"Gulp Valve" - '79 Tioga


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saintanne

New Member
My family took our inaugural trip with the newly-acquired, newly-renovated '79 GMC Tioga. Our four kids had a blast (ages 9 and under). Mom and Dad did, too, truth be told. Lost an AC belt along the way, and I think the AC compressor also, but for a dry run, everything else seemed to go well enough.

One little quirky thing DID start up, though, just before departure. When I drive the vehicle at idle speed, it has an intermittent backfire. Didn't have it before, and I've only noticed it when it's cold (might not be paying enough attention to it to notice otherwise though). I think it's on the exhaust end, but it's fairly quiet most of the time, so it be at the intake. Anyone out there know how I can tell the difference?

So I'm looking around online and found reference to a Gulp Valve, which apparently is part of the emissions system for this thing. Then, I looked at prices for a gulp valve and discovered why it's peculiar name.... They're like $80 each.

I guess I need some help properly diagnosing this problem so I know where to spend my limited $. Gulp valve, or is there a better (ie cheaper) place to start looking? I understand that it requires proper diagnosis to know where to look.

Thanks for the input!

SA
 
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LEN

Senior Member
Re: "Gulp Valve" - '79 Tioga

First places I would look are all tune up parts(plugs wires points rotor and cap) then all vacume hoses(this is time but cheap) plus fuel filters. Then start on to the more expensive parts.

LEN
 
C Nash

C Nash

Senior Member
Re: "Gulp Valve" - '79 Tioga

If that's the valve that fits on all the plumbing going into the exhaust they will cause the problem you are talking about Mike. You can just remove all this Junk and plug the holes but you didn't hear me say that :laugh:
 
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saintanne

New Member
Re: "Gulp Valve" - '79 Tioga

Good advice (x2)!

I already did the plugs (that I could reach, that is). Didn't attempt distributor or wires yet, though I will in the next week. Assuming this does not help, I will proceed to vacuum hoses, which I assume are originals and need replacing anyway. As a last resort, I heard someone say that I can just remove all this Junk (vacuum lines going to the exhaust) and plug the holes. Can't recall where I got that advice from though! =)

Thanks again! I'll let you know what happens.
 
C Nash

C Nash

Senior Member
Re: "Gulp Valve" - '79 Tioga

Mike better watch what you hear :laugh: If you are in a state that requires inspections they might catch that :eek: but I hear a lot of folks remove it. Even know a guy that has been guilty of doin it :laugh:
 
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Aceventura

New Member
RE: "Gulp Valve" - '79 Tioga

Seems to be very close to the problem i have at the moment.I have a missfire on start up that reduces with temperature rise.I have renewed plugs and leads and expecting delivery of fuel filter today.I also was informed to renew carb but prefer to do cheaper diagnosis first and work up the way.I also have a 79 Tioga.There was 2 new coils in one of the drawers which i tried but made worse, so filter and vac hoses on the menu today............ :cool:
 
C Nash

C Nash

Senior Member
Re: "Gulp Valve" - '79 Tioga

Check your dist cap and rotor button. Do you notice ecessive white smoke from the exhaust and odd smell? Doubt that the carb is the cause of backfire unless it happens on quick aceleration.
 
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saintanne

New Member
RE: "Gulp Valve" - '79 Tioga

Ok, so....

Took our first 2500 mile trip six weeks ago. Wow, how fun! The little ones had a blast and so did mom and dad! I can see why some folks do this full time. We may be full-timers someday, too!

Had a front tire blow out on the highway in Minnesota (didn't kill anyone, thanks be to God), the starter solonoid went bad in South Dakota (only $16 at NAPA), and had a recurrent loose alternator belt that squealed now and then. I also discovered that the bathtub drain leaks when I took my first shower. But, all-in-all it was a raving success and very popular with kids and parents alike! I am SURE glad I had half my tool chest with me!

The backfire problem persisted throughout the trip, and, as we drove, it seemed to become less and less dependent on engine temp. It really seems now to backfire, during idle only, whenever it is running. Any ideas out there as to the cause? I am a newbie with carburators, although I don't know if that matters. I am not even sure if it's an intake backfire or an exhaust backfire. Can anyone help me diagnose that part of it?

I haven't disconnected the Gulp valve, although I did go through and replace all vacuum lines before our trip. When I looked at the number of lines hooked to the gulp valve, I felt a little intimidated and wimped out. Is this a logical next step? No worries, there are no inspections where I live.

Thanks so much!
 
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Aceventura

New Member
RE: "Gulp Valve" - '79 Tioga

The carburetor was removed a while back for inspection and cleaning but when i checked it didnt seem to have been cleaned thoroughly so i removed it and returned it to the garage again.I did notice that there was no gasket fitted when i removed it and wondered if it required one, bearing in mind it didnt have one when i bought it and seem to be running ok.Since replacing i have a whistle from the carb which im guessing is air.Gasket required or not?

Also how do i check the coil is in good working order,there was two with the van which ive tried both and they are new but make running even rougher.

Also where is the gulp valve situated.

FOR SALE 1979 DODGE TIOGA LOL

:laugh:
 
C Nash

C Nash

Senior Member
Re: "Gulp Valve" - '79 Tioga

Some had a metal shield type that went under the carb. Did you replace a gasket under the carb? There was different base gaskets and if you get the wrong one it will whistle. There is supposed to be a gasket between the metal heat shield and the intake. Doubt that the coil is the problem. Probably the smog system not working as it should. Remove all the crap and install plugs where it enters the exhaust. To find the whistle spray carb cleaner around the base until you hear the engine rev. Just be careful as the cleaner is flameable.
 
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Aceventura

New Member
Re: "Gulp Valve" - '79 Tioga

Thanks C Nash. I have replaced the fuel filter which was located more or less under the passenger seat and noticed what appears to resemble a 2 large cylinder filter housing which take a lot of the vacumm lines. A/ can i simply remove the vac lines and plug them? and B/ what is the SMOG system.

The carb had NO gasket at all when removed from block,only a seal on the top prior to air filter housing.
 
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GlennT

New Member
RE: "Gulp Valve" - '79 Tioga

I had an MG car years ago and it had the gulp vavle, it is part of the air pump injection system that pumps air into the exshuat manifold. When it failed it would backfire on command, evry time I let off the gas to shift, replaced it and completey cured, sounds like that could be your problem. This air pump system is an emission enhancer
 
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