What's the most important thing in the trucking industry? Getting the load to its destination. On time. The people at a certain break down service don't fully understand that fact. I was called out last night by a national road service provider (like AAA for semis) to go look at a truck that shut down. The driver said he got a "no oil pressure" message from the DIC (Driver Information Center. An LCD display on the instrument panel.) and the engine shut down. Simple enough. The ECM (Engine Control Module) wasn't getting an oil pressure signal so it assumed that there was no oil pressure. Wanting to protect the engine, the ECM cuts off the fuel and the engine stops. Well, not knowing what the exact problem was, I had to consider what would cause a no oil pressure condition. Here's what could cause it.
1.) There's no oil in the engine. Could be from holes in the oil pan (damage due to road debris), a hole in the block caused by engine parts failing and piercing the block, a leak from crank seals, failed turbo lines or the turbo itself, loose oil filter, bad oil filter gasket, leaking head gasket, bad front cover gasket etc. An oil pump can't create pressure if there's no oil to pump.
2.) The oil pump failed. That's pretty straight forward.
3.) Something is blocking the oil pump pickup tube.
4.) The oil pressure sensor failed or the wiring to it has been damaged.
5.) The ECM has malfuntioned.
OK, having considered the things listed above, I loaded up the truck with some oil filters and extra oil. I got the scan tool from my foreman and asked him for a mechanical gauge so I could verify oil pressure, or lack thereof. He told me that I didn't need it because I could check oil pressure with the scan tool. This is a true statement, however stupid it sounds, because the scan tool's data stream shows the oil pressure sensor's data. I made the point that if the sensor is bad, how would I verify the oil pressure? I left without a gauge. There's no point in arguing with the foreman. He can be a stubborn cur. I drove 50 miles to get to the casualty. The truck was pretty much in the middle of nowhere considering the time of day. Parts can't be had anywhere at that hour if we don't have what we need in the service truck or at the shop. Aside from getting the driver to sign my work order, the first thing I did was to look under the truck for a puddle of oil. Nothing. Looked all over the engine for signs of leaks. Nothing. Pulled the dipstick out. Full crankcase. Hooked up the scan tool and found a code for oil pressure sensor voltage. That tells me where to look and also that the ECM hasn't failed since it was able to communicate with the scan tool. So now what? I have no idea where the sensor is aside from that it has to be screwed into a spot that has oil passing by. There's a lot of things attached to engines these days, so which component is the oil pressure sensor? I had no idea. I tried calling the shop, but everyone had already left for the night. OK, time to call the service provider and let them know what's going on.
I called the service provider (SP from here on out) and told them what I had found. I asked them what they wanted me to do. The SP asked if I hooked a gauge up to the engine. I said I didn't have one with me. I could hear the frustration in his voice that was leading to him basically wanting to tell me I was incompetent. I calmly explained what my foreman had told me and he eased off a bit. This particular person is a dick, plain and simple. He never thinks about the most important thing in trucking. He wants to get trucks fixed no matter how long it takes or how unreasonable his requests may be. He didn't understand that this truck wasn't going anywhere regardless of whether I had a pressure gauge with me or not. Here's why.
Let's assume I had a gauge with me and actually found a place to connect it. If the oil pump isn't creating pressure, it's junk. Call for a tow truck. I'm not dropping an oil pan and changing a pump on the side of the fucking road. Where the hell would I get a pump at midnight anyway? If the pump WAS creating pressure there's still the problem of the ECM not seeing any signal from the sensor. Again, where am I going to find a sensor at midnight? The SP dude loves to suggest jerry-rig fixes and I knew he would bring up the stupid idea of bypassing the sensor. First off, that's totally stupid. Secondly, this ain't the old days anymore. You can't just unplug a sensor and stick a paper clip into the plug to make shit work. Thirdly, I'm not stupid enough to put my ass on the line like that. IF I could find where the sensor was on the engine and IF it was possible to bypass it, I would still refuse to do it. What if the pump makes pressure but not enough? What if the pump works randomly? If I bypass an oil pressure sensor, send the thing down the road and the engine seizes, guess who get hung out to dry? Yep, me. Like I said, I'm not that stupid. Time for more hypothetical situations.
Let's say the nearest place for me to get a new sensor was open 24 hours a day and the SP told me to go get one. The nearest place would have been 60 miles away so we would have a 120 mile round trip to get a new sensor. The trip is all interstate highway with a 65 mph limit. That's about 1.8 hrs of just driving. Add in time at the parts house and a couple of traffic lights and we're easily at 2 hrs. You, in the back, what did you ask? "How do I know that the sensor is actually bad?" I don't. Determining that would require diagnostic procedures from a manual or from Insight (Cummins Insight. The truck had an ISX engine in it.) Well, we don't have a manual and our subscription to Insight has expired. If I had information at my disposal, there would still be a good chunk of time devoted to diagnosis. Let's say that I was able to determine, without doubt, that the sensor was bad. Great. I spent an hour on diagnostics (still on the side of the fucking road mind you) and then have to waste 2 hrs getting a sensor. Sensor in hand, I put it in and... the engine still shuts down. Call the SP and update them. The SP in turn calls the truck's owner and updates them. The downtime thus far is... Hmm, let's add it up.
22:15 we get the service call
22:30 Service truck loaded and I'm on the road
23:25 I arrive. Start paperwork and preliminary diagnosis
23:45 I call the SP and update them
00:00 Done talking the the SP, I hit the road to get a service manual and a new sensor
02:30 Return to the site and begin sensor diagnosis
03:30 Diagnostics done. Sensor changed. Engine still shuts down
03:50 Updated SP
The truck was, obviously, sitting still for AT LEAST 15 minutes before we got the call. That would put total downtime thus far at just over 6 hrs. Imagine being the truck's owner. You've just been told that after 6 hrs of downtime, the load on your truck still won't be moving. You'll be paying for 6 hrs of service call to boot. Now, that's about $800 that we would bill the SP. They, in turn, would slap their fee on top of that. Probably $900 - $1000 when it's all said and done. Now, you would find out that on top of the service call you would be paying for a tow (the distances involved would easily make for a $1000 tow bill.) I'd venture to say that steam would be coming out of your ears. Now, guess who the bad guy is in this hypothetical situation? Yep, me. Shit rolls down hill. Customer raises hell with the SP who, not wanting to take the blame even though they ARE to blame for this whole cluster fuck, will contact my shop and raise hell. The shop owner not wanting to lose a good customer looks into the situation. I get interrogated and even though I did exactly as I was told, some fault will be found and I'll get hollered at. I know how shit works around here.
As the service call went in reality. I was only gone for about 2 hrs and the truck's down time was kept as low as it could be in this situation. There's certain service calls where it would be best just to call for a tow truck and be done with it. Service calls are best left for problems you KNOW can be solved. Flat tires, brake chamber or valve leaks, bad air lines etc.
So, you can see that Captain Jerry Rig at the SP likes to have people banging their heads against walls. Hell, it ain't his money that's being wasted. Jerry Rig doesn't understand that sometimes it's best to just get a tow truck on the road and keep the down time to a minimum. Get the load moving!