Community Forums

leadman · 06-09-2019, 07:01 AM

Having worked professionally on many different cars, medium duty and heavy duty trucks since 1969 and the fact that a parts supply house house I deal with list an in tank electric pump you probably have one. It is common for a medium duty gas carbureted truck to have a low pressure electric pump in the tank or outside close to it.
These medium duty trucks need the volume from the pump to help supply the needed fuel. My Itasca had a 1/2" fuel line with an electric and mechanical pump.
It also had an oil pressure switch on the engine tied into the fuel pump circuit. IIRC mine was at the rear of the engine. Even my 1975 Vega had an in tank fuel pump with the same switch on the engine. This switch shuts off the pump if the engine has no oil pressure. It can be jumped in an emergency.
If you have a hand held vacuum pump with the brake bleeder kit you can hook it to the fuel line coming from the tank at the mechanical fuel pump. Work the handle on the pump and you should be able to draw a vacuum on the line and if pumped long enough you should get gas. If not then you have several different things that could be bad. Bad hose connecting the tank to the steel line, pick-up fell of the sending unit, bad hose at the fuel filter, probably on the right frame rail, bad hose on the pressure regulator or bad regulator, probably in a very hard spot to get to inside the right frame rail behind the tires. I did have to replace the pressure regulator on my Itasca, not fun.
I would get a length oh hose and a gas can and hook it up on the tank side of the mechanical pump to see it will run this way.

What is the exact year, make and model you are working on? You can go on-line and check NAPA's website to see what parts like the fuel pump and regulator they list.

Orgotloth · 06-09-2019, 09:50 AM

Quote:

Originally Posted by Mudfrog

Being a carburetor, yours doesn't need 40 psi of fuel pump pressure like a fuel injected engine needs. It just needs enough pressure to push fuel past the float needle and into the bowl. If you have fuel at the carb, then you should at least be able to get the engine to idle.

It will idle fine, once in hear when I hit higher rpm it’ll sputter and die

Orgotloth · 06-09-2019, 09:56 AM

Additional info that Might make this all clearer:

I just got this thing

First 200-300 miles it drove fine, after that this problem started to develop. I’m at about 600 miles all told.

I bought it used from owner, it’s possible I got bamboozled.

Figured this might help

Unplanned Tourist · 06-09-2019, 11:27 AM

That sure sounds like loss of fuel pressure/leaning out.
Any chance you can tee in a fuel pressure gauge just before the carb?
Old hot rodder trick, always have good fuel pressure.
Happy Glamping.

arcaguy · 06-09-2019, 12:07 PM

Yep, if the coach idles OK then I'd bet it's a fuel supply issue. Is there a rubber hose between the fuel tank and the carb that is collapsing? Is there a second fuel filter somewhere in the systems? This may have been added by a previous owner and not reflected in any parts books. The point being that just because you can blow air back to the tank doesn't mean it can get from the tank to the carb. Instead of spinning your wheels and spending money guessing, figure out what the issue is. A carburated fuel system isn't that complex and from the symptoms it's getting fuel, just not enough.

Orgotloth · 06-09-2019, 12:14 PM

Quote:

Originally Posted by arcaguy

Yep, if the coach idles OK then I'd bet it's a fuel supply issue. Is there a rubber hose between the fuel tank and the carb that is collapsing? Is there a second fuel filter somewhere in the systems? This may have been added by a previous owner and not reflected in any parts books. The point being that just because you can blow air back to the tank doesn't mean it can get from the tank to the carb. Instead of spinning your wheels and spending money guessing, figure out what the issue is. A carburated fuel system isn't that complex and from the symptoms it's getting fuel, just not enough.

I followed the line all the way back to the tank, there’s not another filter in there and no crimps, or deteriorated rubber line. I mean, aside from the mobile mechanic guy and the tow I’ve only dropped $200. And the carb work needed to be done. But I do get what you’re saying.

Orgotloth · 06-09-2019, 02:49 PM

Quote:

Originally Posted by leadman

What is the exact year, make and model you are working on? You can go on-line and check NAPA's website to see what parts like the fuel pump and regulator they list.

The only issue I see with that is it’s an old travelcraft. Chevy sold the chassis to them and they modified it for rv’s. I don’t know what modifications were made.

I DO have the assembly diagrams from Chevy, it doesn’t mention a back fuel pump.

CIDE · 06-09-2019, 02:55 PM

Not that I'd want to do it on the side of the road, but back in my race car days we'd add an electric pump back by the tank to supplement the engine mounted mechanical pump. (carbed)

Orgotloth · 06-09-2019, 04:39 PM

Quote:

Originally Posted by CIDE

Not that I'd want to do it on the side of the road, but back in my race car days we'd add an electric pump back by the tank to supplement the engine mounted mechanical pump. (carbed)

If I add the mechanical and it isn’t happy then this is my next step

Rvpapa · 06-09-2019, 04:41 PM

You probably need one of us old f^rts for this. Open the fuel line at the carb. Then take the fuel fitting itself off the carb. Lo and behold, small block Chevys have a wee small sintered bronze filter inside the carb inlet. One drop of water is enough to duplicate your troubles.
Art.

tap4154 · 06-09-2019, 07:38 PM

Quote:

Originally Posted by Rvpapa

You probably need one of us old f^rts for this. Open the fuel line at the carb. Then take the fuel fitting itself off the carb. Lo and behold, small block Chevys have a wee small sintered bronze filter inside the carb inlet. One drop of water is enough to duplicate your troubles.
Art.

Yep most carburetors had a little screen or sintered filter at the inlet. This brings back memories of working on the old carbureted engines. Checking the needle valve to see if it's stuck, see if the accelerator pump is working. Very simple items to check.

neub · 06-09-2019, 07:56 PM

Take the gas cap off and see if the problem persists. Had a 69 boss 302 that started having problems similar...replaced, fuel filter, fuel tank pick up sock filter, rebuilt carb and finally found out the fuel cap vent was clogged when i opened the gas cap and heard the vaccum sucking in, drove with gas cap off and no more problem...new gas cap. Just an easy no cost check for your problem just in case.

Orgotloth · 06-09-2019, 10:39 PM

Quote:

Originally Posted by neub

Take the gas cap off and see if the problem persists. Had a 69 boss 302 that started having problems similar...replaced, fuel filter, fuel tank pick up sock filter, rebuilt carb and finally found out the fuel cap vent was clogged when i opened the gas cap and heard the vaccum sucking in, drove with gas cap off and no more problem...new gas cap. Just an easy no cost check for your problem just in case.

This was the first thing I tried. I wish it had been that easy

Orgotloth · 06-09-2019, 10:40 PM

Quote:

Originally Posted by Rvpapa

You probably need one of us old f^rts for this. Open the fuel line at the carb. Then take the fuel fitting itself off the carb. Lo and behold, small block Chevys have a wee small sintered bronze filter inside the carb inlet. One drop of water is enough to duplicate your troubles.
Art.

I did that as soon as I got into town, I’m still debating if I should put an in-line filter since it’s easier to swap out. (Since I have to get at it from the cab, it’s a rough one