The Stovebolt Site Forums The Shop Area Engine Shop Rochester on a 235

I have a 1947 1/2 ton pickup with a 1959 235 engine. The carburetor is a Rochester one barrel. If I start the engine as often as every few days all I have to do is turn on the ignition key, pull the choke out and hit the starter button and it will fire right up. BUT, if I let it sit for a week or longer and go through the same steps it will not start. It just continues to turn over and doesn't even make an attempt to start. Then, I pour about 3-4 ounces of gas into the carburetor throat and it will fire right up and run as expected. I thought I might have a fuel pump problem but if I did it would stop running as soon as the gas I pour in the carburetor is burned. Also, when running the exhaust discharge is as black as a bowling ball. I have been told this is because the carburetor is set too rich. What say you folks?

Yes, you have a fuel pump problem. The one-way check valves in the pump are letting the gas leak down over a few days of sitting and the pump is unable to refill the float bowl after the gas evaporates/leaks out of the float chamber. Once the engine runs for a few seconds the pump finally starts working, and will do so until it goes dry again from sitting for a few days.

Do a volume/pressure/vacuum test on the pump. I guarantee it will fail.
Jerry

Weak diaphragm in the fuel pump. Fuel being sucked out of the float bowl back to the tank. Low compression. Carb in need of rebuilding. Just a few of the possibilities.🛠

I'm too lazy to do it right so all my old cars/trucks/ tractors/equipment have electric fuel pumps to get the gas from the tank to the carburetor. Once they fire I turn off the electric pump. Usually takes 30 seconds to a minute for the pump to change sound which means it's primed and then two seconds for the engine to fire off. My batteries love me.

Thanks Hotrod Lincoln. I guess I should install a new fuel pump but I don't drive my truck very often. If I do install a new fuel pump.....should I go with a double action pump or just a standard 235 fuel pump? Thanks.

[quote I guess I should install a new fuel pump but I don't drive my truck very often. If I do install a new fuel pump.....should I go with a double action pump or just a standard 235 fuel pump? Thanks.[/quote]

The double action fuel pump is for aux. vacuum for vacuum wipers. If you don't have vacuum wipers you don't want the double fuel pump. If you do have vacuum wipers & want to add the aux. vacuum you will need to add the necessary vacuum lines to go with it.

Buck, if you don't drive very often, I'd cap the hole and just go electric. If you don't like the electric pump, you can always go back and replace it with a mechanical pump. I went electric when a mechanical pump (made in another country) died almost immediately and I haven't been sorry about it at all. Mount it back near the gas tank on the inner frame. They're made to push rather than pull and get a rather low pressure pump. (2 to 5 psi or so is more than enough)

Yes, the electric pump I bought wasn't made in the USA...think it was made in Taiwan if I recall correctly. No problems and very cheap...less than $20 when I bought mine.

In my case (since I definitely was not going back to a mechanical pump) I ran oil lines out for an auxiliary oil filter and that worked well. You can see here:

http://i1154.photobucket.com/albums/p535/JonGoodman/plumbing%20oil%202-1.jpg

Jon

Use a hidden electric. Take the guts and the arm out of the mechanical pump and run the gas thru it like it's a big fitting. Maybe an internal hose/tube from inlet to outlet. Would look original yet be "modren".

If you are considering an electric pump, I would suggest taking a look at this article:

http://www.thecarburetorshop.com/Electric_fuel_pumps_and_old_cars.htm

Jon.

I always refer back to the old Sun test equipment slogan- - - -"We test, not guess!" I suppose in today's "Gotta have it RIGHT NOW!" society, actually finding and fixing the problem just isn't an option. Pity!
Jerry

Buck,

I ran an electric fuel pump on my previous 216 prior to it “blowing up” aka decided to take a dirt nap. If I can offer any advice here, it would be to stay stock with your fuel pump if possible. Keep it simple! As Jerry would say, why are you changing something that they paid millions to test and build?

If you decide to do it there are a few things you need to consider. Electric pump (at least mine was) a pusher pump. That means I had to keep it within 12 inches of gravity flow style tank. (1951 3100 comes out bottom of tank). Ensure you have a safety kill switch for your pump. Think....Incase of emergency, stalling, accident how do I [censored] off fuel? Some guys hook it through key hot, others used a switch that kills fuel pump if loss of oil pressure. You also need to keep fuel pump psi between 4-7psi. Or close to that.

What I am getting at is that it is easier, simpler and safer to keep it stock. I am sure others will input their opinions, but that is mine.

Chris

No one is advocating an electric over a mechanical. Everyone is saying "if you go with electrical" do this or that. It does have the advantage of almost instant gas flow when bowl is empty. The original system is the best way to go. Finding out why it looses carb fuel is the answer. We just got off on a tangent about electric.

I will say that "a few days" has been mentioned and "a week or more" has been mentioned. There is a point where all the bowl fuel will evaporate. At that point, if you don't pump the hell out of it while cranking, with some choke applied, it will take a long time to suck up the gas and start itself. At least that's what I've done for many years on trucks that sit a long time. You can't sit a long time and start right up unless you have an electric fuel pump....ooops! there I go again.
In truth, I have never installed one in my old trucks. Probably never will.

If your truck cranks slow, your pump pumps slow.........so filling bowl takes longer after a week or so of sitting.....up hill.......in the sun...15 seconds max.

Why are the folks glossing over the constant BLACK SMOKE?
This is an indicator especially if he means all the time. Choke stuck/way too much gas. I would rebuild this carb before doing anything else. Need a good baseline. Also make SURE air cleaner is CLEAN....and not a small "Hot Rod" pot pie size.

BTW, pumping like crazy does not fill the motor with gas, it is just that when there is enough to squirt, you catch it right away to save battery and starter. You don't know when it's ready for it's first squirt or two because you can't see inside It's the same as pouring gas down in.

I don't ever leave this truck out in the rain or drive in the rain. Sounds like a basic single action fuel pump will serve my needs. Thanks

Bart - I would agree that this needs to be addressed first.

Obviously, the adjustment on the choke needs to be checked, but the black smoke is also a symptom of either a warped Rochester (open power valve) or a failing or improperly installed pertronix conversion, or other ignition issue. Or a host of other possibilities. The empty carburetor / "pump issue" is probably just the volatility of todays fuel.

Jon.

Agreed- - - -first, fix the carburetor. I'd suggest about a 200-foot "drop test" onto concrete, followed by the purchase of one that doesn't flood. Then, check the fuel pump for proper operation and replace it with one that works right if necessary.
Jerry

don't chip the concrete either...

Before you drop that carb 200 feet onto concrete please talk to me. If it is a BC I'm actually looking for a couple of those. I'm looking for complete ones capable of being rebuilt/repaired and maybe even modified a bit. I'm looking for carbs nobody wants any longer, too. I promise nothing I get will be scrapped or ruined.
Jon

Sounds like someone’s soliciting parts.

Not my style, Martin. If I'd wanted parts I'd not have asked for complete ones capable of being repaired/rebuilt. Incomplete ones will be of little use for what I have in mind.

Call Carb King. He's been trying to GIVE Rochesters away for a long time.
Jerry

Hum, I thought a carburetor was a part. My bad!

Thanks, Jerry...I'll do that.

Sorry Martin...I misunderstood also. I thought you meant parts for carburetors and that idea confused me. For clarification, yes...carbs are engine parts and no, I don't want carburetor parts. At least at this point, parts won't do me any good. Although I can see a possible need to fabricate at least one part and possibly a couple. The power piston/power valve seems to be where a lot of problems in the B, BC, BV originate and loss of vacuum seems to exacerbate those problems and ultimately cause the piston to get stuck, fail and cause the whole thing to go wonky...most especially in vehicles which are only occasionally driven. I've read many of Jon's posts here and elsewhere and I know he's done a lot of work on this. I'm going to see if I can come up with a different idea or two.

new question....on my 235 engine i have the glass bulb mechinical pump , are the inlets and outlets compression threads ? all i found on mine was female threads and can i buy the hoses just to screw into them and then add a fuel line? thanks