Help! Completely stumped on fuel or ignition problem

Hey everybody. I'm at my wits end on my 1968 M715. Here's the (long) history.

About a year ago I went out to the shed to fire up the M715 (works on our small ranch here) and I found the ignition switch on. Needless to say, she wouldn't fire, so a new coil (one of the chrome replacements from Vintage Powerwagon) and points and a condenser later, she would fire and run. But, I could never get her to rev up again very well. The timing was right where it was before (it wouldn't start when hot for awhile but it was because the timing was too retarded, fixing that fixed the problem). I have rechecked point gap.

When I parked it about a week before she was running perfect (other than a rear main that leaks like a sieve).

Sometimes she would get me part way around the section running OK then I had to come home on an idle, barely able to get above idle.

So, I noticed that the clear fuel filter between the pump and the carburetor was only partly full (as in about 1/8 inch in the bottom). This started a fuel system wild goose chase which has ended up with the tank out of the truck.

I took off the old pump and could hook up a hose into a gas tank and it would shoot gas 10 feet working it by hand, but when I put it back on the engine it would not keep the filter full at idle even when I was running from a hose into a gas can on the fender. So I figured, has to be the pump right, even though the manual pump test would not support that.

So, an $80.00 new pump later, I got it to fill the filter at idle, but she still wouldn't rev up. My brother recounted how he had a vehicle fall flat like that once and found a broken wire on the distributor. Sure 'nough, when I put in the new coil, I must have crimped the energizing wire from the ignition switch to the coil and it was grounding out I think. Some shrink wrap (2 layers) and a little coil bracket modification and we are back good. But doesn't seem to make a difference.

So since it was filling the filter at idle, I get brave and hooked the fuel pump back up to the stock fuel lines (hooked to a hose to the stock tank sitting on some boards on the floor) and it would not pull fuel. Just a trickle to keep the engine idling. So, I puit a clear filter between the steel line on the frame and the steel line on the engine. It wont' fill that filter either. I did notice some air bubbles in the fuel trickling into the filter between the engine and the steel line to the tank, and found that the short hose between the two steel lines on the tank had a hole in it and fixed that. So now no bubbles, just a trickle though.

Right now (as of 10 minutes ago) she is idling great and smooth. But open the throttle even a little and she falls flat on her face (I have tried two carburetors, each with a new kit, both act the same). Starts with just a touch of the starter. The accelerator pump is pumping fuel, and when I pull the carburetor (getting good at that) the bowl is full, even though the filter won't fill. This pump will shoot fuel a long ways pulling out of the tank on the fender (taking it off and operating it manually) but it won't fill the filter more than an 1/8 of an inch or so on the bottom of the filter at idle. If I open the throttle, with the choke at any position, she just falls flat and will die if I hold it there very long. I have double checked that the pump is properly engaged to the pushrod off the cam. I have even pulled the valve cover to make sure everything is still hitting there, but I haven't watched it run with the valve cover off.

I am about ready to give up and just repower it, but I have redone the seats and just put a new top on it (about 8800 miles). We are ready to paint this summer and it is 100% rust free, a really beautiful old truck. The 24 volt system still works well and i was hoping for a stock, restored truck to just drive around and show off, later I'll find one to hop up. I have brand new military tires on it and it will be really sweet if I can just get it to run again!

Is this just a junk coil?
Is is supposed to fill the filter at idle?

Any help appreciated.

Thanks!

KansasM715

Hey Kansas, I'm going to watch your thread closely as I am having the same issue. Except that my fuel filters remain full. But it runs rough and won't accelerate either. If I figure anything out with mine ill let you know!

The fuel in the bowl of the carb should be enough to keep the truck running for a bit. If your truck idles good, but drops off at acceleration, then you still have something wrong with the carb methinks. Acceleration won't empty the bowl that fast if you think the pump can't keep up.

What rebuild kits are you using? 45 year old NOS kits or new manufacture. Big difference there.

Scott

First thought...the filter like "sock" on the end of the fuel tanks pickup tube...these tend to get nasty over the years and restrict or even, when they get bad enough, cut off fuel flow.

One way to confront that is to blow strong compressed air into the fuel line thus blowing the sock off the pickup tube or blowing it open enough to let fuel flow again. Then put a fuel filter between the tank and the pump...the see through kind are my choice for that task.

Second thought...there have been issues with the points being installed incorrectly at times...there is a leaf spring arm that puts tension on the points to keep them closed...idle is ok if the leaf spring is installed wrong, but as rpm's rise, the points wont stay closed and there is no spark.

Since you do have limited fuel flow, I would work on the fuel end first...the points thing, just something to check while you are in there...


Whatever turns out to be the issue, please let us know...this is how we learn about new gotchas too!!

After all you have already done, I would swap another coil in.

I have never seen a "full" fuel filter. It is not unusual for them to only be partially filled. I have been down that chrome coil path as well. Started OK. Drive for a while. Shut off, then try to start. Starter spins the engine just fine. But it just will not fire off.

Installed a used coil... No problem and that is with the truck living in Florida now. Just my experience...

Thanks everyone. I will recheck the points and go back to the online manual to make sure they are correct. I actually bought two new sets, so will swap in the other just for good measure. I just bolted the spring on the points to the tab where the wires from the condenser and the coil goes.

Questions:

How do I check if the coil is good?

Will my old dwell meter I used to use on my 64 nova with a 283 work on this engine? Seeing the dwell change as I rev it up would tell me a lot

How many volts actually goes to the coil on these? I know on 12 v points engines (all experience was small block chevys and old straight sixes) we had a resistor that cut the 12 v down to around 6-7 volts to the coil, correct?

I took pictures of how things are set up so will see if I can post those.

Thanks

KansasM715

24v to the coil.

I had a problem with similar symptoms. After fighting with the fuel system (I could keep it running for a while by pouring gas down the throat of the carb so I was convinced it was fuel), an older guy I know told me to change the condenser. I had put a new one on when I rebuilt the distributor not long before, and already checked for spark, but I was at the end of my rope and gave it a shot. It fired right up and ran perfect with what was probably the original 40 year old condenser. Hope you figure it out.

So, a little history on this M715. I bought it on the GSA auction from the Kansas Forestry Service (yes, we have a forestry service in Kansas). They are the ones that supply the used military vehicles to the Kansas Fire Depts. This one came out of the Army in 1975 and spent until about 2008 in the Astoria, KS Fire Dept as a range truck. Here it is being pulled out of the Kansas Forestry Dept. in Manhattan, KS on 4-22-2011. (Slashed front tires and not running).

http://i1333.photobucket.com/albums/...psea897b18.jpg

And here it is in the driveway at home getting ready to be drug off to a new home. My little tractor could lift the front, but I had to go get my wife to hook up to the back of the tractor to drag it off since all the weight was on the front. She used my 1984 1 ton 4x4 chevy with a bigblock and it came right off.

http://i1333.photobucket.com/albums/...ps1ecd559e.jpg

Put in a couple of used batteries around the place, fired it up, replaced all of the wheel cylinders, bled it out, and swapped on some new military treads. The top was trashed so pulled it off. Took off the front and rear platforms. Here she is doing a little work hauling brome hay to the shed with my sons working up a sweat.

http://i1333.photobucket.com/albums/...ps33e22df8.jpg

Here she is with the new hood, repro bumper (from vintage powerwagons) and a new top. That creature to the side is a 1940 something Clarke Trucktractor aircraft tug that was used to drag B29s around at the bomber training base in Greatbend, KS. My Dad had that in the shelterbelt, so it is one of the next projects in line. Number one son hit an owl between home and his girlfriends place in the M715 so it has a new windshield. Luckily the windshield was up.

http://i1333.photobucket.com/albums/...ps69d4ea81.jpg

Here's a picture of how I have things installed in the distributor.

http://i1333.photobucket.com/albums/...pse921bf32.jpg

I'll go mess around with the points again.

Does it have a ballast resistor under the coil? (#4 in the diagram). Now that I have replaced the coil in my ignitor with a used coil (and it works fine) I wonder if my used coil is the newer type that has the built-in ballast. Just more confusion unfortunately! Maybe someone knows if the early and late coils are different lengths. Hopefully, the later coil with a built-in ballast will be too long? I do know that the NOS ignitor that I have has no ballast. I will check that out today.

http://i1067.photobucket.com/albums/...psfcbe4602.jpg

All newer coils have the ballast resistor built in and are taller than the original coils that had a separate ballast resistor. The only ballast resistor that I have seen was about 3/8" thick.

Quote:

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Originally Posted by kwai

After all you have already done, I would swap another coil in.

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Many of us have had problems with the China chrome coils. Either die soon after installing, quit when hot or won't work at speed.

Quote:

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Originally Posted by kwai

All newer coils have the ballast resistor built in and are taller than the original coils that had a separate ballast resistor. The only ballast resistor that I have seen was about 3/8" thick.

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OK. Today, I got the NOS ignitor down from the shelf as promised. The coil inside is ~ 3 inches tall. The "hole" in the ignitor housing is ~ 3 inches deep. So, no way that a coil with a built in ballast will fit into the ignitor with the resistor under it.

Now I will have to check the ignitor in my truck. I won't be satisfied until I am sure the right coil is in there. Too much voltage will cause issues as well. I wonder if the Chinese coils would be OK with a ballast resistor? (I still don't want another one!!!)

Quote:

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Originally Posted by rboltz

Many of us have had problems with the China chrome coils. Either die soon after installing, quit when hot or won't work at speed.

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What he said. I have been down that exact road myself...

I have not noticed one and it appears the energizing wire from the ignition just comes straight in the side to the coil. I ordered the distributor kit (cap,rotor, points, and condenser) and a new coil from Boyce this morning. I plan to pull the distributor to make sure I get the point gap perfect and check out the bushings.

Thanks

Quote:

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Originally Posted by KansasM715

I have not noticed one and it appears the energizing wire from the ignition just comes straight in the side to the coil. I ordered the distributor kit (cap,rotor, points, and condenser) and a new coil from Boyce this morning. I plan to pull the distributor to make sure I get the point gap perfect and check out the bushings.

Thanks

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When you say a new coil, do you know if it is an NOS military coil of a new production coil? Seems that we are having problems with the chrome plated coils that are most likely from China.

running a ballast resistor (ignitor) with a coil already having one internal will be more of a problem than running a coil without one and having full voltage, it would run fine, and than begin to overheat eventually. I think you are going tosolve the problem with the parts, I would change the points and condensor then the coil to islolate what fixed it. keep us posted

Duane

Quote:

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Originally Posted by Duane

running a ballast resistor (ignitor) with a coil already having one internal will be more of a problem than running a coil without one and having full voltage, it would run fine, and than begin to overheat eventually. I think you are going tosolve the problem with the parts, I would change the points and condensor then the coil to islolate what fixed it. keep us posted

Duane

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This is true. However, there is no room inside of the ignitor for a ballast resistor in the bottom and a coil with a built in ballast resistor because the new coil (with built in resistor) completely fills the housing. So, it might not be possible to do that. You are right, "new" condensers can be bad. Most were replaced over the years just as a matter of course.

And as Duane says, "Keep us posted".

Well, some of the advice in this thread was right on for the problem, and all the other advice involved really good things to check out. I have described all I did to give you the investigative process and then what finally fixed it.

First, I pulled the ignitor to work on it on the bench. I found that while I thought I had the points full open when I set the gap in the truck, I didn't. My actual gap was .030 instead of .020, so I was able to get the points actually full open when I put had it out on the bench. And for good measure, I put in a new china coil (I dug out the original one, and it was also a China replacement chrome coil, the one in it I originally replaced was a dull finish, not black, but not chrome).

I fired it up and it ran good for just about 30 seconds and then returned to it's former ways.

Sooo, I then pulled the fuel line at the carburetor and stuck it in a pop bottle with the inlet to the pump plumbed into a gas can bungecorded down on the inner fender. It filled half of the 20 oz pop bottle in about 15 seconds of cranking, so I put the line back on the carb and it maintained it a half full, but still wouldnt' rap up very good.

Back out came the ignitor and I then closely examined the points, they were fried from only about 20 minutes of running. This indicates condenser problems as I understand it, because the purpose of a condenser is to take the voltage spike when the points initially open to prevent arcing across the points. I had put brand new points and condenser in along with the coil when I fried everything leaving the switch on. I also replaced the rotor and cap. I replaced everything, got the points adjusted, put it back in where I had it timed before, and she fired up and ran good. I could rap it right up.

So, evidently it was the condenser even though I put it in brand new with everything else. I also had the points off because they weren't all the way open when I set them.

Now, I did mess one thing up. when replacing everything I pulled the wires off of the rotor cover so I could make sure the new cap and rotor fit just right. After I put everything on I noticed that the threads for a couple of the plug wire attaching points on the ignitor cover were bent, so I used a needlenose to straighten them out. I heard a crack on one and I had cracked the nipple inside on the cap, but the wire fit so I went ahead and installed and fired it up. I now have a steady miss at speed and a skipping idle so I think that cylinder is now shorting across within the cap, so will switch back to the old cap and see if that fixes it.

Having the fuel tank out was not really a waste of time. It was starting to rust on top so I wire brushed it and used some undercoating to get that stopped. I also really cleaned up my ground for my fuel gauge, which always read full and inspected the inside of the tank. I put in fuel and poured it out and saw no goobers to indicate a crud problem. I will get it back in and see how things go.

Quote:

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Originally Posted by KansasM715

Well, some of the advice in this thread was right on for the problem...

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Back out came the ignitor and I then closely examined the points, they were fried from only about 20 minutes of running. This indicates condenser problems as I understand it, because the purpose of a condenser is to take the voltage spike when the points initially open to prevent arcing across the points.

...

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That is correct. So, if you pull out points from any Kettering type of ignition system (breaker points and condenser) and the points are in good condition and not a lot of metal transfer from one contact to the other, the condenser is actually in good condition. Most likely, more good ones hit the scrap bucket than ones that are bad.

So, if you are doing a tune up and find the points in relatively good condition, it would be advisable to save that condenser. It is most likely good.


BTW the original coil was a dull silver kinda color. If you still have that dull one, it could be an original military type. Might be much better than those chrome China coils. I mentioned in another thread that I checked both of my ignitors. The NOS one that I have has no ballast. And, the coil is three inches long from the mounting tang to the bottom. The well in the ignitor is three inches deep. So, a newer coil with a built in ballast will not fit if you try to put a ballast in the well. Maybe these Chinese coils are made for a ballast??? I threw mine away a few years ago so I can't check.

Just a thought...

Thanks. The one I just got from Boyce is a chrome one, but the one I got about a year ago from Vintage Power Wagon in Iowa was the dull silver color, I have no evidence it was a problem in this case, so will be sure to swap it back in at the first sign of trouble

Quote:

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Originally Posted by KansasM715

Thanks. The one I just got from Boyce is a chrome one, but the one I got about a year ago from Vintage Power Wagon in Iowa was the dull silver color, I have no evidence it was a problem in this case, so will be sure to swap it back in at the first sign of trouble

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I would bet that the dull silver on from VPW was a military coil and not a Chinese knock-off. I know that "italylovers" on eBay sells the dull silver coil from time to time. They have items from VPW on consignment (or whatever you want to call it) for sale on "the bay". Buyers know that the dull silver is the right one and pay good money for them. I have seen them go for sale there from time to time. The one in my truck was chrome. It was tossed into the trash when I got a used one that was dull silver. It just works...

BTW, check the length of the coils. If they are three inches long from the bottom of the mounting flange to the end of the coil, they may have the ballast built into the coil. Reason is that the well in the ignitor is three inches deep and the ballast would make the coil stick up too high... I think.

Maybe others have been able to compare them. I don't know if I have ever seen the ballast (#4 in the illustration above).