Hi everyone, Is there an easy way to diagnose a broken timing chain? My 6-300 won't start. The gas is flowing, but I don't have spark to the plugs. I do have spark from the coil. I have replaced the computer to no avail.

Thanks for your advice. Robie

 

P.S. The distributor does turn.

 

So when you turn the engine over the rotor spins. I have not pulled the front end of mine yet so somebody more experienced than I will need to confirm - but I believe the 6 uses gears and if the cam is turning and driving the dist than the gears are more than likely ok. Have you checked out the pick-up and wires inside the dist? Just to be sure you might throw a new dist cap and rotor on. Cracked caps have been known to happen.

 

The I - 6 does not use a timing chain, it is gear driven.

 

What yr is your truck & what ignition system does it use ?

 

It's a '78 and it has that little sensor in the distributor instead of points and condenser.

Are you sure about the gears? There are instructions in my Chiltons for checking chain slackness and replacement.

 

My 84 has gears. I had the similar symptoms to yours when my ignition module (TFI-IV) went out. I think if something catastrophic went like a timing chain or a gear, there would be loud mechanical noises eminating from down there. Also, did this happen when you were driving or after it had been sitting. My ignition module went when I tried to start it up in a Burger King parking lot I had pulled into in the middle of a 1500 mile trip. When I was driving a different car and its timing belt went, I knew it cause I lost power and the oil light came on. Hope this helps.

Will

 

It happened after it was running real rough. When I went to start it next time it wouldn't start.

But anyway I already put in a new module just in case.

What's the chance it could be the sensor in the distributor?

 

the 6 has gears. has for ever. i think your problem is probably in the distributor if you have spark from coil.

 

I've got a Clymer manual that covers the '78. It calls your set up the breakerless electronic ignition. With the symptoms you say (spark from the coil but not the plugs), the troubleshooting section seems to point to either the ignition pick up inside the distributer, the rotor (armature or trigger wheel it calls it in various places) that it gets its signal from (this is separate from the rotor that conducts the spark to the plugs), the control module and wiring. You said you replaced the computer so I assume that means the control module. THat leaves wiring, distributer pick-up (also called pole piece) or the armature inside the distributer. Wiring should be easy to check with an ohmmeter. While you're at it with the ohmmeter, measure the resistance of the pick-up. It is probably just a coil so I'd guestimate an expected value of 5-6 ohms. Anyway, that would leave the pick-up or the armature. Book says to check both for damage or corrosion. Without seeing them, I would lean towards the pick-up since the armature is just a piece of metal shaped into a star shape. Can you buy just the pick-up? Are you sure the new control module is good? More than once I've gotten bad parts from cheap auto part stores. I'd replace the pick-up and if that doesn't do it, I'd break down and take it to an auto electric place. Good luck.

Will
'84 F150
Bone stock but gets me where I need to go at 18.5mpg.

 

If you have spark from the coil wire and not at the plug wires it can only be a problem from where the coil wire plugs in to the distributor and where it comes back out to the plugs. Cap or rotor. All ign. related components have to be working or you would not have spark at the coil wire, right?




2000 XLT Flare Supercab Sport 5.4-Auto-355LS-Tow pkg-Bedrug-Xtang Tonneau

 

Well, first I need to admit that I read the Chiltons book incorrectly about the timing gears. It's not a chain but gears. Thanks everyone for the correct info there.

Secondly, I haven't had too much chance to work on it because of the recent rain. My shade tree is not too helpful agaonst the kind of rain we have had lately.

It does seem to be narrowed down to the Dura-Spark stuff in the distributor, so that will be my next try. Pray for dry weather on Saturday.

Thanks again everyone!!! Robie

 

Well, that did the trick. We had dry weather in Tulsa today so I put in the Dura-Spark sensor and it purrs like a kitten. Sure glad I didn't go to AutoZone and ask for the timing chain, those guys would still be laughing. I'm thankful that no one here on the board laughed, at least not so as I could tell.

Thanks for all the help everyone. Robie

 

 

Glad to hear that did it!