it's travel when the crankshaft mark is at Zero degrees.
There's another weird thing though: Just out of curiosity, I checked the timing by attaching my timing light's inductive clamp on each of the plug wires in turn. # 2 and 3 weren't visible since the timing mark was around the bottom of the pulley when the light was flashing. The strange thing is that the light showed exactly the same timing (about 40 degrees BTDC) on plugs 1 and 4. Since I assume that the light flashes when the spark plug is arcing, this would mean that 1 and 4 cylinders were getting spark at the same time. This is what I would expect in a wasted-spark ignition system, but I'm pretty sure the Tercel doesn't use this system. I wonder if there is a short between the 1 and 4 current paths.

[irowiki]

Hey, I noticed that too, with constant vacuum instead of ported on the top port of my vac advance, both #1 and #4 show up at about 30* BTDC.

If I pull and plug, it goes down to the low 10's. I need to set it for good later this week.

[Mark]

I realised last night after I posted that the same timing for 1 and 4 cylinders is probably normal. Since the camshaft rotates twice for every revolution of the crankshaft, the same timing as indicated on the crankshaft doesn't mean the camshaft is in the same place. #4 is probably firing when #1 is at BDC.

[marlinh]

#1 and #4 would both be at TDC at the same time, #2 and #3 are at TDC together on the next rotation of the crankshaft. When one cylinder is on compression stroke (both valves closed) the matching cylinder is on what is called 'on the rock'. Exhaust valve closing, intake valve opening. Yes the camshaft is always in the same place. The cam lobes determine what the valves are doing on every stroke.

[dlb]

That's a bummer about the US vs UK gallons. You're right, my mileage isn't as good as I thought, but still much better than the US EPA ratings (24 mpg on the highway and 22 in the city).

mark, i bought a 2wd corolla wagon to see what kind of mileage i could get with it. the first tank was 15 km/L, and today's tank was 17.7 km/L. the latter is surprisingly high so i wonder what is going on out here on the island that is giving us such great fuel economy lately. most of the last tank was driven in cold, rainy weather, too. crazy.