Hello, I have a cat 3126 in my box truck and it will not start. It seems that the shut off is sticking or not releasing. Freightliner had it for 3 days and all they did was put a new fuel line on it that didn't help. Does anyone know where i can download a diagram showing where this shutoff valve(solenoid?) is on this thing? It is inside the motor. 340,000 miles on the motor and this is the only real problem i have had with it. There are some things electronically that are starting to act up like my cruise control goes crazy sometimes, fuel gauge acts up and water temperature guage acts up. Any help will be appeciated.
Will it crank with starting fluid and then quit? I seen one of these engines do that in a coca cola truck and turned out to be a allen bolt that holds the oil sending tubes under the vavle cover broke and it wouldn't allow oil pressure to build up so it would crank. Tim
Just a thought!
Start your troubleshooting by grabbing the CAT engine book that came with it. Then use the cruise control switches in the truck to read the codes using the check engine light. On mine, it's usually either one or two things, either the IAC valve on the HPOP or the rubber line from the HPOP to the head (if it has it - early ones had steel - new style had rubber - latest has steel again). Both easy to change. Also known to fail, and much harder to repair, are the two speed sensors behind the air compressor. But we're guessing and possibly wasting money. Start with the codes to narrow it down.
Ok, thanks for your responses. I bought the truck off my brother and i have never seen a book that comes with it. It cranks over good, it just won't fire. I guess i should explain the cruise control better. It doesn't work right because when you go down the road with it on, the speedometer will start going down for no reason which causes the cruise control to speed up, so actually i guess it is the speedometer that is messing up. Sorry i didn't say that before. I talked to a guy today that thinks it is computer or sensor related. He says he knows a guy that has a computer to check it all out. He thinks that is why the relay/switch or whatever you want to call it isn't working. This thing is driving me nuts and i need to get it back on the road making money. Thanks again for any and all responses.
3126 engines don't have a shutoff solenoid, it is all controled by the ECM. Most likely the speed sensors not sending signal, HEUI IAP valve, or even the HEUI pump itself. Longshot might be ECM. Unless you have an active code, the cruise flash codes won't show anything. If you can get your engine S/N I could probably help narrow down the steps. It will most likely start with 1WM, 7AS, CKM, HEP, 9YN. Just to name a few.
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On my KW's, Freighliners, and CCC trucks the cruise control/check engine light WILL point you in the right direction. A 39 flash WILL send you to the IAC valve. A 31 Flash WILL send you to the lost speed signals. Our Cat distributor used to ask what codes were flashing via the check engine light, but have since given me a pocket tec to use. Pages 58 thru 66 in the C7 operation manual (only one handy and identical to 3126E manual), list the procedure for retrieving the codes using the cruise control switches, what the codes are, and the consequences. Usually though, in the case of the speed sensors, with the engine running, the check engine light comes on, depending on how the engine is programmed, the engine may run normal or power down. If the sensor/wiring is bad, it might still run, but once you turn it off, it will not receive a signal, and thus the no start. Here is where a scanner or pocket tec will show you the cruise control flash code, and cross it over to a cat code. The IAC will flash a code 39 with the cruise, but show up as a 164-11 on the scanner. The cruse flashes will point us in the right direction while troubleshooting,and has helped me and my cat distributor repair my problems over the phone, but it is not the see all the scanner is. It will give you an idea where the trouble lies.
Another thought, the problem could be something as simple as the main fuse going to the ecm! Had one of the off the wall chassis that the factory put too small of fuse in, and the engine kept quitting - no codes - no flashes - I think the factory called for a 10 amp and cat called for a 25 amp (long time ago) changed fuese and problem went away.
Thank you 99sd and 04hdf250 for your responses. I feel i'm finally being led in the right direction. The engine s/n is
7As74109 ...The perf. spec is 175-3297 and the ar no. is 154-1054. It is a 1999 year engine. Once again thank you for taking the time to help me out here. I'm going to print out your responses and give them to the mechanic to give him some things to look for.
Mounted in a 2003 330 Pete. Internittant no start. Engine cranking but no start raw fuel smoke out of exhaust. Can be started if put in gear and cranked or tug started after a few feet pops offs. Has 6 new injectors, new batteries and new starter. Cranking speed is ok. Any ideas were to go no engine light or codes thrown.
Purchased a 2000 HR Endeaver Mtr Home about 6 mo. ago. Has 38,000 mi. Runs great down the road. Problem: When started it starts fine, but when left idleing for 2 0r 3 min. it goes to lopeing. If I apply slight accelerator to raise RPMs 2-3 hundred, it smoothes out. If I hold RPMs up for 1-2 min and let off accelerator it stays smooth and does not lope again. I have only put about 1200 mi. on it in two separate trips. Fuel mi. is 8 mpg pulling a jeep. Have not added any fuel additives or made any adjustments at all. Does it just need fuel conditioner, or is there some other problem. I start it weekly and drive it 5-10 miles every 2-3 weeks. Thanks Ed 3126 Cat engine
Last edited by Retired Farmer; 02-28-2015 at 01:08 PM.
Reason: add info
have a 3126 cat engine that will start but only run for a few seconds then check engine light comes on and it dies it is in a 99 gmc 6500 topkick have replaced the heui pump, speed control sensor, cam sensor, fuel filters, oil filters, need to get running asap costing me money