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1971 M35A2C Multifuel starting issue

Jcoffman84

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I just purchased the local Vietnam veterans of America M35A2 and the thing runs remarkably well but as soon as it gets to operating temp and I kill it I have to use starting fluid to get it to fire off again. As soon as it cools back off to ambient temperature it will fire off on its own again like nothing was ever wrong. Any suggestions?
 

frank8003

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I have never found the use of starting fluid applicable in any of the twelve Deuce TMs

 

fleetmech

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While it is cranking but not starting, are you getting any smoke from the stack? A total lack of smoke should indicate a lack of fuel flow through the injectors, and we can go from there. I am operating under the assumption that the truck is cranking with sufficient speed and isn't suffering from some other malady such as overheating... That also goes for the quality of the fuel. While Multi's by design are not overly picky about fuel quality, anything can get sticky if left to sit long enough.

First, make sure the electric lift pump in the tank is running. This switches on with the main power switch on the dash, and can usually be heard standing right by the tank. I seem to recall that one other member here has reported a hot start issue because his fuel pump wasn't operating correctly. Its rare but not totally unheard of for the pump impeller to fail, leading to a loss of pumping action even though the pump motor still runs. A bit later in the diagnosis, it might be wise to crack a bleeder and cycle the pump to see if its pushing fuel. Might be a good time to throw on some new filters too... Is the fuel new and fresh?

Does your shutdown lever (it looks like a plunger on the injection pump) travel correctly? Its conceivable that it could be sticking out a bit when hot, perhaps holding the rack out of place.

If the truck is at the right temp, cranking well, and pushing fuel to the injector pump, that pretty much leaves the injection pump itself. Like most any petrochemical fluid, the hotter the fuel gets, the more it thins. A worn pump may not be able to build correct injection pressure at cranking speed with thinned fuel. The increase in RPM from the ether might be enough to get it over the crest, so to speak. A pump plunger or governor linkage stuck from extremely old dry fuel might act the same way, exacerbated by the heat.

A buddy of mine called me recently about this exact problem with an old loader he's got. A tank of fresh fuel treated heavily with 2 stroke oil and fuel treatment has him going again, your results may vary...
 

Jcoffman84

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The fuel is probably a year old and I topped it off with 5 gallons of fresh diesel. The lift pump in the tank is turning on and pushing good fuel up to the injectors. It cranks good and fast with its two brand new batteries. It is not getting too hot and it’s running at a good temp. It’s just after I drive around for about an hour and kill it it will not start again until it cools back off to ambient temperature unless I give it a small quick snort of ether.
 

Floridianson

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If you have had time to look over the Trouble shooting manual let start off with the easy. Is your FDC bypassed? Yes we can get air in the system and it starts with the rubber line that is on the in tank pump. If you have some pressure at the bleed screw when you open it myself I do not put a gage on the bleed screw just to see if I have the 4/to 7 psi the in tank pump puts out. We check the running pressure at the bleed for our min. 30 at idle and min 70 psi at high idle. You say your truck runs good when it's running so I believe you are ok on that. The injector return lines all ways look like they have air because they do not flow fuel they more just burp once and a while. As long as we have flow from the in tank pump and very little pressure pushing fuel through the head the plunger will push it up to the injectors when all is correct. There have been some cases where the main fuel is turned down to far and the spill port is spilling to much fuel to start. Sometimes the fuel control unit assembly can stick and that is a easy check too. If your FDC has been bypassed we will work on the problem from there.
 

Jcoffman84

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Well I think I have found the issue or at least a good spot to start. My tank pump is turning on and pumping but it may not be supplying enough fuel to the high pressure pump lol. I pulled the tank pump out and it’s gummed up really bad. image.jpgimage.jpg3A22EFCE-2509-42F0-86A0-08155ED214BC.jpegimage.jpg
 

G744

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The rest of the tank innards probably look the same. Time to pull it and have it cleaned before a new pump goes in.

DG
 

fleetmech

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Jcoffman84

New member
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The rest of the tank innards probably look the same. Time to pull it and have it cleaned before a new pump goes in.

DG
I’ve been calling around all day to find someone who will clean it out. Nobody in north Texas seems to know anything.
 

fleetmech

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ayup, that isn't helping. Is that all mud, rust, or Algae bloom?

I dont suppose that tank cleaning is a job too many companies want to dive into, sadly. A big truck or bus service company is probably your only chance.

Since its that bad, Id say to start by pulling the whole thing off the truck and washing it out with water a whole bunch before flushing it out with gas and then diesel.
 

Jcoffman84

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TX
I’ve already got the tank pulled. Was looking up possible ways to clean myself. May try the vinegar and baking soda solution and let it soak for a couple days after power washing as much out as I can first
 

davidb56

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take it to the car wash (at night time) and bring some dawn liquid dish soap with you. Once you get the majority of the crap out, you can try mineral spirits to do some fine cleaning a spray nozzle they sell at HF. I did that with the fuel tank on a D4 Cat I bought, and it has 2 baffles in it, plus weighs a lot.
 

Jcoffman84

New member
15
7
3
Location
TX
take it to the car wash (at night time) and bring some dawn liquid dish soap with you. Once you get the majority of the crap out, you can try mineral spirits to do some fine cleaning a spray nozzle they sell at HF. I did that with the fuel tank on a D4 Cat I bought, and it has 2 baffles in it, plus weighs a lot.
I’ve got a 3200 psi power washer here at home so I may give it a whirl tomorrow
 

frank8003

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These gringeltaube photos of a fuel tank apart might help.
I did read many threads in SS about different ways to clean out the fuel tank but right now can't find them.
Be careful with gasoline. It will help if you can get that large bottom drain open.
 

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