258 Engine starts but won't stay running

[Tony and Nicki]

Hi guys,

As some of you may know I had to replace a couple of push rods recently and since then the engine has been running good and has passed emissions and is registered and insured and was being driven daily.

Now I have a new problem. The engine has died on 4 different occasions (No splutter shudder or anything just like ignition switch has been turned off) for no apparent reason and with no warning when idling and having previously been running  perfectly

Now it starts but won’t stay running unless I keep my foot on the gas and even then it’s a bit rough and you get the feeling it’s gonna die if you take yer foot off the gas which it does.

Symptoms:

Had to keep richening fuel mix screws out ½ turn at a time ‘til it would start and stay running
Had to turn idle speed screw in almost as far as it can go inwards for it to start and stay running
Vacuum lower than usual @ 16 to 17"Hg and steady @ 1,000rpms in P (down by 1 ½" to 2 1/2" Hg)
Holding Choke plate partially closed results in a smoother idle
Fuel is pouring out of passenger side ‘banjo’ area

Work done:

Removed gas cap to eliminate possible vent issue
Pulled fuel hose off carb and cranked to see if fuel is coming out, which it was
Tried electric fuel pump = No change
Tried electric fuel pump with different filter = No change
Noticed Rubber fuel hose at tank end has lost outer wall but is not leaking
Checked Timing and is 8BTDC
Checked for Spark and is present at all spark wires
 
Also, probably unrelated, the fuel gauge needle has been behaving even more erratic than usual and will drop to the position it would be if the ignition switch was in ‘off’ position then later will rise back to where it should be and so on.

I’m thinking, considering it seems like it’s getting adequate spark and the fuel supply seems good all the way to the carb that the issue might be the carb. I don’t know about the carter BBD but I know if I look down Falcon’s Holley 4160 there is no fuel visible pouring out of the 'banjo' so I’m assuming that fuel is coming out of where it shouldn’t and not getting to where it should.

It is also possible that I have a vacuum leak somewhere but I would have expected the idle to increase rather than decrease to the point where I have to turn the idle screw all the way inward.

It could even be that there’s an issue with the ignition system seeing as how when it shuts down it’s very like the ignition being turned off and the fuel gauge is acting like it would if the ignition is off.

However, unless it’s normal to have fuel pouring into the carb ABOVE the throttle plates when they are closed I’d say the carb is the problem. Unfortunately I can’t afford a new carb at this point so I’m gonna have to try and disassemble and clean, partially rebuild or rebuild it if that is the case. Either that or install the jeep’s 1 barrel carb and manifold.

Anyway if anyone has any ideas please let me know and as always any help is much appreciated.

Cheers!
Tony and Nicki

[68AMXGOPAC]

It's a guess , but if fuel is pouring in maybe it is just the float or needle valve stuck. I first thought with mention of the fuel line missing it's outer material ?? that it may be getting sucked closed at some point ??But it sounds more like flooding with the rough running, and fuel or elctric like you think with it dieing.......just my thoughts.Rebuild kits are cheap , you can even take what you have apart carefully and see what is what first.Clean work area, I put paper towels etc down and lay all the pieces out on them in order, take some pics too.

[ammachine390]

Clogged Idle Tubes maybe?

[jim]

A faulty ignition control module can cause the motor to die at odd times.

[Canoe]

A faulty ignition control module can cause the motor to die at odd times.

As can a bad coil. Had one that would die once heated up. Ran fine once it cooled down. Real hard to identify.

That said, the carb sounds suspect.

[eaglebeek]

Based on your description the idle tubes are highly suspect. Try this link for instructions on how to fix it:
http://home.sprynet.com/~dale02/idle.htm

[Tony and Nicki]

Hello,

Since I know the fuel supply is good all the way to the carb, (but the carb has a problem that needs to be fixed anyway,)  I'm going to have to take care of that first...there is no getting around it. Once that is done, I will have ruled out having a fuel issue. If it still dies, I will start looking into ignition.

Thanks for all the comments. Keep em coming. All help is needed and greatly appreciated.

Tony and Nicki

[mudkicker715]

The motor can idle with a bad pump. Than run dry

[Eagleearl]

Sounds like a vaccum leak if closing the choke makes it idle better. The idle tubes do drop fuel in the carb above the throttle plates. You should replace the fuel hose if it is falling apart on the outside it could start leaking  any time. Sounds like a bad ground on the fuel gauge (that would be at the tank) or it could be ignition switch (on steering column). Is it running OK when not idling? If so it sounds like a vaccum leak.

[Tony and Nicki]

Sounds like a vaccum leak if closing the choke makes it idle better. The idle tubes do drop fuel in the carb above the throttle plates. You should replace the fuel hose if it is falling apart on the outside it could start leaking  any time. Sounds like a bad ground on the fuel gauge (that would be at the tank) or it could be ignition switch (on steering column). Is it running OK when not idling? If so it sounds like a vaccum leak.

Thanks,

Yeah I haven't ruled out a vacuum leak but I don't see anything. The only vacuum line I have is to dizzy but that's ported. Wouldn't make any difference at idle. Manifold has not been on long, all torqued to spec and in sequence with new gasket. Carb studs are tight. The only thing in question would be egr which doesn't have any vacuum line going to it but could have a ruptered diaphragm.

Carb is definitely showing symptoms of clogged idle tubes with the fuel dripping down above throttle plates but that would only cause rough idling not stalling as far as I know.

Funny you should mention a bad ground at the ign switch. I was wondering if that might not cause the engine to die also 'cos one time when it died I was fiddling with the lever of the broken turn signal switch and another time I was putting it into Park.

Yes it runs just as rough when you give it gas. The only time it runs smooth is on the choke or if you close the choke plates.

cheers
tony and nicki

[Tony and Nicki]

Ok. I had a chance to work on the Concord today. This is how it went:

Pulled idle tubes, soaked ‘em and later cleaned ‘em out with a .026" guitar string. Noticed that the venturi cover gasket had a piece missing and it wasn’t left in the carb. Not sure if I broke it off while removing or if it was already missing. May have been the reason for the gas pouring in. I ran and got a carb kit and replaced the upper and lower venturi cluster gaskets.
Went to start her up. Wouldn’t run. Checked to see if gas was coming from nozzles when you pumped the gas: DRY. Pulled fuel hose before carb and cranked her over: DRY. Tried pumping with electric fuel pump: DRY. Went and got more Gas and put 1 ½ gal in tank. Used electric fuel pump from engine side again: DRY. Unplugged supply hose at tank and pumped out gas with electric fuel pump. Got gas.
Tried pumping from engine side again with a hose going to a gas can from end of supply hard line before fuel tank. Got gas.
Replaced fuel supply rubber hose that had lost its outer wall between end of hard line to fuel sender.
Started her up. Ran like a charm (1,300roms at first ‘cos I still had the idle screw almost all the way inward).
Checked for gas leaking down above throttle plates: No leak. Checked vacuum: 19"Hg and steady as a rock @ 1,000 rpms in P. Took it for a waltz around the block. Ran fine.

Still need to tweak with fuel mix ‘cos they are still far out rich and will probably reduce idle speed but so far so good.

So, not say I don’t have other issues and that it won’t suddenly die from an igntion issue but the idling/running problem appeared to be due to the Idle Tubes and/or Venturi Cover Gasket leaking.
Not sure if the fuel supply hose at the tank end was helping either.

Anyway thanks for all your help everyone.

Cheers!
tony and nicki

[Eagleearl]

Glad to hear you got it running.

[Hawk258]

Sounds like a heck of a mess on your hands
Good luck, I know that having an air leak through the base plate is bad. I had a subaru once that the gaskets were so old they have literally became dirt. didn't know it till I hit it with some carb cleaner... Boy was that one big mistake... UGh... 

[Tony and Nicki]

Hi guys,

Just thought I'd post an update on this issue.

The original problem of not wanting to stay running unless the curb idle screw was all the way in turned out to be the idle tubes becoming clogged as already stated. I wound up pulling them about 6 times to unclog them and decided to pull the top off the carb and have a look. The fuel in the carb bowl was light brown with darker brown residue on the bottom. I figured it must be from the fuel tank. So I pulled the fuel tank and cleaned it out. It wasn't really that bad with only a little rust on the bottom covering about 25%.

Then I drilled out the idle tubes to 0.40", rebuilt the carb and that was the end of that problem.

However I then started having another problem where the engine would start and run fine but would not start again having reached my destination. I installed a new fuel pump and fuel filter but still continued to have the same problem. Anyway one day I got stuck on the street for about 4 hours trying to figure out how to get her started.
One thing I noticed was there was more fuel going to the return line than the carb. I was using an electric pump to verify fuel supply so I left that installed and eliminated the return line. Still wouldn't start. I then started to suspect the ign so I jimmied with the wires to the coil and she started up and I drove home like that.

I later re-did the wires to the coil and installed the electric fuel pump 'permanently' and it's been running perfectly ever since. Now starts up 1st time every time, even cold starts. The electric fuel pump is a walbro FRD-2-1 on-demand 3psi. At first I didn't think 3psi would be enough but I haven't had any trouble so far.

I don't think I really need the electric fuel pump but I figured as long as it's working I might as well leave it alone. Also not sure if I really needed to eliminate the return line but the same rule applies.

At some point for s&g's I'll probably restore the mechanical fuel pump and return line but for now I'm just glad it's running well. My vacuum is steady as a rock and 19 ½"Hg  @550rpms in P and 18 ½”Hg  @500rpms in D (@ 2,500 ft above sea level).

Anyway that's all for now. Thanks to all who helped out.

Cheers!
tony and nicki

[eaglefreek]

Good to hear you got it figured out.