HEMTT M977 - Crank, No Start

[fuzzytoaster]

No HEMTT section on the forum, no love for them yet?

Anyway.. I'm in possession of an M977 that the previous owner had no desire to own or work on. I've been working on it all day and ended up in a crank no start situation that looks fuel related. I've got strong cranking but like I said no fire/start. I've got 1/4 tank of good diesel and the lift tube is good. I put my fuel tank cap with a schrader valve on the fuel tank and pressurized to 5 psi. Traced all lines with no wet spots. The fuel filter assembly and water bowl looks good and full. I cracked the main fuel line at the front of the engine and I can confirm fuel is making it all the way up.

I've cranked multiple 30 second intervals with no hint of firing, no smoke. The cranking of the engine is moving air as the exhaust cover flap is bouncing. I used starting fluid (yes I know) to make sure the engine would fire off on something and it would run for a second on starting fluid but that's it. The engine sounds fine internally but surely no fuel is the issue. I loosened the return hose on the fuel tank to check for return fuel and it was dry. I repressurized the fuel tank but never got a return flow of fuel. I cracked the primer fuel line on the front of the engine and it has fuel so something is stopping the flow.

I've followed the TM's and many other member's posts about the notorious issue of repriming the fuel system. I've looked over the emergency stop lever/shut off solenoid and they are stiff but appear to be in the "run" position. What am I missing..?

 

[Floridianson]

Did they put on a emergency shut down cable on the motor? My 6V92 and my 8V92 in my dump trucks did not have one but some older Detroit's had the emergency shut down that had to be reset by hand. It was a flapper that closed off the air to the blower. Also Detroit's really like the mechanical primer or hand primer to prime up the whole system / head.

 

[simp5782]

I told him to prime the system in reverse. Starting with the secondary fuel filter to get the air out of that side of the pump. Then prime the tank to the IP to give it a little motivation to start. If you prime it well enough and it still doesnt run and sucks everything on that secondary side dry then you are looking at a for sure pump issue.

Priming the tank to the pump does nothing for the injector sides unless the pump is spinning with the motor. Injector side is full of air and goes into the pump return which in turn puts air right back into that side along with some fuel. Would take forever to get it all out

 

[NDT]

I forgot, are those DDEC or manual fuel, I think manual, the HETs are DDEC, anyway, problem might be the fuel rack is stuck in the off position, remove a valve cover and check that the fuel rod is moving a gear at each injector when you press the gas pedal.

 

[WillWagner]

Or the fuel pump died. Get a pressure gauge, 1/4 NTP and put it in one of the empty ports on the pressure filter, You should have 160 or so PSI cranking. If no pressure, possibly a stuck pressurizing valve in the pump. It is only a gear pump, so not much to go wrong in there. There is a drive tang on the pump, If someone took the pump off and the tang fell off and they didn't notice or know about it, that could be your issue.

 

[Floridianson]

I leave my hand primer hooked up to the primary filter base on the 3-53 in the crane that sits for long times. The hand primer is a nice thing to have if you have the Detroit. You need a gallon jug of clean diesel, and enough hose so you can hook it to the primary filter base and still have enough room to sit / work.

 

[Floridianson]

I forgot, are those DDEC or manual fuel, I think manual, the HETs are DDEC, anyway, problem might be the fuel rack is stuck in the off position, remove a valve cover and check that the fuel rod is moving a gear at each injector when you press the gas pedal.

I was thinking all silver 92 series were mechanical and the DDEC came out with the four stroke.

Google was my friend and some of the silver 92 series did run with the DDEC system. Mine was not but I did not have Allison automatic. Did the 92's that had the DDEC system also have electronic injectors or were they still mechanical injection and the DDEC system just took readings of crank speed and such for the Allison automatic?
Thought the HEMTT ran the HT740 mechanical Allison and the HET ran the seven speed Allison that needed the DDEC support to run it?

 

[marchplumber]

curious minds.................

hope ya had some luck getting her lit off!!

 

[fuzzytoaster]

I was able to get to the HEMTT today during nightfall and made some diagnostic progress. I did my research which coincided with what Wes said and a little more. I primed the secondary filter and system with a hand sprayer and pushed about 3 gallons through, 1 gallon wasn't enough my source said. I did get fuel through the return line to the tank. I cranked her over for about 30 seconds and we had smoke but no start. I can smell fuel in the exhaust so it got a little something. I hit it with snuff of starting fluid and it wouldn't stay running beyond what the starting fluid would do. I wasn't able to check if the primary fuel line had retained prime since yesterday but I'll double check that this weekend to make sure that's still good.

Next step is getting into the engine unless someone has an idea.

 

[Floridianson]

I am liking Will's thought of checking the fuel pump pressure at the secondary.Thought it was 60psi from reading but yea needs no air and pressure. Would seem if you have a full system up to the primary and you primed up the secondary to clear the head then she should have fired. Would seem if the fuel pump is building pressure and the restrictor at the back of the head return line is working she should be holding / making pressure. Now my 60 series has the restrictor plus check valve on the return line to help hold the head full when a filter change was done so the head would not drain. It was the early 1980's when I ran my silver series and have not seen one since so that's about all I got.

 

[WillWagner]

Maybe it is 60 PSI. Too much rolling around in my head. If no pressure, there will be a slight amt of smoke just because it is trying to lite with the fuel in the system. Before you go ripping into the engine, do the simple things first. If it was sitting for a long time and there was any water in the pump, the pressurizing valve could be stuck or the spring broken. If the spring broke, there would be flow thru the system but not enough to fire.

 

[74M35A2]

The Detroits have a gear pump to send pressurized fuel to the injectors. They are unit injectors, meaning each of them is their own high pressure pump. There is a restriction jet on the return side to keep pressure up. It is a pretty simple system.

Yes, remove one valve cover and make sure the fuel control rack moves freely. When they stick, it is usually in the full throttle position because that is where the governor rests. But good to make sure it is free anyway, and not stuck in the off position as mentioned earlier. Would hate to see it start and run away. Very common on those, if they have sat.

If rack moves free, try a new hose from mechanical gear pump direct into a jug of diesel fuel. If that does not work, replace gear pump, it is usually blower driven, and an easy low cost task.

Cool truck.

 

[Floridianson]

Maybe it is 60 PSI. Too much rolling around in my head. If no pressure, there will be a slight amt of smoke just because it is trying to lite with the fuel in the system. Before you go ripping into the engine, do the simple things first. If it was sitting for a long time and there was any water in the pump, the pressurizing valve could be stuck or the spring broken. If the spring broke, there would be flow thru the system but not enough to fire.

The 60 psi was from a motor home forum so I took it with a grain of salt.

 

[fuzzytoaster]

Update:

The primary fuel line lost some prime sitting 2 days so there's an issue there, the racor is full of fuel so the leak must be a pinhole or I didn't tighten the fitting snug as it should. Anyway, I loosened it and primed it again then tightened it down. I left my hand pump on the secondary filter and put another half gallon into the system to purge any air that got in. There is back pressure after the air purges when pumping so I'm inclined to say the pressurizing valve is doing its job. I removed my hand pump and installed a pressure gauge before cranking to read any pressure and the gauge never moved. 0 psi (new gauge).



I removed the driver side valve cover to inspect the rack and it's tough to move but not frozen. The truck was sold running at auction in 2015 with 3100 miles on it and it reflects that. Doing some light research in the field, it seems the injectors freeze up and replacement is the only solution..? This seems to be a whole ordeal on replacing and tuning those. I don't want to jump to that just yet as I'm not getting the fuel pressure I need from the primary pump.


https://youtu.be/FsG8dBAQj0I


https://youtu.be/fsXxlQW52yU

 

[155mm]

I have had a couple (2) in 13 yrs of playing army break a quill shaft that goes to the blower.

 

[Floridianson]

Said I was done but fuel pump/fuel need to see some pressure build up? Just for smitts and giggles and I know they are not the same but. I went out to the 60 series and used the primer ball on the secondary and got a couple of pumps before she was hard. While cranking her over my in dash fuel pressure gage looked like it said nothing. Now it is electric so I took it with a grain of salt. Do you think if you left out the plug on the out going fuel side of the secondary it would seem that fuel should be pumping out if the fuel pump was working correct? To me you checked one bank of injectors and it looked like none were sticking open. Would believe when you tried the rack control rod from the governor yea to me it should feel tight as you were wanting the rack to open by hand but the governor was saying no and showed some resistance. What I did not see is when you said try and start the rack control rod did not move but maybe you had the master power on before hand and the governor was in the run position. Also my system has the check valve as said in the head to keep the head full when a filter is removed. The other check valve that was a work order from Detroit was a check valve just before the primary filter to also keep from loosing prime up to the fuel pump. Just guessing here so don't spank me too hard in less you pull my hair too.

 

[fuzzytoaster]

Said I was done but fuel pump/fuel need to see some pressure build up? Just for smitts and giggles and I know they are not the same but. I went out to the 60 series and used the primer ball on the secondary and got a couple of pumps before she was hard. While cranking her over my in dash fuel pressure gage looked like it said nothing. Now it is electric so I took it with a grain of salt. Do you think if you left out the plug on the out going fuel side of the secondary it would seem that fuel should be pumping out if the fuel pump was working correct? To me you checked one bank of injectors and it looked like none were sticking open. Would believe when you tried the rack control rod from the governor yea to me it should feel tight as you were wanting the rack to open by hand but the governor was saying no and showed some resistance. What I did not see is when you said try and start the rack control rod did not move but maybe you had the master power on before hand and the governor was in the run position. Also my system has the check valve as said in the head to keep the head full when a filter is removed. The other check valve that was a work order from Detroit was a check valve just before the primary filter to also keep from loosing prime up to the fuel pump. Just guessing here so don't spank me too hard in less you pull my hair too.

The governor rod was very stiff and I couldn't move it by hand. It doesn't move when the power is turned on or cranking. In the video the power starts in the off position but because I'm using an LVS buzzer the buzzer likes to stay on regardless of ignition switch position (a problem I'll deal with later). I can pull the plug on the secondary filter head and crank it over to see what comes out.

 

[WillWagner]

If an injector is stuck, the fuel the pump puts out is shunted to return, it. Pull the return from the engine and see if there is juice there when cranking. If no fuel out the return, the pump has an issue, or, there is a giant restriction before the pump.

The M106 I did recently had a plugged quick disconnect fitting. It ran then shut off, no/low fuel pressure when cranking....you should probably try and get a gauge that is graduated in 1/2 lb increments...way easier to tell if something is happening. Try getting a compound gauge and install it on the suction filter outlet.

 

[WillWagner]

Any luck?

 

[fuzzytoaster]

Any luck?

I ordered a new fuel pump. Just waiting on that..