Jdiesel25 Posted January 18, 2013 Share Posted January 18, 2013 I have an 06 Mack with a 427. Motor cranks ( like it ran out of fuel ) then fires. But I have to crank the piss out of it. Once it's started it runs fine. Changed the pump and checked all check valves and pressure valves etc. bleed injectors etc. motor is holding a prime to the pump atleast. Any ideas? Quote Link to comment Share on other sites More sharing options...
staxx Posted January 19, 2013 Share Posted January 19, 2013 Do you have a glass bowl raycore fuel/heater ,if so there is a check valve on inlet side. Quote Link to comment Share on other sites More sharing options...
lucerne tractor Posted January 19, 2013 Share Posted January 19, 2013 air is leaking around the bottom of the inverted glass/plastc bowl over the fuel filter, check to see if it looks real low or empty after sitting over night before cranking. Quote Link to comment Share on other sites More sharing options...
lucerne tractor Posted January 19, 2013 Share Posted January 19, 2013 if the fuel is right to the top the filter is clogged, change it at every oil change. I do every 10 to 12 k at most. chances are it's air leaking and and letting fuel go back. I had it happen a few times. Once I just tightened the bowl once I had to change the rubber O ring. Clean it good in the slot. Quote Link to comment Share on other sites More sharing options...
Jdiesel25 Posted January 19, 2013 Author Share Posted January 19, 2013 I bypassed the filter completely and it still doesn't start right Quote Link to comment Share on other sites More sharing options...
Jdiesel25 Posted January 19, 2013 Author Share Posted January 19, 2013 Put an ecu from 1 of my other trucks n the issues still there Quote Link to comment Share on other sites More sharing options...
staxx Posted January 19, 2013 Share Posted January 19, 2013 Check the overflow valve at the back or fuel rail it rite above you air compressor if its stuck open it will let your fuel reture to the tank when engine is off , also no malfunction lite rite if the the cam or crank sensors one or the other not working the engine has to turn over sevral time before computer can figure out were timing is to start so check both sensors. Also could have a power relay sticking not turning engine ecu power on rite away the relays are glove box to the left labled power relay 1,2,3,4. Quote Link to comment Share on other sites More sharing options...
Jdiesel25 Posted January 19, 2013 Author Share Posted January 19, 2013 How do I test the power relays? They're off to the far left correct ? I changed the pump, pressure valve in block, bypassed fuel filter, tried another ecu offa working truck, bleed injectors. Etc. I had it on a comp the only thing that came up was low voltage cylinder 1 any ideas?? Quote Link to comment Share on other sites More sharing options...
staxx Posted January 20, 2013 Share Posted January 20, 2013 Sounds like a unit pump code maybe thats no big deal that code comes up alot . Relays have 2 big wires going in and 2 small the small wires energize the relay to close and let the power go across the 2 big wires so if you back probe the relay or just pull it out a little take a test lite with key on make sure the 2 big wires have power both sides. Quote Link to comment Share on other sites More sharing options...
Jdiesel25 Posted January 20, 2013 Author Share Posted January 20, 2013 Ok thanks! I have my Mack mechanic coming out Monday w his computer hopefully that tells us something. So far everything has led to a dead end. The truck runs fine once it starts Quote Link to comment Share on other sites More sharing options...
Jdiesel25 Posted January 22, 2013 Author Share Posted January 22, 2013 I checked the power relays and they seem to be working fine. Any other ideas? Quote Link to comment Share on other sites More sharing options...
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