Timing Issue

1959 - 1978, M151, M151A1, M151A2, Technical questions and discussions, regarding anything related to the M151.
CaptB
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Timing Issue

Post by CaptB » Sat Mar 20, 2021 3:19 am

Hi guys, looking for some help. After many months I now have a chance to work on the mutt again. When I tried to check the timing I could not get the timing marks to line up under the timing light. Pushed the distributer as far towards the firewall as possible but still not enough. It was suggested to me that the oilpump may not have been reinstalled correctly (previous owner) and that I would need to pull the engine and check. Before going down this road I have pulled off the timing gear cover and checked the alignment, removed the distributer and checked alignment and to me it looks ok. The dots on the crankshaft gear and the camshaft gear line up, the slot on the oilpump drive is parallel with the block and the little notch is facing the front of the engine, and when I refit the distributer the rotor arm is facing no 1 plug lead position. Any suggestions what I do next.


Rickf
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Re: Timing Issue

Post by Rickf » Sat Mar 20, 2021 7:13 am

Check under the points/electronic ignition plate to see if the weights are gummed up and stuck. I can't picture the timing being that far off and it starting and running. Firing order in the correct order and in the correct holes on the distributor?
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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muttguru
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Re: Timing Issue

Post by muttguru » Sat Mar 20, 2021 1:40 pm

It is possible to have the distributor mis-aligned for two reasons.

The first and easiest one to correct is when the intermediate distributor shaft (a short extension of the drive bar) is placed in the engine 180 degrees wrong. What happens then, is that the engine will not fire, because everything is 180 degrees out. So amateur mechanics swap around the ignition leads in the distributor cap to compensate for the 180 degrees. What SHOULD happen is that the distributor is removed and then the intermediate shaft is withdrawn and re-installed with a 180 degrees rotation.

Much more difficult to correct is when someone has removed the oil-pump, which also mates with the distributor drive. When the oil pump is removed, it must be re-installed exactly as per the TM. If the Manual is not followed, then the oil-pump can be inserted in one of several positions. This affects the location of the distributor, and subsequently, the rotor arm....it points at the wrong angle at TDC.
This misalignment can usually be compensated for by rotating the distributor until the rotor arm aligns with one of the distributor cap segments. This is then selected as No.1 spark-plug segment and the other three leads are connected accordingly.
But it doesn't always work out as fortunately as this. Sometimes, the location of the oil-pump means that there is little or no adjustment for the distributor, because the shape of the distributor prevents further adjustment - it catches on the engine block. It sounds like this is your problem.

To confirm that this IS the problem, take out the distributor and the intermediate distributor shaft. Turn the engine crankshaft until the piston is at TDC of the COMPRESSION STROKE. Now look down the distributor mounting hole using a torch if needed, and note the position of the oil-pump drive tang (raised notch). It should match the angle shown in the TM. If it isn't in the right position, then you will need to remove the engine sump-pan and re-locate the oil-pump.
You say that you have checked the oil=pump alignment and the crankshaft-camshaft alignment and I assume you did these checks with the piston in cylinder no.1 on compression stroke? I know you've done these checks but just for old time's sakes, do the checks once more.

Make sure you have the distributor's intermediate shaft installed the right way round. It will install either correctly or 180 degrees out. If you then shift the spark plug wires to try to match the firing order, it then won't match how the TM shows the cable installation. If you don't think things through carefully, you'll end up with the cables in the wrong order, or 45, 90 or 135 degrees out-of sync.
First thing to start with is to turn the crankshaft pulley nut CLOCKWISE (as seen from the front) and make sure that both valves for no.1 cylinder (nearest the radiator) are closed (compression stroke).
Step 2 is to remove the distributor and double-check that the little arrow faces forward.
Step 3 is to remove the timing cover and ensure that the dots on the crank and camshaft line up together.
Step 4 is to check that the spark plug leads (at the distributor cap end) are installed exactly as shown in the TM.
Step 5 is to remove the distributor cap and turn the base of the distributor drive so that the rotor arm tip is exactly where the inner cap tower for the spark plug lead for No.1 cylinder is located.
Step 6 is to install the intermediate shaft into the distributor shaft and turn it until it engages with the oil pump drive.
So far, so good. Now check where the distributor drive tang is pointed. Does it match the intermediate shaft? Yes? You can re-install the distributor. If you have to rotate the distributor drive to get the distributor located in the intermediate shaft, then take out the shaft, rotate it 180 degrees and try re-installing the distributor again. It should now slot in easily. And if the rotor arm is still directly beneath the No.1 tower of the distributor cap, then the vehicle should start up and run sufficiently enough to fine-tune the timing.

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Always wanted - Details and pictures of M416 Trailer data plates & M151 data plates & body-tags for my research. Thanks!

CaptB
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Re: Timing Issue

Post by CaptB » Sun Mar 21, 2021 4:00 am

thanks for that, I have checked through everything again and it looks ok (see photos) as soon as my timing gear cover gasket arrives I will re assemble and try and set the timing with the strobe again Image

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Re: Timing Issue

Post by Rickf » Sun Mar 21, 2021 6:49 am

Another thought, The strobe you are using, is it a dial back timing light? Does it have a dial on the back so you can set the timing to the mark you want to see? If it does make sure it is set to zero since the marks on the cover are already set to the required 6 degrees BTDC. And are you running the timing light on 12 volts and not the 24 volts from the mutt? I don't think it would last long on 24 volts unless it is a 24 volt light.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

CaptB
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Re: Timing Issue

Post by CaptB » Sun Mar 21, 2021 7:31 am

thanks for that, I have checked through everything again and it looks ok (see photos) as soon as my timing gear cover gasket arrives I will re assemble and try and set the timing with the strobe again Image

CaptB
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Re: Timing Issue

Post by CaptB » Sun Mar 21, 2021 7:33 am

it was a 12volt strobe, with dial back. It was ages ago, hoping it was the dial back causing the wrong reading, will report back once gaskets arrive

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Re: Timing Issue

Post by markrdje » Sun Mar 21, 2021 9:46 am

I have used a ohm meter to set the timing, but that was on a points type distributor whereas on electronic type distributor I do believe that method wouldn't work.
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Gary Turman
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Re: Timing Issue

Post by Gary Turman » Sun Mar 28, 2021 4:58 am

My timing marks were way off after replacing components. I set my timing by a vacuum gauge. Simple and inexpensive.
1941 Dodge WC-7 Command Car
1942 Ford GPW
1968 M151-A1
1967 M416
1945 Gemco 1/4 ton trailer
US Army 1979-1984
Houston Police Officer 1984-2016 (Retired)

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Re: Timing Issue

Post by markrdje » Sun Mar 28, 2021 5:24 am

By way of getting the most vacuum with hose connected to a port on intake manifold?
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Rickf
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Re: Timing Issue

Post by Rickf » Sun Mar 28, 2021 5:32 am

Setting by vacuum will give you far too advanced timing.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

Gary Turman
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Re: Timing Issue

Post by Gary Turman » Mon Mar 29, 2021 3:08 pm

It worked great for me. The gauge even has marks to show proper timing. I hooked it up to the port at the rear, firewall side of the intake manifold.
1941 Dodge WC-7 Command Car
1942 Ford GPW
1968 M151-A1
1967 M416
1945 Gemco 1/4 ton trailer
US Army 1979-1984
Houston Police Officer 1984-2016 (Retired)

Rickf
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Re: Timing Issue

Post by Rickf » Mon Mar 29, 2021 5:01 pm

It will sound good at low rpm but at highway speed your timing will be far to advanced. You will certainly not be able to hear any preignition with road noise and gear noise. Your vehicle, your choice. As far as the gauge having marks to tell you the correct timing I simply do not see how that can work considering that different engines run different vacuum at the prescribed timing at idle. Plus bore and stroke can have a large affect on vacuum, as does compression ratio. o there is no way they can put settings on a vacuum gauge that will tell you where the timing is correct on every vehicle. The one thing I can assure is that when you set the timing on a 151 you will notice that if your timing is set to best idle (vacuum timing) and then you bring it back to the timing mark the idle will drop. You have to take into consideration that this engine has centrifugal timing advance so you do not want a ton of advance at idle.
I will say no more on the subject. I will just leave you with this info to think about.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

CaptB
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Re: Timing Issue

Post by CaptB » Tue Mar 30, 2021 9:51 am

Ok as promised here is the update. Gasket arrived and I proceeded to put everything back together, at this point I realised that there was no oil throwing washer fitted to the end of the crankshaft (before anyone comments, I took photos during the strip down and checked, it was never there). So, first off, engine was rebuilt by previous owner but never driven, I have done around 400 miles. I know it needs it otherwise they would not have fitted it in the first place. What damage could this cause, what is the part number, as I could not find it in the manual and does anybody know where I can get one. Ok sovas it was never fitted I proceeded with putting everything back together. Checked and adjusted the valve springs (cold), spark plug gaps, set distributor to two fingers and cranked her up. Started first time and ticked over no problem, adjusted tick over to 800 rpm using digital laser tachometer. Set timing with timing light at idle and checked that it advanced when revved. Then set mixture on carb. So far all good ( can only think that previous attempt failed due to, too high tick over speed and advance dial on strobe not all the way back). Engine idled no problem. But when I put the accelerator down I get a slight stumbled, and if I rev it really hard I get a back fire. What's my next sep guys

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Re: Timing Issue

Post by Rickf » Tue Mar 30, 2021 3:33 pm

A stumble on throttle apply is the accelerator pump not working right and the backfire depends on when it is happening. Does it backfire as it is revving up? Or does it backfire as it is coming back down? Going up is usually a lean condition and also could be caused by the accelerator pump and if coming down that can be, and usually is, caused by a leak in the exhaust. This will be close to the manifold. It is usually the gasket between the manifold and the exhaust pipe but sometimes it can be caused by a leaking exhaust manifold itself. Have you ever had the carb apart?
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone


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