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willysmjeeps.com :: View topic - Stammering engine.
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Stammering engine.

 
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sportpilot
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Joined: May 26, 2012
Posts: 5

PostPosted: Sat Apr 19, 2014 11:05 am    Post subject: Stammering engine. Reply with quote

Hello Everyone. I have a 53 M38A-1. It has a new Willys rebuilt F head engine from Kaiser Willys. It also has a new Carter carb, plugs, ignition, fuel lines, fuel tank, clutch, etc.
Issue: After engine is warmed up, and throttle is punched, it stammers and stutters and then smooths out and runs great. Checked float and it is adjusted to specs. Called carb rebuilder and he's said my problem could be I have carbon ignition wires going to coil and all plugs from distributor. Anybody know if braided wire should be used on these engines? I am at end of my rope, There is not to much left to replace on this vehicle. I have had two mechanics look at it, and they think the carb could be bad. Anybody have experience with carbon vs braided steel ingestion wires? Carb is under warranty and rebuilder is more than cooperative. Thanks.
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wesk
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Joined: Apr 04, 2005
Posts: 16225
Location: Wisconsin

PostPosted: Sat Apr 19, 2014 1:23 pm    Post subject: Reply with quote

1-The engine works just fine with either rubber coated carbon core wires or rubber coated stranded steel core wires or shielded military wires.

2-If the engine ran ok before the carb then the carb is the problem.

3-If the distributor is not a fresh overhaul it may be that your centrifugal advance weights are sticking or corroded tight. Remove the cap and try to rotate the rotor. It should move easily a few degrees in one direction and spring back when you let go.

3-If the carb and engine ran for the first time together then carb installation or the carb could be the problem. The most common causes for carb stumble on a fresh rebuilt carb is:
a-Missing parts.
b-Incorrect assembly or adjustment.
A good place to start is inside the accelerator pump cover. Make sure the correct spring is installed and that it is installed between the cover and the diaphragm. The parts illustration in the Carb manual shows the spring in the wrong location on the other side of the diaphragm.
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php
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artificer
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Joined: Feb 16, 2007
Posts: 206
Location: Gold Coast Australia

PostPosted: Sat Apr 19, 2014 7:51 pm    Post subject: Reply with quote

About 90% problems considered to be fuel related turn out to be ignition related. Ask any good mechanic & something one should always be aware of before diving off the deep end.
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John GIBBINS
ASE Master Medium/Heavy Truck & Auto Technician 2002 USA
Licensed Motor Mechanic NSW # MVIC 49593 Current
YOU CAN'T TROUBLESHOOT WHAT YOU DON'T UNDERSTAND
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Bearbait
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Joined: Aug 24, 2013
Posts: 19
Location: Saskatchewan, Canada

PostPosted: Sun Apr 20, 2014 1:54 pm    Post subject: Reply with quote

Have you checked for vacuum leaks?
The other thing to have checked would be the ingnition timing.
I've seen either of these cause a stammer on hard acceleration.
Also as WesK said if your accelerator pump is not working properly, it could be getting to little or to much fuel when accelerating quickly.

Good luck

Brad
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artificer
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Joined: Feb 16, 2007
Posts: 206
Location: Gold Coast Australia

PostPosted: Sun Apr 20, 2014 2:46 pm    Post subject: Reply with quote

Concise answers can only relate to accurate, detailed descriptions.

Although NOT described this vehicle's problem may be missing under load/acceleration.
If so spark plugs are the most common cause/contributor to missing when trying to accelerate, under load. An EZ test is:
On a slight incline lug the engine down in top gear then slowly accelerate. Missing or kangaroo-ing is usually related to spark plugs or leads.
Isn't this what your carburettor specialist indicated?

Plugs may fire OK when not under load but fail or fire intermittently when subject to increased compression pressures.
We used to test spark plugs for this type breaking down by simulating compression pressure increases in the old spark plug testers.
These machines were hooked to the workshop's compressed air supply.
No one seems to use or have these anymore as new spark plugs are considered relatively inexpensive compared with labour cost/s.
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John GIBBINS
ASE Master Medium/Heavy Truck & Auto Technician 2002 USA
Licensed Motor Mechanic NSW # MVIC 49593 Current
YOU CAN'T TROUBLESHOOT WHAT YOU DON'T UNDERSTAND
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wesk
Site Administrator
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Joined: Apr 04, 2005
Posts: 16225
Location: Wisconsin

PostPosted: Sun Apr 20, 2014 3:07 pm    Post subject: Reply with quote

Quote:
No one seems to use or have these anymore as new spark plugs are considered relatively inexpensive compared with labour cost/s.


If you are in the aircraft maintenance business we do. I have three of them. Two I use for aircraft maintenance and one in my home shop for testing all my personal equipment spark plugs. It is always nice to know that the money you spent on the new set of plugs was money well spent or not!

The biggest waste you will see on these jeeps boards is the throwing away of money on new parts that were never needed. Most folks seem to prefer going broke rather than learning how to properly troubleshoot issues.

The next biggest waste you will see is folks ignoring troubleshooting tips and then throwing money at parts that are not needed.

Thorough and careful road tests followed by the required shop tests IE compression tests, leak down tests, vacuum tests, spark tests, voltage checks, battery load tests, starter load tests and the list is endless but instead of learning how to do these tests and interpret their results folks just spend the money. Crying or Very sad
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php
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BullRun
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Joined: Mar 10, 2009
Posts: 459

PostPosted: Sun Apr 20, 2014 7:30 pm    Post subject: Reply with quote

One more idea and not saying it is the cause... check your fuel lines for their position in relation to the exhaust manifold.

I had a Land Rover that gave me trouble like this and eventually figured out the fuel was vaporizing before it got to the carb causing it to sputter. I repositioned the fuel line a little further away and the problem was solved.
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