Engine: Problem with 259 Engine

[Bo Markham]

Engine will crank up, run for a few seconds and quit. Pump the accelerator a couple times, will start again and run for a few seconds. Start it again (without pumping the accelerator and engine will run for a few seconds and quit. Pop the horn off and bowl is full of fuel. Hold the choke closed and engine will continue to run. No problems with fuel to carb, both mechanical pump and electric pump produces 5-7 lbs pressure. Everything in WCFB carb reworked, setup correctly (as per shop manual), timing spot on, ign. spot on. New pistons, rings (+.030), compression a bit lower then I like at 130psi, but it hasn't been run more then a couple minutes??? I'll recheck compression tomorrow, but should crank and run with 130psi. I'll be checking vaccum tomorrow, but appears to be plenty. Any ideas??? What am I missing???

[Jerry Forrester]

Engine will crank up, run for a few seconds and quit. Pump the accelerator a couple times, will start again and run for a few seconds. Start it again (without pumping the accelerator and engine will run for a few seconds and quit. Pop the horn off and bowl is full of fuel. Hold the choke closed and engine will continue to run. No problems with fuel to carb, both mechanical pump and electric pump produces 5-7 lbs pressure. Everything in WCFB carb reworked, setup correctly (as per shop manual), timing spot on, ign. spot on. New pistons, rings (+.030), compression a bit lower then I like at 130psi, but it hasn't been run more then a couple minutes??? I'll recheck compression tomorrow, but should crank and run with 130psi. I'll be checking vaccum tomorrow, but appears to be plenty. Any ideas??? What am I missing???

Sounds like you have a severe vacuum leak. Probably the carb./manifold gasket.
That's where mine was. Same symptoms.

[Bo Markham]

Sounds like you have a severe vacuum leak. Probably the carb./manifold gasket.
That's where mine was. Same symptoms.

Jerry,

Tapped into the throttle body at back of carburetor. Holding choke closed, engine running, 21 HG vaccum, constant at high idle. Let the choke off, engine dies??? I'm beginning to think something internal to front half of carburetor???

[sals54]

Ditto to above comments. If the engine is getting enough air to stay running while the choke is closed, then its getting the air from somewhere else. Before you start pulling the heads off, check all your other areas of vacuum. PCV, carb to manifold gasket, vacuum lines to distributor, vacuum line to brake booster. Check every avenue of whatever attaches to the intake manifold to see if there are loose hoses, cracked hoses, missing hoses. Last resort.... pull the intake and see what the gasket looks like.
As an aside.. I've re-used intake gaskets for these kinds of checks by spraying the copper gasket sealer over a wire brushed, used steel gasket with great success.
I've also cut my own gaskets with the thick gasket paper for a quick check of sealing. These will eventually blow out at the heat riser cross over, due to the heat. 5 minutes with a ball peen hammer will cut a gasket in short order, as sometimes they are not readily available locally. Why wait?
Good luck with the search. Here's hoping for an easy fix, eh?

[Bo Markham]

Ditto to above comments. If the engine is getting enough air to stay running while the choke is closed, then its getting the air from somewhere else. Before you start pulling the heads off, check all your other areas of vacuum. PCV, carb to manifold gasket, vacuum lines to distributor, vacuum line to brake booster. Check every avenue of whatever attaches to the intake manifold to see if there are loose hoses, cracked hoses, missing hoses. Last resort.... pull the intake and see what the gasket looks like.
As an aside.. I've re-used intake gaskets for these kinds of checks by spraying the copper gasket sealer over a wire brushed, used steel gasket with great success.
I've also cut my own gaskets with the thick gasket paper for a quick check of sealing. These will eventually blow out at the heat riser cross over, due to the heat. 5 minutes with a ball peen hammer will cut a gasket in short order, as sometimes they are not readily available locally. Why wait?
Good luck with the search. Here's hoping for an easy fix, eh?

Forgot to mention, engine is on test stand. 60 model 259, so no PCV. Only thing Vaccum operated is the modifier on the distributor. Installed a thicker carburetor to intake gasket. I've checked the steel line going to the modifier, not leaks. No leak under the carburetor. I've not been able to check the intake, that't next??? I think I'll try the copper coating on the intake if it is the problem.

Thanks

[gordr]

I will chime in to say that 21" of vacuum with the choke closed is meaningless. Vacuum reading at idle, choke open, will tell the story.

[jackb]

I'm unsure as to "WCFB re-worked ???

[Bo Markham]

I will chime in to say that 21" of vacuum with the choke closed is meaningless. Vacuum reading at idle, choke open, will tell the story.

Well gordr, if I could get the engine to run at idle without the choke closed, I probably wouldn't have a problem. Since the engine starts, runs for a few seconds then quits, what's a fella to do??? I've found no vaccum leaks either between the carburetor and intake, intake and block, or in the steel line to the modifier??? There are not other vaccum connects, except the rear of the throttle body and the plug isn't leaking.

[Bo Markham]

In this case, it means a working WCFB that got a good cleaning/dipping in carburetor cleaner vat, a new kit put in it and put on the engine. I've got it apart on the bench now, checking to ensure I made all the adjustments correctly.

[bezhawk]

Could have been the metering rod vacuum piston sticking, or the metering rods off the mechanical lifting tab, located on the shaft under the top small cover. Also a bent float rubbing on the sides won't meter fuel properly. Height as well as side to side alignment is critical on WCFBs.

[bensherb]

You also might want to check that your vacuum Ignition modifier (I love this term, it's actually a more appropriate description) will hold vacuum. Sometimes the diaphragm will crack and create a vacuum leak.

[gordr]

Well gordr, if I could get the engine to run at idle without the choke closed, I probably wouldn't have a problem. Since the engine starts, runs for a few seconds then quits, what's a fella to do??? I've found no vaccum leaks either between the carburetor and intake, intake and block, or in the steel line to the modifier??? There are not other vaccum connects, except the rear of the throttle body and the plug isn't leaking.

Well, about all you can do is to get it running on choke, watch the vacuum gauge, and then open the choke. See what the gauge does. Watch the momentary reading as soon as the choke is opened; it should drop from 21" to somewhere between 12" and 18", for a rough guess. If it plateaus at some level, and then drops again steadily as the engine dies, then that's going to be close to your true vacuum reading. I doubt the distributor vacuum line is the source of your vacuum leak (if one exists at all), because the line is simply too small to matter that much.

[altair]

Check that you metering rods are not bent, they are tricky to reinstall, the top cover has to be removed to set them in correctly then the cover replaced. When I firstly re and reed my afb I bent one of the metering rods and didn't notice it. The next thing I would check is the idle jet and confirm it is clear. I had a jet on a small motorcycle that had a small piece of machining stuck in it. Looking through the jet at the sun you could see it but it would not come out. The jet was replaced with a new one and it was like magic. There is/was small jet cleaning tools I, have a set they are very old school but work well. They are like very small round files but made for carburetor jets. Even though it is assembled correctly, each component must be inspected for condition, something in the fuel delivery system is obstructed.

[thunderations]

Disconnect and plug the vacuum line to the distributor. See if the engine runs OK. If so, the problem is the vacuum advance in the distributor.

[altair]

I don't think the small amount of vacuum from the modifier would make any difference, it is disconnected on a regular basis to adjust and check timing and the engines run fine with it or with out it. You will get a difference pitch in the engine but it will not die if you open and close the vacuum to the carburetor.