Knocking and back firing when gas panel is down

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
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artificer
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Re: Knocking and back firing when gas panel is down

Post by artificer » Thu May 25, 2017 5:31 pm

I'm @ my brother's & friends in the Southern Highlands now & then, so will let you know next time I'm coming down.
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.


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Re: Knocking and back firing when gas panel is down

Post by Wolfman » Fri May 26, 2017 4:40 am

Food for thought.
Peters jeep was running OK.
When this started, he was driving down the road when the carb blew off.
It was not something that started after service or maintenance.
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Re: Knocking and back firing when gas panel is down

Post by Joe Gopan » Fri May 26, 2017 4:58 am

Best to stop and get a grasp on the present condition and an inventory of the engine in it's present state of assembly or disassembly. It ran once. Post some pics of the engine compartment showing the the wiring, the fuel system, and the general appearance so that others can get a feel of the Jeep.. One can only imagine from all the poking, removal, and reassembly that a mess exists under the hood.
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Re: Knocking and back firing when gas panel is down

Post by Wolfman » Fri May 26, 2017 5:10 am

I am starting to think John's offer is a good one.
Been there myself.
Sometimes you try so hard you over look the problem.
A fresh mind will find the problem.
Hint. Gather all the intel but do not assume ( there's that word ) that what has already been done is good. You will end up in the same trap ! :wink:
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Re: Knocking and back firing when gas panel is down

Post by Chuck Lutz » Fri May 26, 2017 8:46 am

I'm guessing here, but I don't think for one minute the carburetor "blew off" the engine...not while it continued to run down the road.

1) was the air horn attached to the carburetor at the time?
2) was it even a Carter 539/636/698 carb?
3) did you mean that the CHOKE plate suddenly blew back up out of the carb when the engine backfired and was lost on the road?

Photos, photos, photos please.
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Re: Knocking and back firing when gas panel is down

Post by Peterdodge6volt » Sun May 28, 2017 4:34 am

Hi guys back home from farm as my farm does not have signal.
I have a look around the engine and sprayed WD40 and clean it and shine it with a very bright hunting lantern torch and found a crack in the block in the where the valves and manifold block.
We had enough trying to fix it on the jeep. So we decided that we are going to change the engine and also take the gearbox and transfer case and get it rebuild, as it leaking oil every where and all over the floor.
This will be my first time going to do this on the jeep.
I had fix to many times on the WC dodge as I have three WC51 dodge and they are my favourite toys
I have 5 spare engine for dodge as 3 engine is fully rebuild and 2 needs rebuild.
I have 2 spare original GPW jeep engine as 1 is full rebuild and I needs full rebuild as it very bad condition.
I have to many spare parts as well for dodges.
I went with father to have a look at my spare rebuild GPW engine at the other shed oh god how long we haven't went in the other shed like a years or maybe more. We have 6 sheds
As soon as we find the jeep engine :shock: aaarrrrhhhh someone stole my original F stamp bell housing on my rebuild jeep engine. There also no clutch disc, flywheel and pressure clutch plate. All gone :( .
We are so pissed off :evil: as some one sneak in to our shed my father was also screaming.
We load the rebuild engine on the truck and took it home and going to make engine frame stand.
And now I am going to have a hard time looking for a
original F stamp bell housing,
Original F stamp clutch disc.
They are so hard again to find.
F stamp water pump it was also gone as well.


I will take picture but I had so much trouble trying to post picture for 1 and half year on this form and I am using iPad 2.

The butterfly choke blew off so I have no choke. I will check if the other butterfly for accelerator if it's still there I forgot to check that one.

Cheers Peter

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Re: Knocking and back firing when gas panel is down

Post by Chuck Lutz » Sun May 28, 2017 9:05 am

So....you WERE running with no air horn on the carb and the choke plate was ejected when the engine backfired up through the carb. Where the two brass screws that held it to the choke shaft are now is anyone's guess but #3 cylinder comes to mind!

I don't understand the statement "found a crack in the block where the valves and manifold block".

OK...maybe this is a problem lost in translation, but even a cell phone can take pretty good pics so that might explain what you are referring to:
1) crack in the block where the valve stems pass through it below the valve guides?
2) crack in the valve guide
3) WHICH valve guide is cracked
4) If it is the intake on #3 then maybe we are beginning to see a pattern here.

It is tough to help with the jeep when 75% of the post is referencing Dodges....that is not helping ANYONE diagnose ANYTHING with the jeep.

I think you should do absolutely NOTHING until artificer can come by and take a fresh look at the jeep engine as-is!
Chuck Lutz

GPW 17963 4/24/42 Chester, PA. USA 20113473 (USA est./Tom W.)
Bantam T3-C 1947

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Re: Knocking and back firing when gas panel is down

Post by Peterdodge6volt » Sun May 28, 2017 11:13 am

My jeep is all original as we keep it original. We use for films and reenactment.
My jeep does has an air horn and Oaks air cleaner.
Yes I am sorry that should not post anything about dodges only jeep.
We live in Campbelltown and our farm is in Goulburn this is where we store our military vehicles.
Yes that was a brilliant idea of taking picture on phone I will try that thanks. I am not very good at sentence as I am young and deff sorry.

The carby I bought from milspare was a repro and new it had the butterfly on both side end.
I just heard from my other friends late last night as they are now having problems with their jeep. With new parts from milspare. They believe it's the carby that's hurting the engine.


Cheers Peter

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Re: Knocking and back firing when gas panel is down

Post by Peterdodge6volt » Sun May 28, 2017 8:46 pm

This weekend I have a jeep expert mechanic coming to help me fix the jeep.
So I will let you know how it went.

Cheers Peter

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Re: Knocking and back firing when gas panel is down

Post by Ian Fawbert » Mon May 29, 2017 2:07 am

Peterdodge6volt wrote: original F stamp bell housing,
Original F stamp clutch disc.
They are so hard again to find.
F stamp water pump it was also gone as well.
Pete, if you need a bell housing, i think I have a MB one which you can have. Also have a spare MB waterpump if needed, no cost, its yours if you want it.

Glad you found the problem. Good luck with the inspection and work on the weekend.

Cheers,
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Re: Knocking and back firing when gas panel is down

Post by artificer » Mon May 29, 2017 3:30 am

Peterdodge6volt wrote:This weekend I have a jeep expert mechanic coming to help me fix the jeep.
So I will let you know how it went. Cheers Peter
That's good to know. There are a group of Jeep guys around in NSW including Ian that you can get to know & if not involved currently, for $25 (lifetime) you can get a great monthly newsletter plus belong to a group with many outings/meetings.
One contact to join: mitchtez@gmail.com
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: Knocking and back firing when gas panel is down

Post by Peterdodge6volt » Mon May 29, 2017 3:38 am

Thanks artificer

I am already in Mitch jeep club.
I am also in ww2 reenactment club, civil war reenactment club, AMVCS club.
Ian lives 30 minutes from me as I will see him sometimes this week.


Cheers Peter

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Re: Knocking and back firing when gas panel is down

Post by Chuck Lutz » Mon May 29, 2017 7:49 am

So...I take it this is a "Joe's Motor Pool" reproduction of the Carter 539S carburetor and the two screws that hold the plate to the choke shaft came loose and the plate itself is missing or was blown back up through the Air Horn into the Crossover tube and somehow lost.

Do nothing at this point Peter....it sounds like the Cavalry is coming to your assistance!
Chuck Lutz

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Bantam T3-C 1947

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Re: Knocking and back firing when gas panel is down

Post by Peterdodge6volt » Tue May 30, 2017 11:53 am

Thanks chuck
I will not touch it until my jeep expert machanic. He will be coming this weekend.
He sells a lot of ww2 original jeep parts not repro parts.
The carby I got from Milspare jeep parts from Queensland.

Cheers peter

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Re: Knocking and back firing when gas panel is down

Post by Peterdodge6volt » Fri Jun 16, 2017 4:40 pm

Hi folks
So far me and my friends jeep expert mechanics do some work on her.
We fix the crack on the valves engine block, we change timing chain, we change distributor plus cables, we did some new wiring on her.
We also did find one conrod nuts loose so we replace new nuts and washer on.
Everything is back on except the head as I am still waiting on new head gasket.

We check all the valves they were all fine no cracks, damage, burn out, no broken springs and nothing is loose..


I will let you know when the head is on and how it's running. Finger cross

Me and my friends suggest that we are going to go 8 volt on her.




Cheers Peter


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