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Gary, ASE Certified Technician
Category: GM
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Experience:  Senior Technician
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I have a 1981 Itasca Motorhome with a 454 engine.......starts

Customer Question

I have a 1981 Itasca Motorhome with a 454 engine.......starts great when cold but when it gets hot and I turn it off it wont start till it cools no spark or fuel ( i cant smell fuel in the carb)
JA: Sometimes things that you think will be really complicated end up being easy to fix with GM. The GM Mechanic I'm going to connect you with knows all the tricks and shortcuts. Are you hoping to fix this yourself?
Customer: yes
JA: Great! What have you tried so far?
Customer: nothing yet...but has a new fuel pump
JA: So many things can cause fuel pump issues. Some simple, some complicated. Fortunately, the mechanics we work with have tons of experience dealing with them. Is there anything else important you think the GM Mechanic should know about your GM?
Customer: I dont think it is a fuel pump issue
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the GM Mechanic about your situation and then connect you two.
Submitted: 5 months ago.
Category: GM
Expert:  Gary replied 5 months ago.
Hi there,Your engine has which carburettor fitted?Sounds like is suffering from fuel percolation, you may need to insulate the carb from the manifold, add a heat shield, add some insulation to the fuel line etc, all or any of these.Will it start if you hold the throttle open, as if the engine is flooded?Gary
Customer: replied 5 months ago.
carter carbno I tried pushing pedal all the way down and just cranks over but wont start
Customer: replied 5 months ago.
do they make specific heat shields for carbs?
Expert:  Gary replied 5 months ago.
Ok.Carter are good carbs, do you know which one, thermoquad, avs, afb?The first thing I would do is observe how "hot" the carburetor is.Sometimes you even hear fuel boiling in the carburettor.The first easy thing to do is add a heat shield between the carb and the manifold. would dare say the carb has boiled the majority of the fuel into the manifold, the engine is heavily flooded at the point.Does it have any other issue besides hot restart?Gary
Expert:  Gary replied 5 months ago.
I would also consider a carb rekit if you take it off to fit a heat shield.Gary
Customer: replied 5 months ago.
Is the only way to tell if the carb is hot is by seeing if fuel is boiling?
No other issues at all.have to take the carb off to install heat shield? sounds like alot of work!
Customer: replied 5 months ago.
how do I know what model carter carb I have? avs, afb?
Expert:  Gary replied 5 months ago.
If you can't keep your hand on the carburetor, I would say it is too hot.Yes, the carb needs to come off to fit a heat shield.About half of the heat will be reflected away from the carb with a shield.If the air temp is around 180F without a shield (typical), it should drop to under 110F.Is your carb all aluminium?An AVS has an airvalve at the top of the secondary side like the choke plate on the primary side.Gary
Customer: replied 5 months ago.
Here are pics of the carb, someone had said Quadrajet? Not sure if it is aluminum.
Expert:  Gary replied 5 months ago.
Hi again,Your carb is a Rochester Quadrajet, typical for Chevrolet.It is all aluminum alloy, 3 piece construction, the top 2 are prone to warping, junk metal. Looking at it and its surroundings, I would recommend a carburetor overhaul and a igntion system tune-up. We called it a major tune years ago when everything had carburetors. At one stage, I was doing about one a week, still have about 10 in my shed.There are many tricks for making a quadrajet go well.Gary
Customer: replied 5 months ago.
ignition system tune up? what does that entail?
Expert:  Gary replied 5 months ago.
Remove spark plugs, compression test engine if needed, inspect distributor cap, rotor, ignition leads for wear etc, measure lead resistances within specs or replace if outside spec, check wear of sparkplugs and replace if necessary, reassemble all components, start engine, warm to operating temp, check and adjust idle speed, idle mixture and ignition timing at hot idle speed as necessary.Quadrajet is a great carb, BUT they do suffer from many issues if not addressed.Gary
Customer: replied 5 months ago.
where do i get all this done at?
Expert:  Gary replied 5 months ago.
Hi again,Your local mechanical shop should be able to do all of this, but a carburetor tuning shop would be a better option.Do you have a workshop near you to do this sort of work?Or a good mechanic friend like me that would do the whole job for you for lunch and a few laughs etc?Hope this helps you.Gary
Customer: replied 5 months ago.
you in Reno by chance? lol
Expert:  Gary replied 5 months ago.
Sorry I'm in Brisbane Australia.Hope you can find a good mechanic to do this for you.I hope my advice has been of assistance to you.Please rate my service at your nearest convenience. Kind regards Gary

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