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Happy Holidays All, I haven't started my coach in several years. Went to start and engine turns over but there's no light for the preignition heater. It didn't start even after several tries and the pre-ingnition light never illuminated. I checked wiring around the starter, all around engine area and no evidence of wires damaged or chewed through by critters. Any idea of where to look next? Everything else in startup sequence appears operational. Thanks in advance and Happy New Year! Tom
1997 Safari Ivory 3730, 3126 CAT/4060 Allison

Have you checked for power at the intake manifold heater solenoid (top of engine) when the key is turned to the first position?

BTW, you will have the Allison 3060, not 4060 with the Caterpillar 3126.

Hi Tom,
You mentioned that "everything else in the startup sequence appears operational." Does this include the Check Engine light illuminating for 3 to 5 seconds after "Key-On"? If the Check Engine light does not illuminate when the key is switched on, the ECM isn't powered up. Without the ECM powered up, the starter will still crank but nothing else on the engine will function. Power to the ECM is controlled by a relay on the wiring harness between the batteries and the engine. I located mine attached to a frame member behind the battery tray, had to roll the tray out to find it. I've had problems with it multiple times.

Best of luck,

I believe I have a similar problem but unfortunately, I'm having a lot of trouble finding the ECM relay. Does anyone know where this relay might be located on a 1996 Safari Sahara? Thanks in advance for your help!
Patrick
Safari Sahara 1996
CAT 3126b

You need to take a real good look inside your battery compartment, original factory had a box with exposed fuses and relay behind the batteries and power came from 1 wire off the engine batteries ( so trace from there). However lots of people drove the battery tray in too hard and smashed the box. Mine was a series of newish wires bunched up on one of the engine battery terminals with inline ATC fuses meaning the "box" was smashed. As I traced the wires back towards the engine I came across a relay mounted on the framework over the batteries that I saw from the bed box looking down (I immediately changed it for a new relay). Also in that "box" was fuses for the RVA leveler control switches in the service bay, Allison ECM, service bay power (probably the service light and power for the 2 gauges, not the hourmeter that one is in the bedbox on an ignition wire), alternator (not sure what for!, maybe original alternator terminal2) and fuse and relay for the Cat ECM. Also the "3126B" in your rig should have a 1WM serial number meaning it is an original 3126, 275hp, 300hp or if flashed a 330hp. 3126B were built from 1998 with 7AS, 8YL and 9SZ serial numbers.

My brother, who knows more about mechanics than I do, tested a bunch of relays and fuses (including what appeared to be the "ECM relay" and the "ignition switch" relay), but unfortunately, everything seems to be in good condition. Could it ultimately be that the ECM is no longer functioning? Is there a way to test if the problem is the ECM itself? Thanks again Len for the help.

Patrick
Safari Sahara 1996
CAT 3126

Patrick,

Contact your local Caterpillar dealer about testing the ECM.

If no joy, I would do a search for "repair Caterpillar ECM's".