NO ENGINE POWER BACKFIRING

[echelon1]

Gindi, I will remove the rubber boots today and check. I know I touched a boot when it was running and I got shocked.

Mark

The chance is real, many have found the shortest way from the jeep to the bin in my shop.

Yours,
Gindi.

[Stir-Stick]

Howdy,
Don't forget that the distributor has a notch that the cap has to fit down into . Sounds silly , but it happens .
Stick

[051743GPW]

Hi

I removed the rubber shields with no change. So, this turned into a bigger job, one spark plug hole was bad/stripped. The machinist that sold it to me, said it was NOS, obviously not so, he had filled the plug holes with paint so I could not see how bad they were. I had used shim stock to fill the threads and screwed the plug in. After all the power and backfiring issues, I knew that was not helping my case. So, I pulled that head and installed a really good one today. I picked up a new condenser and set of plugs. And I actually have 2 distributors, a repo and the original I rebuilt. Tomorrow morning I am going after it again (as soon as the head gasket Copper Permatex dries), armed with all of the above. I triple checked my static timing and it appeared to be OK. I will report one way or the other tomorrow.

Thanks to all for all the help.

Mark

[051743GPW]

SUCCESS, at least some. I replaced the condenser and distributor cap, but I could not even get it started again until I moved the plug wires 180 degrees from where #1 was at TDC and IGN on the flywheel. Once I moved the wires it started right up and now idles good and it is pouring cats and dogs outside, so I just drove it up my steep drive way and it appeared to have plenty of power. So, I then lined up the IGN spot on the flywheel and the window and removed the distributor cap and took note of the position of the rotor and points. To make it run, with the IGN at the line in the window, the rotor was pointing directly at the contact #1 and the points were 100% open? This is not what all the directions on the internet state?

Champion J8C plugs.
Copper core wires, no boots on plugs.
Open point gap .020

But, now there is a real dead spot when I give it gas it wants to die out, then it will catch up and have plenty of power. The one thing I noticed was the throttle plate stays almost closed until the throttle is 1/3 of the way open, and it sounds like it is trying to suck air hard during that initial die out? I used the base carburetor gasket with the metal V shaped device in it. The accelerator pump appears to be putting out plenty of gas.

Mark

[echelon1]

I think that the throttle plate you are talking about is actually the shocke plate.
A dead spot when throttling up is usually the rod conecting the throttle body linkage with the acelerator pump and high speed circuit needle that need to get a little bend.
But in your case it might be the shocke that is not properly open.

Gindi.

[artificer]

the rotor was pointing directly at the contact #1 and the points were 100% open?

the points should be JUST opening when the IGN mark is in the window.
I would set this properly before going further.

You can do this 3 ways....with ignition on rotate distributor until you see or hear the spark as the points open, tighten, do the same with a test light hooked in & when it extinguishes, tighten or with your auto multimeter set on ohms, ign OFF & hooked in when the reading goes total resistance, tighten.
These methods are called static setting.

What Gindi says is correct for the fuel/carburettor side....adjust the throttle linkages [from the pedal to the carburettor] so that when the accelerator is pushed to the floor the throttle plate [the one @ the bottom of the carburettor] is fully open.
While someone pushes the accelerator pedal to the floor....check this with a flashlight.

The choke plate [the one @ the top] should always be in the vertical [off] position when the dash cable is pushed right in....about 30 seconds after startup usually.

[signsup]

You guys have forgotton more about these engines than I'll ever know, but what am I missing? I'm still in the process of restoring my Ford Script 1942 GPW so I'm trying to do some preventative learning here.

If the engine runds fine in park, even with the rpm's up, no missing, no backfire and no rough running and has plenty of power, when he puts it in gear, the problem arises.

Wouldn't fuel/spark/air etc., all show up in park as well as in gear? If the Jeep is in gear and under load and something in the drivetrain is bogging down or binding up, wouldn't the "sympton" be the loss of power in the engine and running rough and backfiring? When he rides the cluth, the problem goes away or certainly gets less of an isue. He doesn't say how much speed he is getting, but I'm thinking that when he rides the cluth, he is removing most of the load and the engine is no longer bogging down and appears to be running fine.

Isn't this probably more dirve train related than engine?

I'll hang up and listen. Trying to learn by osmosis.

[artificer]

The engine has plenty of power!
When he rides the cluth, the problem goes away....that when he rides the cluth, he is removing most of the load and the engine is no longer bogging down and appears to be running fine.
Isn't this probably more dirve train related than engine?

The engine actually does not have plenty of power. It may have what appears to be good RPM for the spark or fuel the engine is getting on NO LOAD.

Not really....usually anything drive train related will be just as evident when riding the clutch or when the clutch fully engaged.

The important thing is something is causing the engine not to run @ full efficiency....either ignition related or fuel [including a blocked or restricted fuel filter]. Many times the condenser has been mentioned as a possible cause [can be tested & should be 20-25 mfds [microfarads].

In a no load condition all these things may appear fine....apply a load & whatever is causing the problem & as we can see from the posts there can be many & they are all simple, comes into play.
Riding the clutch does nothing except lower or relieve the load....plus screw up a good clutch eventually.

Real mechanics go through possible causes in a logical sequence easiest to hardest then ticking off each possible contributor when they are found to be OK [often done in the head].
With a problem like this it would be take well less than 1/2 an hour possibly 5 to 10 minutes. DO NOT forget there may be more than one or a combination of issues.
Eventually they will find the issue & fix it up without replacing numerous parts along the way [or overhauling good components] before finding the real culprit.

Some here endeavour to help others save money & learn how to diagnose & troubleshoot the right way....& asking questions like Robert just did, is how that is facilitated.

[Ben Dover]

It apears Mark has for the most part discovered the problem. A timing light and a little fiddling with the carburetor just might button this job up.

[artificer]

It apears Mark has for the most part discovered the problem. A timing light and a little fiddling with the carburetor just might button this job up.

That may be so, but is precisely what I am talking about....replace enough parts & eventually you must get lucky.
Mark did not indicate he checked the condenser or that there was anything wrong with the distributor cap.
If he puts the old distributor cap back, all may still be fine....why spend the $20 or whatever?
Something wrong with any distributor cap, like carbon arcing & it is very visible. Rotor button shorting is a different story & testing is needed.

[Ben Dover]

Gotta see how the next test drive goes, looks promising.

[051743GPW]

Hi to all on G503

Thanks to everyone for all the great help. I could not have ended up with a finished product this nice if it were not for all the knowledgeable help on this site.

It quit raining and I adjusted the carburetor again and it ran great. Throttle has a very small dead spot, but very small now. No problems, plenty of power. However I did replace the condenser and the distributor cap. Now I do not understand why, but it is true, if I adjust the points so they are just opening at the IGN mark, it has all the backfiring low power problems. I am almost positive that the reason I have to set the points open at IGN lies in the advance and springs, but that is for another day, today my family and I drove down the road in my 1943 GPW and it ran great and brought us back home.

Mark

[artificer]

No one is trying to rain on the parade & you have done a wonderful job plus won a prize to boot, which is more than most of us can say.
The Jeep is running, so we could just let things be....I would like to help you get right to the bottom of this issue so it no longer exists in any form.
Jeeps run very well & are a powerful little beast, so what might seem OK could actually be underperforming

With each added element, you give others more information, as you just did with

I am almost positive that the reason I have to set the points open at IGN lies in the advance and springs

It has me puzzled, why you would suggest this?

If the distributor is assembled properly along with the 2 advance springs....@ rest, setting up static timing by the book or any of the 3 ways suggested, there is nothing in this mechanical advance area that affects starting & idle or low speed running.

SO

If you can't get good starting with static timing [considered slightly retarded when using modern fuels] & retarded usually means easier starting, without the points just beginning to open I am thinking you may have solved part of your problem by changing something else thus not achieving a 100% result.

BTW backfiring, which it appears is not there now, usually means you have ignition with a fuel air charge in a cylinder when a valve is not fully closed. This may be related to crossfiring [leads touching & shorting one another] or a bad distributor cap [carbon tracking or cracked].

Here is what I would suggest....not what I would do & that is test with a "vacuum gauge".

Get an old spark plug & knock out the centre porcelain [be very careful this is like breaking glass & wear safety glasses].

Screw this SP base into No. 1, then with an elastic band hook a condom/balloon over the plug & turn your engine over until the rubber inflates to max then starts to deflate & rock around this point until you have maximum inflalion indicating No 1 is @ TDC Compression.
Check where the TDC mark is in the timing window & let us know what you find.

[Ben Dover]

What's the story on your cylinder head, did you resolve it? Do not forget to retorque the head (hot) after initial warm up.

[051743GPW]

Hi and thanks for your concern.

Good point to re-torque the head. I had another good head and used that one. I am going to have a time-cert put in the bad spark plug hole in the head that was on the block.

I was thinking that it must be in the advance, because I can't think of anything else that could cause me to have to set the timing to wide open at IGN? With the distributor set according to the book and by now I have done it 10 times it starts and sounds good, at any RPM but will not take ANY load at ALL.

When changing heads I noticed this motor has the intake valve on #1 hanging open a little. And I did not fix it and wish I had it to do over again. I would not think this would cause that timing issue. I can hear the open valve now causing a slight miss, but when the timing is set by the book, it is not that hanging valve on that 1 cylinder causing all the backfiring, I don't think. When I say no power and backfiring, it blows gas all over the engine compartment and sounds like it is running on 1 cylinder, but it cleans up completely at "wide open at IGN" and is strong and the only think I can here then is that open valve, and it is very slight.

When I had the head off, I checked the timing mark in the window and the TDC is lined up with #1 and #4 being TDC.

But this block (a post war Willys) is a placeholder for an original block I found here on G503 that was only 2 digits off from my frame number. I also have the motor pool exchange VEP block that came with my jeep that I am going to restore as well. I plan on going through the close to matching number Ford foundry block this fall and winter and install it in my GPW. I hated to do all this work and then have to pull the motor in a few months, but I did not have enough time to properly restore the matching block and get it going for the summer.

I am better at restoring cosmetics than being a machinist that is why the hanging valve eluded me when I replaced all the seals and gaskets on it originally and the oil pump gear is not set according to the book. I know all this now and when I rebuild my GPW blocks those items will be right.

Mark