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> Stumped, motor won't fire on #1
Rusty
post Sep 17 2018, 04:25 PM
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We're stumped. I even caved and took it to my local VW expert for help.

Background: The car had been stored for 7-8 years. Before storage, it had been worked on by a third party (including replacing the distrubutor, IIRC). When the car was stored, it was running poorly.

Symptom: Car won't fire on cylinder #1, but fires fine on 2 thru 4. (Was it firing on #1 prior to storage... I dunno. I stored it out of frustration.)

Motor: 1973 1.7L, dual Weber carbs, Pertronix points replacement in 009 distributor.

Details: Car has air, fuel, and spark.

Air: Valves are adjusted correctly (.006) and timing is on. Compression on all cylinders is 90-95 pounds. Heat exchanger removed and checked for obstruction. Covering/blocking the air intake on #1 has no effect to the motor running.

Fuel: Carb on cylinders 1/2 has been cleaned and adjusted. We can watch fuel go into the cylinder. Some of it ends up as white smoke going out the exhaust. There is an oil leak on the drivers side of the motor and the oil smells faintly of fuel.

Spark: Plug wires are routed correctly. Taking a plug out and laying it on engine tin, spark is strong. Wires, cap, rotor, and plugs have all been swapped out. Pulling the plug wire on #1 at any RPM results in no change.



I talked to my guy today... he's very well regarded in the area. He's as stumped as I am.

Any thoughts?
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nickg
post Sep 17 2018, 05:00 PM
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check to see if the cap is secure on the distributer and the firing order. put a test plug on the wire and see if it sparking or replace the wire with a known good one from a working cylinder
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Rand
post Sep 17 2018, 05:04 PM
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QUOTE(nickg @ Sep 17 2018, 03:00 PM) *

check to see if the cap is secure on the distributer and the firing order. put a test plug on the wire and see if it sparking or replace the wire with a known good one from a working cylinder

He already said he tested for spark at that cylinder with success. Is the compression ok on that cylinder? If all the others work it can't be timing, and you've proven spark. Must be fuel or compression. I'm zero help when it comes to carbs.
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rudedude
post Sep 17 2018, 05:15 PM
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Did you test the plug from that cylinder for spark? I've seen plenty of bad new plugs
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Rand
post Sep 17 2018, 05:19 PM
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Did you read his post? Not trying to sound krusty, but...

QUOTE
Spark: Plug wires are routed correctly. Taking a plug out and laying it on engine tin, spark is strong. Wires, cap, rotor, and plugs have all been swapped out. Pulling the plug wire on #1 at any RPM results in no change.
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Rusty
post Sep 17 2018, 05:26 PM
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QUOTE(nickg @ Sep 17 2018, 05:00 PM) *

check to see if the cap is secure on the distributer and the firing order. put a test plug on the wire and see if it sparking or replace the wire with a known good one from a working cylinder


Yes, to all questions.


QUOTE(Rand @ Sep 17 2018, 05:04 PM) *

<snip> Is the compression ok on that cylinder? <snip>


I did not personally do the compression test. My mechanic did and reported all cylinders were between 90 and 95. Not great compression, but enough.

QUOTE(rudedude @ Sep 17 2018, 05:15 PM) *

Did you test the plug from that cylinder for spark? I've seen plenty of bad new plugs


Good point. Yes, sir. I can see the spark with the plug on the engine tin with the engine at idle.


QUOTE(Rand @ Sep 17 2018, 05:19 PM) *

Did you read his post? Not trying to sound krusty, but Rusty would know to swap the plug before being stumped. (Wouldn't you, Rusty (IMG:style_emoticons/default/poke.gif) )


It's all good. I'm not assuming anything at this point. (IMG:style_emoticons/default/confused24.gif)
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iankarr
post Sep 17 2018, 05:40 PM
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maybe the fuel isn't fully atomizing? Try switching the jet stacks and see if the problem follows...
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Rand
post Sep 17 2018, 05:44 PM
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I like Ian's thinking. Fuel has to be the highest suspect. Is the color of the plug different on this cylinder than the rest?
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worn
post Sep 17 2018, 05:51 PM
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QUOTE(Rand @ Sep 17 2018, 04:44 PM) *

I like Ian's thinking. Fuel has to be the highest suspect. Is the color of the plug different on this cylinder than the rest?

(IMG:style_emoticons/default/agree.gif)
Are the carbs such that each cylinder is off a different choke/throttle body? Silly thought, but you could switch the carbs around to see if the problem migrates with the carb. I bought an excellent book about Weber’s that had a section on Zenith-strombergs that was what i was looking for at the time. I can dig it out.
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iankarr
post Sep 17 2018, 05:55 PM
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Depending on the linkage, swapping the full carb from one side to the other could be a big deal. I'd def start with the jet stacks on the same side. It shouldn't take more than a couple minutes to switch 1 to 2. Hopefully the problem will follow and all that will be needed is a good jet cleaning.
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Chris914n6
post Sep 17 2018, 05:58 PM
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intake valve not opening, bent pushrod or something?
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michael7810
post Sep 17 2018, 06:00 PM
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Also check the idle jets and mixture screw port for obstruction
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Rand
post Sep 17 2018, 06:03 PM
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QUOTE(Chris914n6 @ Sep 17 2018, 03:58 PM) *

intake valve not opening, bent pushrod or something?

Goes back to my compression check question. He said his mechanic tested. Rusty, do you trust said mechanic's answers? We know it isn't timing, so it has to be fuel or compression. (Assuming the plug you tested for spark was actually the one pulled from that cylinder.)
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flyer86d
post Sep 17 2018, 06:08 PM
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Weber carbs run on the idle circuit about half way thru their range. A clogged idle jet or idle passage will cause this. It is much more common than you would think. Pull the idle jet and check it for infinitesimal debris and blow it out. If that does not cure it, pull the carb and clean the idle circuit with carb clean. Install a new inline fuel filter. Clean fuel is the key to Weber’s.

Charlie
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VaccaRabite
post Sep 17 2018, 07:34 PM
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Dirty plug? Pull the plug and wire wheel off the carbon?

Zach
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Rusty
post Sep 17 2018, 07:50 PM
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I do appreciate all the replies. I'm taking notes.


QUOTE(cuddy_k @ Sep 17 2018, 05:40 PM) *

maybe the fuel isn't fully atomizing? Try switching the jet stacks and see if the problem follows...


That's an interesting idea. As part of the troubleshooting process, he tore down the carb and cleaned it. I can try swapping the jet stacks though.

QUOTE(cuddy_k @ Sep 17 2018, 05:55 PM) *

Depending on the linkage, swapping the full carb from one side to the other could be a big deal. I'd def start with the jet stacks on the same side. It shouldn't take more than a couple minutes to switch 1 to 2. Hopefully the problem will follow and all that will be needed is a good jet cleaning.


More work, but it would certainly be a good test.

QUOTE(Chris914n6 @ Sep 17 2018, 05:58 PM) *

intake valve not opening, bent pushrod or something?


TDC on number one feels right. Valve adjustment went okay.

QUOTE(michael7810 @ Sep 17 2018, 06:00 PM) *

Also check the idle jets and mixture screw port for obstruction


Roger.

QUOTE(Rand @ Sep 17 2018, 06:03 PM) *

Goes back to my compression check question. He said his mechanic tested. Rusty, do you trust said mechanic's answers? We know it isn't timing, so it has to be fuel or compression. (Assuming the plug you tested for spark was actually the one pulled from that cylinder.)


Yeah, I do. But a second look at the compression on #1 might not be a bad thing. Yes, the plug I tested was the one pulled from that cylinder. Got the same result with the replacement plug.

QUOTE(flyer86d @ Sep 17 2018, 06:08 PM) *

Weber carbs run on the idle circuit about half way thru their range. A clogged idle jet or idle passage will cause this. It is much more common than you would think. Pull the idle jet and check it for infinitesimal debris and blow it out. If that does not cure it, pull the carb and clean the idle circuit with carb clean. Install a new inline fuel filter. Clean fuel is the key to Weber’s.

Charlie


Thank you. I'll double check his work if all else fails.


QUOTE(VaccaRabite @ Sep 17 2018, 07:34 PM) *

Dirty plug? Pull the plug and wire wheel off the carbon?

Zach


One of the first things I did when I pulled the car out was clean the plugs. I've since replaced them with another set. (IMG:style_emoticons/default/smile.gif)


I'll pick up the car tomorrow.
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Spoke
post Sep 18 2018, 08:17 AM
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Have you checked the airflow into each cylinder using a sync meter? This will let you know that each cylinder is pulling the same volume of air. Even by putting your hand over the opening of the carb you should be able to feel the vacuum.
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struckn
post Sep 18 2018, 08:54 AM
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I'm know expert but I had a similar condition that turned out to be a dropped a Valve Seat?

Also, was a Cam for Carburetor conversion from FI made. Might cause for a rough running engine condition. Did it run right before you put it in storage?

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IronHillRestorations
post Sep 18 2018, 11:29 AM
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I too suspect a fuel delivery problem for that barrel. Look down the throat of #1 carb barrel, you should see fuel squirting when you open the throttle enough to actuate the accel pump. Spraying some fuel down the barrel (with spray bottle in a leather gloved hand, and fire extinguisher within reach) will tell you if you have a fuel delivery problem.

Could also be a valve problem, if so, probably intake, such as stuck valve, bad rocker arm, bad lobe on cam. This could be seen by taking off the valve cover and turning the engine.

First thing I'd do is warm it up and block the throttle at about 1800 rpm's and squirt some fuel down #1 barrel. Just be really careful. In theory you could use ether, but that's not good on your engine.
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7TPorsh
post Sep 18 2018, 12:02 PM
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Vacuum leak on the intake top or base? I would try switching the carbs.
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