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cox438
Novice
Mar 14, 2009, 2:30 PM
Post #1 of 10
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84 5.7 start and stall
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Year of vehicle 1984
Make of vehicle chev
Model of vehicle 3/4 ton 2wd
Engine size ( 5.7)
Mileage/Kilometers1500
I just put this rebuild in the truck. Engine rebiult by factory engine exchange. It ran fine after install but now it starts and stalls can keep it running if gas is feathered but runs extremely ruff.
lots of gas to the carb and good spark to the plugs no vacuum leaks
IF fuel has condensation would this cause this start and stall issue?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Mar 14, 2009, 3:47 PM
Post #2 of 10
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Re: 84 5.7 start and stall
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Probably one of the last Quadrajets and there's a ton of item on and in those to clean, adjust and inspect.
There should be an electric choke (heat up electrically to shut off) and two vacuum diaphragms as "pull offs" that are critical to open when cold and warming and then behave by not doing anything when warm. Pull offs, and the choke are the common items to cause problems so I'd start there.
It wouldn't hurt to spray good old carb cleaner in and out getting any stickyness off of the levers on outside and pivots for the choke plates inside,
T
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cox438
Novice
Mar 14, 2009, 4:26 PM
Post #3 of 10
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Re: 84 5.7 start and stall
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Thanks for the reply tom
I forgot to mention that I installed a 600 cfm edlebrok carb with matching intake when I installed this engine to be rid of all the qudrabog issues.
The entire engine is new from top to bottom
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Mar 15, 2009, 3:11 AM
Post #4 of 10
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Re: 84 5.7 start and stall
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You mentioned "condensation" up top. Is that to say you are concerned about water in the gas or something? Isopropyl alcohol based dry gas should remove moisture from fuel if concerned about that or change out all the fuel for known good new.
No matter who makes the carb it still need to deal with the sensitive warm up period - then behave consistently when warmed up and deliver the appropriate mix ration at the right time which apparently it isn't.
The base concept of a carb is universal. Just three modes - Idle, Intermediate, and WOT (wide open throttle) - that's about it! A Choke is just for cold starting and warm up then done.
If it behave at mid and wide open throttle then concentrate on just idle issues. Idle mixture screws should be at a pre-set on a new carb - most shouldn't require messing with. Idle speed does need to be set now with non OE.
The things to look for with all things new are still vacuum leaks and the base settings. Adjust only when all other things are known ok - tune-up items etc.,
T
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cox438
Novice
Mar 16, 2009, 12:21 PM
Post #5 of 10
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Re: 84 5.7 start and stall
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Thanks again for the reply tom.
I'm suspicious of condensation (water) causing all this start and stall headache as it was an all of a sudden issue parked on night then go to start next day start and stall issue. I had seen some kids playing around the truck that night kicked them off the lot didn't think any thing of it. This is why i suspect water in the fuel. I also see water drops in the clear filter
I have added sea foam to the fuel system now hopping this will dry her out as alcohol did not do the job.
It fires right away then dies. I can keep it running by feathering fuel and I get surging it will run good then drop then up again then down and dies. This engine will not stay running at 1/4,1/2 or wide open throttle. wthf is going on
If this does not work I will try a test fuel tank to eliminate the fuel issue.
I have to get her to stay running hot or cold before I can make mixture and timming adjustments
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Mar 16, 2009, 2:07 PM
Post #6 of 10
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Re: 84 5.7 start and stall
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General about water, condensation, gasolines and alcohols:
Water is in the air as we know and with the right dew points will make abundant droplets as seen with a glass of ice tea on a hot day sweating as if leaking thru the glass. The same thing goes on with air in a gas tank and the temp of metal over the day's fluctuations. I used to advise folks that when they needed wipers for the dew on the windshield that same dew could be in the fuel and with PURE petrol/fossil fuel (we aren't using that in almost anyplace anymore) it separates like good old oil and vinegar salad dressing.
Assorted types of alcohols do prevent water from freezing and some will cause it to suspend and mix in with the fuel to be burned off. Isopropyl is best known for being the catalyst for that.
With some proper dry gas formulas and using up the fuel it shouldn't be a problem and most will sit on low spots and stay there - like the bottom of gas tanks but can get shaken up and pumped along.
A nice hot dry day and using a whole tank of fuel seems to help too. Engine heat should help with water that made it to the carb float bowl over some cycles as well.
No joke history!: Virtually everything back when used glass sediment bowls such that you could see it and when to dump it out. Laugh - Even Granny Clampit knew how to do that!
Carbs had drain plugs to let the water out (I own one!) and all gas tanks had a plug at the lowest spot for that purpose as well.
The moisture, goo, junk, gunk in fuel issue has been brought up here a few times. Now that many area mandate use of ethanol mixed in to fuel debris doesn't just set on bottoms of tanks and filters need to work overtime. Gas stations used to filter fuel before you bought it but quit as it was clogging them up too fast to keep up with - so you get it. Gas in transit and storage has the same issues!
So it's now up to us to deal with more than places we get it. The additives can and will help if used selectively and don't overdo them either.
If the water is excessive for some reason the system needs to be emptied and cleared out and start fresh,
T
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Loren Champlain Sr
Veteran
/ Moderator
Mar 16, 2009, 5:20 PM
Post #7 of 10
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Re: 84 5.7 start and stall
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cox483; Pardon my jumping in here. Water in the fuel will cause a backfire when you try to accelerate. Have you thoroughly checked for vacuum leaks? If you can't get it to idle hot or cold, doesn't sound like a fuel related problem, to me. If you replaced the manifold, that means that you had the distributor out. Are you certain that the timing is close enough? So many possibilities.
Loren
SW Washington
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cox438
Novice
Mar 20, 2009, 2:13 PM
Post #8 of 10
(2135 views)
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Re: 84 5.7 start and stall
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Thanks Loren for the reply you were right on the money with the timing I pulled the distributor again moved it 2 teeth and away she went was able to warm her up and put the light on to make final timing adjustment. There is a bit of water still in the fuel but it should run trough ok now hit with the alchol products but I do still get that hesatation when she burps that water into the carb every now and then but all and all she is running great.
Thanks agian Loren for your help.
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Loren Champlain Sr
Veteran
/ Moderator
Mar 20, 2009, 3:24 PM
Post #9 of 10
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Re: 84 5.7 start and stall
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Cox; Thanks, so much, for the reply. Glad to hear you got 'er going. Have a great weekend.
Loren
SW Washington
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Mar 20, 2009, 3:55 PM
Post #10 of 10
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Re: 84 5.7 start and stall
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Great catch Loren!
"Get'er done"
One more for the wallpaper....
T
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