NHC 250 No start-fuel problem

[WillWagner]

I did crack loose the setscrew but tightened it right back up once I realized what I was messing with. Had the shaft spun in there then it might not be lined up correctly and not allowing any fuel to pass? I'm going with 99.9% sure it didn't move so I'll try the bucket method. Which I have no idea what that is. Any tips?

Yes, IF the throttle stop was moved, the holes won't line up with the drilling in the housing, but, it might start with the pedal depressed. Do the bucket thing first so you know if the gear pump is working. I might be an assembly issue.

 

[tobyS]

Just an FYI, Be careful with smelling salts, it can and will hurt the engine very bad.

Yes, I know. Once was enough. No lube.

 

[sed6]

Yes, IF the throttle stop was moved, the holes won't line up with the drilling in the housing, but, it might start with the pedal depressed. Do the bucket thing first so you know if the gear pump is working. I might be an assembly issue.

For the assembly idea; below is a pic of the governor weights. They can flop around, I wonder if they go in a certain way?

A buddy thought maybe I got some crud in the IP or fuel line that might be causing a blockade. Although I was super careful I suppose it's possible. I wonder if I can blow compressed air into the outlet of the IP to possibly dislodge any contaminants?

Off to to get hose for the bucket test.

 

[wrenchturner6238]

It not only has no lube when either is used it also pre ignites and breaks the fire ring!!

 

[WillWagner]

So, you took it apart from the rear forward? Wow, lots easier to remove four capscrews! The issue might be that you didn't get the gov weights on the plunger correctly. If you installed the housing with the weights in the position shown in the pic, one of the weights is pushing the plunger all the way back, it won't start. You should most likely start over with the pump removed.

 

[sed6]

Sooo, you had a running truck and took he pump off and apart to repair a throttle shaft leak. the pump was reassembled and now zero delivery? Did you remove the stop from the throttle shaft? Try running it directly from a bucket and see if it lights. If not, take the fuel inlet fitting off and look in the hole at the inlet to the gear pump....use a mirror, if it is a 90 degree fitting you will need to remove the pulsation damper to get the fitting off.....have someone crank the engine and see if the gear pump is turning.

Tried the bucket method tonight. Didnt work. I think my procedure might have been flawed. I stuck a 3/4" tube on the IP input fitting with a hose clamp and the othen end in a bottle of Gatorade. Filled with fuel. I had no soldier B tonight so I had to video the bucket (bottle) instead, but it didn't look like the IP even attempted to draw fuel up. Even so fast priming sucked up the fuel so I feel like it is all plumbed correctly. But I said my process may be flawed because you can't prime the engine, or at least I couldn't. It seems an airtight fitting on the bucket might be required to prevent fuel from draining back out during priming. Did I do this wrong? Without priming it seems theres just way too much empty fuel line to fill with just cranking. Or am I wrong here too?

So then I moved to exposing the pump gear. I got the pulsation damper off and the fuel inlet fitting off. Again no soldier B tonight, so the cranking will have to wait until tomorrow. What does everyone think about the possibility of a clog and reverse blowing it out?

Pic 1 exploded view diagram of pump
Pic 2 inlet fitting location shown in green, pulsation damper in red
Pic 3 a view into the pump showing the shaft and gear

 

[sed6]

So, you took it apart from the rear forward? Wow, lots easier to remove four capscrews! The issue might be that you didn't get the gov weights on the plunger correctly. If you installed the housing with the weights in the position shown in the pic, one of the weights is pushing the plunger all the way back, it won't start. You should most likely start over with the pump removed.

I did. TM kinda fell short in this area so I just used the exploded diagrams. Plus I had the gasket with six holes that seals up the fuel and not the four hole gasket that seals the compressor. Off to research where to find that part. Delays delays. Heck maybe I'll just reuse the old one.

I don't understand at all how the governor works, what the weights do or the shaft with the spring they surround. Can you shed some light? If I did have them aligned improperly (I'll take it apart and check) would it not draw fuel anyway? Again no understanding of how this pump works, but it seems that if its cranking it should draw fuel. No?

Thanks for the help!

edit to add: speaking of cranking, it better get her going soon otherwise I have to pull the batteries, lug them home and charge them. They were fresh off a deep charge and have held up well to lots and lots of cranking.

 

[sed6]

So I swung by the cummins replace place that I'm fortunate enough to have nearby; they got me a new pump to compressor gasket so I can take the IP off the right way and the big star shaped washer they said everyone replaces while they are in there. I quizzed the repair tech and he explained how to properly align the gov weights. He also cautioned that I could have damaged them if I was unlucky. So, off to go give it another shot at getting her started. Finger crossed!

 

[sed6]

I broke parts

Well, finger crossed didn't help. I broke it. Bad. The coupling between the compressor and fuel pump is destroyed. About 3/4 of it is accounted for the rest is shredded shrapnel stuck in the gears of the pump and also jammed in the compressor. I haven't yet cracked open the pump to see what damage there is in there, like to the gov weights.

Getting the compressor off is going to be another pain. The TM says remove six bolts, but like the pump there's four bolts right next door that look like they will be easier to remove. Any ideas which I should remove?

Pic 3 -should I remove the compressor at the green arrow per the TM or the red arrow?
Pic 4 -the exploded view. Im talking about splitting it at gasket 57 or 5. Coupling 56 is within the housing 10 when assembled, just for reference.

 

[brazengoat06]

Well, finger crossed didn't help. I broke it. Bad. The coupling between the compressor and fuel pump is destroyed. About 3/4 of it is accounted for the rest is shredded shrapnel stuck in the gears of the pump and also jammed in the compressor. I haven't yet cracked open the pump to see what damage there is in there, like to the gov weights.

Getting the compressor off is going to be another pain. The TM says remove six bolts, but like the pump there's four bolts right next door that look like they will be easier to remove. Any ideas which I should remove?

Pic 3 -should I remove the compressor at the green arrow per the TM or the red arrow?
Pic 4 -the exploded view. Im talking about splitting it at gasket 57 or 5. Coupling 56 is within the housing 10 when assembled, just for reference.

man i wanna party with this guy!

 

[sed6]

man i wanna party with this guy!

Soon enough. Once I get her running we'll get together. WillWagner has been a big help with his PM's and talking to me on the phone. Thanks Will! I have the pump cleaned up and ready to take to the local pump shop. Hopefully I can get away with just a few hundred in repairs.

 

[brazengoat06]

are you taking it to cummins or an independent shop?

 

[acesneights1]

so what exactly did you do wrong that this happended in case I ever have to do it to mine ? I'm not seeing where that flange was.

 

[sed6]

so what exactly did you do wrong that this happended in case I ever have to do it to mine ? I'm not seeing where that flange was.

Good question! As supposed by me and Will a few days ago, I failed to line up the governor weights proper upon reinstallation.

Specifically, one gov weight was in the correct position and the other in the wrong position. The wrong position one jammed on the inside of the pump housing and caused the fuel pump input shaft to stop spinning. This in turn caused the coupler between the fuel pump and air compressor to fail, spectacularly! The inside of the coupler housing is scratched, pitted and gouged. Fortunately the damage is superficial. One big fragment of the exploded coupler is lodged in the bottom of the air compressor. I'll probably leave it there.

Dropped the pump off this AM and the guys at the shop didn't bat an eye. They expressed a little initial concern over having the correct gov weights in stock but it turns out they had then! 5-6 hours later they called and said it was fixed and suggested the put it on the bench to check for leaks and make sure the gov kicks in. I agreed and asked them to turn it up a little. He said he could change a spring and some shims and give me about 10% more. RPM's that is, I believe. I'll get the low down on how it performs when I pick it up Monday.

Pic 1 -Two gov weights on right, leftmost weight is in the correct position, rightmost weight is flipped out and in the wrong position. Reason being is this pic is sideways so the oil filter is actually at the bottom. So gravity flipped and kept the lower weight in the wrong position. Solution? Rotate the gov weight carrier 90 degrees left or right. This leave the weights horizontally opposed and the weights will stay in position during installation.

 

[sed6]

are you taking it to cummins or an independent shop?

A great local place called Thompson Diesel. Their service in my several visits has been excellent!

 

[WillWagner]

The hard part of doing this on the truck, like has been done here, is the weight alignment onto the tang on the governor plunger. It is tough enough doing on a bench. Honestly, this type of repair should be left to a shop, it's a simple, inexpensive repair, but the possible outcome is not worth the risk. The pump can be assembled in multiple ways that will cause a failure, one like this and a couple of other ways that can cause the engine to start and run, but wide open. Not governed speed wide open, but as fast as the engine will turn with the amount of fuel being delivered. Think of it like an older chevy big block with a non electric Rochester carb. If you put you foot to the floor the rpm will keep on going 'till it breaks. That's what can happen, seen, heard it and seen the aftermath, kinda cool sounding though, they get real quiet!

The reason the coupler shattered is because that is the engineered weak link. If a failure happens in the pump and it lockes up, the coupler is the sacrificial lamb that will break up to prevent damage to the components down stream, the compressor crank, splined coupler, accessory drive shaft, pin and gear.

As for the pieces of broken coupler, fish the big ones out, small ones, pea sized or smaller, can be left in the bottom of the compressor and they will be washed out and down into the pan via the front of the engine. Don't freak out at oil change time when you see metal. It might take a couple changes for it all to wash out.

Scott, I never saw pics of the parts in the compressor. Post them up and i'll look at them to see if they need removing.

 

[sed6]

Here you go. Obviously the large piece came out but the
smaller piece by the gasket fragment it wedged in there.

 

[sed6]

Alright. My pump is back from the pump shop. Cost me three bills,but oh well, lesson learned! They replaced the pump shaft, tach shaft, several o-rings, gaskets and the gov weights. They hooked it up on the bench to test it. They said fuel pressure was above the minimum spec maybe 30% IIRC so he said I didn't need to change the button to a smaller one. He felt the pump was performing great and suggested a pyro before I mess with any fuel pump changes. I hope to get it installed by weeks end.

 

[WillWagner]

Dig the piece that is wedged under the gasket out, you should be fine.

 

[sed6]

Dig the piece that is wedged under the gasket out, you should be fine.

Thanks! Will do.