| hepkat63 | -- 08-25-2018 @ 3:53 AM |
|
Hi All, I finally have got around to looking at my 'new' 47 coupe. It seemed to start first time and run fairly well. However, on closer inspection, the plugs were really rusty and the leads were very corroded. I changed all the spark plugs, fired up the car and all of a sudden it was missing. Sounded like it was running on 7 cylinders. So, by process of elimination, found it was no.8 that was not firing. So, suspecting a dud 'new' spark plug, I put on of the old ones back in - same thing - missed. So, decided I'd change the leads - just as well as they were all corroded at the distributor end - so much so, three would not even come out! Decided to put new rotor button, new distributor cap and new 8mm silicone leads along with a new coil lead on. Fired the car up and it is still missing on no.8 - but NOT as badly as before. only seems to be under load when I rev the car, with a back firing of sorts from the right exhaust bank. Given that it was running fine before i changed anything - is it just a coincidence that this has happened? Maybe a sticking valve now? Firing order is definitely correct. Has anyone had this happen before? Really don't want to start pulling off heads and manifold if I can get away with not doing so. I've only ever driven the car about one mile.
|
|
| cliftford | -- 08-25-2018 @ 7:15 AM |
|
With engine running, pull the plug wires one at a time, hold 1/4" from block and see if you get a hot blue spark. If not clean out the holes in the dist. cap with a piece of sandpaper wrapped around a pencil, then wipe or blow them out.
|
|
| 40 Coupe | -- 08-25-2018 @ 7:18 AM |
|
New plug wires should be copper wire core and not resistor or radio suppression type. Is your distributor the crab type mounted to the front of the cam ? Look inside the distributor cap #8 terminal make sure appearance is correct. Take an ohmmeter across the #8 inner and outer terminal and look for 0.0 Ohms. connect Ohmmeter across both ends of #8 spark plug wire again 0.0 Ohms. This message was edited by 40 Coupe on 8-25-18 @ 7:23 AM
|
|
| hepkat63 | -- 08-25-2018 @ 11:54 AM |
|
thanks guys for the replies. I changed the distributor cap to a brand new one (yes, crab type) but problem still occurs. Previously, the car had 7mm silicone wires, now it has 8mm silicone wires - same issue. Maybe just to clarify, I've only started the car about ten times. I then drove it about a mile to get it registered and back home again - all was running well. I drove it into my shed, changed the plugs and it started to miss on no.8 cylinder. I then have tried the old plug back on no.8, but same issue. Checked the gaps on the plug - 0.25. Changed all of the plug leads , changed distributor cap, changed rotor button. Still misses on no.8, but not as badly as previously.
|
|
| supereal | -- 08-25-2018 @ 12:26 PM |
|
If you changed to a "crab" distributor caps without also changing the rotor, you probably will cure your problem, but carefully inspect both the cap and the rotor for interference damage.
|
|
| 40cpe | -- 08-25-2018 @ 12:26 PM |
|
backfiring from exhaust indicates possible stuck valve. Check the compression on all cylinders. Marvel Mystery Oil according to the directions can help with sticking valves.
|
|
| pauls39coupe | -- 08-25-2018 @ 5:51 PM |
|
Time to run some tests. A vacuum gage will tell you a lot about stuck valves, and other engine problems. They are cheap and easy to use. A compression test will tell how this cylinder compares to the others. Make sure all your plug wires are in the correct place in the cap. Check the #8 plug wire, you should see a fat blue spark if you hold it about 1/4 inch from the plug, ( use an insulated pliers to avoid shock). Chances are you improved the other 7 cylinders, and now you notice the really bad one. I would bet on a stuck valve if everything else checks OK. Let us know what you find
|
|
| shogun1940 | -- 08-25-2018 @ 7:08 PM |
|
I agree checking compression and i know you have new wires , but shut of all the lights in the shed at nite and pipe the exhaust outside and then look under the hood while it is running and just see if you have any leakage of spark, corona effect. It takes your eyes 2 minutes to adjust to the dark. I have put brand new wires on and seen them leak like sives.
|
|
| Drbrown | -- 08-28-2018 @ 10:39 PM |
|
I'm with paul..... : vacgauge will tell the story. Google for how to read and interpert vacgauge reads ..... very helpful.
|
|
| hepkat63 | -- 08-29-2018 @ 1:41 AM |
|
so, after changing all the leads again - i found my problem. Hiding under the heater hose wire , the vacuum three way plastic piece was cracked - obviously when pulling out the old spark plug leads, it's hooked up and split it. yay me!!
|
|
| EFV-8 Club Forum : | https://www.earlyfordv8.org/forum |
| Topic: | https://www.earlyfordv8.org/forum/viewmessages.cfm?Forum=18&Topic=12274 |