Hello,

Does anyone know the easiest and most accurate way to get a motor to TDC on the COMPRESSION stroke? I have done this before with the 0 degree marking on the crankshaft pulley etc but I had the valve covers off at the time so I knew TDC compression (as opposed to exhaust) by looking at the movement and position of the valves.

Any "tricks of the trade" to align the motor at TDC and ensure it is on the compression stroke? (the engine is complete and in the truck - plugs will be removed).

 

The easy cheap way, have someone place finger or thumb over sparkplug hole on the #1 cylinder. Turn crank over, when it is the compression stroke, the pressure will push their finger/thumb off of the hole and whistle. Then place a small rod or stiff wire into the spark plug hole of the #1 cylinder and as you turn the crank see when upward movement stops. Your at TDC. With the balancer on the pointer should be at 0 degrees.

If you are by yourself, screw a spark plug in loosely, and as you turn the crank listen for the air hissing out. You may have to play with the amount the plug is screwed in to get the hiss.

Someone makes a tool to screw into the spark plug hole that will whistle on the compression stroke. There is also a tool with markings on it to place into the spark plug hole to read upward piston travel.

Hope this helps.

 

I figured that using the "friend with a thumb" method might be the way but as you suggested I might be on my own so I'll try to use the spark plug idea.

If I can find a cheap tool to aid me I'll pick one up.

Thanks for the information.

Gil

 

Since we are dealing with Fords here, remember that #1 is on the passenger side front. This puts it right near the starter relay. You can jump the battery side to the "S" terminal wth a srewdriver, while putting a finger on #1 plug hole, or use a remote starter button switch (most parts stores should have one). Bump the engine a little at a time until you feel pressure. then turn it to TDC on the balancer.

 

Interesting idea. Seems easy enough. Never thought of that.

 

I have used a compression tester in #1 cylinder to find out when you're on the compression stroke. Bump it over until compression starts to build on the gauge. It helps to position it so you can see it under the hood. Now you're on the compression stroke. Find TDC and you're there.

 

The relay is not always on the passenger side. Any piece of wire can be used to activate the relay and bump the starter. Just connect the + battery terminal to the relay terminal momentarily. A finger will detect the compression stroke. No need to buy anything.

 

I guess you have to trust advice from a guy with 23,000 posts!

My relay is on the passenger side near the battery on the fenderwall so it should be a simple procedure. I'm not exactly sure which terminals to cross but I'm sure I'll figure it out. I remember doing this once to start a guys car (in neutral) when he had a defective switch from the transmission (you know the one that won't allow the car to start when it's in gear). It got him to a shop where they could do the job for him.

I'm replacing a CMP sensor which is a real pain so I'll need to wait for some decent weather. I'll let you fellas know how it turns out!

Thanks,

Gil

 

I have been bumping over engines FAR longer than I have been posting, over 40 years. Some new vehicles do not have starter solenoids (relays). They have a relay in the power box that does the same function. If the relay/solenoid is mounted on the inner fender there are either 3 or 4 terminals. The two large terminals are the high current battery and starter terminals. Some people jump those with a pair of pliers etc but that is horribly abusive to tools and dangerous. If there are two small terminals they are sometimes marked S and I. The S terminal is the one you want. If in doubt disconnect the vehicle wire from the terminal you want to test. If there is only one small terminal that is the one you want. If you can then turn the key to start and nothing happens you have the right terminal. You can wrap a scrap of wire around that terminal or use a wire nut or even use a fancy starter switch. Some guys use a screwdriver or pliers or other metallic article. I don't like to see arc burns on my tools etc. Connect the other end momentarily to either the battery power terminal on the starter relay or to the + battery terminal, or even connect that fancy starter switch and press the button momentarily.

Of course if you don't want to or can't turn the engine over with the starter... -Take the plugs out and use a ratchet wrench on the harmonic dampener bolt to turn the engine over. You can still use the finger method to find the compression stroke.

 

Thanks for the information. I will have a look at the relay and see if what your telling me makes sense (I'm sure it will).

I will have the plugs out to do this job. Once I find TDC (compression) I need to get to 26 degrees ATDC, then install the CMP, then spin the motor around twice to take up the slack in the chain and then do the fine adjustments on the CMP. I have 26 degrees ATDC marked so my problem was finding TDC on the compression stroke by myself. Turning the balancer is easiest from the bottom so it is difficult to put a thumb over the plug hole at the same time!

I should be good now. Thanks.

 

Not to step on any toes, you said easiest and most accurate way.
Well you have been informed on the easiest way, but the most accurate way I know is with a degreeing wheel and a positive stop.
I can explain totally if you are willing to buy a kit, or maybe you have a friend that has one you can use, then he could show you.
If you lived close, I would show you with mine.

Good luck.

 

I did check on the degreeing wheel when I looked online (searched "TDC" on Google) but that seemed like too much trouble for what I was doing. I assume that if you do a rebuild and need accuracy when setting the cam and crank to each other this device is necessary.

If I can get the balancer pulley to the 0 degree notch I'll be OK I just was looking for a way to check for compression. It looks like the 'ol thumb will do.

Thanks for the feedback.

Gil