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My Mack CH 600 Has Trouble Starting


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I have Mack CH-600 with a mack 300 motor. We have difficulty starting it when it is warm and cold. It's wierd you spray either to it and it fires right up. Fuel filters are tight, no leaks on any fuel lines, it has a new drainback valve. So I got curious and tap on the actuator on the fuel pump and it started. Now was that just luck or could that actuator be bad. If it is bad how do you test it.

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I have Mack CH-600 with a mack 300 motor. We have difficulty starting it when it is warm and cold. It's wierd you spray either to it and it fires right up. Fuel filters are tight, no leaks on any fuel lines, it has a new drainback valve. So I got curious and tap on the actuator on the fuel pump and it started. Now was that just luck or could that actuator be bad. If it is bad how do you test it.

I'm assuming you have an electric solenoid mounted to the injection pump governor: This solenoid would pull the fuel rack that is internal to the pump to the no fuel position to shut down the engine by starving it for fuel. Usually when these work correctly power supplied by the ignition switch releases this hold on the fuel rack allowing the governor to control curb idle. If this solenoid is sticking in the off position you can have the problems you experience. When you hit the engine with a shot of ether you have supplied fuel to it and the engine vibration probably causes the solenoid plunger to release. This is just a guess and again an assumption. In this case you would be best replacing the shutdown solenoid and not screwing around. Citing the engine does start and not shut back down until you want it to lends creedance to the ignition switch is supplying power to this solenoid. The same scenario could play out with a manual cable shutdown also if it is out of adjustment.

Rob

Dog.jpg.487f03da076af0150d2376dbd16843ed.jpgPlodding along with no job nor practical application for my existence, but still trying to fix what's broke.

 

 

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i was driving a 1996 dm688 had the same problem they put a cable shut off on it.

they had about 20 trucks like that, it was a common problem, they kept cables in stock.

hope this helps.

the first time it happened to me me they told me to tap on the pump..

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I'm assuming you have an electric solenoid mounted to the injection pump governor: This solenoid would pull the fuel rack that is internal to the pump to the no fuel position to shut down the engine by starving it for fuel. Usually when these work correctly power supplied by the ignition switch releases this hold on the fuel rack allowing the governor to control curb idle. If this solenoid is sticking in the off position you can have the problems you experience. When you hit the engine with a shot of ether you have supplied fuel to it and the engine vibration probably causes the solenoid plunger to release. This is just a guess and again an assumption. In this case you would be best replacing the shutdown solenoid and not screwing around. Citing the engine does start and not shut back down until you want it to lends creedance to the ignition switch is supplying power to this solenoid. The same scenario could play out with a manual cable shutdown also if it is out of adjustment.

Rob

What about a ground relay on the firewall next to the starter soleniod, could that be a problem to, because it smokes sometimes and I'm replacing that.

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What about a ground relay on the firewall next to the starter soleniod, could that be a problem to, because it smokes sometimes and I'm replacing that.

Generally speaking an electrical component that smokes is usually no good itself, or a component it supplies current for has gone bad. In you application I do not know for sure. Mack did in many applications use a large, round metal cased contactor referred to as a power relay. These usually audibly clunked upon turning the ignition key to the run position. Electrical power was then routed throughout the truck via this contactor.

Rob

Dog.jpg.487f03da076af0150d2376dbd16843ed.jpgPlodding along with no job nor practical application for my existence, but still trying to fix what's broke.

 

 

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That relay on the firewall would be the starter relay. It receives it's "signal" when the key switch is twisted all the way to the start position,at that point the starter relay relays current to the large solenoid on the starter, thereby activating the starter.

The accessory relay (the one that "clunks" when you turn the key to the "run" position) is under the dash.

.

"If You Can't Shift It Smoothly, You Shouldn't Be Driving It"

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what about the nylon fuel pump gear? seen it where it will run due to torque on gear but would not start. just a guess!?

This here is too vague. Is this a VMac engine?What is fairly common on a vmac pump is the rack actuator fails!In this case the pump has to come off to be repaired!

HK brings up a good point is the dash lighting up when the key is turned on?The acc relay will cause the heater and dash not to work! And will not let theengine light up!

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This here is too vague. Is this a VMac engine?What is fairly common on a vmac pump is the rack actuator fails!In this case the pump has to come off to be repaired!

HK brings up a good point is the dash lighting up when the key is turned on?The acc relay will cause the heater and dash not to work! And will not let theengine light up!

Oh sure center me out! LOL I agree what motor is it?

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  • 1 year later...

I found the problem. Up on the firewall you have your starter relay and beside that is square box that has two prongs and that is a ignition ground relay and that burned up.

hello everybody! i have the same problem with my CH 1994, can you tell me please, where the starter relay is?

in the cab or under the hood?

may be my truck have the same ignition relay burned up, if you can send me a picture please

thanks for your help

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Generally speaking an electrical component that smokes is usually no good itself, or a component it supplies current for has gone bad. In you application I do not know for sure. Mack did in many applications use a large, round metal cased contactor referred to as a power relay. These usually audibly clunked upon turning the ignition key to the run position. Electrical power was then routed throughout the truck via this contactor.

Rob

hello everybody! i have the same problem with my CH 1994, can you tell me please, where the starter relay is?

in the cab or under the hood?

may be my truck have the same ignition relay burned up, if you can send me a picture please

thanks for your help

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I'm assuming you have an electric solenoid mounted to the injection pump governor: This solenoid would pull the fuel rack that is internal to the pump to the no fuel position to shut down the engine by starving it for fuel. Usually when these work correctly power supplied by the ignition switch releases this hold on the fuel rack allowing the governor to control curb idle. If this solenoid is sticking in the off position you can have the problems you experience. When you hit the engine with a shot of ether you have supplied fuel to it and the engine vibration probably causes the solenoid plunger to release. This is just a guess and again an assumption. In this case you would be best replacing the shutdown solenoid and not screwing around. Citing the engine does start and not shut back down until you want it to lends creedance to the ignition switch is supplying power to this solenoid. The same scenario could play out with a manual cable shutdown also if it is out of adjustment.

Rob

hello

what tap on the actuator on the fuel pump mean? can you explain?

thank you very much

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