6.2L Anti Drainback valve?

[pfer10]

Is there an anti drain back valve in a 86 6.2L? Every once in a while mine will fire up then start to miss after a couple seconds and die. Once it does this I have to crank for 30 seconds, stop crank again then it will start to sputter. Crank some more and it will finally start and run fine. It does this random and so far I haven't see a pattern. Usually occurs after it sits for at least 5 hours. When it starts right up it runs fine. Sometimes it won't do it for a 5 days then it acts up again.

I assume fuel is draining back out of the filter so today when it did it I was going to crack the bleeder on the filter and the plastic valve broke on me. :>( Anyone know where to get the little plastic valves?

I am thinking of putting in an electric lift pump and going away from the mechanical. Anyone got a good lift pump part number?

[wthif]

Did you replace the fuel cap recently? One not relieving the vacuum could possibly cause your problems.

I don't think the early 6.2 had a antidrainback device on the IP. An antidrainback device would probably keep you from having your problems.

You might also be getting air into your fuel lines causing your problems.

I've had a few drinks tonight and if I'm not making sense that is why. Hopefully others who know better than to drink a lot on Tuesday nights will respond.

[john8662]

Sounds as though you have an air leak somewhere, likely a rubber line or a fuel filter (if two) that is not sealing to the base properly.

Check there first.

There isn't a drainback valve. The later 87+ MFI pumps supposedly did, but I can't verify this.

The IP doesn't drain back unless it's got a leak itself, which is indeed possible, check the usual suspects around the pump, which include the throttle shaft and advance piston areas, among otheres, perhaps the bolt on the back/top of the pump, this leaks too.

J