M135 spit'n and sputter'n

[Greensteel37]

My buddy has a nice M135 which, for nearly the last year, has given him fits. He's replace/adjusted the points, removed, cleaned and timed the distributor, checked the plugs and wires, cleaned and reworked the carb twice...and it will start (most of the time) and even run for a bit but quickly begins to sputter and miss.

He has replaced the fuel filters, checked the tank for trash and tested the non-original fuel pump. He tested the pressure regulator on the fuel line also.

Yesterday, we decide to pull the plugs and do a compression test. We had two at 100psi, one at 75 and two which would make the needle jump to 100 but then dropped back to zero. We tested the guage and it's working properly.

Is this sticking valves??? It seems the only explanation. Do you guys think we can just pull the valve cover and give it a good cleaning or is this a rebuilding the head sort of situation?

(In case some of you are counting, yes I only listed five cylinders above as he has yet to get #4's spark plug to come out.

 

[Barrman]

I would suggest draining the fuel tank, putting in new fuel to start with. If it runs and then once warm begins to go bad. I think coil. My Gasser M35 did this a few years ago. Purred like a kitten and roared like a lion until I got more than 2 miles from home. Then it would sputter, die and not start for about 20 minutes. Then just fine until I actually went somewhere.

Pull the coil and shake it a little. If you hear oil sloshing around, it is bad. Oil leaking or evidence of oil leaking also means it is shot. Mine tested just fine by the way.

 

[YkDave]

not sure what the specs are supposed to be for these old pigs, but the compression does seem pretty low...

Generally i like to see ~120psi min and ~10% variance between cylinders. but then again, these old pigs could be much more tolerable.

I agree that it could be an ignition issue. like mentioned, typically when a coil is failing you do not see the symptoms until the coil warms up, then all **** breaks loose.

 

[n1bnc]

It seems everything else has been looked at... I had an AMC that missed behaved weird like this too.

 

[hippiedude]

I dom1t like the compression test #`s ...... I think you got bigger issues ....... You could try a new coil but I think you need to dig deeper ........ Make sure your fuel pressuer is less than 5lbs. ..... How much time is on the engine ??? .......Tim

 

[woodywood]

OLD TRICK!when its running hold a dollar bill at the end of the exhaust pipe if it tries to suck it in its a valve issue!

 

[woodywood]

 

[YkDave]

I dom1t like the compression test #`s ...... I think you got bigger issues ....... You could try a new coil but I think you need to dig deeper ........ Make sure your fuel pressuer is less than 5lbs. ..... How much time is on the engine ??? .......Tim

True enough, but what i have found is that a low compression issue tends to smoothen out a bit after it has been run and warmed up, not get worse. (compression rises on a warm engine)

But still, those compression test #'s sucked badly...

 

[butch atkins]

could be a vaccum leak,was diaphragm in governor checked/replaced,there are couple of rubber hoses between carb /dist/governor,pg 118 TM 9-8024,30 -40 psi is not time to repair engine ,do manifold vaccum test BY THE BOOK before doing anything else,READ EVERYTHING BEFORE DOING ANYTHING,this simple test will tell you if it is a valve or head gasket problem,get manual read the pgs i have listed,good luck with your project

 

[butch atkins]

OOPS my bad ,pg 188 ,COMPRESION AND VACCUM TESTS,TM 9-8024

 

[Greensteel37]

He's replaced the coil and been through the govenor. I'm not sure of the mileage but as far as I know, it's never been rebuilt. He's had it at least 10 years and he's put maybe 1000 miles on it, mostly for parades and such.

Here's the obligatory photo taken last year when it was running:


http://apollosaturn.smugmug.com/Mil...Olive-2009-Show/DSC4536/608672447_r8ysP-L.jpg

Me and the board are not agreeing on attaching photos....

 

[nattieleather]

Nice looking truck!

 

[Barrman]

Very nice looking truck. Follow the advice a bunch of us should have mentioned earier. Read the manual and follow the steps.

Something else to keep in mind since it seems he has been throwing lots of money at this thing. Is he getting new parts or NOS 50 year old parts? Anything like the fuel pump, governor diaphram, accelerator pump, fuel hoses and such don't like the new fuel and can fail in just a few minutes if they are original parts not meant for the new formulas.

 

[Greensteel37]

I wouldn't say he's "throwing" money at it. He's terribly slow and deliberate on things like this. It's taken him all year to get to this point. He will always try to rehabilitate an old part before he'll spend money on a new one.

I think he is going to pull the valve cover in the next day or so and see if anything jumps out.

All good advise guys. I read all the posts to him over the phone as he doesn't have interwebz access.

I think he needs a carb kit (I found out he boiled the gaskets on the old set :O when he rebuilt it).

He actually changed the gas way back in January to some non-ethanol fuel an always puts fuel preservative in. The coil is new too.

 

[drgreg]

Always suspect the fuel pump, those engines seem to run, somehow, if you get fuel to them.

 

[Greensteel37]

The pump is an externally mounted 24v civilian pump. I gave him another new one to swap it out and he hasn't done that yet. I'll remind him to try that.

 

[YkDave]

what type of pump is it and what is set up for a regulator?

These carbs require very little fuel pressure, 3-5psi max

 

[Greensteel37]

It has a separate regulator. This arrangement was on the truck when he bought it years ago. It doesn't seem to be flooding out.

 

[Greensteel37]

I wanted to update this thread as we have been working on the truck today and it still won't run. Matter of fact it is worse.

Over the last month or so, we got a rebuild kit from a member here on SS. It was dated sometime in the late '80s. My buddy rebuilt the carb with the kit and after reinstalling it, the truck won't idle now. It won't start at all. So he "unrebuilt" it and put the otherwise good but original parts back in. It still won't start.

We fiddled with it most of the afternoon today and all we could get was a studdery attempt at starting. The gaskets in the kit were thinner than the old ones and allowed it to seep gas from the bowl so we put the old ones back in. After much teeth knashing we got it to stop leaking.

We eventually got it to start backfiring out the exhaust and finally out of the carb on the same attempt to start.


THis whole unpleasent episode started months ago when he changed the fuel filter. It ran great for about a day and the started to spit and sputter. Since then it has been downhill.

He 's at his wit's end on this truck. It ran fine for 10 years until last year in November right before parade season started.

Anyone got any more ideas? I'll pass along any questions to him.

 

[butch atkins]

i have TM 9-1826D ORDNANCE MAINT. manual for HOLLEY carbs and governors,mlooking inthe trouble shooting section ,MAX fuel pressure is 3 lbs,anything else blows the power valve,backfiring sounds like an ignition/timing problem to me,keep posting will try to help,good luck