Pete1

I have a '83 G30 van that is a Motorhome conversion. It's a 350ci and the last owner has replaced the air cleaner with a K&N air cleaner. I've recently had it in the shop and the Mechanic got it to run good around town. The only problem is that when I made a trip north up I-5 from S. Oregon when I started to climb the Mt. passes the engine would start to miss, running rough and losing power. The temperature was hot, around 100˚ and the engine temperature was hovering around 210˚. I talked to my mechanic about the problem and he is of the mind that I need to get back to the original or stock air cleaner. He says that the original air cleaner had a snorkel that funneled cool air from outside the vehicle back to the air filter/carburetor. I went to my local Chevy dealer and they showed me the schematics for 1983 G30 vans and it doesn't show the snorkel type system that my mechanic described. I have been to several wrecking yards and recently found a snorkel that I think I can adapt to my '83 van but I'm sure it's off a later year, possibly a 1987. I did look at the 1987 schematic and it does show the snorkel type air cleaner system. Interesting that on my van there is an opening in the frame above the radiator that looks like it was intended for the snorkel attachment, although it is slightly smaller than the snorkel I pulled from the '87 at the wrecking yard. The wrecking yard owner said that there were some vans that were manufactured for the California market that had a different type of air cleaner. He said that there would be sticker under my hood that would indicate if the vehicle was set up for California emissions. I checked and any stickers that were attached under the hood are no longer there.

Here are my questions:
1) Does it make sense to return to the original / stock air filter system?

2) How do I determine if my vehicle is one of the California emissions type?

3) Are there any problems adapting the snorkel air cleaner system, that I recovered from the later model 1987 Chevy van, to my '83 van?

canucklehead

I would not worry about it. engines like warm air to burn. As long as that K and N filter has enough flow to not starve your engine your fine. If it did, you would be running rich, and so on.
210 is not far off from the 195 degrees the thermostat opens at.
Missing, and running rough under power could be a timing issue, or maybe bad or fouled plugs.

canucklehead

Here is a solution from what looks like a similar complaint.....


It was the fuel pump. After all the work, after trying 3 different carbs, float levels, timing, plugs, wires, fuel quality, and checking fuel hoses, we decided to just throw a fuel pump at it. What the hell, nothing to lose, pump's only 20 bucks. I had no confidence it would work. Nothing I know would allow for a pump to fail while under light to moderate load going uphill at any speed, but still work fine when under max load on level ground.

Lesson learned: Should have gotten into computers. I nice quiet desk job that pays hourly or salary instead of flat rate. No really weird funky problems that don't make any sense. Computers either work or they don't. No working on a friends truck in the cold rain.

Pete1

Thanks for the response! There are a couple of other items I wanted to mention that may pertain to the situation.

Last summer I had the Van tuned up and they replaced Spark plugs, spark plug wires, distributor cap and rotor. After the tune-up van ran good but then I started to have problems. The van would cut out and miss terribly when you stepped on the gas, no matter what the outside temperature was. I talked to the mechanic and he said that I needed a carburetor rebuild. At this point I started asking around and found my present mechanic who worked on the van and indicated that he did a lot of work on the vacuum system. He also checked the fuel filter and determined that there is no fuel filter other than the one at the tank and then a small stone filter at the carburetor. He has recently suggest cutting the fuel line and installing a in line filter. I haven't had that done but I may in the future. Now the van runs really good and I can drive it around town and up into the hills and it runs strong. Stomp on the gas and it responds in a solid way. It seems that my problems don't come to the surface until I try to go on a trip in very hot weather and it includes long steep grades. When I told my present mechanic what was happening he says that the gas is boiling in the carburetor and causing the van to lose power. I told him that when I stepped on the gas and the van shifted into a lower gear the engine runs strong. His response: The fuel is going through the carburetor quickly and doesn't have a chance to boil so the engine runs strong until it shifts back into the higher gear. He seems convinced that going back to the stock air filter system with snorkel drawing cooler air from outside will help my solve my problems.

The information about the fuel pump is interesting, but I'm wondering if the fuel pump were malfunctioning wouldn't I have the same conditions I'm experiencing in high gear when the vehicle shifts to a lower gear and the secondaries kick in? At that point the van runs strong and there is no indication of lack of fuel.

greenfire

I don't see how cooler air from the outside will keep the fuel cool enough to prevent the vapor lock. The fuel lines heat up from engine heat. Yes cooler air is better.. so if you can modify the intake.. it certainly wouldn't do any harm.


If the fuel is not circulating quickly enough.. it could heat up and vapor lock. Fuel pump pressure is constant regardless of rpms. I would replace the fuel pump, rebuild the carb, and modify the air intake. The van is 32 years old.. the more new parts the better. You mentioned the fuel filter in the tank... replace that too.


Another item is the timing.. It needs to be set properly and will vary per climate. Can be done with a timing light or vacuum gauge. Carb should be tuned at the same time.

canucklehead

Engine cut out, and missing is most likely an ignition issue. Fuel starvation will cause it to bog, and lose power and lightening up on the gas pedal will restore normal running.
If you have this issue only when you go past half way on the gas pedal then it could be an obstruction on the fuel system.
An in line filter isn't a bad idea. but you may want to drop the tank and pull the sending unit, and make sure there is no crud, and such in the bottom of the tank.
You have a mechanical pump right? Have you checked it? If the carb is original, then I would just buy a new rebuilt one from a parts dealer. ( I got one cheap from Autoline)

Pete1

Thanks for your comment. I plan talking with my mechanic about the different possibilities that could be causing the my problem: Vapor lock, Fuel pump and Air Cleaner. Or possibly a combination of the two or more of the three. I'm leaning toward Vapor Lock since the van runs really good around town when the engine is cool and before it has encountered a sustained climb on a severely hot day. I'll be sure to discuss Fuel Pump replacement as part a possible solution.