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View Full Version : Wedge Finally! I figured-out the TR7 backfire problem!!!



sammyb
07-14-2004, 06:48 PM
When we last left our hero, he was still battling the dreaded TR7 backfire problem. With his forum friends' help, he tracked down a number of problems, but still the backfire remained.

-We checked the carb bypass valves, which both looked perfect, and we set them, which solved the slow throttle drop-off...but the pop remained.

-We checked the carb piston movement, and with only 2000 miles on the car since new carbs, they were perfect, and the back-fire was still present.

-We checked the exhaust manifold, and found a bolt missing. We replaced stripped and missing bolts, torqued them all down, but still the pop remained.

- We checked all the hoses, and all seemed tight.

FINALLY...

- We checked the smog pump check valve -- pulled it off and breathed through it. It seemed tight. Put it back on, and after a minute of no backfire, the backfire returned.

...so today I clamped the rubber hose leading to the check valve, and (drum roll please...) the backfire disappeared.

Now all I have to do is find a source for a new air pump check valve! /ubbthreads/images/graemlins/cool.gif

Hegg
07-14-2004, 08:31 PM
Haha, funny narrative! Glad you got it figured out!

I'll make a note to myself to double-check that next time I get my car running and it backfires.

Bugeye58
07-15-2004, 01:48 AM
Sam, shouldn't just a generic check valve work? I mean, all they are is "Anti-Backfire Valves", right??
Any junkyard should suffice.
Jeff

martx-5
07-15-2004, 08:17 AM
I agree with Bugeye58 . You should be able to find a valve at the local auto parts store. On my Miata, when I supercharged it, one of the parts in the kit was one of these check valves. It had a different purpose then for an air (smog) pump, but the part is a STANDARD #AV-23 from a NAPA store which fits a Ford air pump application. I'm sure you can find something to fit.