99 Pete 379 HELP PLEASE

Tiffany

Member
99 Pete 379, 60 series Detroit, 840000 on miles. Just had full rebuild with new crankshaft (spun a bearing) When we took to the shop jakes were working perfectly, now half the time they are not working more specifically while on the HWY. Mechanics says maybe computer?? But we took it to the shop with no problem with the jakes! Oil pressure is also acting up but after testing the pressure on the motor and the gauge it is said to be running correctly. Just don't know if these coincide together so wanted that to be thrown in there. Any help would be greatly appreciated! We are new to the trucking industry and still learning.
 

Truck Shop

Well-known member
You say oil pressure is acting up, does the check engine light or gauge drop when jakes are on? If so it probably has an issue with missing
oil galley block off plugs in one or both jake heads. Did they test the solenoids on the jake and or re-oring them before putting them back
on? And the wire connections to the jakes need to be checked, plus the terminals are tight to the wires. It's easy to over look the galley
plugs, Normally you find them stuck to the magnet on the oil drain plug. One other thing the switch's in the dash have those been checked?

Truck Shop
 
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Tiffany

Member
You say oil pressure is acting up, does the check engine light or gauge drop when jakes are on? If so it probably has an issue with missing
oil galley block off plugs in one or both jake heads. Did they test the solenoids on the jake and or re-oring them before putting them back
on? And the wire connections to the jakes need to be checked, plus the terminals are tight to the wires. It's easy to over look the galley
plugs, Normally you find them stuck to the magnet on the oil drain plug. One other thing the switch's in the dash have those been checked?

Truck Shop
The oil pressure doesn't drop, nor does the engine light come on. We will test the switches in the dash, he said he check everything and couldn't find anything. He seems to know his stuff pretty well and we have never questioned anything but this. I appreciate your feedback and will bring these things up to him so we are reassured everything is perfect! If not time for a second opinion I assume.
 

Truck Shop

Well-known member
Has anyone checked for codes? The cruise and jakes are tied into the ecm. If you had bad connections at ecm- open cuircuts, it should be
showing something. The jake wiring under the valve cover are built into the injector wiring harness. The only other switch I can think of
is the clutch switch.

Truck Shop
 

Tiffany

Member
Great, thank you! We are going to be going through everything on Friday and will keep yall updated! Hopefully we can figure it out!
 

Welderguy24

New member
60 series Detroits are very common for under valve cover wiring harness failures. What happens ins engine oil gets between the copper and the insulation of the wires, which then wicks all the way down the harness into the ECM, causing an internal ECM issue. I would disconnect the Jakes wires from the injector harness, and test for current output to see if it is a ECM or wiring issue.
 
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