Tune Up Problem?????

[Tim Powell]

Next Question Crew.
We've had our M37 tuned up twice in as many years.
Seems like every time I get her out of the shop it has a "miss" in the motor at an idle?
Just had new plugs, distributor and timing set last fall.
Got her out yesterday and it's was missing so bad I didn't want to drive it.
I keep fresh fuel and fuel additives in the tank. It sits in the shop not outside.
It doesn't get driven much but this seems a bit extreme for tune up and repairs??
Any ideas?? VPW suggested I check the intake manifold bolts. All tight. Checked the compression, it's ok. I'm lost.

[milstencil]

Tim,
Vacuum leak at the manifold. Check with ether.
A little spray and if it picks up, you found the leak.
Rick
PS- be care full, you can put somebody to sleep if you use
too much. Ask me how I know!!!!

[Tim Powell]

I'll give that a try. Starting to get a bit frustrated.
Been throwing money at the problem but my Lori is running out of money!
Darn Trophy Wife.

Hot Custom Genuine Trophy Wife & Accessories

07-04-13 Lori & Aussie DSCF1698 (250 x 188).jpg (13.29 KiB) Viewed 2633 times

[T. Highway]

Hi Tim,

I would look at the distributor cap and rotor.

Bert

[Tim Powell]

Hey Bert.
Had 3 (three) new distributer caps, rotors and points in the last 3 years????????????
I think there is an electrical problem, but I also agree it could be a vacuum leak.
I just can't pin-point the problem.
It never fails to run, it just don't run right.
Going back to my original post, I'm sure it's not a fuel problem.
Will check for vacuum leaks and check the cap and rotor again.
Could it be drawing moisture from sitting?? It always sits in the shop, seldom below 40 degrees.
The last time we had it tuned up by a professional shop. Didn't seem to last any longer than when I work on it??
Not complaining, just frustrated. Gotta' run right when we haul "Troops" in parades. I own them that much.
Hoorah!

[T. Highway]

Tim,

I understand what you are telling me. Take time and do a step by step inspection of all the components yourself. I highly recommend pulling the whole distributor out so that you can easily work on it.

I was helping a fellow club member with the same issue on his M37 last spring. He stores his M37 in an unheated airplane hanger.

The problem was moisture from the engine block sweating in the temperature changes. The waterproof distributor cover seal was flattened out to the point that it wasn't a seal anymore. When we pulled the distributor to do a bench inspection and found a comedy of errors.

1.) The bracket that holds the condenser to the points backing plate was incorrect and the condenser was rubbing on the lobe for the points.
2.) The internal distributor cap had a carbon trail on it that was causing issues.
3.) The lead to the points had been pinched severely when the last person installed the outer distributor cover.
4.) One of the point base retainer tabs was mutilated and needed to be replaced.

We ended up doing the following repairs.
1.) Installed new condenser and made sure the new bracket allowed for clearance between the condenser and timing lobe. New rotor also installed.
2.) Bought new internal cap only to find out that the Chinese manufacturer had the wrong sized holes for mounting and the cap. Vendor said to drill it out. I told them that wasn't acceptable and wanted money refunded. Got the correct cap from second vendor and installed.
3.) Replaced lead with slightly longer new wire (high strand count) and new termination.
4.) Dug through my spare parts and found two unmolested slotted screws and point base locking tabs.

I couldn't talk him into installing a Pertronixs electronic ignition. I did end up smearing a bit of Di-electric grease around the base of the waterproof outer cover when reinstalling the cover.
I did talk to him a couple of weeks ago and he said that the truck fired right up this year with no issues.

Bert

[Tim Powell]

Bert, Thank You My Friend.
I will follow your lead. About that electronic ignition. I was wondering about that.
Although I'm trying to be close to original, I would prefer reliable anytime.
I really think a tune-up should last longer than a year.

[DJ]

Go to the manual and follow the troubleshooting guide step by step. An electronic ignition won't cure the problem if it is elsewhere.

[Tim Powell]

Hello "DJ".
I will purchase an owners manual. Should have done that a long time ago.
Thank-you.

[DJ]

You can get them on cd for a very reasonable price. Print the pages you need and take them right to the shop and " git r dun ".

[just me]

90% of the 'tune' issues with old vehicles is fuel related. Today's fuel turns to little crystals when it sits and plugs the tiny passages in the carb. Also, there are less btu's per lb in the new fuel due to oxygenates. This means a lean burn with stock jetting. Upping the jets a size and adjusting the metering along with driving weekly really help to keep the tune.

[Tim Powell]

I will order a manual either paper or CD, been going to do that, been putting it off.
No more excuses.
As far as the fuel!
I can guarantee it's not my fuel. 40 years of over the road trucking has taught me one thing, ya gotta' have good fuel.
I use good gas with no ethanol. I use Lucas Fuel Conditioner. I also add Marvel Mystery Oil additive.
The fuel tank was sent to Gas Tank Renew and has the bladder lining. New fuel pump and lines.
Carburetor was overhauled by a professional shop. All they do is work on M/V's.
It's either vacuum or ignition. (or both?)
Last but not least maybe I'm too damn picky? It is a year older than me. Sometimes I don't run the best.

[Elwood]

I will order a manual either paper or CD, been going to do that, been putting it off.

Tim, I have both paper and CD versions of the military manuals for the G-741 trucks, and I rarely use the CD ones. Having both, and being able to compare them, revealed that the scanning process for the CD version (at least the ones I've seen) garbled or omitted a fair amount of information. Text such as fractions was often either skipped or incorrectly interpreted by the scanning software. I wouldn't buy the CD versions again.

The softbound paper copies are good, but the bindings are weak, especially if you use them in the shop a lot. The best ones I've found are sold by Canham & Sons Books (http://www.themanualguys.com): he prints them on standard 8-1/2 x 11 paper, and then will either three-hole punch or comb bind them. Both work well for use out in the shop.

[Tim Powell]

Paper it is.
Looks more original anyway!
Thanks Elwood.

[m-37Bruce]

Tim,

I understand what you are telling me. Take time and do a step by step inspection of all the components yourself. I highly recommend pulling the whole distributor out so that you can easily work on it.

I was helping a fellow club member with the same issue on his M37 last spring. He stores his M37 in an unheated airplane hanger.

The problem was moisture from the engine block sweating in the temperature changes. The waterproof distributor cover seal was flattened out to the point that it wasn't a seal anymore. When we pulled the distributor to do a bench inspection and found a comedy of errors.

1.) The bracket that holds the condenser to the points backing plate was incorrect and the condenser was rubbing on the lobe for the points.
2.) The internal distributor cap had a carbon trail on it that was causing issues.
3.) The lead to the points had been pinched severely when the last person installed the outer distributor cover.
4.) One of the point base retainer tabs was mutilated and needed to be replaced.

We ended up doing the following repairs.
1.) Installed new condenser and made sure the new bracket allowed for clearance between the condenser and timing lobe. New rotor also installed.
2.) Bought new internal cap only to find out that the Chinese manufacturer had the wrong sized holes for mounting and the cap. Vendor said to drill it out. I told them that wasn't acceptable and wanted money refunded. Got the correct cap from second vendor and installed.
3.) Replaced lead with slightly longer new wire (high strand count) and new termination.
4.) Dug through my spare parts and found two unmolested slotted screws and point base locking tabs.

I couldn't talk him into installing a Pertronixs electronic ignition. I did end up smearing a bit of Di-electric grease around the base of the waterproof outer cover when reinstalling the cover.
I did talk to him a couple of weeks ago and he said that the truck fired right up this year with no issues.

Bert

Morning Bert, What was the part # /model # for your buddy's Pertronix Ignition, I have looked around, but thought the offerings were a bit confusing, I need the 12 volt version.
Thanks,