Caterpillar 3126E Cranks But Won’t Start

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We have a 2003 Cheetah Safari with  less than 30K miles on the Cat 3126e. We just had a major service done at a Cat dealer in WA who detected that the fuel actuator injection pump wasn’t working correctly so we had it replaced along with the fuel sensor.  The only symptom of was one low power issue last year but she was otherwise running great.

So here we are in Idaho, again been running great with no issues and after setting overnight in a remote state park, the engine cranked but wouldn’t start. Checked the onboard diagnosis and the fault indicated an issue with the fuel actuator fuel pump. Had it towed to the closest Freightliner who got  the engine running but said they needed to do further diagnostic on Monday when their one and only Cat mechanic was back.

We drove the coach about 4 miles to the closest KOA an it seemed to run fine but may have been a bit more black smoke than usual. 

Any thoughts on what could be going on? I think the engine also has a fuel booster pump...could this be the issue? We need to have a conversation with the service manager to understand exactly what diagnostics they have done and try to have a somewhat educated conversation with them.

Thanks for any help you can provide.



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I shot your post off to a hands-on Caterpillar tech.  Here is his reply:


Hi, first place to look coming off the chassis batteries: look for two wires connecting the positive and negative post.

Possible broken connection, dirty connections. Then follow red and black wire to inline fuse holder or fuse block and look for blown fuse 7.5 amp or 10 amp. ( no power to ECM).

At fuse block look for fuse for neutral safety switch or little square relay that says neutral safety relay or start relay first.

If major work was preformed, check to make sure connection at wire harness at ECM is not loose if removed.

Let’s start in this area first.

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Thanks ...

The shop got the engine running but did not tell us how so I don’t know if they checked all of that. The engine would not be running if those issues your tech described were present? Since it is running, we don’t know what they plan to do on Monday. All we were told was that the problem could still be related to the pump but they needed to do further diagnostics. 

We are wondering if our engine has a fuel booster pump that sends fuel to the fuel actuator pump as I have read that this could be a issue. Any idea how we could tell if our engine has this set up?



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