when starting up my jeep the glow plug light stays on for 2 seconds. when it is cold that seems like it is not long enough to get it going. what controls the glow plug duration? would that be a glow plug relay?

The red light isn't a good indicator of how long the plugs are one. They actually stay on a bit longer than the light. Others will hopefully chime in with more info

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2005 Crd Silver Limited- arps, rockers, 7v etechno's, egr deleted, v6 airbox, metal cac's. Yeti's stage 2 tune. Euro TC, Ram tcm, pml transmission pan, facet lift pump

Is your jeep having a hard time starting?

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2020 Ram 1500 CC Ecodiesel Limited
1995 Dodge Ram 2500 4x4, 5.9 Cummins, 47RH, Reg Cab
2005 Liberty CRD,fixed the rockers and a couple more things,GDE Hot tune,Weeks Stage 1 and 2 EGR delete,Hot Diesel solutions Tstat assembly(wonderful heat!), ARP studs, OME 1.5" lift.....thanks Seth! (Sold)
2006 Liberty CRD....The Moose Hit

How cold is it where you are?
Are you using the factory original ceramic 7v plugs, metal 7v plugs, or metal 5v plugs?

Glow plug on time is entirely controlled by the ECU.
Turning off and on again will force the glow plugs to cycle again and may help with starting.
Also check the health of your battery.

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U.S. Army Retired

With my GDE hot tune and a voltmeter, I recorded a total of 12 seconds that the glowplugs were powered on after turning the key on.

Duration is controlled by the ECU as well as possibly the voltage.

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2006 CRD - GTB2056 turbo by Dieselguy86, Eco Trans Tune, Lift Pump, Week's, HDS Tstat, Racor Filter, ARP's, OME 790's+Top Plate, JBA 2.5", JBA UCA, Moab's+265/75R16, ARB Bull Bar, 4.10's, TrueTracs

The ECU controls the duration that the light is ON for and for how long the plugs themselves are ON for.

The light goes off for a very short time while the ECU continues to cycle voltage using Pulse Width Modulation for several seconds onwards.

Some owners find it useful to cycle the ignition ON/OFF a few times before cranking while other owners have had better success with other voltage plugs and plug controllers.

My 2002 Export CRD uses a very basic system of 11 volt Glow plugs powered ON for a few seconds by the ECU with no error checking other than that the two large relays for the plugs are not open circuit or short circuit.

In the warm climate I am in I can start my Jeep with the plugs dis-connected.....sounds rough and lots of smoke but it works.

I have seen on one of the Jeep sites that a lot of Austrian CRD owners are unhappy with the system that the newer CRDs have and so they revert to fitting the old style 11 volt glow plugs!

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2002 Export CRD 2.5 Sport