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W5 - Zenith B gas ( I think ) problem.... Help Required

I put 500 miles on this carburator last year and am working on my 2nd 100 miles for this year.. So my old car is getting around somewhat. But I inherited a new problem.

The problem, I think, seems to be a gas problem....
My car has a Zenith Model B carburator.
Seems like car will start (after sitting 3 hours or after a carburator tear down) and idle (quite roughly) as long as I want..
I have put a vacuum gauge on the engine ...at previous good idle I was getting 20lbs of vacuum. Idling rough shows about 10lbs vacuum.
Pressing on gas for more revs invariably results in a ?? gasping ?? engine... it does not rev up but will die...

I have float indicator hooked up and my float top is the appropriate 9/16" below casing top.
Gas float indicates same height before start and after stall.
With testing, needle controlled by float is working ok (i.e. allowing when needed and stopping appropriately.
I have taken apart carburator and blew air in all orifices, etc and this has not helped matters.
I have unscrewed and blew out 2 small valves at bot of carburator bowl.
Linkages are ok and opening valve as required in carburator...

Put everything back together and SAME PROB.

Double HELP required here.


Where Are You From? Peace River Alberta

Re: W5 - Zenith B gas ( I think ) problem.... Help Required

Hi Guy....

I'm wondering what the real problem is, it wasn't the coil and it may not be the carb. You need to do a couple routine checks and narrow down the problem.

Electrical and fuel problems can appear very similar.

Couple things I would check next:

1) Do a cylinder compression check, this would rule out a sticking valve or blown head gasket.

2) Check for a vacuum leak, plug off as many possible sources as possible. Don't forget the vacuum tank and windshield wiper. You can use the propane torch trick to locate a potential problem on the intake side.

3) Are points set correctly and timing on the mark? An intermittent condenser could also be a culprit.

These types of problems can be a bear to track down. Try and eliminate each possibility before moving on to the next.

Hopefully others can add their advice to help you get back on the road......


Where Are You From? Hookstown, Pennsylvania

Do You own a car built by Durant? 17 Durant & Star cars and a Durant-Dort buggy (one horse power)

1st coil, 2nd carburator 3rd ??? Help from Frank and others required.

To Frank and others : (since Frank reply #1)

So far :

1. Compression is:
#1-50, #2-45, #3-45, #4-55 lbs respectively.
Is this ok compression ? Engine has about 700 miles and 40 hours idling , ha.

2. Carburator:
I have retaken apart carburator and blew air in all orifices, etc
After 1st starting well and seeming to run ok.. for about 2 minutes , I put saprk to known sweet spot and attempt to accelerate engine... cough, cough, gasp, gasp, it wanted to die. Leeseinng on trhrottle and reapplying a bit goes it soo interim life but it is headed for a stall. Tried this procedure twice.

Will mention plugs are quite blackish after these attempted runs. I undersstand that black means that I am not burning my fuel (ie that is wht the bl;ack is .. unburned fuel) and yet the plugs are dry;.... no gasoine moisture prsent. All plugs look the same.

3. Coil:
Have gotten new coil from Napa OPHMS at distributor connection to positive pole shows 9900 OHMS. Highest yet on 4 coils I possess.
No changes on install.

4. checking for vacuum leak:
I only have line from intake manifold to vacuum fuel pump and to gauge I installed.
I seem to remember 20 or a little less lbs. vacuum. Now. though not idling great shows about 16 lbs.
By the way I don't know the propane trick !!!

5. One more test done :
While idling, I have pulled plug wires, the engine slows whenever a plug is removed. #1 and #2 cylinders not so much of a change as #3 & #4 cylinders which seem to distinctly affect engine performance when disconnected.
This I do not understand (ie.cylinder differences).

6. Currently How to build up revs.
Using throttle lever if i go up in little gulps... allowing engine to catch... and repeating this a few times I can get the revs up there. But sounds rough...but any abrupt changes to throttle position will make engine gasp and stop...

7. Spark: points 25thou and all plugs 35thou
with distributor off, watched points as engine was turned ... getting a spark each time a top point is reached, very consistent spark... white blue in color.
put distributor back on and checked each plug on its appropriate wire, each plug showed consistent lite blue spark.

8. ReStart Test Again:
Starts, runs really rough and hard to get up revs. At exhaust seems like its "missing"..and running rich although no black smoke (as if too too rich)
just not consistent put put put...

7. Question : How does one check a condenser ?

Any and all help appreciated


Re: 1st coil, 2nd carburator 3rd ??? Help from Frank and others required.

Is that the correct setting for gapping the plugs 35, seems a bit high. I know my 15L is around 25.

Where Are You From? Oviedo (near Orlando) Florida

Do You own a car built by Durant? 1928 Durant Model 65 4 dr

Re: 1st coil, 2nd carburator 3rd ??? Help from Frank and others required.

Sounds like you may have solved your problem with the loose condensor...But looking at your test results I question the amount of compression that you have on your 700 hour engine (I'm thinking that It should be about twice that amount), and the fact that it starts hard when warm, and you may hear a put-put from the exhaust...I believe that I would check your valve clearance and be ascertain that you don't have tight valves (hopefully not burned), this is something that should be done ocassionaly and especially after an engine rebuild.

A condensor is usuall either good or it is bad (either it is shorted or has an open) since a condensors job is to load and store current, I have found that a simple little test can be done to check those conditions, just remove the condensors pigtail from the circuit, turn the engine until the points are open, with the IGN turned on scratch pigtail lead to its post/circuit, their should be an arc while condensor loads, emediatly scratch the post again if each time their is a heavy arc the condensor is bad and shorted, also if condensor is good, after a few seconds ground pigtail and their should be an arc while condensor unloads.


Where Are You From? Leavenworth, WA / Yuma, AZ

Do You own a car built by Durant? '23 Durant Touring / '29 model 40 coupe

Re: 1st coil, 2nd carburator 3rd ??? Help from Frank and others required.

I also should have mentioned that after you take and record your dry compression test that you should follow with a wet test to determine if the rings are worn or possiably not yet seated properly. Put about 3 squirts of motor oil in each cylinder and retake the compression test and record, if the compression increases a conciderable amount than the rings could be the problem.

I just ground the valves on one of my 4 cylinder model R Hupps this past winter and as I recall 45 lbs compression was my lowest cylinder, I found 2 burned and one warped exhaust valves....Hope your problem doesn't turn out this serious.

Where Are You From? Leavenworth, WA / Yuma, AZ

Do You own a car built by Durant? '23 Durant Touring / '29 model 40 coupe


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