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Hard start /No start


R.E.D
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Hi everyone

Since I bought my 96 RD it seems to start real rough when cold.I don't mean below zero but a slight chill (50 degrees) causes it to rough start like if the pistons were firing unevenly .Sometimes it wont even want to start , it would just crank until the batteries are drained.I would like to solve this issue since it creates a real PITA when you show up ready to work and truck wont start.Here are some facts that could narrow down the issue.

Batteries are new.

Starter seems kinda week compared to our other Ch's (96 & 98)

The u shaped fuel line between the two head is wet.

One injector line is also wet.

The nut in the front of pump also wet ( See Picture)

Truck has 50,000 miles on inframe and burns no oil.

Please advice on how to tackle this problem.

Thanks RED

post-16358-0-35791600-1456021051_thumb.p

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Im not sure if the injectors were changed at the inframe , but the heads were gone thru and fixed of any defects.Besides the hard start/no start issue is a trouble free truck.No smoke whatsoever and depending on air density 26psi of boost unloaded and 27 to 28 psi loaded.

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when the inframe was done, did they replace the gaskets on the u-shaped tube?

being a '96, they are old and brittle. That is a return line.

Should not effect starting.....have you plugged truck in to see how it starts on cooler mornings?

Success is only a stones throw away.................................................................for a Palestinian

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I have a bottom running exhaust and haven't really looked if any smoke comes out while cranking.the only thing I know about the heads is that they were sent to a shop to get worked on and they were brought back painted and cleaned.just now I got to the yard and it was around 65 degrees and didn't turn on.i used a shot of ether to get it going.

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first thing to check does smoke come out the stack when winding over ???? that will tell most of the story

Im guessing not at the start of winding ??

Paul

That's where I'd start. Have someone hit the key and watch the exhaust. The first few spins shouldn't yield anything, but it should start puffing smoke if it's getting fuel. But taking care of the leaks won't hurt anything either

:)

Lack of planning on your part does not constitute an emergency on my part....

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I have a bottom running exhaust and haven't really looked if any smoke comes out while cranking.the only thing I know about the heads is that they were sent to a shop to get worked on and they were brought back painted and cleaned.just now I got to the yard and it was around 65 degrees and didn't turn on.i used a shot of ether to get it going.

65 degrees and you needed ether?

check that filters are tight, all connections are tight.

Would normally see leakage if loose, but may be just enough to let air in.

Once started, does it pop, and run rough for a few minutes?

Success is only a stones throw away.................................................................for a Palestinian

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A 96 year pump should have a over flow valve which is a check valve also being used to regulate the fuel pressure.It will be located on the return side of the injection pump.If it leaks backwards it will lose prime.Also in the transfere pump it has check valves and it can cause same problem if they are not holding the fuel up.If it has been updated to the orffice fitting type over flow valve I feel like it can lose its prime due to the u/shape tube leaking or plactic line on front return or the injectors having bad o/rings drain backwards thru the orffice valve to the tank.what ever you find let us know.

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glenn akers

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Thanks to everyone for replying.Once the truck fires it idles normally after 3 or 4 seconds.i thought about a broken tank pick up tube but the trucks uses all the fuel in the tank and never dies once it's running.i will try to take care of the leaks asap.i believe changing the fuel lines from pump to head from the two piece nut to the new style one piece should solve that leak.What do you guys think about the leak in the pic posted above?can that influence anything?

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ok if it never looses prime when running and is hard to start after sitting for some time it means the leak is in the return line have been down this a few times with different people

All other theories we have go out the window and mean nothing it really is this simple if it looses prime when its running it is in the supply side if it looses prime when its stopped it looses prime when the fuel siphons back into the tank which is what its meant to do siphoning back into the tank when not running

You should have smoke the instant the motor winds over gotta remember air start Macks only have a few seconds of air and always start when everything is right it should fire instantly

let us know what you find

Paul

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With the cracked pickup tube, it will only be an issue on start up as when it's running it draws enough fuel with a small portion of air to keep running and working under most conditions. Once you shut down it throws an air bubble into the system that would normally be either full or submerged in fuel. The truck may start an run and then stall out and need to purge the air bubble. Not saying it's the issue here. Just explaining the theory depending on the size of the crack. Dropping the fuel suction line into a bucket of fuel would be a test. Anything on the return that is on the outside of the engine would leak and is not under suction before lift pump or pressure after lift pump. Unless the section of return that is being questioned provides a restriction for keeping fuel pressure in a feed cavity it won't effect loose of prime.

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Whoops, need to make sure. From the picture of the pump it looks like a mechanical pump but want to be sure. It's not an electronic injection pump is it? Can't see the rear section of the pump for rack actuator or linkages. If it's V-mac it's your rack actuator or pump plug loose/worn. I see the timing sensor port plugged but that could have been from the rebuilder.

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