can't get engine to start

aforests · Post by **aforests** » Mon May 09, 2016 9:02 am

I'm hoping for some advice and suggestions!

Background: I had this engine rebuilt about 25 years ago. I only ran it a couple times (12 volts), then it sat until now. I have put all the 24 volt components back on and have a new harness that is hooked up far enough to turn her over.

I had to find the correct carburetor last year and i put a kit in it. I also had to find the correct fuel pump. put a new kit in that as well.

I went through the generator, regulator and distributer. New wires, new plugs, new rotor, new condensor.

I have 24 volts at the coil and have spark.

I had a major brain fart last week and to make a long story short, i messed with the oil pump index and had to go back and try to put it back where it belongs. I spent a long time trying to get the index right. With a timing light at this point, it is flashing on the TDC mark and the rotor is pointing to #1 at TDC. The only questionable thing on timing at this point is I had to position the oil pump index to around 3 oclock so i could retard the distributer far enough to get the points to close. then advance just enough for points to open. I hope I am making sense?

Anyways, I know I am getting fuel to the carb and pistons but am thinking i have a problem at the carb now?

It cranks, but i can't get it to even want to begin to start.

Any suggestions at this point would be appreciated.

Are my wires hooked up correctly?

Post by **wesk** » Mon May 09, 2016 9:38 am

Let's start with the model engine you have. If it is an MB and still uses the timing chain instead of gears then your M38 distributor will be turning backwards forever!

The MB engine cam rotates the opposite of the M38 cam and it is the helical gear set on the cam that drives the pump and the pump then drives the distributor. The MB oil pump's helical driven gears are the opposite of the M38's pump. If this is true then your choices narrow quickly!

With a timing light at this point, it is flashing on the TDC mark

I will assume the positions your refer to are with the engine cranking and NOT RUNNING. Your timing light is telling you that your points are starting to open at TDC instead of 5 Deg BTDC. This is where you loosen the distributor hold down bolt and rotate the distributor to get it at 5 Deg BTDC. This all baffles me because I don't even take the timing light out of the box until I have the engine running. The timing light is used for making the FINAL FINE adjustment.

The reason the two o'clock position is specified for the oil pump shaft is because it assures you will have sufficient adjusting room for the distributor.
It is always best to start at the beginning with a correctly set oil pump. Many people will argue that the distributor can be made to function with the oil pump anywhere but those people also cruise in the left lane on the freeway at 5 below the speed limit.

Set the pump correctly first!

It appears your wires are indexed correctly for the M38.

Then follow the initial static timing directions using a test lamp or ohmeter to tell when the points just start to open or just use the simple small piece of paper to tell when the points just start to open.

aforests · Post by **aforests** » Mon May 09, 2016 10:44 am

This is a willys pickup truck engine, not an MB.

The timing light position is while cranking. This was just to confirm that the timing was close and not way off!

When I set the oil pump shaft at 2 o'clock, the only way I can get the points to close is to advance the distrubuter all they way. At that point once I get the paper between the point, the only way to get them to open enough to slide the paper out is to retard it.

Post by **wesk** » Mon May 09, 2016 11:05 am

When I set the oil pump shaft at 2 o'clock, the only way I can get the points to close is to advance the distrubuter all they way. At that point once I get the paper between the point, the only way to get them to open enough to slide the paper out is to retard it.

This is not making any sense to me. If the pump is set correctly at 2 o'clock, the # 1 piston is TDC ON COMPRESSION, and the distributor is installed with it's tang engaging the pump correctly the distributor will be sitting in the exact correct position to allow proper static timing. This has worked well for me since my first jeep in 1971. This will have you at this point:

Only a small movement in either direction keeping the rotor pointing to # 1 wire is needed to get the points open. Insert the paper and retard until the points close. Then advance until the paper slips and lock it down.

When you rebuilt the distributor did you separate the cam from the rotor shaft?

Hawkshadow · Post by **Hawkshadow** » Mon May 09, 2016 11:34 am

Will it make any coughs or farts at all with a shot of quick start in the carb? That would just help to let you know that you're getting spark at the [ballpark] right time.

Also, have you visually confirmed that the rotor is turning as the engine is cranked?

oilleaker1 · Post by **oilleaker1** » Mon May 09, 2016 12:50 pm

If you have the timing gears and not the chain, you have the correct firing order on the wires. Pull # 1 and turn the engine over until you have compression pushing your finger out of the # 1 hole. When it stops, you are at TDC. Take the cap off and see where the rotor is pointing. Start with the # 1 wire here. Then 1342. To static time the points, first slightly move your crank until it is 5 degrees BTDC. Then after gapping your points to .020, retard the distributor and then bring it back advancing until the points just begin to open. If you have the pump indexed closely, you should be in the center of the adjustment arc on the distributor plate. This should be very close and the engine should start if you have spark and fuel. I hope you primed the pump, and gallery, and spun it over until you had oil pressure first. You want oil at the new bearings immediately. John

oilleaker1 · Post by **oilleaker1** » Mon May 09, 2016 12:54 pm

I forgot to mention that you should tighten the adjustent bolt on the arc until you can just move the distributor. The engine gets hot fast, and since it's a pain to get at that bolt, you can easily burn your hand. Don't ask me how I know this. Too bad you are at the other end of the world from me in SD. John

aforests · Post by **aforests** » Mon May 16, 2016 9:06 pm

Finally got the oil pump index set right! Made a huge mistake not taking my wedding ring off while adjusting the distributer though... Ended up with a 3rd degree burn on top of my ring finger and destroyed wedding ring after hitting it on the starter post. Just a reminder to everyone to take your ring off! Should heal according to surgeon without a skin graft.
Anyways I need some further advice. Jeep starts good and idles good for about 1 minute then gets doggy and dies out. Advice?

Post by **wesk** » Mon May 16, 2016 10:31 pm

Check the fuel delivery. Often we overlook the fording valve's positions and the fuel tank vent valve position in the cap. Result: runs ok for a short while and quits. Then sit for a short while and starts right back up and repeats the cycle.

aforests · Post by **aforests** » Thu May 19, 2016 7:34 am

First problem I found and fixed was the centrifugal advance on the distributor was frozen.

This is my fuel cap. Correct me if I'm wrong, but this appears to be a non-vented cap?

Post by **wesk** » Thu May 19, 2016 7:41 am

If you suspect the cap just run without it.

The stuck centrifugal advance is a common issue, easily detectable and is usually caught early on by folks familiar with old distributor maintenance.

4x4M38 · Post by **4x4M38** » Thu May 19, 2016 7:56 am

Wes,
Please correct me if I'm wrong but I think all older fuel caps have
vents except the ones the military vehicles intended to use for fording.
In that cap there is a valve one turns on the bottom to open or close
the vent.

The cap above has a small hole you can see that should vent
the cap to atmosphere.

Modern caps are not vented to reduce atmospheric emissions,
something builders in the 50's had no interest in at the time.

Without the complete fording kit and equipment installed and
functioning, closing the cap vent can cause increased vacuum
on the fuel system upstream of the fuel pump, resulting in loss
of fuel to the pump.

Does that sound right?

Post by **wesk** » Thu May 19, 2016 8:25 am

Military used three caps that all fit on your big mouth tank inlet.

Vented
Un-vented
Selectable vented/un-vented

The hole in that photo is for the rivet that attached the chain. To be able to vent that cap needs a hole in the outer skin. In other words a path past the seal is needed.

4x4M38 · Post by **4x4M38** » Thu May 19, 2016 10:31 am

Ok, now I'm confused.

His chain is attached in the same place as my vented/unvented cap, i.e., near the center. You can see the chain in the photo.

My vented/unvented cap does not have a hole in the outer skin, on top or the sides. I assumed there was a path somewhere for the venting to occur but I do not see it. I assumed it was somewhere between the outer skin and the inner skin.

Maybe we should open another thread on gas caps?

Post by **wesk** » Thu May 19, 2016 8:11 pm

The only way air can escape through the hole you see is if there is a hole in the outer skin of the cap. The picture does not show the outer skin. I am not so sure that chain is attached to the cap. It could be just lying there. Anyway as I said earlier the military used three caps. The unvented cap was used on tanks that were vented other ways and on tanks that were required to be pressurized. It is not an important issue here and as you said could have been a chat box subject for those interested in beating gas caps around.