Engine backfire.

XP29 · Post by **XP29** » Sun Jun 19, 16 7:41 pm

Hi, car has been running great, have recently done motorway driving at 70-80 no issues. Today had a slow drive out to local show, again no issue, but after we went on somewhere else, I'd been at around 70-80 for about two miles then then was a sudden loss of power and two big backfires from the exhaust. It seems fine now and I pulled all the plugs to check, they all look the same as below. Anyone got any ideas what would have caused this? My big fear is if I have or can cause any damage?

Rebel · Post by **Rebel** » Sun Jun 19, 16 11:55 pm

I had a couple of issues with my '68 backfiring and then refusing to start a few years ago.
The first time was the condenser in the distributor breaking down, if yours is still on points in the distributor, check the condenser.
The second time it turned out to be the ignition switch which lead to a few lifts home from the AA before finding out what it was.

XP29 · Post by **XP29** » Mon Jun 20, 16 9:07 am

Don't have the condeser now as there's a Petronix module in the dizzy.

I've not as yet had a starting issue, just this one instance with the backfire. If it helps the second backfire was instantly after the first.

Rebel · Post by **Rebel** » Mon Jun 20, 16 11:26 pm

In the two pics, the first plug looks OK to me, the second one is a bit darker in colour at the tip, there's no burnt electrodes though and they're not soaked in anything. Might be worth trying just changing them.
Other than that someone with more knowledge than will hopefully be able to help

ANTON · Post by **ANTON** » Tue Jun 21, 16 7:32 am

I would check the float height as it could have over fueled and caused the miss fire leading tot he back fire once the plugs fired again.

DaveBishop · Post by **DaveBishop** » Tue Jun 21, 16 1:11 pm

I agree with Anton. Has it still got the carter afb carb I have had trouble withy them in the past

SJH · Post by **SJH** » Wed Jun 22, 16 7:51 am

Have you got a decent in line fuel filter . Particles getting into the carb/float bowls can cause these symptoms

Shayne

XP29 · Post by **XP29** » Wed Jun 22, 16 10:14 am

Cheers guys, it's not a new Edelbrock 650, fitted a while ago as the Carter was problematic, it has run fine since fitting including at speed on motorway.

I put a meter on the coil and was getting 0.00 between the poz and neg terminals, maybe that is starting to fail? Ordered a new coil which I have ready to fit.

XP29 · Post by **XP29** » Wed Jun 22, 16 1:43 pm

Just tested the new coil and it's giving the same reading, so maybe not that. I have to fit the new one as the neg post snapped when I over tightened the nut.