Guest Posted January 5, 2011 Share Posted January 5, 2011 They were kidding Wheels (as far as I have never heard anyone doing that?) A truck wheel goes from about 160 lbs to 190. You only need about 100 lbs to spin the engine but its the volume of air that does it (hence the large tanks). The Mack airstart tank is totally seperate to the brake supply and has a fitting for a hose to be plugged in for inflating tyres or for pumping up should it run out of air. As most trucks have these its easy to simply recharge the start tank off the air supply of another truck or compressor. I once drove a V12 2 stroke GM powered Oshkosh in W.A. The mechanic converted it over to electric start one day only to find it simply burnt the motor out after a while! The air start was re-installed! (1200 HP!) (You should hear a Mack start with the baffels missing!! Link to post Share on other sites
Noodles 0 Posted January 6, 2011 Share Posted January 6, 2011 Used to get the same thing starting tractors and dozers (having been out doors in the rain most of their lives). It will be the solenoid and a sure fire way to test this is to get an OLD screw driver and carefully cross the two terminals of the rear of the starter motor. Expect some sparks! But if everything else is fine the engine should turn over. Make sure the ignition is ON as some fuel pumps shut the fuel off when the power is not on. Also alternators don't like to be run without a field voltage. A good way to get out of trouble if everything else fails! Don't try that with anything new- it will damage the ecu's etc Link to post Share on other sites
Guest Posted January 15, 2011 Share Posted January 15, 2011 So the conclusion was the addition of a relay between the switch and the solenoid seems to have solved the problem. Link to post Share on other sites
wheels 543 Posted January 15, 2011 Share Posted January 15, 2011 Also alternators don't like to be run without a field voltage. Only briefly if switched off while running at speed and charging. The produce a very high voltage spike that cna destroy electronics etc. Make sure the ignition is ON as some fuel pumps shut the fuel off when the power is not on. It's not the actual Fuel pump, unless someone has fitted an electric one, but a solinoid in the fuel line that switches in and out. Don't try that with anything new- it will damage the ecu's etc Bit of a myth that one. The batteries are pretty good sinks to electrical spikes likt that. The battery acts like a large Capacitor. Link to post Share on other sites
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