Once again, "The Guy's" from Texas have come through big-time with this step by step tutorial. Soon the Cerlist motor in your M-series truck will be purring like a kitten! Many thanks for this in depth article on getting these motors back in shape & hopefully back on the road!
-
Part I, “Save the Cerlist”
-
-
Reasons why your Cerlist won’t start or runs awful, and ten things to do to bring it back being useful:
-
First off, these engines are not that complex, yes there are a lot of variables but most of the time decent performance comes down to one or more of the following five things: good compression, good glow plugs, a good injector pump, 3 good injectors, and proper injector fuel timing. Yes, there are a lot of peripheral issues that can be problems as well, but most probable it’s one of the five areas just mentioned. Don't be afraid to dive in, again these are not that complex….hope the following will be helpful, read all points before you start, especially if your Cerlist does not currently run:
-
The first thing you want to do is to rock the accelerator linkage back and forth on your injection pump. If it stops part way to full throttle then the plastic disc or plate inside has disintegrated and chances are your motor won’t start. This is because the centrifugal counterweights that advance fuel timing are stuck due to a disintegrated plastic disc inside the pump. Even if it does start, it will run very erratically or at high RPM. Best not to try to start it - your pump needs rebuilt. Any good injector pump shop can rebuild it. Cost is $600-1200. Note that If your accelerator linkage has full travel it’s definitely a hurdle cleared, but it is no guarantee it’s fully up to the task, however usually it’s likely enough to get you running to see what you’ve got. Ours had not run in years, it had full throttle linkage movement, started and ran fine for about 15 minutes and then the aged and fragile plastic inside the pump gave out - requiring a rebuild. But that 15 minutes of run time was critical in evaluating the rest of the motor and helped ensure our injector pump rebuild was worth it. Now, before you even consider rebuilding your pump, read on as there may be other issues.
Let’s assume you have two good 12 volt batteries, if not you will need them. A few critical areas on the Cerlist require a good 24V power source (starter, glow plugs, injector pump circuit, etc). If you don't already have good batteries we have found that the combo of one group 24 and one group 24R battery work best in terms of fitting in the original battery trays and enabling the same “series”’ layout for the cables that the factory used. (A factory negative to positive connector cable is perfectly spaced to have one of the two batteries with reversed terminals versus two identical batteries, so if you are going back all original, go with the batteries just suggested).
-
Now that you will be able to crank the starter…..next you might move on to a compression test. But only if your compression tester has a fitting that will thread into your glow plug ports. If not and you need to use the injector holes…a bit of caution here. Before you start unhooking lines and injectors that might be corroded, might not come apart easily, and not reseal upon reinstalling - you need to consider if it’s absolutely critical at this point in time to test compression. You can create a lot of issues given there are six different sealing points at each injector site that might not easily reseal. You can also also run the risk of damaging the injector lines and respective line crimps (which are unavailable from what we have found). So the compression test is important, (but if you cant take it through the glow plug holes) it may take some judgment on your part. It’s great to have that info from the start, but may create other issues in determining it. Might be a judgment call based on what you already know about the motor, example “ran fine before sitting” (skip test) or “looks like it had significant problems before you got it” (test might be critical). After you have made your determination, move to next step.
-
-
Fuel. Do yourself a favor, to isolate what’s happening with your Cerlist, eliminate “old or contaminated fuel issues” right at the start. Additionally your injector pump will hold a full load of fuel inside it for decades - so flushing it out before your initial firing of the motor is a good move. So, get a five gallon gas container filled with fresh diesel and add an additive to compensate for today’s low sulfur. Place it on the floor by the drivers side rear passenger door (in the case of an M677). Run one 7 foot 5/16 ID hose out of the can and put an inline fuel filter in it and a 24V inline fuel pump (2-4psi), you can go a little higher on psi but around 8 psi you can damage your injector pump. These inline pumps are on Amazon at $15, the fuel filter are $11 for a pack of five, also Amazon. Run this line up to the high point on your injector pump lines - in the front center of the pump (this will serve as your “fuel input line”). Next you will notice that there are two hoses connected together to the same ports lower down on your pump These two are your “fuel return lines” that flow unused fuel back to the tank. Disconnect the current rubber line from the pump to the tank (not the line that flows back to this joint from the injectors) and for now, don’t run it back into your five gallon diesel can but instead into an open container. This will enable you to use your inline 24V inline pump to flush your injector pump and injector lines and ensure that the fuel that would normally return to the tank is good and clean before you place this fuel return line back into your clean 5 gallon fuel source. So you are now ready to flush this fuel except for one thing. See next item.
-
-
There is a 24V electrical circuit that takes a positive battery lead connection to open. Normally this is activated through the ignition switch. Depending on the status of your trucks wiring harness, it may or may not be in working order. So either as a test, or as a temporary start up fix, run a jumper wire from the positive battery terminal (not the one that is jumped to the negative terminal of the second battery) to the injection pump circuit terminal on the front of the injector pump. If you get a slight spark and a click, you have now opened the circuit that enables fuel to go through the pump. Conversely disconnecting this jumper wire will prevent the motor from running or shut it off. As a “run away” fail safe there is a a governor shut off T-handle that is hooked to a pull cable on the front center floor tunnel between the seats. Hopefully your cable is hooked up, perhaps not. Either way make sure the linkage to the governor is rotated clockwise as far as it will go on the injection pump or your motor will not start. Rotating it counter clockwise (IE: the direction the pull cable would move it - will shut the motor off if anything else goes awry)
-
-
Glow plugs: if you have removed them for your compression test, they are easy to check. All you need to do is to ground the threaded area of the glow plug and jump the electrical tab in the center to your positive battery post. We only had six of these laying around to test and they either worked fine or didn’t work at all. We also used a cheap digital heat gun to test the temperature climb. Here is a tip, if you are not checking your compression via the glow plug holes and have no need to remove them, simply arc a positive wire to each glow plug. If it sparks, the glow plug is likely fine to get you started, no spark means it’s dead and needs replaced. Yes this is a crude approach but again we are just trying to fire the motor to see what we have got.
-
-
Injector pump, and fuel timing: if you must remove your injector pump be careful as to how you approach it. Remove it by simply removing the two nuts at the base of it (versus unbolting the right angle gear drive that it sits on). Note that the two holes at the base base of the pump are oval shaped. This allows for you to loosen the two mounting nuts and rotate the pump a limited amount to tweak your fuel timing. According to our local diesel guy, it’s likely that 90 percent of motors leaving the factory had the pumped dead center in the middle of these two ovals. But as your pump breaks in or is perhaps rebuilt, the fuel advance counterweights might find a different resting place and you can compensate for this in slightly rotating the pump at its base and tightening the nuts when it runs the best. After our pump rebuild the motor ran ok but had a slight surging to it. Moving the pump a bit clockwise and retightening it made all the difference and it now runs great.
-
-
Finally depending on the status of your truck and its wiring, you might want to isolate electrical circuits to make sure sure that wiring is not an issue. We made a temporary start up panel and bought two surplus 24v gauges (temperatures and oil pressure) and bolted them to a piece of of flat bar. Also on the flat bar is an on/off switch for the injector pump circuit, an on/off switch for the 24v inline fuel pump, a monetary contact switch for the glow plugs and a momentary contact switch to engage the starter.
-
-
It’s also good to loosen the three injector line nuts at the injectors, then activate the injector pump circuit and the 24v inline fuel pump and then crank the motor to fill the injector lines to ensure you have fuel being delivered to each injector. No need to crank the motor at length only to later find there is no fuel reaching the injectors.
-
-
Fuel Injectors: We and our diesel shop personnel have searched high and low for a replacement injector or for NOS ones that might be laying around. No luck to this point - someone out there might have a solution that works? These original injectors are rebuildable, we paid $80 per injector to have ours rebuilt. Although it’s critical that these are functioning optimally for best performance, chances are they won’t prevent your motor from starting up. We had some extra laying around in different levels of condition, and the motor started off any combination of them. It did run differently, smoked differently etc with different configurations of these in place, but it always started. There is a real benefit to just getting a Cerlist fired up and it will “tell you” what isn’t working properly via several symptoms.
-
In closing let’s discuss exhaust smoke. There is ample information online as the what contributes to white smoke, black smoke, etc. You can read that on your own, no point in rehashing it here. These engines do smoke even when running well. How much they smoked when all the components were brand new is a benchmark we wish we had - but we don’t. So best bet is to get yours running and diagnose additional actions that will address whatever color smoke it’s putting out and hopefully you will be able to use, enjoy and “Save a Cerlist”
Part II, Injector Pump Removal & Reinstall.
“Save the Cerlist”
If you are reading this you have likely concluded it’s time to remove and rebuild your Cerlist Roosa Master Injection Pump.
The careful removal and replacement of this pump is critical to the future performance of your Cerlist Motor. Less than a well executed replacement can lead to more problems than you started with although this is not terribly complex, patience and a little extra care go a long way.
-
There are two ways to remove your pump. Remember your pump is driven by a vertical shaft that is timed to your crankshaft. There is no need to risk reinstalling this shaft and its respective drive gear “out of time”. So DO NOT remove your pump by removing the lower aluminum casting that bolts into the side of the block, if this part must be removed you can do it after the pump is off and after you can see the clocked position of the pumps vertical drive shaft - this will be critical information to retain to keep your pump properly timed. But you shouldn’t need to remove the lower casting unless you have much bigger problems, so leave it in place for now.
-
Note that you are ultimately going to remove the pump via the two nuts that hold it in place at its base, but don’t loosen those nuts quite yet. First you need to remove the injector lines, partially or completely. Anything you can remove from the pump while it is well anchored in the block puts you a step ahead. Some of these fitting may be corroded and take a great deal of force to loosen and there is no easy way to secure your pump in a vice without damaging it. So, remove what is needed before you pull the pump out.
-
Next you can begin loosening the injector line fitting at each injector site on the top of each head….but note that there is a risk you may break other threads in the assembly loose first (several pieces threaded into each other). So place a wrench at the base of the injector, (not at the head plug the injector threads into but at the lower hex on the injector itself). Use this wrench to lever against while you loosen the injector line. So now all three injector lines should be loose and the line separated from the injectors. A word of caution here. These original injector lines are all equal length and need to be for proper operation of your Cerlist. There are fittings crimped onto either end of these lines that the tapered injection line nut and tapered mating part crush into place for a good seal. Be gentle with the lines when removing as making up new lines won’t be simple since this style line crimp fitting no longer seems to be available. At least we have found no source for them.
-
Ok the next part which can be a little trickier and may require some judgment. Depending on what level of moisture your Cerlist has been subjected to over the years, removing the injector lines at the pump may be a little more tedious. Of our two Cerlist motors one set of injector lines easily separated at the pump, the other set was corroded into the banjo fittings at the pump. If your lines are corroded into the banjo fittings, or trying to loosen the injection line nut seems to be resistant f the banjo fitting….no worries, just remove the banjo fittings at the pump itself and leave the connections to the injector lines intact. Note that there are hard washers on either side of the banjo bolts so it’s critical to keep those for the reinstall. So now your injector lines should be off. Next remove the positive circuit wire on the front of the pump and the three fuel lines to the pump noting the original location of each.
-
Next slightly loosen the front nut that holds the pump down but not so loose that it is not still bearing down on the base flange of the pump. Then completely remove the rear nut and take a photo of where the stud sits relative to the oval hole in the base of your pump. This is to capture how the pump timing was set for your Cerlist (as rotating your pump back and forth in these oval slots, either advances or retards fuel timing). So whenever you reinstall the pump be sure to duplicate the position it was in before you removed it. Ok now remove the front nut and your pump is almost ready to come out.
-
Note that unless something has badly failed, there is still a lot of fuel inside of your pump. This fuel doesn’t evaporate or leak down after even decades of sitting so you need to be prepared for the gush of old fuel when you remove the pump. Note that there are two flared seals on the drive shaft of your pump, the top seal is flared at the top to prevent diesel fuel from leaking into the crankcase, the lower seal is flared at the bottom to prevent crankcase oil from working its way up into the pump. If your Cerlist is “making oil”, the top seal is shot. Note that these two seals are the same PN, they just get installed with the flare pointed up or down depending on where they sit on the pumps drive shaft. - Stopped Here
-
Ok to crank the motor while the pump is out.
-
Clocking the pump to shaft
-