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Cat C7 No Go--Flat won't run--Help troubleshooting please

rshackleford

Senior Member
Joined
Jan 19, 2009
Messages
400
Location
North Dakota
Serial number 7AS07315 arrangement number 154-1062.

The truck broke down on the side of the road and we replaced a timing sensor and were back up and running.

Two weeks later it died on a job. We have spent 40 hours on it and T&E Cat has spent 40 hours on it. We replaced the lift/transfer pump and HEUI pump and all the injectors. We've also replaced all of the electrical harnesses.

The engine will fire with ether but only runs long enough to use up the ether. Nothing else.

The Cat mechanic completely disconnected the engine from the truck so we believe this is not a truck problem.
 

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Mike L

Senior Member
Joined
Dec 1, 2010
Messages
1,901
Location
Texas
Occupation
Self employed field mechanic
An engine will fire on ether as long as it has compression. What has cat done? Does the ecm have power? Does it smoke? Does he check engine light come on with key on engine off? What kind of truck is it in? Did cat verify all the inputs to the ecm? We need a lot more details
 

crane operator

Senior Member
Joined
Mar 27, 2009
Messages
8,275
Location
sw missouri
My 3126 (which is pretty close to the same engine, just older), had a crank, no start issue. It ended up simply being a ground issue at the starter. Fortunately I didn't start throwing parts at it. I was ready to start throwing parts, but got stubborn.

If the CAT man has been there for 40 hours working on it, its going to be tough to diagnose over the web.
 

Mike L

Senior Member
Joined
Dec 1, 2010
Messages
1,901
Location
Texas
Occupation
Self employed field mechanic
This is why I’m asking questions. K.I.S.S. Keep it simple stupid. I almost bought an ecm for my Ford when a cummins tech I spoke with reminded me to load test the battery power to ecm wires. Green wires and a couple butt connectors cured my issue.
 

63 caveman

Senior Member
Joined
Nov 11, 2017
Messages
340
Location
western Pa.
Serial number 7AS07315 arrangement number 154-1062.

The truck broke down on the side of the road and we replaced a timing sensor and were back up and running.

Two weeks later it died on a job. We have spent 40 hours on it and T&E Cat has spent 40 hours on it. We replaced the lift/transfer pump and HEUI pump and all the injectors. We've also replaced all of the electrical harnesses.

The engine will fire with ether but only runs long enough to use up the ether. Nothing else.

The Cat mechanic completely disconnected the engine from the truck so we believe this is not a truck problem.

If the timing sensor "fixed" it the first time. Then I would look at all the connectors that may have been moved when changing it and check for pin fitment and continuity back to ECM assuming the Cat man looked at timing on his/her laptop while cranking. Even with a new harness a sender or sensor pin/pigtail could be damaged.

Man shot gunning parts can really make it tougher some times may have to start all over power, grounds, and reference
 

Junkyard

Senior Member
Joined
Jun 5, 2016
Messages
3,621
Location
Claremore, OK
Occupation
Field Mechanic
This is why I’m asking questions. K.I.S.S. Keep it simple stupid. I almost bought an ecm for my Ford when a cummins tech I spoke with reminded me to load test the battery power to ecm wires. Green wires and a couple butt connectors cured my issue.


Seen quite a few VP44 injection pumps deemed bad when it was a wiring issue all along. The more erratic the issue the more I dig into wiring.
 

stinky64

Senior Member
Joined
Feb 25, 2017
Messages
860
Location
java center ny
Occupation
big truck wrench/fixer of things
Worst part of this whole ordeal is there's already been too many hands in the cookie jar...Nothing worse than getting a job that's been prodded, poked, changed parts,wires swapped, yuch...Did you try swapping out a good ecm? Several times at my last employer with a very large Volvo fleet, even when the TechTool software didn't indicate any problem with the ecm after all other ideas were exhausted, a good ecm from a wreck that I had stashed in my box saved the day...The new ecm had to be programmed to the truck, but the used one will tell ya what you need to know....
 

Per Eriksson

Senior Member
Joined
Oct 24, 2007
Messages
650
Location
Sweden
Give us something to work with,
Does it throw codes?
Register cranking rpm?
Does it build actuator pressure? needs to go above 900psi before the ecm activates the injectors.
Fuel pressure?
 

Per Eriksson

Senior Member
Joined
Oct 24, 2007
Messages
650
Location
Sweden
If you can connect to it with cat et there's lots of interesting stuff to do,
injector solenoid test for example
Or look at delivered fuel volume while cranking.
 

rshackleford

Senior Member
Joined
Jan 19, 2009
Messages
400
Location
North Dakota
We replaced the harness. That was our first thought. After that, all parts were at the troubleshooting and recommendation of CAT tech. I hope that's not considered shotgunning parts.

I agree on the ether. That just means it's getting air.

Cranking oil pressure is like 1200 or something. It's in the good range.

CAT is able to communicate with the EMC. They have flashed it several times. When they are connected to it the computer shows all good.

I don't know for sure that it reads good fuel pressure but the fuel system is all new. Transfer pump, HIUI, and injectors are all new. All installed by CAT. All recommended by CAT.

No smoke on engine crank.

Local CAT techs gave up. They have sent this to their engineering headquarters. They sent someone out with a super ohm meter and they weren't "happy" with the readings they got from the timing sensor. They want to take the front cover off and see if the timing gear has come off the crank.
 

Vetech63

Senior Member
Joined
Aug 10, 2016
Messages
6,362
Location
Oklahoma
IDE bet something is getting overlooked repeatedly. It doesn’t sound like much else can be replaced, it’s almost like a parts changing scenario from the very beginning. How many Cat techs have worked on this? I have a customer here local that called Cat field service for some A/C work and he is on the 3rd tech in a week.
 

63 caveman

Senior Member
Joined
Nov 11, 2017
Messages
340
Location
western Pa.
We replaced the harness. That was our first thought. After that, all parts were at the troubleshooting and recommendation of CAT tech. I hope that's not considered shotgunning parts.

I agree on the ether. That just means it's getting air.

Cranking oil pressure is like 1200 or something. It's in the good range.

CAT is able to communicate with the EMC. They have flashed it several times. When they are connected to it the computer shows all good.

I don't know for sure that it reads good fuel pressure but the fuel system is all new. Transfer pump, HIUI, and injectors are all new. All installed by CAT. All recommended by CAT.

No smoke on engine crank.

Local CAT techs gave up. They have sent this to their engineering headquarters. They sent someone out with a super ohm meter and they weren't "happy" with the readings they got from the timing sensor. They want to take the front cover off and see if the timing gear has come off the crank.

Was the "super ohm meter" a lab scope that could record and look closely at the wave form? I can see burning 40 hours chasing an intermittent problem but a straight no start you would think would be a straight forward diagnostic. This thing stumping a few cat techs and bringing in the big guns; I sure hope you get it fixed and let us know what the problem was (My money is on something simple that was overlooked, of coarse that is easy to say after you figure it out). Good luck!
 

Mobiltech

Senior Member
Joined
Jan 14, 2014
Messages
1,680
Location
Sask.
Occupation
Self employed Heavy duty mechanic
All this and they don’t know if it has any fuel pressure? It could have a cracked or blocked line from the fuel tank. Very common in trucks with plastic lines.
The timing sensors run off the back of the camshaft and will be easy to check either through the sensor port or taking off the tin plate ahead of the cam gear.
 

Vetech63

Senior Member
Joined
Aug 10, 2016
Messages
6,362
Location
Oklahoma
All this and they don’t know if it has any fuel pressure? It could have a cracked or blocked line from the fuel tank. Very common in trucks with plastic lines.
The timing sensors run off the back of the camshaft and will be easy to check either through the sensor port or taking off the tin plate ahead of the cam gear.
I suspect et said everything was fine. LOL
 
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