1976 dodge 360 b300 rv jamboree wont start, spark only in key off position

what in the world is a SUN REST, (crest RV?) if RV post to RV not cars.

Q1, WHEN DID RV LAST RUN GREAT, LAST YEAR, LAST DECADE OR NEVER SEEN BY YOU EVER.
Q2; IS FUEL ALL GOOD,? NOT OVER 1YEAR OLD>?
CLASS A CHASSIS BY GM


the starter motor must spin fast, and be robust.
battery good, and fully charged, it must be.
MOST ENGINES THIS OLD ARE NOT GOOD, TEST THAT YET USING REAL TOOLS?
NEXT IS
if spark is good, for sure not that old ever.
the test fuel works ever use instant spray start in a can
3 second spray gets 3 seconds run (at least)
and engine sounds good , repeat 3 times
is this TBI> throttle body injected? OR CARB>? OR MPI INJECTED
GUESS GM L19 ENGINE
GEN IV:
General Motors introduced EFI in 1987, which was found on GM C1500 SS, C/K2500 and C/K3500 trucks. The 454 EFI version was rated from 230 hp (172 kW) to 255 hp (190 kW) and from 385 lb?ft (522 N?m) to 405 lb?ft (549 N?m) of torque.

THE 89 , C/K3500 CHASSIS, 454 HAD TBI INJECTION HORROR AND A DISTRIBUTOR
THE LATER NEEDS, NEW ROTOR,CAP, HV WIRE SET AND 8 NEW SPARK PLUGS IF NOT NEW AND FRESH NOW UNDER 60MILES OR 5 YEARS OLD.

i WILL STOP HERE AT TBI MESS.
I;D FULLY KIT OUT THE TBI, NEW FUEL FILTER AND FOR ONLY FRESH FUEL.

If your 1976 Dodge F40 Sportmann RV starts up only when you put gas directly in the carburetor, there might be an issue with the fuel delivery system. Here are a few things you can check:

1. Fuel Pump: Check if the fuel pump is working correctly. Listen for a buzzing sound when you turn the key on (without starting the engine). If you don't hear anything, the fuel pump might be faulty, or there might be a problem with the electrical connection.
2. Fuel Filter: Check if the fuel filter is clogged. If it's been a while since you replaced the filter, it might be clogged with debris, preventing the fuel from reaching the carburetor.
3. Carburetor: If the fuel pump and filter are working correctly, the issue might be with the carburetor. Check if the carburetor is dirty or clogged with debris. You may need to clean or rebuild the carburetor.
4. Ignition System: If the ignition system is not working correctly, it might not be providing enough spark to ignite the fuel in the engine. Check the spark plugs, spark plug wires, and distributor to ensure they are in good condition and functioning correctly.

If you're not comfortable checking these components yourself, it might be best to take your RV to a qualified mechanic for diagnosis and repair.

its super old, and needs lots of work
the books may be hiding in any cabinet, look deeply
if not there , ask last owner (none)
if not there ask and RV center
if still none, find he maker of actual RV and ask them. for books.
backfire means what.?
1: to carb? end (coughing )
2: or the tail pipe end. or rich muffler explosions.?
the former #1 has lots of causes sure timing or even burned up exhaust valves.
it has bad fuel too, no fuel lasted that long. or new fuel over gunk fuel.
name one car or RV that runs 1987 perfectly , there is none. In real life.
it will need all that checked out
an engine this old needs compression test (at get go) all even over 150psi,
cleaned fuel system end to end
cap rotor and spark wires and new spark plugs.
carb will be sick and nasty inside. needs cleaned and kitted.

This seems the best resource.

https://www.irv2.com/forums/f65/fleetwood-electrical-schematics-349406.html

There is a video as well.

https://www.google.com/search?q=2006+Fleetwood+Jamboree+Motorhome+AC+wiring+diagram&rlz=1C1QJDB_enCA643CA644&sxsrf=APq-WBuYf035heuV6j8J3xfopKJY-wBv9Q:1648939150664&tbm=isch&source=iu&ictx=1&vet=1&fir=i4WF5NpoZh6zFM%252CnEFnAV8fpRkARM%252C_%253BwrA0L-jA6tX1iM%252CNrph4n8a8zDacM%252C_%253BXwDjfb-1srmwcM%252CzeTm-wqufr9eDM%252C_%253B30E8Es1XPkMRRM%252CnEFnAV8fpRkARM%252C_%253BoDpcU-yZPx8u7M%252CMiFqCfELwZBpsM%252C_%253BBH4RCdgFMvb-hM%252CzeTm-wqufr9eDM%252C_%253BaWNDrXWXEdZPjM%252CBiib5rybUy5zeM%252C_%253BEwNSF8coq8os9M%252CWytUIwpciEyMGM%252C_%253BaKp0D_BLmnl3lM%252C5BaQHQFnv2jLBM%252C_%253BxhvksR5FMXkMlM%252CyizZAiKieJdIGM%252C_&usg=AI4_-kR5i3gdnz1YZrxeVZqgL4XUa-Uu0Q&sa=X&ved=2ahUKEwiKitOCufb2AhWUPM0KHVYEB-wQ9QF6BAgDEAE#imgrc=i4WF5NpoZh6zFM

..

no information generic answer --since they range from 16.5 to 32.5 ft and different make chassis --as well as gas or diesel=== notify an rv dealer or shop ---rv forum ---a bunch of the manual sites have jamboree manuals to download but you need to pick the one for what you have

Here is a site that seems to maintain copies of maintenance manuals.
http://goodoldrvs.ning.com/page/rv-repair-manuals

How old is the unit?

That is a Heartland RV. Contact your local retailer directly or online here: Customer Service Center

Champion built motorhomes from the early 1970s until the mid-1980s. While Dodge powertrains supplied the momentum for Champion Class A motorhomes through the 1970s, the Class C between 16 and 22 feet were powered on General Motors chassis frames. 1986 was the final year of Champion motorhome production.
It will be nearly impossible to find a chassis wiring diagram for a vintage orphan RV. Perhaps an online enthusiast forum or keep an eye on eBay.

check heater box filter