C60X running not as well as it should....

[warren brown]

Hi everyone - had to move the C60X to our new house (about 40km) and for the first time since I've had it the truck was struggling up hills - or under load. At idle it sounds fine but it develops a chug - as though it's running on five cylinders and runs out of puff. Normally it lopes along pretty well - it starts and idles very well but once you give it a few herbs it doesn't sound quite as smooth. I'm going to remove the plugs and leads and probably replace them - and have a squizz at the distributor cap in case there's a crack - I hope it's not something catastrophic but I'll start with the simple things first. Are there other things I should check I haven't thought about? Does anybody know what size spark plugs they are for the GM c60X engine and any tips on plug removal before I start dismantling the cab? Cheers and many thanks - Warren

[hrpearce]

It sounds like a dirty carbie problem, restricted air intake or worn accelerator pump.

[Howard]

When you say 'chug', do you mean like a missfire? Or more of a surge?
Do you feel this chug? or hear it? or both? Will it rev OK standing in neutral or does it only play up when moving along? All gears?
CHeers
H
PS Where is the new home?

[warren brown]

Hi Howard! - couldn't hear the 'chug' from inside the cab - it wasn't apparent at idle at all - a couple of mates said it sounded chaff-cutterish from outside ... I'll post an iphone video they took ...

[motto]

G'day Warren
The GMC is a good engine and I doubt there is much wrong with it.
You're problem may be simply that the fuel has gone off from standing, it can have quite a short shelf life these days.
If the fuel is fresh then you're next suspect is the ignition system and that means plugs, leads, points, condenser and coil.

David

[Phil Waterman]

Hi Warren

Start with a list of possible causes once you have a list of possible put the list in order of difficulty to check and fix. Once you have done that start with simple end of the list.

Now for my basic list for loss of power:

1. Bad gas or water in the fuel
2. Plugged or nearly plugged fuel filter, this fits your runs but doesn't take a load
3. One at a time unplug and replug each spark lead from plug and distributor (if you have had any of the leads off just before this problem started check the firing order)
4. Loose or broken spark lead, quick check for this is to ground a screw drive with a jumper lead, then with engine running ground out each spark plug one at a time see if find a plug that when you ground it out doesn't make a difference. If you find a plug check or replace the lead you can check it by unhook in it from the plug and holding it 1/8 - 1/4 from block if you get a good spark pull the plug.
5. If the plug looks good swap it with a another and see if the problem moves.

Now to start checking for internal

6. Connect a vacuum gauge and look for a quick fluctuation, which would be an indication of a problem.

7. Do a compression test look for low readings - if you find one low cylinder do not assume it is time for rebuild another test.

8. Check the valve clearance, you are looking for exhaust valves in particular that have no clearance. If you find that you have less than what the manual calls for you may get lucky and adjusting the valves may restore the power. The problem is that with no clearance the valve doesn't seal. This assumes that your engine doesn't have hydraulic lifters.

All of the problems I've described have happened to one of my trucks.

Cheers Phil

[warren brown]

Thanks Robert, Dave, Howard, Phil and Neil - hell or high water I'm going to solve this. It's possible/likely it's dragged through some crook fuel as I don't drive the C60X much at all - for the drive last week I filled up one tank completely (at an alarming cost!!! BTW) - there wasn't much in the tank at all. I've discovered an inline ryco-style fuel filter that's probably been there since Federation. It's a starting point. So I'll take all the advice on board and methodically go through it - I'm going to replace the plugs, condensor, coil and leads anyway - if I'm pulling out plugs etc I might as well do it. I love it being in top form - it's always been such a smooth, wonderful engine - I'm just hoping it's not a sticking valve - or worse... So I've made a list to follow from your input and about to get cracking. Been on the phone to Ross Prince who's saving the day. Thanks so much for your help with this - I'll keep you posted...

[warren brown]

Oh Howard - sorry - we've moved from Sydney to a property about 20km from Goulburn. I think I'm running a truck farm...

[Mike Cecil]

Watch out for the Yass Boys: you're in their territory now!!

[warren brown]

I'm already worrying about that Mike...

[Tony Wheeler]

Originally Posted by warren brown

it starts and idles very well but once you give it a few herbs it doesn't sound quite as smooth.

Sounds like fuel starvation to me Warren, although spark breakdown can produce similar symptoms. Best way to diagnose is to play with the choke while driving. If it responds to choke under load you know it's a fuel problem rather than spark. In this case I suspect you may have sucked up some water into the small inline fuel filter. They stop water getting to the carby but the wet paper element restricts fuel flow. It's certainly the first thing to replace as you say, and you may also need to drain the tank to prevent recurrence. Often there's quite a bit of water swilling around the bottom, which accumulates through condensation over time, esp. if the tank is near empty. Alternatively you can run it without a fuel filter, which allows any water to pass harmlessly through the carby. Fuel filters are quite unnecessary in my experience, provided of course the fuel tanks are free of rust flakes and wasps nests!

I agree with Phil re valve clearance adjustment, which is generally routine with a major tune up like this. Anyway good luck with it all and I'm sure there's no major problem.

[Phil Waterman]

Hi All

Here are some photos of the inline filter on my Pat 12 C60L that started burping and farting recently when under full throttle on long up grades.


First two photos are with the regular fuel pump sucking fuel the last is with the electric fuel pump at the tank running note what happened to the length of the filter element.


Yes replacing the filter did solve the problem.

Cheers Phil

[warren brown]

Phil thanks so much for the tip - I'm heading in to pick up new fuel filters as we speak. When I get back I'll do an autopsy on the old filter and post a photo. I think my filter was personally installed by King George VI when the truck was built. Next step - air cleaner...and then onto the ignition system... wish me luck...

[Robert Farmer]

Originally Posted by Mike Cecil

Watch out for the Yass Boys: you're in their territory now!!

Yes and there's one in particular who has wanted a C60X for years!

[warren brown]

Hi everyone - removed the inline filter - it's black plastic so you couldn't see inside but when I removed it - oh brother... so no wonder it's been having difficulty. I performed an autopsy on the filter with a hacksaw - and wow.... So I'm going to go through the truck end to end. I replaced the filter and flexible lines - and the fuel coming through now seems pretty good - removed the oil bath filament and have cleaned it and will replace the oil - and have removed the plugs. They're a bit Keith Richard - old and coked up. So I'm now in the process of knocking over each possible problematic problem one after the other. New plugs, leads, coil, condenser and so forth. So - the truck has been an older restoration - and since I've had it it's been in storage pretty much - and it would run like a sewing machine when I give it a short run - but short runs aren't what it needs - and sitting around obviously hasn't been great but I'm determined now it'll be crackerjack.

[hrpearce]

Good job that muck didn't make it to the carbie.

[Mike Cecil]

Be a run to Corowa and back maybe next March, then? Good round trip from near G'burn.

Glad to see you isolated the problem(s).

Mike

[Richard Farrant]

Originally Posted by Mike Cecil

Be a run to Corowa and back maybe next March, then? Good round trip from near G'burn.

Quite right Mike, a C60X would fit in the GM theme next year. We will have to work on Warren.
Think the last time you were there was 1996 Warren? You drove your jeep down, remember about 7 of us in it on a trip to Rutherglen on Sat night.

cheers Richard

[motto]

I take it that you don't have an original fuel filter on the truck Warren. Granddad knew what he was about. They are perfectly adequate, function as a water and sediment trap and are easily serviced. It puzzles me why people replace them with in line filters, especially ones you can't see through.

David

[warren brown]

I couldn't agree more Dave - my 1928 Dennis Fire Engines(s) have quirky old petrol filters filled with countless brass shims as thin as a hair - and the filters work marvellously. I never had a problem with the original steel jeep-type filters the truck originally had- if I can find a couple I'd be keen to reinstall them. In time...

[Tony Wheeler]

Originally Posted by warren brown

I performed an autopsy on the filter with a hacksaw - and wow....

Well done Warren, it's always pleasing to prove the fault, esp. with tuning problems which can be tricky to isolate. Generally we simply replace everything without learning the precise cause.

Just to expand on the diagnosis - I believe your CMP was suffering from Sceliphron caementarium - commonly known as the mud dauber wasp! It so happens my F15A suffered this particular ailment when it first hit the road. It drove perfectly well until I filled the fuel tank at the servo, which would have been the first time in many years, and must have dislodged a mud wasp's nest adhering to the upper tank area. After that it lost power up hills and could barely hold top gear on the flat. Like your truck Warren it was an older restoration which had been stored for many years, and since I lacked confidence in the restoration I fitted an inline filter initially, in case the tanks hadn't been cleaned out properly. As you can see the brand new filter was already badly clogged, which confirmed my fuel starvation diagnosis, and I was able to identify the culprit by comparison with a mud wasp's nest, of which there were many throughout the vehicle. Mine were built in Northern Victoria, whereas yours appears to be Riverina red variety!



The moral of the story in my case is never trust a previous "restoration". Both tanks had undergone extensive solder repairs to the usual rust holes beneath the tank straps, but apparently no attempt had been made to remove the rust from inside the tanks! Obviously the wasp's nests appeared much later during storage, and having taken the precaution of fitting an inline filter I discovered the nest in the fuel tank purely by accident. Likewise in your case Warren - assuming it's a mud wasp nest as I suspect, then without a filter the fine red dust may have passed through the carby unnoticed, because it's thoroughly dispersed in the fuel, as seen in the cloudy sample below. Much of it would be expelled through the exhaust, but some of it would inevitably pass into the engine oil, where who knows what havoc it would wreak on soft white metal bearings.



The upshot here is that by causing fuel starvation, our cheap plastic fuel filters alerted us to a potentially serious problem - Sceliphron caementarium! These critters are definitely bad news, and not just for CMPs. They've even brought down commercial airliners, by building mud nests in pitot tubes. In one case in 1996 the death toll was 189: "Investigators believe a colony of black and yellow mud daubers got into the tube and built their cylindrical nests inside, causing faulty air speed readings which were a large part of the crash. This species also brought down another plane in Washington during 1982."

Now that I've thoroughly cleaned out my tanks and lines I'm no longer running a fuel filter, but in light of these encounters with Sceliphron caementarium, it's even more imperative with fuel tanks of unknown condition. Rust flakes will merely cause fuel blockage, but any mud nests present could potentially ruin a motor, and we'd never even know how it happened!

On a proper resto of course I'd be using an original filter, however I'd probably use a paper element, because I believe they provide much finer particle filtration, by virtue of microscopic packed fibres. Certainly they're standard in critical applications like engine oil filtration. The downside of course is they're prone to clogging, as seen with these inline filters, including Phil's example. I suspect that would rule out paper as a fuel filter medium in WWII military application - even a large paper filter may clog quite rapidly on fuel poured from POL cans during a Libyan dust storm! The packed shim filter may reduce engine longevity in such conditions, but that's hardly a consideration in wartime, and certainly preferable to constant stoppage in convoy to replace clogged paper filters!

[warren brown]

Wow Tony!!!!! Thanks so much for all this!!! Sorry I've been up in Lithgow for a few days and just got back!! Richard Farrant has suggested I clean the tank out - which I'll do - but your experience absolutely mirrors mine!! Blasted wasps... I'm onto it! Learning a lot here - thanks everyone - I'll keep you posted!

[Tony Wheeler]

Originally Posted by warren brown

your experience absolutely mirrors mine!! Blasted wasps... I'm onto it!

Yes it's not something I would ever have imagined occurring, but on reflection it's a genuine occupational hazard for us. Most if not all our MVs have at some stage in their history lain idle for long periods, often for decades, and unless the fuel cap is fitted and seals perfectly, the tank will eventually dry out. These critters are ubiquitous and they can probably crawl past the dried out shrunken fuel cap gasket, which is often found cracked or even disintegrated. Once inside the tank they construct a time bomb for us! Without a fuel filter it could potentially wreck the motor, particularly if it lacks an oil filter, as did early production CMPs, and we'd be none the wiser. I wonder how many blitz motors have clapped out prematurely in this way - invariably the original fuel filter has long since been decommissioned by the time we acquire them. Certainly in light of our own experience it's something we need to be onto from the outset as you say Warren.

[Barry Churcher]

They're a bit Keith Richard - old and coked up.

Nice one Warren. That gave me the morning smile I needed.
Barry

[Phil Waterman]

Hi Guys

Another place mud wasps up our way like to build nests is in the vent pipe from radiator or the coolant recovery tanks. All three off my trucks have had this problem, my HUP's coolant recovery vent tube was so well that it sealed the system to the point that the top radiator hose blew off.

They also like the coolant drain valves which is annoying but not dramatic.

Cheers Phil

[rob love]

Let's not forget their nests in the tubes leading into the vacuum wiper motors. We used to remove them all the time from the jeep wipers.

[warren brown]

Well - drained the fuel tank and to my surprise, very little rubbish came out. About 60 litres of new petrol came out - I only filled it up the week before and in the first tranch of fuel removal only a miniscule bit of ...rust? Black grit? I was expecting shards of rust and detritus - but the fuel flowed freely and came out clean. There wasn't enough rubbish to photograph - but I'm not happy until I've really checked out whether there could be a wasps nest up inside. Certainly we get wasps nests around here - I have a brand new Davey Firefighter pump sitting in the shed - the dealer covered up the outlets/inlets with paper coffee cups and taped them up to stop wasps nests. I'm waiting now for the arrival of the new plugs, points, leads, dizzy cap, oil filter, rocker cover gasket (just in case) etc. See how we go...

[warren brown]

Ready to check the inside of the tank - at last, I finally get to use this...

[Richard Farrant]

Always the joker Mr Brown

[motto]

Be bloody careful Warren. You run the risk of going off with a poof if you use that thing.

Dave