Rochester issue

[SeriesShorty]

Now that my rewire/conversion is finished and my truck is running again I am noticing a new problem.

Right before I took my truck out of service I rebuilt and installed a Rochester and it seemed to run great for the few days that I drove it before parking it as far as I can remember. It sat for about 15 months before attempting my first drive this morning.

From what I have researched it sounds like a possible accelerator pump problem. Idles just fine, but as soon as you give it a little throttle it dies, like it sucks air (hesitates) and just shuts down. If I can keep it running through this hesitation phase and get the throttle up a little higher, then it hesitates again around 1200rpm. Does this sound like an accelerator pump issue to guys, too?

I also read this on TeriAnn's site: "There is a pressure valve inside the carburetor body that consists of a steel ball and a spring. There is a metal rod across the top of the opening to keep the parts in place. A rebuild kit comes with a new ball and spring. Be advised that the spring rate is different than the original and replacing it can cause problems. Leave this pressure valve alone if you can when rebuilding the carburetor If you need to open up the passage reuse the old spring."

When I rebuilt he carb I used all of the new components in the rebuild kit. Could this new spring cause this type of sucking/dying problem?

Thanks all!
Jen

[mongoswede]

Now that my rewire/conversion is finished and my truck is running again I am noticing a new problem.

Right before I took my truck out of service I rebuilt and installed a Rochester and it seemed to run great for the few days that I drove it before parking it as far as I can remember. It sat for about 15 months before attempting my first drive this morning.

From what I have researched it sounds like a possible accelerator pump problem. Idles just fine, but as soon as you give it a little throttle it dies, like it sucks air (hesitates) and just shuts down. If I can keep it running through this hesitation phase and get the throttle up a little higher, then it hesitates again around 1200rpm. Does this sound like an accelerator pump issue to guys, too?

I also read this on TeriAnn's site: "There is a pressure valve inside the carburetor body that consists of a steel ball and a spring. There is a metal rod across the top of the opening to keep the parts in place. A rebuild kit comes with a new ball and spring. Be advised that the spring rate is different than the original and replacing it can cause problems. Leave this pressure valve alone if you can when rebuilding the carburetor If you need to open up the passage reuse the old spring."

When I rebuilt he carb I used all of the new components in the rebuild kit. Could this new spring cause this type of sucking/dying problem?

Thanks all!
Jen

Could the fuel in the carb gummed things up in the 15 months of sitting?

[Momo]

Could be, but Rochesters are also notorious for warped base plates, which a rebuild will not fix. Here's a test you can do:

Let the truck idle and have a helper spray WD-40 around the base of the carb as you operate the throttle linkage by hand.

If you find that with the application of WD-40, the throttle response is smooth and even, then the air leak is at the base.

If the air leak is at the base, it would indicate a warped or otherwise faulty/poorly sealed base. Google "Rochester carburetor warp" for more.

**NOTE: Obviously, have a fire extinguisher handy, preferably a CO2 type. However, the risk of fire is low if the engine is just warming up. WD-40 will smoke on a hot manifold but usually won't ignite unless it finds an open flame, and it burns off quickly. A wet rag will extinguish it very effectively but take care not to get the rag caught in the fan belt or fan itself.

[siiirhd88]

The accelerator pump seal on my Rochester is made of leather, and after 15 months it could have dried out and shrunk. It is easy enough to check. Remove the inlet tube from the top of the carb so you can see down inside. Actuate the throttle linkage and you should see fuel spray into the carb venturi.

Bob
'02 Disco II SD
'80 SIII 109
'75 SIII 88 V8
'68 SIIA 109 V8

[mongoswede]

Dry leather....could be. If the base plate is warped can a you just have a machine shop machine it flat?

[SeriesShorty]

Thanks guys, I'll do the tests recommended and see if I have to end up yanking it out for another rebuild.

I knew about the Zenith warp...but Rochester, too? Can't we catch a break here? ROFL Fire extinguisher will be at the ready and hope that warpage is not revealed.

I'm ready for my first spin around the block darnit!

[73series88]

yeh
15 months is a long time for gas to be sitting
fresh fuel and fuel filter.
maybe some carb cleaner down the jets.
good luck
aaron

[SeriesShorty]

Been at it all morning and boy do I stink like fuel!

1. tested the accelerator pump, couldn't see the squirt but I could hear it and see a fine mist of gas vapor appear, tested after engine was warm to make sure there would be fuel in the bowl.

2. my fuel tank was in much worse shape than I originally thought. I just drained all the fuel and am soaking the mounting bolts in PB so I can yank the tank for a good cleaning.

3. tied the WD-40 around the base trick and didn't notice any difference. But now that my truck is out of driveway and in the sun I can see some slight varnish build up in several places.

I'm gonna go ahead and rebuild the carb again, flush the fuel lines, and clean up that fuel tank, then try it again. I'm a slow worker so it'll be a while before I post an update.

Thanks for all the knowledge and help!
Jen

[Momo]

Wow... I guess I missed the part about sitting for 15 months. That will really gum up a carb. Definitely a good idea to clean the tank and pickup as well.

Good luck, let us know how it turns out.