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fast truck
New Member

2 Posts

Posted - 12/09/2012 :  4:56:22 PM  Show Profile  Visit fast truck's Homepage  Reply with Quote
I have a 2008 Cat C7 with 92,500 miles on it and it dies very erratically, usually when coming to a stop sign or railroad tracks. It dies like you turn the key off and to restart it requires alot of cranking, but it starts. it starts like it ran outa fuel. No codes. We did just put two injectors in it, 3 & 4 becasue they where weak or out, but it had the dying problem before that. After the injectors, the driver of bus said truck runs much smoother now. I put a fuel pressure gage on the Compucheck fitting on fuel filter and 100-110 psi was constant, even on my 30 mile stop and go test drive I took it on, which by the way, never died on me. Give it to a differnet driver and died immiedately. We removed fuel tank, cleaned it out, repalced entire fuel line from tank to primary filter, remove primary filter housing, inspected, no debris, removed all inlet fuel lines and inspected, no debris. the return line to tank was free of debris. I'm running outa options.....anyone have any suggestions??? Thanks

tigger2
Advanced Member

USA
281 Posts

Posted - 12/10/2012 :  04:32:31 AM  Show Profile  Reply with Quote
Sounds like the fuel system is in good shape your pressure is a bit high though full throttle should be @ 75-85 psi.You may have a high pressure oil problem, when checking for codes check active, logged, and logged events most mechanical problems show up as an event. We have had several of these pumps disintegrate and fill the injectors and oil galleys with metal shavings. Cat injectors hate dirty oil if you have not changed oil recently that may help, high soot levels wreck havok on the system. If this pump has the two wires coming out of the top of the pump the icp valve is internal. You will have to hook to a Cat E/T scan tool to watch the inj. controll pressure to see if the desired and the actual pressurers are within range of each other. You can also watch to see if the pressure jumps all over the place. While you are there also check for erratic cam position signal (engine speed).
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007
Active Member

United States
13 Posts

Posted - 12/11/2012 :  05:12:18 AM  Show Profile  Visit 007's Homepage  Reply with Quote
If your fuel filter is one that is mounted high on the firewall you might try replacing the housing. We had similar issues with one of our buses and the Freightliner shop finally by-passed the filter and it ran fine. They replaced the housing and problem was solved. They said it's not unusual for these to be cracked and allow air into the system causing the issues.
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fast truck
New Member

2 Posts

Posted - 12/11/2012 :  05:45:09 AM  Show Profile  Visit fast truck's Homepage  Reply with Quote
Thanks folks. We are going to work on it this afternoon. I will post the eventual fix. If anyone else has input, still very welcomed to it.
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offroadwolf1
Active Member

33 Posts

Posted - 12/11/2012 :  1:35:51 PM  Show Profile  Reply with Quote
You didnt tell us if you found any codes or events in the ECM. I am not sure it you have CAT ET service tool or not, this would greatly help. You still may not have eliminated a fuel problem. Best way is to install a piece of clear tubing in the fuel line as close to the fuel pump as you can get. It sometimes takings a little rigging to get enough fittings and hose clamps to fit it in place, but thats OK. Run the bus long enough to purge the air from the sight line. Then watch the line and have someone stand on the throttle and run it at full engine speed for a couple minutes. If you see bubbles forming in the clear line then your sucking air somewhere. You can then move the line further from the pump prior to the filter housing and water seperator housing. You can narrow down the point its sucking air and repair it. I have seen a large number of water seperators sucking air from the o-rings on the bowl and water sensor. This will tell you if the fuel system is intact or not.
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sambrutay
Advanced Member

United States
235 Posts

Posted - 12/12/2012 :  05:40:45 AM  Show Profile  Reply with Quote
same type problem in the thread. See my response there. Good luck

http://www.schoolbusfleet.com/forum/topic.asp?TOPIC_ID=16403

Bruce
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