8.3 CTA Cummins won't start

[GIJoeCzar]

I've got a M931A2 with 8.3 CTA and it won't start. I replaced the fuel transfer pump and I've got good fuel pressure to the IP fuel inlet line. I've also changed the electronic fuel shutoff solenoid and that didn't help either. The truck does fire just fine with a shot of either. Do I assume at this point that I've got a bad injector pump? Are there any electronics, other than the fuel shut off solenoid that would cause the IP not to function properly? The NHC250 Cummins has a manual override knob on the fuel shut off mechanism; does the Bosch pump on an 8.3 have anything similar to that? Thanks for any suggestions. Joe

 

[sandcobra164]

Raise hood, go to drivers side of motor, push solenoid in and rotate throttle clockwise. Truck should start now. I've seen bad solenoids straight out of the box, if it remains stuck out when you turn the ignition on, check your wiring and repair as needed. Let us know. I've seen this many times on A2's.

 

[NDT]

If Sandcobra's diagnostics are good and engine still won't bust off, unscrew the 6 injector lines and check for lots of diesel when cranking. Could still be air-bound after having the supply disconnected. No diesel ever is a sure sign of needing the pump fixed.

 

[Chief_919]

If all else fails, I have a fresh IP sitting here.

 

[markmontana]

Very common to see Nellis trucks with this problem. This motor does not like to sit out in the 120 degree sun for months or years!

 

[chess]

Mine didn't want to start either it would catch air somewhere in the tank selector. It should pump fuel but catch air so here's What I did is make another hose from the fuel tank ( from the driverside happened to be full) straight to the cannister filter. Loosen up the main ip feed line and primed it till maybe a quart of fuel leaked out to make sure there's no air And bled all the ip injector lines ass it's cranking and it starts right up now. Since there's a lot of feeds returns for the selector if one catches air it's all over. Now I'm just going to make an equalizer line from the passenger side tank to the drivers and be more simple.

 

[GIJoeCzar]

Thanks everybody, very much, for all of your input and help; the problem continues to be terribly frustrating, but I'm not convinced that the IP is bad yet, because I'm not convinced that the pump is getting appropriate fuel pressure.

The fuel shut off solenoid was the very first thing that I checked, as that is an extremely common problem; that wasn't it.

I swapped out the fuel transfer pump with a new one, and in the process tested the check valve mounted to the fuel transfer pump and it seems to work fine (could blow air through, but not suck air back). With the IP fuel inlet screw removed I pumped, and pumped, and pumped on the manual priming pump; I can get solid fuel flow, but only after pumping a LOT of air out, and as soon as I stop pumping for 30 seconds or so, and start pumping again, I get mostly air coming out of that line. I'm going to go back to the truck tomorrow and hook a fuel line directly to the fuel transfer pump and run it to a jug of fresh diesel fuel to see if I can get solid fuel pressure to the IP.

Throughout all this, I have not once been able to get fuel to come out of the IP fuel delivery lines, so there's still a good chance that it's the pump ... but it just doesn't seem right as this truck is rebuilt and the IP is like new.

I think (hope) that as chess mentioned above that I'm pulling air from somewhere...

 

[chess]

Take starting fluid and lots of it. The guy I got mine from couldn't start it and was swearing up and down it was the ip pump. It wasn't went to my local fitting and hose store bought the fittings and hose I did what I mentioned above and it's all good now. I did hook up a hose from the lift pump to a jug filled with diesel it worked that's how I ruled out I had a bad ip. But if u do get it running. And hook up a hose like I did your going to have to rebleed everything again. But at least you know it's going to work.

 

[Fredo Corleone]

I was starting up a M931A2 today and it would only start with alot of either. Maybe a common thing with the 8.3?

 

[greenmonster]

I had this very same problem from a Nellis truck and just behind the cab is the vent line for the fuel tank on the drivers side disconnect line and pressurize tank. We had a rotten line with many pin holes in it. It was not wet until we pressurized the tank. if no leaks loosen banjo bolt on injection pump and pressurize tank again until solid fuel comes out of banjo. I ran mine out of fuel had switching valve on right tank and gauge on left and it took a very long time to get all air out and get it reprimed. The crazy thing was I got good fuel flow and no air for about four pumps then foam and then nothing then back to good fuel flow. You can hear the overflow valve in the pump bypass when you pump the lift pump manual prime when it is fully primed. Hope that helps, I had a bad lift pump with a slight intermittent air leak so I have gotten really good and roadside fuel priming.

 

[rangereter]

I am not sure how difficult it is on the 8.3, but if you have several pounds of consistant pressure from the mech trans pump to the ip inlet, next install a clear line between the two pumps to rule out air infiltration. Odds are your ip fuel pressure regulator may be stuck open (chunk of o-ring or other debris) and not allowing enough pump housing pressure (min 5 psi) to adequately load the delivery valves to feed the injector nozzles. I think that the check valve/regulator is in the pump outlet/return line elbow on the front of the pump, engine side (looks like a 3/4 inch wrench size banjoe-bolt). Could be a pretty cheap fix for you hopefully. Regards,
Bob

 

[GIJoeCzar]

Thanks again for all of the comments!!! I spent a good amount of time this morning on the M931A2 and am really no further ahead, with the exception that I still have good reason to believe that my injector pump may not be the culprit. The first thing that I did was to replace the fuel filter, just in case. Then, I ran a line directly from the fuel transfer pump to a fresh jug of diesel. I disconnected the line that runs into the injector pump into a glass mason jar and pumped; as you greenmonster, I got good fuel flow and no air for about four pumps then foam and then nothing then back to good fuel flow after about 100 pumps (literally). Then, after just five seconds or so I'd pump and the same thing, good flow for three or four pumps, then foam, then nothing, then about 100 pumps later good flow. The only thing that I can think of is that the check valve is bad and as soon as I stop pumping the fuel runs back into the jug. I did take the overflow line off of the IP and run that into a mason jar and was never able to get fuel to come out of that. I'm just really at a loss. The other concern I have is that maybe, just maybe, someone filled the tank with regular gasoline; I'm hoping that's not the case, but the fuel in the driver's tank is full and it's pink. I first assumed that the Nellis folks simply filled it with off road diesel, but now I'm not sure so I drained a bit of fuel from the driver's tank into a mason jar and am going to take it somewhere Monday or Tuesday to get it tested, to see if it's diesel or something else. But, regardless, I have not been able to get and keep fuel pressure to the IP, so am not sure yet if the IP is bad or if the IP simply isn't getting fuel flow when I'm cranking the motor. I've cracked the injector lines on the top of the pump and never once yet have gotten fuel to flow out of them, but again, I've never had good fuel pressure to the IP. It's quite a frustrating problem. I did want to pressurize the fuel tank, because that IS a tell-tale way to find air and fuel leaks, but both tanks are covered by metal plates, so didn't have time to remove one of them yet. Greenmonster, when you said the vent line behind the cab on the driver's side, do you mean the one that runs up the air intake snorkel??? Again, thanks all for the comments and ideas. Joe

 

[GIJoeCzar]

Bob, I just read your post, thank you. Unfortunately I'm not following what you mean by "if you have several pounds of consistant pressure from the mech trans pump to the ip inlet, next install a clear line between the two pumps to rule out air infiltration." What does that mean? Also, I've had the fuel outlet bolt cracked several times and I've even run the overflow line into a mason jar, but can't get fuel out of the outlet even when I pump fast 100 to 120 times (hard as **** on the thumb I'm guessing (hoping really) that my fuel pump is OK, but I'm no closer to a solution and unfortunately will likely have to drag the truck to a mechanic who, unlike me, has a clue as to what he's doing This is simply a really frustrating problem ... but, at least no one shot at me or tried to blow me up today, so that's perspective that keeps a smile on my face Thanks again!!!

 

[GIJoeCzar]

Had the fuel tested today, it is in fact ultra low sulfur off road diesel fuel (15ppm); that's at least some good news ...

 

[greenmonster]

Yes the line behind cab I did not pull any plates off when I did it I was in quality towings yard in Vegas and they were pissy pants about me working on my truck in their yard. So I did it as quick as I could. I just undid the coupling by the intake tube and behind cab, it is a threaded connection. It only took a few minutes just follow the line up and you will see it. I hate to say it but you may have got a bad new pump as well it will do the same thing. Can you have someone crank the engine while you pump the primer? That may help as well.

 

[rangereter]

Joe,
# 1: If you do not have fuel on the return side of the injection pump, then you do not have fuel into the injection pump. Of course you know this already. I say this because if your F.S.O. solenoid is not throwing the shut-off lever far enough when energized, the fuel will not be loaded into the inj pump housing no matter how much you feed to it .
# 2: Either your transfer pump is faulty, your transfer pump is pulling air, or you have a restriction (june-bug or piece of plastic, etc. floating around in the fuel tank). If you replaced the transfer pump, then odds are it is ok... but would not bet my smallest dog's life on it (I don't particularly care for the small one).
#3: You said that you were not getting fuel out of the return side of the pump while pulling from a fuel can (you did have the key on and the engine stop solenoid sucked-in right?) I would also make sure that the fuel S.O. solenoid lever is making it's full travel when the solenoid is energized. Check the lever splines to pump shut-off shaft? (not sure on that one).
#4: I think (anyone please correct me if I'm wrong) you ought to see somewhere between 5-10 psi from the lift pump to the injection pump (consistent pressure) and your fuel supply to the pump is not inundated with air as checked with a clear line before the inj pump (small bubbles ok/normal...big bubbles/pockets of air won't work to bleed lines and nozzles).
#5 The overflow valve/check valve/ low fuel system pressure regulator must keep a few psi of back pressure in the inj pump, if it does not, the fuel will just return to the tank and you won't get fuel out of the delivery valves into/out of the injector lines.
#6 Try not to get emotionally involved when troubleshooting (wrenches cost cost more money the farther you throw them?) Sometimes if you stay on track with a checklist, you can double-check your work without duplicating too much effort (don't think that makes much sense, but sounded kind of reassuring). Regards,
Bob

p.s. You could always wire in a little 12 volt electric pump from your fuel jug to the injection pump and return back into the jug depending on how far you have to go (just have to strap it to the whatchamacalit good).

 

[63foxtrot]

Hi Joe, you need crack each injection line, and bleed the Ip. 1 line at a time. If you don't get any fuel out of the lines. You will need a new Ip. I have 15 M931a2s, 3rd of them starts right up, the others all loose prime after sitting.

 

[WillWagner]

If it's a Bosch P pump, no need to bleed the injectors they will bleed themselves. If it is a P pump. you need to have a MINIMUM of 12 psi to light it. Check the return line at the pump/overflow valve. If there is any flow at cranking speed, the valve is junk. be EASY on the starting fluid, the pistons protrude above the deck and you could mess up a head and or a gasket or wash the rings out. As stated above, run a line from a bucket to the lift pump and a clear line from the lift pump to the injection pump inlet to check for air. If there is no air, no flow through the overflow valve and no smoke when cranking, chances are the inj. pump is junk as long as you know the FSOV and shaft are going to the start position. You can try holding the throttle to the floor and see if it lights. On a P pump, the magnet at the end of the FSOV holds the throttle in the WFO position until it starts, then it moves to the idle circuit position.

 

[WillWagner]

Hi Joe, you need crack each injection line, and bleed the Ip. 1 line at a time. If you don't get any fuel out of the lines. You will need a new Ip. I have 15 M931a2s, 3rd of them starts right up, the others all loose prime after sitting.

If your stuff looses prime after sitting, you have a delivery issue like an overflow valve leaking down. The engine SHOULD be able to sit years and light right off.

Where are you in LA?

 

[GIJoeCzar]

Thanks for ALL of the help, I really, REALLY appreciate it!!! I'm off to Reno through Sunday, so this project will wait until Monday ... and the next step will be to pull directly from a 5 gallon can and push from the fuel transfer pump to the IP pump with a clear line and ensure that the FSO lever is all the way open and crank and pray that I get something out of the injector lines coming out of the pump. This saga to be continued; I will definitely let everyone know how it goes. Again, thanks, Thanks, THANKS!!!!!!!!!!!!!!!! Joe