1983 carbed 454 RV vapor lock fixes ?

[leroyd92]

So last year, my 83 454 decided to crap out on me while driving in 95°f ish weather.

Thankfully we didn't reach the really steep grades yet and we were able to limp the rig back home @ 35mph.................

Carb had no fuel in it when it died. Couldn't hear the electric chaser pump pumping so it either over heated or was fully primed. Waited a few minutes and it started, made it half a mile and died again. Turned around and coasted back home.

In the near future, when it's not 117-120°f outside, I'm going to put a Carter 4070 After the dual tank switch valve

From the looks of things, my return line from the mechanical pump is kinked half way down the frame rail, that will be the first thing replaced. I bought a new mechanical pump as well. Lastly, I'm going to put the fuel pump on its own circuit to know it's getting a true solid 12v. Unless I should run a solid circuit AAANNNDDD put a ballast resistor in there???

The one thing I can't decide on is adding a fuel cooler that sits in front the radiator or add a filter with a bypass outlet right in front of the carb. I'm leaning towards the splitter because it seems most efficient to recycle the fuel than to just hope you cool it down enough. Everyone claims the vapor lock starts in the mechanical pump, so I feel cycling fuel is the best way to remedy this

Anyone have suggestions on anything? I'm open ears to things known to fix these issues.


We got the RV from family who only used it during winter months for camping. They never had vapor issues but they only used it when it was 50°f or cooler outside.

 

[Chris142]

The mechanical pump is where the fuel gets lots of heat. Also blocking the heat crossover under the intake will help. Where does it get it's air from?

 

[leroyd92]

The mechanical pump is where the fuel gets lots of heat. Also blocking the heat crossover under the intake will help. Where does it get it's air from?

Heat crossover? As in ?

The goofy Winnebago opening in front of the RV.

Someone told me to block off all the areas around the radiator. So that the air is shoved past the engine without chance of recirculating

 

[bluesmokertdi]

So last year, my 83 454 decided to crap out on me while driving in 95°f ish weather.

Thankfully we didn't reach the really steep grades yet and we were able to limp the rig back home @ 35mph.................

Carb had no fuel in it when it died. Couldn't hear the electric chaser pump pumping so it either over heated or was fully primed. Waited a few minutes and it started, made it half a mile and died again. Turned around and coasted back home.

In the near future, when it's not 117-120°f outside, I'm going to put a Carter 4070 After the dual tank switch valve

From the looks of things, my return line from the mechanical pump is kinked half way down the frame rail, that will be the first thing replaced. I bought a new mechanical pump as well. Lastly, I'm going to put the fuel pump on its own circuit to know it's getting a true solid 12v. Unless I should run a solid circuit AAANNNDDD put a ballast resistor in there???

The one thing I can't decide on is adding a fuel cooler that sits in front the radiator or add a filter with a bypass outlet right in front of the carb. I'm leaning towards the splitter because it seems most efficient to recycle the fuel than to just hope you cool it down enough. Everyone claims the vapor lock starts in the mechanical pump, so I feel cycling fuel is the best way to remedy this

Anyone have suggestions on anything? I'm open ears to things known to fix these issues.


We got the RV from family who only used it during winter months for camping. They never had vapor issues but they only used it when it was 50°f or cooler outside.

I would junk the carb and install fuel injection

https://www.summitracing.com/parts/fif-30003

 

[leroyd92]

I'd rather not spend $900 on an electrical injection system. I have thought about it though.

 

[Chris142]

Heat crossover? As in ?

The goofy Winnebago opening in front of the RV.

Someone told me to block off all the areas around the radiator. So that the air is shoved past the engine without chance of recirculating

There is a heat crossover between the heads. It lets hot exhaust gasses pass through the intake. Heats up the intake for emissions reasons.

Blocking it off will help keep the intake and carb cooler.

 

[Chris142]

Ford engine but same idea.

 

[Jethro_Bob]

An in tank fuel pump would be best to keep the fuel pressurized and prevent it from vaporising but would likely require expensive modifications. I would install one as close as possible to the fuel tank while adding a fuel cut off switch from a ford, (seems to trip the easiest). Carburetors require much less pressure than fuel injection, so I'm not sure how much this will help.

 

[ripcord]

You might consider removing the mechanical fuel pump altogether and go with electrical pump(s). That will allow you to route the fuel lines as far from the engine as possible. Converting from a deadhead system to a recirculating one sounds like an excellent idea, too. Also, you might consider adding a phenolic carb spacer. Edelbrock sell ones made out of wood laminate specifically designed to reduce conductive heat transfer to the carb. A four hole one would be better for your application than an open spacer.

 

[leroyd92]

If I start the RV, should fuel be coming out of the return line at idle or just high rpm ? While I was replacing the kinked line I wanted to test and see if it was circulating at all

 

[ripcord]

How many lines does your mechanical pump have? If it just has two lines like most types, then you don't have a return line. The one coming from the back is the suction side and a kink in that line could very well be your problem. If that is the case, then you probably have a fuel starvation problem more than a vapor lock problem

 

[NYEngineer]

A couple of years ago, a friend built a big block Pontiac in a 69 Firebird. I told him to go with EFI before spending any money at all on the fuel system. He didn't listen and bought this huge Rob Mc mechanical fuel pump and this ridiculous Holley carb with no choke. They set it up old school with the fuel line dead heading at the carb. Car would run until it got hot and then would vapor lock. He called and asked for help. I suggested EFI and an in tank pump. He wanted the car old school.
So... First, I added a Moroso fuel log and fed the carb from that and plumbed a return line. I also routed the fuel line as far from the headers as possible and insulated the line. Car ran fine after that. BUT, when the car was in his garage, it made the entire house smell like gas and his wife lost her mind. Guess what he ended up doing? Putting a FAST EFI system on it with an in tank pump. Now it runs really nice.
My take on this is the 15% alcohol we have in our gas now has lowered the boiling point.

 

[SwampSurvivor]

My take on this is the 15% alcohol we have in our gas now has lowered the boiling point.

I have an EFI jeep that will boil the fuel in the rail on a warm day of it it is turned off hot and sits a few minutes. Luckily I can get it to run by releasing the fuel rail pressure via schrader valve. That gets it sorted out and it runs normal again

 

[350Rocket]

Fixing the return line and adding a carb spacer would be a big help. All good suggestions above.

 

[DuckRyder]

Carb - Return line ?

 

[NYEngineer]

I have an EFI jeep that will boil the fuel in the rail on a warm day of it it is turned off hot and sits a few minutes. Luckily I can get it to run by releasing the fuel rail pressure via schrader valve. That gets it sorted out and it runs normal again

I had a 98 Yukon that did exactly the same thing. Had to be a perfect storm. Hot day, run somewhat hard, shut down and restarted after a few minutes.

 

[leroyd92]

How many lines does your mechanical pump have? If it just has two lines like most types, then you don't have a return line. The one coming from the back is the suction side and a kink in that line could very well be your problem. If that is the case, then you probably have a fuel starvation problem more than a vapor lock problem

Mine is a 3 line pump. I just didn't know if it would return at idle or higher rpm

 

[leroyd92]

I had a 98 Yukon that did exactly the same thing. Had to be a perfect storm. Hot day, run somewhat hard, shut down and restarted after a few minutes.

My 99 suburban 5.7 vortec does this when it's hot like it it's now. Today will reach 120°f
It gets really bad when I don't have tcw3 in the gas

 

[leroyd92]

While at work today, I'm going to look at the 50 gph Carter mechanical pumps and see if I should run one of them. This way I leave the return line free for the fuel filter splitter. Not to mention, I'm sure the extra 15gph would help.

I had this idea initially, but didn't want to cut the steel factory fuel lines. But I've lost interest in that concern. Not to mention, O'Reilly sells steel tubing if I ever decided to replace it

 

[bunnspecial]

I know mechanical on-engine pumps were used successfully for a long time, but I don't like them since vapor lock can always be a problem(plus the fact that if the bowls are empty, it takes a decent amount of cranking to get enough there for them to start).

If it were me, I'd put an appropriately rated(both flow and pressure) electric pump back by the tank, and ideally positioned lower than the tank so that it will gravity feed or siphon out. A lot of British cars were set up that way, and for all their other ascribed ills(including pumps that need occasional and often forgotten maintenance) they do not vapor lock.

The Carter gear pumps are really well liked, flow well, and are seemingly dead reliable. Check the pressure specs on your carb and make sure you match it-I doubt it would be an issue on a big American V8, but it's something I've seen done on little British cars where someone puts a 10+ psi meant to feed a 4 barrel Holley or the like on a little carb that wants 3psi or so(and will overflow with those kind of pressures).