*sigh* Bus will not start - '71 1600DP

[Maz804]

I'm at my wits end and need to reach out for help. 1971 bus with 1600 DP, stock carb, and dizzy. During the last few months during starting I could fire it up but would not hold idle. I go to the back and rap on the carb with my leatherman and try again... It starts and idles fine. Runs great but everytime I stop I have to rap on the carb to "unstick the float bowl." At least that is my understanding of what is happening.

Last week I noticed that I didn't have to rap on the carb, it started just fine. For a few times... Then it was kinda intermittent. Hmmm...

Then one morning I hopped in the bus, started it up, and warmed it up for just a couple minutes, then drove easily 6 blocks to the coffee shop. I decided to let it idle while grabbing my 12oz double Americano. It took longer than I thought. It was about 5-7 minutes. I walked out to my bus quietly sitting there with the lights on. f@ck. I turned the bus off, pulled the key out, put the key in and tried to fire it up. It would not fire. It turns over, but it won't even cough or hiccup. I tried rapping on the carb. Nothing. I replaced the points, filed and cleaned the cap and rotor, replaced the coil thinking I might've burnt them up. I replaced the fuel filter, and have verified that I've got compression on all 4, getting spark to the end of the plug. I have gas pressure going into the carb. I took the carb off and verified that I'm getting fuel sprayed down through the throat as I pump the throttle. Cut-off switch clicks when I put power to it.

I've got compression, spark, and fuel. Vacuum leak? Aside from the brand new intake boots, brake booster, and the advance port going to the carb, what else is there? I'm sure the manifolds are fine. Something tells me it's carb related, but what the heck?!

I've pulled the carb back off and have it with me at the house. What should I check for?

Thanks!
Michael

[tristessa]

Are you getting spark at the right time?

How do the plugs look? Gap?

I'm groping in the dark...

[Sylvester]

It may be a combo of things, if you rap on the carb and it starts, it may be the float having issues. Do you have a carb rebuild kit? Also, when is the last time you timed the Bus? I had the same issues on the same set up, but mine was choke and timing combined. BTW, how is your choke?

[Maz804]

Hmmm... THe timing was good before it died. I'm not sure how the timing would change, I mean the dizzy hasnt moved. Like I said, all of a sudden it stopped, but I wasn't out there to hear how it stopped! Dangit! I DID put new points in, so that would change the timing but not enough to not get it to cough to life. I double checked the point gap too. The spark plugs look very healthy and I'm getting strong spark.

About the float bowl issue. I did take the carb off and verified that it spraying a healthy dose of gas down the throat whenever I pull the accelerator pump. So with this, I'm assuming it was still spraying before I removed it. COuld it be leaking and running rich? I DO have a rebuild kit, but I'd like to get it home first. It's still parked in the street outside a coffee shop in NE.

The choke. My choke works pretty well but it will not go through its full range, so I can set it so it will open all the way when warm and have it slightly open when cold, or vice versa. I currently have it set to just open all the way when it's warm. The spring is not strong enough to kickdown the cam so when I pump the gas I can hear the idle come down.

I'm also guilty of using bad gas sometimes, you know, the cheap kind. I've heard that can clog things up...

[sped372]

If you've touched the points you've gotta check your timing. You should verify it anyway as part of the investigative process. "Was good before it died" doesn't cut it... you gotta make sure!

[tristessa]

Just 'cuz the accelerator pump squirts gas doesn't mean the entire carb is functioning properly -- make sure the jets & passages are clear.

[hambone]

Sounds carb/float related based on your troubleshooting. Seems like your gut is telling you that's the problem. I'd also check that timing. And make sure the distributor is advancing or firing.
Get a gallon can of parts cleaner, take the carb apart and let it soak if you suspect it, put it back together in a couple days. Don't fret it's usually something basic and inexpensive.

[RSorak 71Westy]

I think you may have a sticky choke and all the rapping on the carb is helping it to move. Does the choke plate at the very top of the carb move freely? Is it opening when the engine gets warm. If not, it ptobably flooded, and this will prevent it from firing. Once it sits and cools off though it should fire right up, if this is the case.

[Amskeptic]

I think you may have a sticky choke and all the rapping on the carb is helping it to move. Does the choke plate at the very top of the carb move freely? Is it opening when the engine gets warm. If not, it ptobably flooded, and this will prevent it from firing. Once it sits and cools off though it should fire right up, if this is the case.

Along the above diagnostic track, I was thinking that we have a slow failure of the cut-off solenoid, where a rap allows it to pull back and give you the idle circuit.

Turn on ignition and lightly touch the cut-off solenoid wire to the terminal. A "clock!" is better than a punky "click". Feel free to unscrew it and clean the hole and the plunger and make sure it does the full travel under voltage.
Colin

[Maz804]

So I rebuilt the carb. Mmm... Nice and clean now! Installed it and tried to start it. Not firing BUT, I heard a loud pop! So I have compression, fuel and evidently spark. The timing is off. When I put new points in I took the dizzy out with the clamp still on it so I wouldn't have to mess with the timing. But I must've put the dizzy back in with the rotor facing the wrong way or something. I marked the dizzy, loosed the 10mm and raised it a bit and moved the rotor till it seated back in facing the other direction then verified the static timing and it was spot on. Turned the key and it instantly came to life. Purrs very smoothly.

I'm embarrassed... But happy once again. It instantly comes to life when I turn it on, and instantly shuts off when I cut it. Awesome!

[Amskeptic]

But I must've put the dizzy back in with the rotor facing the wrong way or something. Awesome!

Lifelong lessons, myboy. I remember many on my path to .... um .... fewer lessons.
Colin

[dhoch14]

ohhhhh how I miss troubleshooting random carb related bus issues.

Glad to see your back on the road Michael!

[Maz804]

Oh man, and I so LOVE being on the road in Miles! Still have a full to-do list with him, but he's still roadworthy. How is Dave doing? I should be at the lab this next Monday now that I have a lot more free time since being laid off...