Have a customer truck in the shop and trying to figure out a no start issue. Truck cranks like crazy but won't start unless it gets a sniff of ether. Doesn't matter whether it was running and shut off for only a half second. Always needs ether. When it is running, it runs fine and it will run all day until shut off. Getting active injector current faults on all 6 injectors while running. Cylinder cutout test works fine. It's a 1992 7LG 3176 All this is leading me to think that the ECM is shot. Which is weird since I can connect to it and it does run. Have not installed sight glass in fuel system since I don't think it would lose prime that fast. Plus when I pump the primer hand pump it's stiff right away. I have checked the timing sensor. It is receiving and sending proper voltage during no crank and cranking conditions. Any other opinions?
How about the harness to the sensor? If ECM doesn't realize the engine is turning it might not turn the fuel on? Also, I'm not 100% on that engine, but does the ECM have to realize rail pressure before it can start? Finally, I had a similar problem on my Cat 75C Challenger. There is a check poppet in that return fuel housing on the head, driverside, towards the front. When that was faulty, it would not make rail pressure. Figured it out by hooking a pressure gauge to the pressure tap on that housing. If I remember, it needs 75 psi to start. Mine was making about 40.
I seem to remember that these had to have a certain pressure to start firing injectors...but I thought it was hydraulic oil pressure of 400 some psi. The test was to remove the sensor connector and the ECM would assume some default value and start but set a code. But it would allow the injectors to fire when they otherwise would not. The ether might be allowing the engine to start fast enough to get that oil pressure up where it needs to be. On edit: I was thinking 3126/C7 but it might still be applicable.
3176 has electronic unit injectors......3116/26 has hydraulic electronic unit injectors. You are correct about the 400 psi. That is the oil pressure required to turn on fuel. A 3176 is basically a destroked C12. I hope timbruun comes back.
I have checked the harness to the sensor. All checks out. Also I am getting rpm when the truck is running. I will look into the fuel tomorrow. I haven't found anywhere that says it needs pressure anything to start. As long as there is engine timing, fuel and proper voltage ECM signals injectors to fire. Was in the middle of going through the injector current fault trouble tree to finish the day. And yes these are not HEUI. The thing that troubles me is that I can have an active current fault on all six injectors and it still runs fine. Even doing the cylinder cutout. So far tomorrow I will finish the current fault troubleshooting and then look into a fuel issue.
Definitely need to finish injector fault testing first. I have seen more then one ECM fail with odd current fault issues but still communicate fine with ET. What is the fuel pressure while cranking ? If your injectors are getting some internal wear on the plunger sometimes it takes more fuel supply pressure or a shot of ether to start. Sometimes if I suspect worn injectors I will try replacing just 2 of them. If it starts firing on 2 and then fires up you know to replace the rest.
I will check fuel pressure tomorrow. Would I not have other issues/faults or codes if there was more problems? The engine doesn't even run rough.
We have a Cat C-7 that absolutely will not start until it runs through the glow plug cycle..... At least i assume thats what it is. Its in a Ford F700. Not even sure if that engine has glow plugs but its just a thought.......
No glow plugs. I really feel it's the ECM since I have active codes on all 6 injectors. Plus no matter how long I crank it, it will not start. Unless it gets ether it's almost instant.
The 3116 sometimes (?) had an intake heater, same difference. Running fine and starting are two entirely different things on a common rail engine.
Exactly, Delmer. I am leaning towards the return check being hammered out in the return housing up on the head. When I checked fuel pressure, I had about 40 psi. Cat said it needs 60-70 to start.
K. I will be checking that tomorrow. That's why I join these forums. And I do hope it is a fuel problem. Will be much cheaper.
I good friend of mine had the exact same symptoms on his 3176. Listening to the mechanics and test computers he replaced every injector and wiring harness with no luck. It was the ECM.
In my limited understanding of common rail systems, any of the injectors, or a couple other places can leak and it can't build enough fuel/rail pressure to start. One pop from starting fluid and there's enough speed/pressure that it runs fine, but won't start the next time.
So I read pressure from the port on top of the adapter manifold. Do not have the correct gauge or fitting to take it from the plug on the filter base. During cranking I am getting 20-30 psi. So that being low. Should I be replacing the regulator in the adapter manifold or the relief valve in the transfer pump?
You don't actually need 60 to 70 to start . 45 psi will do it . if its taking more then that your injectors are getting weak.
I am only getting around 20-30 psi at cranking. approx. 50psi running. Going to removed the transfer pump and have a look at it. Already took the valve out of the siphon block and can't see anything wrong. Replaced both fuel filters again and blew through all the lines to make sure there is no blockage. With the fuel/water separator off I air up the fuel tank and made sure fuel came from the hose as well. Still haven't finished troubleshooting the injectors codes though. Trying to do everything at once so I don't have to be constantly taking apart and reassembling parts and harnesses.
Yair . . . timbruun Dunno mate, I have not worked on modern equipment and I understand where you are coming from but I always found it better to work through issues methodically . . . nothing worse than "fixing" something and not quite knowing what you did. In no way am I being critical it is just a casual observation. Cheers.
You can cap off the line coming from the fuel transfer pump to test, it has a built in relief valve that should build around 100-110 psi before the relief opens. There should be a regulator valve in the fuel filter housing, they must be torqued to spec or can be distorted and will leak, leaking injector orings will dilute the oil, you can remove rocker covers wile running and see if they are leaking. ( oil will be real thin and overfull ).
Ok. So I removed the transfer pump. Other than the pin that drives the one gear being a bit worn a tiny bit, giving a bit more play there is nothing wrong. The relief valve has some very minor scratching on one side only part way up. Just noticeable by eye. Can not feel it with a finger or nail. Removed the manifold/siphon block and took out every plug and the regulator valve. Only thing I can find is a small piece broken off of the end of the regulator valve. It shouldn't matter since it's where the spring is resting and has nothing to do with fuel flow. I blew through the lines to make sure there wasn't a blockage. There are no valves in the fuel filter housing from what I can see and what cat parts tells me. Is there a spec for if fuel should hold pressure for a length of time? If I pump up the fuel with the hand pump, the pressure is gone pretty quick.
I will look in sis about filter housing, I must admit I work on more machines than trucks.
I am on SIS. Actually as I type I am reading compete fuel troubleshooting steps. I have No start condition. Crankshaft turns. No smoke. Active injector codes on all 6 injectors. Only fuel thing I have not checked is pulling the injectors. The fuel regulator in the siphon manifold I might just replace anyways since it's cheap along with the spring. And I will check oil level in pan and possibly send a sample in to see if fuel is going in there. So onto completing my injector electrical testing. And hopefully finding a rental/loaner ECM. Even a salvage truck ECM for cheaper wouldn't be so bad.
This might sound crazy,hook up fuel pressure gauge, watch rpm on ET, crank over watching rpm and fuel pressure, ad a small mist of ether or propane and see at what rpm or pressure it fires on its own,
50 pounds fuel pressure running is low, no complaints of low power?
I can't do cranking rpm on ET. It looses connection with laptop. Unless I'm doing something wrong. I did test cranking rpm by doing voltage from the timing sensor and it's within spec for voltage. Also, the tach does show rpm when cranking. Plus it does not sound slow by any means. Usually have the booster on it at the same time to make sure I'm not losing rpm or voltage to ecm while trying other things. No complaints of low power. Although this is not a driver that is used to large trucks. Still can't find where my loss of fuel pressure is though. Just finished checking continuity of injector harness from head to ecm. Quick history now that I heard it from the owner. He was just backing up slowly one day and it just died. Would not start back up. After towing it home someone mentioned to try ether and it's been that way since.
Next step is to pull valve covers and check/test all injector electrical and then either ecm or start pulling injectors.
On some trucks tach rpm comes from timing sensor in bellhousing, ecm uses rpm from timing sensor on cam gear, does your have one sensor for cam behind air compressor and one on crank behind front engine mount from the bottom? You could watch rpm on tach and use ether or propone to watch as rpms come up fuel pressure should rise as rpms do.
With key on did you try to start it at the starter leaving the key in run, could be loosing key power to ecm while cranking, with ether it might be turning over fast enough that when key returns to run ecm is powering back up?
This one has a sensor that is on the top right hand side of the front gear train. single 3 wire sensor. Haven't checked to see if the tach actually does use a different sensor or not but I was getting rpm in ET showing that the sensor does work. And it was same as the tach in the dash. I have tested power to ecm while cranking at the ecm harness. No crank I'm at 12.3 volts, cranking it's at 8 volts. That is without the booster on. Obviously the numbers are higher with the booster on.
I believe 8 is to low,10 plus in minimum, should have two, battery voltage all the time, key on or off and one key on. 8 volts won't fire the injectors.
According to SIS anything over 6 volts while cranking is good enough. The numbers are higher with the booster on though. There is no voltage drop from the batteries to the ecm. This ECM only has 2 key on voltages and 2 grounds. The positives come from the same wire on a harness farther up and the grounds go to one wire which is grounded on the cylinder head.
You need to get that fuel pressure resolved. 20-30 cranking is way to low. 50 running is terrible as well. The fitting where the actual return line that goes to tank hooks onto that housing on the head; turn that fitting out. That little poppet under it is your return check. Either replace that poppet and the spring, or change the whole housing. I believe it's around $200. I firmly believe that is your starting issue. After your fuel pressure is solved, you can fix the injector faults.
I have ordered the relief valve and spring for the transfer pump as well as the poppet/regulator valve and spring in the siphon manifold. Should have it all tomorrow and will put it all together and try again from there. Didn't think I needed the whole manifold but I will see how the poppet fits when it shows up.
Yeah, what happens is the seat gets hammered out and the poppet doesn't seat. Can you see wear around the tip of the poppet? Mine looked pretty good, just some scratching, but when I changed it my pressure went from 40 to 70 cranking. Runs about 80-100 while running. Cat told me if the poppet didn't fix it I would need to change the housing. Hope it fixes yours.
I hope it fixes it as well. Still going to have to deal with injector codes at one point I assume though. Can't see fuel pressure fixing injector codes.
Be prepared if you pull injectors the injector tubes should be done as well. Injectors on a 3176 are not as simple as a C12, which has stainless tubes. The 3176 has copper tubes. They like to leak. Good luck.
Can you get a full serial number. Fuel pressure should be 70 to 80 at least. ET should not lose power while cranking. You may have to feed power to the power supply terminal on the plug so you can read it while cranking. There should be two keyed and at least 1 battery fed terminal on the ECM I will get you the power supply terminal numbers later.
Wireing I have is for a 3176b shows one key power pin 6 and one constant power pin 4. You will have to use alternative power when cranking with the key, should be able to jump solenoid at starter and be OK I believe.
Serial number I have is 7LG10625. Can't see arrangement number. Should get parts today to see about the fuel pressure. This is not a 3176B. 1 and 11 is battery positive, 12,21 battery negative
Just found out parts are earliest tomorrow. They are in the US, so hopefully tomorrow noon. This plug is not in the truck either. It is on the block, above and to the left of the ECM. It is a different 9 pin than usually on trucks. I think it's what gensets might have? It's a 9 pin but doesn't have the notch on the one pin. When I get the fuel parts I will put everything back together and put the ECM back in and try it all again. I will try putting power straight from battery to data link connection and see if that fixes ET losing connection.
Found this. Seems slow. SMCS - 0374; 1000; 1450 All Caterpillar Diesel EnginesGenerally, the cranking speed needed to start Caterpillar diesel engines is in the range of 100-120 RPM. When warm, the engines will start at a lower cranking speed. In cold temperatures, battery, starting motor, glow plugs, oil viscosity, starting aids (ether, jacket water heater) and type of fuel used have an effect on how rapidly the engine will start. At all times, the engine must be in good condition to start at the normal cranking speed
So there is a sensor on the flywheel. I guess I didn't look hard enough before. It says freightliner on it so I'm guessing it's on the oem side and will have nothing to do with starting. Probably how tach works in dash.
Probably, would be nice to check rpm on et while cranking. That's where the jumper harnes come into play with a remote battery in the trouble shooting.
I will give it a try once the parts are all installed.
Good luck, keep us posted.
Looking fwd to seeing how this turns out. My old case farm tractor won't start unless the oat is about 90 deg or above or you give it a bit of eather. I'm figuring its low compression but have not had time to check it yet.
830, 930, 1030? Newer? Those old indirect Case diesels didn't start when they were new. Anything with a 504, however, can start down to 10°F as long as they have a pump that has the starting grooves on the pump plungers and the magnet for the rack.
It's a 730
Quick update. I received some parts. Of course the relief valve for the transfer pump was the wrong one. I reassembled the pump anyways and put it in the truck since the relieve valve looked fine and I didn't want to wait to do more testing. The regulating valve and spring for the siphon block was installed. Didn't really change much. So my question now is when I pump the priming pump I can hear fuel getting dumped back into tank from the fuel return hose through the regulating valve. At what pressure should that be at and is there any other valves that I should be looking at? I'm not getting too high of pressure. If it's not high enough I should probably try changing the complete manifold block as well. Unless the fuel is bypassing by the injectors. I am going to quickly try the buzzer TIB and see if that solves anything as well.
This is the only information I can find on SIS in regards to fuel pressure. Does not give a starting psi. I'm getting around 60psi at low idle. I'm going to install a liquid filled gauge as well so I can give a more accurate number.... Fuel Transfer Pump With the engine operating at rated rpm and load condition, the fuel transfer pump moves fuel through the ECM, fuel filter base, and fuel supply and return manifolds. A pressure regulating relief valve, in the return fuel manifold, regulates the fuel pressure at approximately 550 kPa (80 psi) at rated rpm. The minimum fuel pressure must be 445 kPa (65 psi) or greater at rated rpm. If the fuel pressure is not above the minimum specifications, stop the engine. Make a replacement of the fuel filter, and make sure the fuel lines are not plugged or damaged. Start the engine and again check the fuel pressure. If the fuel pressure is not above the minimum specification, a repair or replacement of the fuel transfer pump or a replacement of the pressure regulating relief valve is needed
Cranking speed is from 155-205 which is within the 100-300 to start according to SIS. Still waiting on proper fittings and gauge to get accurate fuel pressure while cranking and running.
Also, disabled the engine monitoring parameter and that did not solve it. So the TIB did not work for me.
As you already know, the fuel rail pressure is limited at 80psi so you should be able to get 80psi with the hand primer. As a quick and dirty check, once the air is out of the system the hand primer will be so hard to push in that you pretty much have to lean your bodyweight against it. If it's pumping fuel back to the tank freely then you still have a problem with the relief valve in the return manifold.
Ok. So, found a used ECM. Installed it and within half an engine crank it fires right up. Now I just need to transfer ECM information to get the same HP settings. Haven't checked fuel pressure yet. Might just do it anyways so I know for future reference.