The Stovebolt Site Forums The Shop Area Engine Shop Impossible to start 250

The 250 that I have in my '66 C-10 has gotten really difficult to start when cold. I had the head complete rebuilt back in June/July and I tuned everything to spec then and rechecked it after 100 miles. Back then it started on the first try with no more than half choke. The fuel pump was replaced about 2 years ago and works perfectly.

I have a remanufactured Rochester B on it now. Here's what it takes to start it: I have to have someone cup their hand over the tube on the air cleaner, use full choke, and pump the pedal a few times while cranking. Once it catches, I have to keep the engine up to about 1000 rpm or more to keep it running with full choke once my helper takes their hand away. Once its running and will stay running, it warms up like normal. As an example of how it runs once warm, I hauled a load of firewood to a local farmer and the wood was stacked halfway up my sideboards, putting the top of the wood about 1/3 of the way up my back window. And a few weeks before that I carri... 1" of rear suspension travel left.

If I don't have an extra set of hands, it will cough and sputter and want to run on the first few cranks and maybe even run for a few seconds, and then cut off. Once it sputters or cuts off, it will crank until the battery is dead unless I get some ether and give it a sniff or two.

Once the engine is warmed up, it can sit for several hours and it will start prefect with little to no choke.

I talked to the machine shop/FLAPS (my favorite one and the employees all know me by name) that rebuilt my head and I purchased the carb from and they said that I need to check and see if anything is clogged up internally and the float level. Another one said that I need to look inside and see if there was a crack in the metal or something that would have caused it to be returned off of its original vehicle and was overlooked when it was remanufactured.

I'm looking for any suggestions on fixing my Roch. B.

Second question: what is the bore of the hole in the intake manifold that the carb mounts over and what is the on-center bolt spacing? I'm very tempted to replace my Roch. B with a Carter YF, but I don't know what it came on other than the 153 I-4 and 230's and 250's with the A.I.R. pump. Is there something better than the Carter YF that I could use instead?

From the way yu explain that it sounds as if you have a vacuum leak. If I were within 50 miles I would come take a look for you. Original B's run at about 11:1 air/fuel ratio in my experience, so even with a big vacuum leak, it will still run.

Devin

Thanks Devin, I'll take a look at that tomorrow if its warm enough. I guess its time to invest in a good vacuum gauge and would it be best to start with replacing the rubber line that goes from the steel line hooked to the carb to the vacuum advance followed by the steel line itself?

A vacuum leak is the first thing I thought of also. The line from the dist. to the carb would not cause that problem though. That is ported vacuum & only a small amount can go through it. First check your accel. pump. After you shut off the engine look down the carb throat & work the throttle from a closed position. Each time you move it a squirt of gas should go into the carb. throat. If not you have a problem with the pump in the carb. Check the link that goes in the lever to the pump rod. It can fall off. That carb is basic & simple to work on as carbs. go. They work good when right. It is easy to take the top off & check the float level & power valve. You may be getting some water in it.

I wonder if you don't have a hole in your intake manifold. I had that happen on a 292. It was very frustrating to find. I believe this is a weakness of those engines.

I had those same symptoms in my 250 and I found a tiny hole in my intake. Now I can start it on a cold day, (for me cold is 45 degrees), and it will idle under 400 rpms

Wrenchbender, I got it running today (having to go through the cupping my hand over the top of the carb routine again) and warmed the engine up so the cold light cut off and shut it down. I let it set for a few minutes to cool back off and tried pumping the throttle and shining a flashlight down the throat. If I was looking at the correct hole, its about 1/4 of an inch below the choke shaft on the cab side of the carb, it didn't make a nice steady stream out like it was supposed to, it made more like a slow dribble or a couple of drops came out.

I have my '63 shop manual out and opened to the Rochester B rebuild pages, and what part am I exactly going to be looking for? Is it the vertical rod that is attached to the pump plunger assembly and is it attached to the "throttle kicker" or is it attached to the bar connected to the throttle shaft??

There is a tiny link between the lever on the throttle shaft & the verticle lever that the pump hooks to. It is known to fall out. It has hair pin clips retaining it. Sounds like your problem is with the pump itself. Take the top off the carb & take the link out of the pump lever & remove the pump. If its leather sometimes it has to be soaked in oil & messaged a little. Work it manually & see if it will squirt a good stream of gas in there. Check the float level like it says in the manual. Make sure the power valve piston goes up & down & pushes the ball off its seat. There is a small freeze plug in the side of the carb top. If it is missing it can cause a bad vacuum leak. If the acell. pump is working you should bev able to pump it enough to get it started with out putting a hand over the carb. If you get it started & it still runs lousy you have to work on the rest of the problems.

I'll take a look at it this Friday when I get home from school for the weekend. I'll start with the vertical lever and go from there. Once it gets started, it runs great and doesn't give me any trouble at all, its only the cold starts that are the issue.

be careful when you cup your hand over the carb....folks have known to be burned bad doing such things.......

The whole problem must be in the accel pump. Ther ought to be enough gas in the bowl for about 24 hours to start it by pumping the gas a few times. If the plunger is OK. you might pull the T out for the check ball. There should be a little spring & ball under the T. The ball should not be stuck to the bottom. Just because its a "reman" starter doesn't mean its right. About half of them aren't.

joker, I make sure to have the air cleaner on as a spark arrestor. I lost part of an eyebrow and some of the hair on my left arm in a nasty backfire when I first got my truck.

Thanks Wrenchbender, I'll look at all of that this weekend. Like I said, there wasn't any spray of gas when I moved the throttle shaft from idle to full throttle several times, only a slow dribble. Having read all of your advise, I'm leaning towards the vertical bar having come off of the throttle shaft because it only started doing this maybe 2-3 months ago, before that it was as good as good can get. I'm still going to check everything in case its something else a little deeper inside the carb.

I think it would start even if the accelerator pump didn't work if you had the choke completely on. This is just the way my 292 acted when it had the hole in the intake manifold.

It will be interesting to find out how this turns out.

Sounds like the carb could use cleaned out then, maybe somehting is clogged on the inside, and while you're at it, you could change the fuel filter too, it could be clogged.

Tomorrow morning I'm taking the carb off and checking everything listed here. I'll keep you guys posted how it turns out.

I didn't get a chance to take the carb off today like I wanted to, but I did take another look at it and the little link between the throttle lever and the vertical lever was in its proper place, and I still got only a small trickle of gas when pumping the throttle.

Dad asked me if I could use some Lucas Fuel Treatment and it would de-gunk the inside of my carb without having to take it apart. Would that be worth trying before tearing into it? And is what is the best way to drain the gas out of it when I take it off, just tip it upside down and let the gas drain out of the air horn and into a glass jar for later?

These carbs are so easy to work on. Take off the top & remove that link from the top hole & pull out the pump plunger. It is either rubber or leather. It probably will be obvious what the problem is when you get it out. You can dump the gas out anytime or anywhere depending on where you are.

I ordered the carb rebuild kit from my FLAPS (they recognize my voice on the phone now, lol) and I'm going to tear it down this Friday and Saturday. I'll keep you guys posted on what I find in there.

I'm curious, where was the hole & how big was it? Could you tell what caused it? Was this a stock manifold?
Thanks, Doug

It has been a long enough time ago I don't remember the exact location, but I think it was in the area of where the exhaust and intake bolt together. I think the heat and exhaust gas over the years did it. I worked on the carburetor for a long time before I realized there had to be something else wrong.

This was a stock manifold.

Here's an update on my issue: my FLAPS ordered a kit for a Rochester Monojet instead of a B model, and couldn't get a B model kit. I've ordered the correct kit from LMC and it will be here sometime next week. Starting next weekend is my Spring Break, so I'll tear into it the since I'll be home for 9 days and can really look at it. I'll let all of you know what turns up when I take the top off and dig into it.

Thanks for your help,
Drew