coastwise

Hey guys, I've been having some trouble with my trailing spark (as in: no spark). I got a new set of plugs and was replacing them, but I've found that the trailing plugs don't seem to go in all the way.

I'm only going finger tight and I get them really far in with no trouble. After about 12 or so full rotations they stop. Then I noticed theres a half cm gap between the nut on the the plug and the housing. My leading plugs are almost flush (can fit a fingernail in between).

Sorry if this is a really newbie question, but is that normal? I don't know how it could be crossthreaded that deep. I tried cleaning out the hole in case there might have been deposits from running the engine with them sticking out like that, but it didn't help.

I've found a shop with a thread chaser in stock, but the idea of messing with the threads is frightening and I want to leave it as a last resort.

Thanks guys

gerald m

Always tell people what you have for model and engine so that they can help. Some of the guys are so tired of asking the same things that sometimes they just ignore threads until they are posted correct . Are the old washers stuck in the hole so that you are doubling up on washers ? I don't see how it can be cross threaded if the plug goes in that far the shape or length of the plug might be a little different in length outside the engine .. Put the old plug alongside the new ( are they the same brand )and compare and see if there is any difference and where the difference might be .. even if it is the same type and brand there still might be a slight difference between them .. if the threaded end is the same and it tightens up nice they should be fine .

coastwise

Sorry, of course. Its a 89 FC. My bad.

The new plugs are NGK BUR9EQP trailing and BUR7EQP leading. Replacing the same, minus the P. I compared the new set to the old when I got them and as far as I could tell they were identical. (I'll compare them again tomorrow, just to be sure)

All the old plugs came out with their washers. I also tried putting the old plugs back in and the trailing plugs stopped in the same place. I'm not sure if they were like that before, as I didn't check before pulling them out the first time.

Thanks for the reply

gerald m

The trailing plugs holes I think have a small hole inside check down inside the plug hole and make sure there is nothing in the bottom for the spark plug to hit if it is clean and the plug isn't bottoming in the hole . Maybe the washers came out with the plugs but is their another in the hole ?? take a picture or two show us what you got ..

coastwise

Thanks again for reply, I finally managed to get some photos in daylight. Heres what I'm looking at:



and the same plug seen from below through a mirror:


As you can see, the nut is way out there compared to the leading plug below it. Normal?

I also tried to take some pictures into the hole itself as you suggested. It doesn't look like there's a washer in there to me, but the last three threads look a little discoloured... thoughts?
Into the hole
Another angle
The plugs I'm using

gerald m

I think you are worried about nothing ,, you never know maybe the plug seat just never got machined as deep as the rest .. The discolored threads are where the plug threads stop , the discolor part is the exposed part of the thread that is not used .

Just measure from the plug seat to the brown thread you will find if you measure the thread depth on the plug it's self with washer installed it will measure the same .

Check that install the plugs and enjoy your little car .