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Tim, Foreman
Category: Heavy Equipment
Satisfied Customers: 356
Experience:  23 Years Heavy Equipment and Truck Repairs Shop and Field in the Minning and Construction Industry
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Starting fluid..runs of i will not restart on cranking you

Resolved Question:

i have a kenworth with a cat c10 in it and changed to a c12 motor will not start only with starting fluid and runs fine if you shut it of i will not restart on cranking you can hear it trying to fire
Submitted: 7 years ago.
Category: Heavy Equipment
Expert:  Tim replied 7 years ago.

Hello, My name isXXXXX will try to help, are you sure that the engine is cranking enough and the speed sensor is picking it up, the sensor needs to see 50 rpm to start reading, you symptoms sorta sound like a slow cranking engine, If you have ET and lap top you can give it a external power source and watch the speed sensor with ET.. Just a thought..let me know.


Thank you,




Customer: replied 7 years ago.
its cranking fine rpm on lap top is good all it takes is 1 shot of starting fluid and starts right up
Customer: replied 7 years ago.
its cranking fine rpm on lap top is good all it takes is 1 shot of starting fluid and starts right up i dont have et to give it external power
Expert:  Tim replied 7 years ago.

Hello, thank you, XXXXX XXXXX do you have ET ( cats Electronic technition) on a lap top, you would have to give the data link external power so the lap top could stay on when reading the speed sensor.. lets go back a little though , you say you replaced fuel pressure valve.. was this the regulator valve in the filter base or the relief valve in the transfer pump.?/, also were are you testing the fuel pressure?and what is the cranking pressure?



Customer: replied 7 years ago.
the regulator is on the the filter base also the transfer pump was changed. testing fuel pressure on top of the filter housing cranking pressure is 30 then it jumps up to 50 and drops to 30 and goes back and forth 30 to 50
Expert:  Tim replied 7 years ago.

Ok regulator filtered pressure tested and at 600 rpm should be 65-87 psi, this test port is on the r/s of the base, it sounds like you are almost there just the engine is spinning below 600


the unfiltered pressure is done at 2100 rpm at the top of the filter, and you should see 104-114 psi


what are your cranking RPMs? does the tach register?.. once you get it to start on either what ist the filtered pressure at 600?. If you have changed the regulator and spring, and the transfer pump all these pressures should be good..


if these are ok.. you have to plug it into CAT ET with the external power connector and monitor the speed sensors, to make sure they are getting a signal to fire the injectors..





Expert:  Tim replied 7 years ago.

here is the procedure..the other thing it will tell you is that the ECM is even on you did check the fuse to the ECM. it doesnt need the ECM to start on either..the ECM does need at least 11 volts and the engine to starter ground and starter to chassis ground on and clean connection.


  1. Observe the engine rpm on Cat ET while the engine is being cranked.

    Note: This may require Cat ET to be powered directly by the vehicle batteries or by a separate power source. If this is necessary, use the 167-9225 Harness (Service Tool Adapter). Connect the harnesses 70–pin connector to the ECM J1 connector. Connect the harnesses 9–pin connector to the adapter for the Cat ET service tool. Connect the red cable clamp to the +Battery terminal. Connect the clamp for the black cable to the −Battery terminal.

  1. If Cat ET displays 0 rpm and the engine is cranking, there is a problem in the circuit for the engine speed/timing sensors. Refer to Troubleshooting, "Engine Speed/Timing Circuit - Test".
  1. If an engine rpm is present, check the sensor installation. If the sensor is not properly installed, the sensor may read RPM but the sensor may not be able to sense the tooth pattern. The ability to sense the tooth pattern is necessary to determine the crankshaft position. Engine rpm is present when the engine rpm is 50 rpm or more
Customer: replied 7 years ago.

motor running at 600 rpm fuel pressure is 85 psi and at 2100 it is 106 psi the tach did work untill the motor was changed now it moves very little off the bottom also it is trying to fire when cranking.i have another c12 and check the fuel pressure with the ecm fuse out and at cranking it holds at 40 psi it might not be the fuel pressure it just seemed weard that they were not the same.

Expert:  Tim replied 7 years ago.
I gotta say your fuel pressure is good your ecm is either not on, or its not picking up the speed sensor..
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