1973 chevy pickup v8/350 Rochester quad carb

I bought this truck for my 13 year old to learn about engines. When we got the truck, it would start if you primed the carb, run for awhile and die. So far, we have: Rebuilt the carb Replaced plugs and wires dist. cap and rotar points oil/filter fuel pump put in an inline fuel filter timing looks good

Now the truck will eventually start. Seems it takes awhile to get gas from the tank to the carb. Then it will run pretty good in park or neutral, and can rev pretty good. I can see gas going through the inline fuel filter.

I have taken the truck for approx. 1/2 mile ride, then it dies. Problem seems to be when truck is moving and gas is sloshing around. Right now I only have 1/8th of tank while I'm playing with it. I really didn't want to put more in, in case I had to drop the tank. When truck dies, I don't see any gas going through the inline fuel filter. Like it can't get it out of the tank. I took the gas cap off in case the gas cap was causing a vacuum. That didn't help. Any ideas?

Reply to
knitey
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Could be clogged sock or broken pickup tube.

Reply to
« Paul »

What happens if you just run a hose from the fuel pump to a gas can (temporarily?) If it runs well, time to siphon the tank dry and start over, ASSuming that the fuel line isn't pinched or rusted through between the tank and the engine (a distinct possibility.)

You could even run a hose into the pass. compartment and set a 5-gallon can on the floor for a test run to see how it works under load (NOTE: this is dangerous, use precautions, carry an extinguisher, and try at your own risk)

IIRC a '73 uses a return line off the fuel pump, so you'd actually need two hoses to make this work properly.

The best upgrade you could possibly do to this truck is to add a HEI distributor from a later (but not too late, you want one from a non-computer vehicle) HEI so you don't ever have to mess with points again. Also be aware that there are a very few weirdnesses with a '73, as it was the first year of that body style... the headlight switch is one, I believe the knob/shaft is different than later years. Not sure of all the others, but there are some.

good luck,

nate

(whose dad has a '73 Stepside that became just such a project while I was in high school, it's now his baby... also bought another '73 as a parts vehicle for a '49 Chev street rod project, so I have some experience with these.)

Reply to
Nate Nagel

Also, have you cleaned or replaced the sintered bronze filter element in the inlet to the carb? My dad ended up tearing down the original engine in his own '73 (a factory 2bbl/307, FWIW) because he didn't know about the filter in the carb inlet... D'OH!

nate

(in my defense, I was maybe 5 years old at the time and had never heard of a sintered bronze filter element, much less knew that Rochester used them. I soon learned about them however, along with a few words that previously I had no idea were part of the English language!)

Reply to
Nate Nagel

Reply to
knitey

Sorry, but I don't know what a clogged sock or broken pickup tube is?

Reply to
knitey

Pertaining to the return line. When I got the truck, it didn't have a return line on the fuel pump. I got a new pump and saw 3 tubes instead of 2. The guy at the parts store said the 2 tube fuel pump was for manuals, and the 3 tube was for automatic. Which is what I've got. I went a head and got the two tube since that was what was on it. Where the heck does the return line go to? Could that be my problem?

Reply to
knitey

On the end of the pickup tube there is a filter commonly called a "sock" = or "filter sock". The pickup tube is the part that extends down from the to= p of the fuel tank to the bottom of the tank where the fuel is. I am assuming tha= t this vehicle has the fuel pump on the engine and not in the tank. Nate has some good ideas, too: broken line or clogged sintered filter.

Reply to
« Paul »

You are correct in that the fuel pump is on the engine. There is a rubber hose going into the tank. It is about a foot long and leads to a pipe that runs to the engine where it connects to a rubber hose which connects to the fuel pump. I have tried wiggling the hose going into the tank, but it seems to be hooked on to something pretty good. I was afraid to pull it out because it seemed stuck. Could I try blowing air through the fuel line from the fuel pump to the tank with my air compressor? Should I drop the tank and clean it out?

Reply to
knitey

Going into the carb was the original fuel filter. I took that out because I have an inline filter. When we rebuilt the carb, we cleaned that part out.

Reply to
knitey

based on what others have said, here's my 2 cents on troubleshooting it:

Before starting it, take off the air cleaner and pump the gas - do you get a squirt of gas in the carb? If not, you've got the problem my race car had where the gas was all gone after it sat for a while - either leaked from the carb into the intake or somehow "backflowed" back into the tank. (we ended up upgrading the tank, the fuel line, the fuel pump, and the carb anyway so I never did figure out what was wrong.)

to eliminate the fuel tank, run the truck off a rubber line going into a jerry can in the bed and go for a quick spin. Obviously you need to make sure it's properly secured. :) Better = plugged tank pickup or fuel line

You might want to plumb in a fuel pressure gauge - I believe 5-7 psi is normal for a QJet.

Last but not least, the choke works properly, right? If it's stuck on or not coming on at all it'll be hard to start and will stall. It doesn't sound like you've taken it for a test drive after it's had a chance to warm up.

You could also pull a plug and have a look after it dies - are they soaked in gas? Maybe it's not lack of fuel, maybe it's an ignition problem? Have you checked the timing? Does it backfire through the carb or exhaust? What happens if you ease into the throttle vs standing on it?

Ray

Reply to
ray

You have pretty much checked everything external to the tank except for t= he fuel line. Any way you borrow or rent a manual vacuum pump - the kind that you squee= ze (like a Mityvac hand vacuum/pressure pump)? Remove the fuel line from both end= s and vac up on it - watch for leaks.

Reply to
« Paul »

Ok, I'm going to throw this one out there!! Is it possible that your gasline to the fuel pump is conneted to the return line instead of the pickup line from the tank...with only an 1/8 tank it might have run for awhile like that till the level reached a curtain point, The return line from the pump was use to return unused gas back to the tank.

Reply to
thetoolman

You sure could be describing a pinhole leak on the suction side of the fuel pump. A small leak will suck air into the line and empty it when it sits so it is a bugger to cold start. As it gets worse it can air lock the line.

Depending on where the leak is, all you might see is a stain on the metal line where it clamps to the frame rail or a stain on a small crack in one of the rubber lines at the end of the steel tube. Lots of times these suction leaks don't drip on the ground.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >
Reply to
Mike Romain

I'll try running a hose from the fuel pump to a gas can so I can see if it is the fuel line or gas tank. Also, currently the fuel pump on it does not have the return line to the tank. Does that matter?

Reply to
knitey

I took your suggestion and ran the fuel tank off a 10foot section of hose from inside the cab. I had the windows open and fire extinguisher...just in case. Within a few seconds the fuel filter was totally full of fuel, instead of about 1/4 full. Ran the truck up and down some hills for 10 minutes and everything worked great. Seems problem is in the fuel line, or tank.

Before I drop the tank, could I hook my air compressor up to the fuel line and blow air through it to see if it helps? Also, can I do anything with the hose that goes inside the tank? Replace it or something? It seems lodged pretty well into the tank. I was afraid to move it around too much. Anything I can do there?

Really appreciate all your help.

Reply to
knitey

I ran the fuel pump off a 10foot section of hose from inside the cab. I had the windows open and fire extinguisher...just in case. Within a few seconds the fuel filter was totally full of fuel, instead of about 1/4 full. Ran the truck up and down some hills for 10 minutes and everything worked great. Seems problem is in the fuel line, or tank.

Before I drop the tank, could I hook my air compressor up to the fuel line and blow air through it to see if it helps? Also, can I do anything with the hose that goes inside the tank? Replace it or something? It seems lodged pretty well into the tank. I was afraid to

move it around too much. Anything I can do there?

Really appreciate all your help.

Reply to
knitey

The gas gauge sending unit, and hose outlet are all one unit. Drop the gas tank (should be only 2 bolts) and you will then see a few screws holding the unit to the top of the tank. You probably want to clean out the tank anyway.

-jim

Reply to
jim

If you have a plugged up sock in the tank, you can 'sometimes' blow them out with compressed air. You also can blow the sock off... If you keep the air low, you might be able to hear the leak if it's in the line. I have always been able to see the stain though, it is usually obvious.

On my 75 Chevy pickup I could blow through the gas line up near the pump to clear my sock in the tank. I just used lung power. Had a lot of crap in the tank, it worked.

Back at the tank the gauge sender unit has the tube and sock attached as well as the return line if any. They are hard copper nipples you put the rubber line on to. If you have 2 lines coming out of the top of the tank side by side, the larger one is the gas line, the smaller one would be a return line if you have it.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06
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Reply to
Mike Romain

absolutely. Couldn't hurt.

not sure re: the tank, but I can offer this - if you choose to remove the tank for replacement or servicing, it's actually easier if you remove the bed from the frame first. This is actually easier than it sounds, there's maybe only 8 bolts and a couple electrical connections, but will require at least two people (more if it's a stepside; those wood floors are heavy!)

good luck,

nate

Reply to
N8N

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