DT466e Fuel System Won’t Prime

[a1268]

Hey everyone, just drove this truck home a couple weeks ago. About a 15 minute drive, ran it for an hour or so prior to that drive. When I got it home it sat for a few days. I changed the glass water separator as it had a bit of gunk in it and forgot to prefill it. I started the truck, ran great for a 5 minutes idling then died when air got to the pump. Now I can’t seem to get it to prime at all, I pressurized the driver side tank and got fuel geyser’ing out of the inlet line to the fuel lift pump/pump where I have the red arrow. Not that When I pressurized it, instead of the clear tube on the bleeder valve (blue arrow) I had the bleeder valve in. I connected all the lines again but I can’t get fuel past the lift pump, which I believe it needs to go past it to get to that bleeder. The hand primer pump isnt that great and wouldnt or do much, got a new one and it doesn’t do much good either even after 100 pumps. I did have to replace the check ball also as it was all mangled, strainer was replaced but pretty clean. Fuel filter replaced and pre filled. It’ll run on a shot of ether otherwise. Fuel grommets changed as needed. It almost seems like the fuel pump is completely blocking fuel getting past it? I don’t know if that’s normal for these. At a loss, been out in the rain trying to get it going. any help/ideas is really appreciated

 

[BamaBus]

Isn't there a small orifice in the pump end (by your ring finger) that could have some of the check ball debris clogging it up?

 

[a1268]

Isn't there a small orifice in the pump end (by your ring finger) that could have some of the check ball debris clogging it up?

Hey thanks for the reply! Honestly 100% there could be. I have no clue how these pumps work except that they are cam driven, that check ball looked super bad like half of it was missing. Do you have any insight of how these work? Like are they a flow through design where if the engine is off, liquid should flow through it? I would think so but I’m not entirely sure.

 

[BamaBus]

See EGES175 page 532 in THIS link. It warns against cranking engine without priming the fuel system. It gives a procedure to prime that takes time to get the primer firm.

 

[a1268]

See EGES175 page 532 in THIS link. It warns against cranking engine without priming the fuel system. It gives a procedure to prime that takes time to get the primer firm.

Thanks, I’m definitely trying to crank it as little as possible. Only the few times I thought I had it primed but didn’t. Some seem to suggest to prime by cranking but I feel that wouldn’t be great to do.

 

[BamaBus]

To clarify, are you getting fuel in the line after the filter housing just before the pump? Are you getting any pressure/fuel from the test port where the clear line is?

 

[a1268]

To clarify, are you getting fuel in the line after the filter housing just before the pump? Are you getting any pressure/fuel from the test port where the clear line is?

Yes, if I pressurize the tank, fuel sprays out of the line just before the pump if I crack it. But I can’t force any fuel past the pump itself where the red arrow is if I reconnect the lines and crack the bleeder. I don’t know much about the pump so I don’t know if fuel is supposed to freely flow through it when the engine isn’t running or not.

 

[BamaBus]

I don't know about bypassing the pump manually since it is mechanically operated. If you were to dry up around the area were the arrow is, can you crack the fitting and crank and get fuel? You should if the pump is clear and operating properly.

 

[a1268]

I don't know about bypassing the pump manually since it is mechanically operated. If you were to dry up around the area were the arrow is, can you crack the fitting and crank and get fuel? You should if the pump is clear and operating properly.

I mis spoke sorry, to reiterate, I only can get fuel up to just before the fuel pump, if I crack the inlet fitting on the fuel pump I get fuel. Past the pump, I don’t. Any idea how to check the pump? I tried pushing the plunger a bit but doesn’t seem to do too much.

 

[BamaBus]

Only to crack a line just past the pump and briefly crank the engine to see if fuel flows. If so, then check the test port just after the filter. At that point you should have 65psi to the fuel rail. After that it returns to the tank. The rail may be full of air and need to be purged by following the instruction in the manual.
You may have debris from that check valve in the pump, or blocking the small orifice just inside.

 

[a1268]

Only to crack a line just past the pump and briefly crank the engine to see if fuel flows. If so, then check the test port just after the filter. At that point you should have 65psi to the fuel rail. After that it returns to the tank. The rail may be full of air and need to be purged by following the instruction in the manual.
You may have debris from that check valve in the pump, or blocking the small orifice just inside.

I’d definitely think the rail is full of air. If I’m reading the right instruction to purge the air (pg 532) they say to disconnect the CMP sensor. Does that prevent the injectors firing or something?

 

[BamaBus]

That's what I presume. But if you have fuel to the pump but not after then air may not be an issue. I would check for fuel first.
Some have a schrader valve in the test port instead of a plug to relive air pressure. But I guess that could be another fail point.

 

[a1268]

Yeah, I that’s exactly what I have, fuel at the pump but not after. I don’t really see a great way of taking the pump apart, I tried blowing air through it when I had it out and I couldn’t feel anything on the other side.

 

[Timeline]

From what I've read here is you may need to push that plunger a long time like hundreds of times. On this bus with the same set-up, pumping away I can feel a slight pressure and then test the schrader valve it may burp some air, keep pumping until finally it gets firm, then each pump will shoot fuel out the schrader.

Key on to run the tank pump?

I'm also a newby so very well could be wrong.

 

[a1268]

From what I've read here is you may need to push that plunger a long time like hundreds of times. On this bus with to same set-up, pumping away I can feel a slight pressure and then test the schrader valve it may burp some air, keep pumping until finally it gets firm, then each pump will shoot fuel out the schrader.

Key on to run the tank pump?

I'm also a newby so very well could be wrong.

No tank pump unfortunately. There is a thumbscrew I leave open to bleed air when pumping. Yeah I’ve pumped it a lot without much luck. Seems like I wear out the primer pump before I get fuel.

 

[BamaBus]

Yeah, I that’s exactly what I have, fuel at the pump but not after. I don’t really see a great way of taking the pump apart, I tried blowing air through it when I had it out and I couldn’t feel anything on the other side.

What I would want to know is what is the performance of the pressure pump when actually cranking and the only way would be to crack a fitting past the pump. Is it possible to try that?

No tank pump unfortunately. There is a thumbscrew I leave open to bleed air when pumping. Yeah I’ve pumped it a lot without much luck. Seems like I wear out the primer pump before I get fuel.

I wonder if you are leaving it open the entire time you are pushing the primer is an issue. It may not allow the primer to build pressure, Kind of like when I had a bad leaking primer. It can take a lot of pumps to get where you need to be. That is why the manual says it takes three cycles to properly prime.

 

[a1268]

Right, I can try to crack that fitting Past the pump, going to try to unplug the CMP and continue priming today.

I am leaving it open the entire time, I’d be surprised if I was supposed to close it but maybe you are supposed to? Problem is, the primer pump doesn’t get hard ever. I can see if it does when I close it but not sure if it will.

I may put a ball valve and a vacuum pump on the thumb screw on the pressure side to try and vacuum bleed it all in a bit.

 

[Ziptie_Mechanic]

Hey everyone, just drove this truck home a couple weeks ago. About a 15 minute drive, ran it for an hour or so prior to that drive. When I got it home it sat for a few days. I changed the glass water separator as it had a bit of gunk in it and forgot to prefill it. I started the truck, ran great for a 5 minutes idling then died when air got to the pump. Now I can’t seem to get it to prime at all, I pressurized the driver side tank and got fuel geyser’ing out of the inlet line to the fuel lift pump/pump where I have the red arrow. Not that When I pressurized it, instead of the clear tube on the bleeder valve (blue arrow) I had the bleeder valve in. I connected all the lines again but I can’t get fuel past the lift pump, which I believe it needs to go past it to get to that bleeder. The hand primer pump isnt that great and wouldnt or do much, got a new one and it doesn’t do much good either even after 100 pumps. I did have to replace the check ball also as it was all mangled, strainer was replaced but pretty clean. Fuel filter replaced and pre filled. It’ll run on a shot of ether otherwise. Fuel grommets changed as needed. It almost seems like the fuel pump is completely blocking fuel getting past it? I don’t know if that’s normal for these. At a loss, been out in the rain trying to get it going. any help/ideas is really appreciatedView attachment 870048View attachment 870049View attachment 870051View attachment 870052

Just replaced my fuel pump after trying new filter thinking that would solve it. I had same issue with priming and no start. Decided to take a peek at the fuel pump and found it had blown the gasket at the bottom Removed it and it made a squeezing sound when pressed. Took a chance and got a new one to find that I could NOT depress it so after a few tense moments it started right up. I'd look at the pump and go there next.

 

[a1268]

Just replaced my fuel pump after trying new filter thinking that would solve it. I had same issue with priming and no start. Decided to take a peek at the fuel pump and found it had blown the gasket at the bottom Removed it and it made a squeezing sound when pressed. Took a chance and got a new one to find that I could NOT depress it so after a few tense moments it started right up. I'd look at the pump and go there next.

Doesn’t look like mine has a gasket on the bottom, it’s just a solid pump with inlet and outlet on either side of it for fuel. I’m posting an update here in a sec as I did get it fixed!

 

[a1268]

Everyone, wanted to give a final update to the issue. So after priming using a ball valve and a vacuum pump off the port pictured with the tubing attached, it got to a point where only air would come out and it held vacuum. I looked at it for a few minutes thinking. Out of nowhere I heard a “thunk” sound as if something dislodged, probably the check ball pieces in the lift pump. As soon as it made that sound, clean and clear air free diesel flowed. I pulled the CMP sensor, cranked about 4 times for about 10-15 seconds each, plugged the sensor back in, cranked twice for about 5 seconds each and it started up! It did run pretty poorly for about 5-10 minutes, however it cleared up after that and ran smoother and smoother. Let it sit for a couple hours and it started up nice and smooth. It was idling like it was missing on a cylinder, almost loping. I imagine it was air still in the system. Sounds healthy now though!! Thanks everyone for the assistance.