8V92 Coughs but Won't Start (SOLVED!)

[matt2491]

I don't think I have any fuel pressure though. After cranking the engine a bunch after the filter replacement, I still wasn't getting any significant smoke out of the exhaust. If anything, less and less. And when I removed the plug in that port on the secondary filter housing, zero fuel came out. It's like the fuel system is just full of air.

I could certainly be wrong. You guys know more than I do. I will figure out how to check the injectors next, per your suggestion (which I greatly appreciate).

 

[BaconFarms]

I don't think I have any fuel pressure though. After cranking the engine a bunch after the filter replacement, I still wasn't getting any significant smoke out of the exhaust. If anything, less and less. And when I removed the plug in that port on the secondary filter housing, zero fuel came out. It's like the fuel system is just full of air.

I could certainly be wrong. You guys know more than I do. I will figure out how to check the injectors next, per your suggestion (which I greatly appreciate).

I am not very schooled on the 8V91, even though I owned one for a short time, but I do have excavator with a 4-71. So, pretty much the same, but split between to heads, etc. I am attaching a video that shows how to bleed a Detroit. Pretty straight forword. You could gravety feed the mechanical pump and have someone try and start it. It should run as long as you can keep fuel in the hose. If not, you pump may not be working. I have had the pump off mine and it is pretty simple. Like a small hydralic pump. Make sure the shaft isn't twisted off or the key, etc. Anyway, watch the video and give it a try. It was 5 below yesterday and we froze up the loader moving snow. Turned out to be water (ice) in the fuel filter, so, new filter, bleed the pump, bleed 4 injectors, and it caught and runs great. 8 below when we got done. We had dumped some summer off road fuel in it and hadn't run it all out and it didn't have any addatives in it. So, we got 10 more gallons on "on-road", plus added some addatives. We good.

Appearently, you can use a fuel pressure gauge, if your unit dose not have one. That would be a way to see what is up. The detroit has a return fuel line, so bleeding should be relatively easy. The Ford in the loader dosen't, so you have to crack each injector to get the air out.

Anyway, enough rambling. Watch the movie and see if that helps your situation.

 

[wrenchturner6238]

I don't think I have any fuel pressure though. After cranking the engine a bunch after the filter replacement, I still wasn't getting any significant smoke out of the exhaust. If anything, less and less. And when I removed the plug in that port on the secondary filter housing, zero fuel came out. It's like the fuel system is just full of air.

I could certainly be wrong. You guys know more than I do. I will figure out how to check the injectors next, per your suggestion (which I greatly appreciate).

You are correct you have a fuel problem. You should have some fuel run out after cranking for a bit if it were primed properly. You may also have other issues like a stuck injector or something of that sort but with the smoke getting less and less confirms not the proper fuel to the engine.

 

[87cr250r]

The fuel pump is driven by the blower so this all goes back to the broken blower drive shaft mentioned by another user. Have you verified the blower is turning?

 

[BaconFarms]

Here is the diagram for the pump, which is driven by the blower as stated above. I did not circle and draw the arrow ( got this of the internet), but if you take the front off the pump and can spin the gears, something broke. Also, with the cover off and the pump gears in place, someone could "bump" the key and you could see if the pump is turning or not. If not, then it could be the blower gears, pump shaft (#5), etc...

 

[BaconFarms]

However, before I did all that I wrote above, I would take the inlet side of the pump and fill the hose with fuel and see if it runs. If it does than you have a fuel tank, filter or hose issue. You can gravity feed the pump by filling the hose. Not a high pressure system, the injectors make the pressure. They just need fuel. Also, make sure the return line is not plugged. The fuel has to get out, for more to get in, and a locked air bubble can cause grief. Hope this helps..

 

[wrenchturner6238]

This is just my opinion but I would not tare anything down until you can verify that you have the system primed up( getting returns into the fuel tank while priming the system) and the engine still doesn't start. this doesn't cost much in the scheme of things. If you have a psi gauge (80 or 100 psi) after priming into the secondary fuel filter put the gauge in where you took out the plug and you will know if you get psi on the gauge if it runs.
If you would want to you can send me a pm

 

[bigmike]

In regards to the engine stop solenoid, it should open when you flip on the engine “on” switch and close when you push down the engine off toggle.

After I finished my rebuild, I pressurized the fuel system with about 5-10 psi thru the fuel return line. I then put the loose fuel return line in a bucket until fuel started flowing. once flowing I let it go for a good 20 minutes to get all the air out. Truck fired off immediately.

 

[BaconFarms]

I just had to go back and read this entire thread again, and I would redress what I have written of late. I would make this comment. If it don't run on ether, it is mechanical and not fuel. The blower aint turning which was stated right up front, but rather rare, maybe.

Or easier, the shutoff is off, or damper (?) if it has one.

All you need fuel and air for a Detroit. Ether works for fuel, and they will run on it, no doubt. Done it a bunch of times. So, you are down to air. It aint getting any air if it dosen't run on ether. Ether eliminates all the fuel problems, pump, injector, etc, etc..

Then all the other stuff.

 

[matt2491]

It fires right up on ether, albeit only for a second before running out of it.

Here's my plan of attack, based on all feedback:
- Pump fuel in from the secondary filter port. This should prime everything from the outlet side of the gear pump, through the engine, and back to the tank. I'll verify fuel is actually coming out the return line at the tank.
- Gravity feed fuel in from the feed line. This should prime the inlet side of the gear pump.

- If those fail, then I'll get into the engine, starting with popping off the valve covers and checking the injectors. Then maybe check if the gear pump is even turning, which may or may not indicate other problems (broken blower shaft, etc).

Problem is it just got cold here and will remain so for a few days, so I may not have much luck working on it till later on this coming week.

Merry Christmas and happy holidays everyone.

 

[davidb56]

chec

It fires right up on ether, albeit only for a second before running out of it.

Here's my plan of attack, based on all feedback:
- Pump fuel in from the secondary filter port. This should prime everything from the outlet side of the gear pump, through the engine, and back to the tank. I'll verify fuel is actually coming out the return line at the tank.
- Gravity feed fuel in from the feed line. This should prime the inlet side of the gear pump.

- If those fail, then I'll get into the engine, starting with popping off the valve covers and checking the injectors. Then maybe check if the gear pump is even turning, which may or may not indicate other problems (broken blower shaft, etc).

Problem is it just got cold here and will remain so for a few days, so I may not have much luck working on it till later on this coming week.

Merry Christmas and happy holidays everyone.

checking the fuel pump discharge side for fuel delivery should be your first move, but if you prefer to do all the other stuff first....enjoy.

 

[Floridianson]

Seems like most everything has been covered. Yes as long as the fuel pick up / line up to the fuel pump and fuel pump is working then we go from there. Ever DD I have had / worked on the fuel filter blocks after the fuel pump had two inlets and two outlets. The correct primer pump that was listed in the thread is then used. Hooking it to the in port of the fuel block and the outher end into a clean jug of fuel. You pump the primer till it get hard then lock the pump down. Then go for a start. If it starts let it run a little then shut down disconnect primer and replace the fuel block plug. Also no need to bleed the injectors on common rail system. To add if it has been a while and you have a helper you can keep working the primer pump while helper hits the starter to keep rail pressure up.
Just to add more the correct fuel primer pump is a good thing to have if you have a DD it makes fuel filter changes and for quicker starts. Myself add clean fuel to filters and install. Hook up primer and build up some rail pressure. This will clear the filters of any air left and as said and builds pressure in the rail. If the engine fuel pump is working it will prime itself as it is a positive displacement gear pump.

 

[matt2491]

Problem solved! I used the cheapo hand pump to pump some fuel into that port on the secondary filter block and it fired right up. Capped the port and went for a good 30 min test drive. Ran great.

So it had just lost prime somehow. A bit concerning, considering I had just driven it 3 days prior. We'll see if it does it again...

Good to get a new filter installed in the process, along with a block heater (although it doesn't really seem to need it - 30F today and no problems starting). I've learned quite a bit about the engine and fuel system, and know how to prime it again if necessary. Thanks to everyone for all the help and ideas.

 

[davidb56]

figure out why it lost prime or it will come back and bite you on the ....

 

[matt2491]

I wonder if it's because the last thing I was doing with the truck was donuts in a snow covered parking lot. Maybe that whipped the fuel around too much?

It had never done it before...

 

[87cr250r]

We had a defective run of aftermarket fuel filters on our John Deere 6081 engines. The metal housing would bottom out against the filter adapter before the rubber seal would compress. They would never leak outwardly but would admit air when the fuel level got low enough causing the engine to shut down. That was a challenging one to find. Not saying this is your case but is an example of what can go wrong. It makes no sense that your engine pump couldn't self-prime. The unit injector engines use fuel for cooling so the flow rate is very high.

 

[matt2491]

Yea, I verified it was in fact not self-priming. Before I manually primed the system (which is what fixed it), I did what davidb56 suggested in post #71 and disconnected the return hose at the tank, draped it over the side of the tank pointed at a bucket. Cranked the engine a bunch; nothing ever came out.

 

[BaconFarms]

Great to hear you got it running. It would be interesting to see what the fuel pressure is between the pump and the injectors, and to see if its up to spec, which I have no idea what it is. But it could show a week pump, etc. I would have to research, but I believe there is a restriction on the return line that builds pressure in the line that feeds the injectors, but not sure. I read too much sometimes and confuse the different systems. We have about 4 different styles and they are all running and from time to time one goes down and we have fix it. And remember how, LOL...

 

[87cr250r]

Unit injector engines all have some type of back pressure control. The 71 series Detroits used a drilled orifice in the return line adapter fitting. Other engines may use an actual regulating valve. I think they used to call it an R80 fitting.

 

[wrenchturner6238]

Problem solved! I used the cheapo hand pump to pump some fuel into that port on the secondary filter block and it fired right up. Capped the port and went for a good 30 min test drive. Ran great.

So it had just lost prime somehow. A bit concerning, considering I had just driven it 3 days prior. We'll see if it does it again...

Good to get a new filter installed in the process, along with a block heater (although it doesn't really seem to need it - 30F today and no problems starting). I've learned quite a bit about the engine and fuel system, and know how to prime it again if necessary. Thanks to everyone for all the help and ideas.

I am glad you were able to get your engine running with no other issues so far. If you truck does this again you are probably bringing in air on the suction line.