Cummins 12-valve stalls when hot

[towbar]

....
With nothing to lose I bypassed the entire heater and everything snapped into place instantly.

Looks like I didn't invent the fuel-heater being a source of freakin' headaches

https://fostertruck.com/products/la...ter-eliminator-kit-for-dodge-cummins-12-valve

But with the fuel-heater now gone I want to heat the fuel some other way. Since I found ice crystals formed on and in the tank inlet line tip (inside the tank) I figure it's tank fuel that needs to be heated, period. So I'm looking for a way to raise tank temperature to above 25c before engine start and to keep it there while operating. This would mean two heaters, one 110vac and another 12vdc.

Beyond preheating before engine-start, wouldn't routing overflow from the injectors directly into the tank uplift line tip solve the problem once running? I mean the cylinder head mass (where the overflow line that ties al the injectors together in series runs) gets warm pretty fast, and from that point on only warm fuel would squirt into the uptake pipe forcing the unneeded extra to spill over into the tank to keep that warm as well.

 

[Truck Shop]

Arctic Fox.

 

[towbar]

No longer sure it's an icing prob. It increasingly seems to be an air-lock, a possibility raised earlier. I've been misleading myself with ideas like 'it's when the engine gets hot' whereas it's more like 90 minutes of operation with the engine already hot for over an hour. But I think I'm slowly cornering the issue, my own
incomplete familiarity with air-locks being an additional obstacle.

Where it's at now is this: The engine operates normally and snow-blowing is without any problems. After about 90 minutes it starts to falter and just 'spools down dead'. A restart barely seconds later is almost always successful but it will stall down again. The last time I had an idea and went and primed manually just before such a restart, then went and operated without further issues for another half an hour until done. Did I purge an air-lock? Just maybe.

The 'shakedown' setup is a transparent plastic fuel tank right next to the lift pump. There's about a 16" transparent 1/4" hose to the lift pump. The lift-pump output is not transparent so I cannot eyeball for air in it. The overflow line is also a 1/4" transparent hose and I can see any air if it's present and the return is almost always a little milky as if it had some air in it but this is too fast and not conclusive and I'm not there to see anything when it starts to falter.

The lift pump is expensive so I want to be sure before ordering another one, and the electric one I had turned out to be a total dud nowhere near capable of 20+ psi. for troubleshooting. I remember now that I HAD installed a new lift-pump one when I built the engine but don't know if it's a Bosch (getting to the point now that almost anything that has to do with fuel is likely to go ape unless its Bosch). My next TRY might be to lift the tank above the lift pump as that I think should make an air-lock impossible. It's a fire hazzard but the bottle is small and I do have a huge extinguisher handy. The next snow-removal might not come around for another week. I'll be back with the results.

 

[thepumpguysc]

U still haven’t put a pressure gauge at the inlet..
What I’ve done is drill and tap a 5/16 or 3/8 pipe fitting to hook up a gauge.. & when ur done, install a pipe plug..
Btw, that 047 overflow valve is 1st generation.. u need an 083/084 or 101 valve..
Idk how u have your return line hooked up, but I used to run the return into my feed bottle, that way u never run outta fuel..
The pump returns 2-3x the fuel that it uses..
Hope this helps..

 

[towbar]

U still haven’t put a pressure gauge at the inlet..
What I’ve done is drill and tap a 5/16 or 3/8 pipe fitting to hook up a gauge.. & when ur done, install a pipe plug..

Inlet to the injection pump? I was thinking of the filter drain fitting as one youtuber did. I haven't done it yet cause the only way I get to have a gauge is off the net and it's two weeks delivery. Also, I cannot tell WHEN it's gonna start surging/faltering as I'm sitting in the hosting backhoe loader 20 feet from there. When it stalls it's over in seconds. This behavior is better known now (below) and it might open new approaches.

Btw, that 047 overflow valve is 1st generation.. u need an 083/084 or 101 valve..

This _COULD_ be an issue, I'll see what I can find.

Idk how u have your return line hooked up, but I used to run the return into my feed bottle, that way u never run outta fuel..

haha, I like that one

The return from the injectors is T'd into the filter inlet where I suppose it helps to de-ice if required. I run the overflow from the injection pump into the fuel bottle but when thinking about icing I had considered letting it squirt RIGHT AT the iced-up intake hose-end in there. But since then I'm no longer convinced that it's an icing issue so much, that may be an additional factor at times.

Today I moved the tank so that it sits 2 feet higher than the lift pump and this, unless I'm mistaken, should preclude any and all vacuum air being sucked-in. The outside temperature was +4c and I went and did some otherwise optional snow-blowing. After about an hour, with the engine LONG warmed up, the bugger started surging again. Set to about 2200 it just surges +/-200 rpm without stalling for a while and eventually it does drop dead. If this starts when operating at lo rpm like 1400 then it'll just drop dead on the first fallback. If I had time to run down and take a look at a gauge I might see some sign of something. Maybe I could pipe a gauge up to where the tach and others are at the beginning of the video:

Back to the overflow valve, would that be temperature or time-elapsed dependant in the sense tha it could start acting up well after the engine is at operating temperature? It seems like a time-elapsed trigger more than a temperature one. Anyone know exactly what is wrong with these older overflow valves? I'm a little stumped at this point, I see no air lock, no icing, just deep-into-mission surging and then PLONK but usually a good relight after a few seconds.

 

[towbar]

Take pressure reading at the main pump inlet..
I’ll bet my last dollar that the overflow valve is weak or broken..
The Cummins application overflow valve opening pressure is about 25 psi..if u change it to 35 psi it cures a bunch of problems..
I’ll get the p# for ya tomorrow..

I missed this one somehow. In order to change the pressure to 35psi that would be one of those valves that you can break open, right?

 

[towbar]

One thing I never hear anybody talk about or perform-adjusting the valves on a 12V 5.9.
It has a flat tappet cam and valves were to be adjusted in the 75 to 100,000 mile range.
I rebuilt several of those most had scrubbed cams and that's where I found the two with
bad fuel pump lobes. I have asked several have you had the valves adjusted, No it's got
250K on it and runs great, especially after I put a big turbo and did the pump.

This engine came out of a '95 Dodge 2500 or such, it had 'supposedly' 100,000 on it and was being used indoors in a warehouse. I rebuilt it completely, the block, crank and cam went to the engine shop and came back specced as *very OK*, don't remember the numbers but I think the crank was turned 010. The injection pump went back on the engine as-was, and I put a new lift-pump on it.

 

[towbar]

I've put a Bosch 2-417-413-101 overflow valve into the pipeline, though it's listed as a replacement for a 093 and not for a 047. Also the electric lift pump used in later ram-2500's capable of 25-30psi, my rationale being that if it does NOT fix the bug then I don't end up with a useless mechanical pump but with an electric one that I can use for other TS now and then. Both should be here early March. IF the electric lift pump should fix the bug THEN I'll get a new mechanical one if I can find one made by Bosch.

 

[Camshawn]

Our 96 lift pump died. The symptom was a gradual power loss over a few hundred kms resulting in a loss of speed on the freeway. New pump fixed that up. We also had to replace the little short fuel line sections between the lift pump and fuel heater and injection pump. We would get air into the system if the truck sat for a few days. Made for long cranking until it primed itself. Replaced the hoses before we had an airlock. Cam

 

[towbar]

The bug my rig is having has a fairly sudden onset after more or less 90 minutes. I'll change some parts one at a time for now, nothing to lose since I keep them for spares if they don't fix the problem. But many of the typical symtoms don't apply, like I just noticed in one of the ads that a weak overflow valve will usually impact on cold operation and not hot, nor would it be likely to throw a fit regularly after so many minutes. Based on observed symtoms (surging that relatively quickly gets worse) an air-lock is a very distinct possibility though I see no trace of it, so far... any air-lock should, I think, definietly bite the dust with a good electrical pump connected in series before the mechanical lift pump. I've had one similar problem a long time ago but I no longer have a good electrical pump. Now there's one coming.

 

[Delmer]

With it consistently acting up after 90 minutes, my first guess would be an electrical issue, then a rubber hose leaking. There should be enough fuel moving that a small air leak shouldn't be a problem, but who knows what's going on, plugged, etc. Could be a combination of two issues also, just because an engine is simple, doesn't mean it always acts simple.

 

[Camshawn]

Is your fuel shutdown solenoid starting to fail when it gets hot?
Cam

 

[towbar]

No solenoid, it's a p-7100 and I shut it down by pulling the shutoff lever held in 'run' by a spring. For a while I had two springs on it so that pulling back to slow idle would also do a shutoff (the Deutz way) but precisely because I also had a similar suspicion I've disabled that for troubleshooting. Other than the starter and gauges there is no electrical dependancy.

I can visualise an air-lock scenario easy enough but finding it is another matter since the lock need not be colocated with the air entry point. I've ordered some bajo2hose fittings as well and intend to replace the filter to injection-pump line with a transparent piece to eyeball that line for air. One problemn is that I'm not a diesel shop and everything I need takes two weeks to get here, or three! Another one is that the end of the snow-removal season is approaching and once I'm done with it I'm likely to just park the rig for 7 months, having a tractor engine-build waiting for me

The symptoms could be said to resemble an air-lock: let's suppose that air starts entering the fuel stream at engine start, for a long time it's not a factor because the pulsating lift-pump cycles the initially small lock back and forth without causing fuel interruption as the fuel squirts do get across it. Then at one point the lock is big enough to begin such iterruptions, that's when surging begins. The lock continues to build until the point where the last surge is not recovered from. Something like this, though I 'm no pro mechanic. March 10 is the anticipated delivery date for my electric pump, it could arrive before then.

 

[towbar]

I set up a gauge on the fuel-filter drain fitting and put a transparent hose from the filter to the injection pump, most hoses and the provisional tank are also see-through and the tank sits 2 feet above the lift pump. Did a snow sortie but broke it up into 10 minute low-load runs around 1800 separated by 7 minutes of cooling (to be sure of getting the work done). The engine was warm after the first run, the second run was also uneventful but at the end of the 3rd run of about 10 minutes the engine died. I knew it would restart without any problem but I waited about 5 minutes to make sure that when I do relight it it will keep runing at least a short while before surging onset. I went with the electrical control panel beside the engine and started the engine as well as the camera.

The engine ran at 1800 and there was no sign of ice or of any air in any hose. After a couple of minutes I turned it up a notch by ear to set up for surging without stalling too soon. After aout a minute of that 'estimated' 2100 rpm run surging began and I cought the gauge on camera.

On the basis of this data I cannot say what the problem is. Fuel pressure is low at around 20-25 psi but steady until surging begins. Chicken or egg? The last few seconds of the sound wave file show SOMETHING and I could hear it too (which is why I went into the sound editor). This something pikes every 6/100 seconds but becomes louder in the last 4 seconds as surging begins.

The season is drawing to a close, my electric lift pump should arrive on the 12th and I hope to find out more then. There's drifting snow so I anticipate a clean-up run tomorrow. After the first stall I'll try to set up for an exact rpm, like maybe 2300, to get more meaningful sound data to examine, a precise speed (and some math I haven't tried in 30 years) will make it more possible to pinpoint the sound source in the audio (lift pump. injection pump, piston failing, etc.)

 

[towbar]

This site has been down for maintenance so there's a bit to catch up

I received the electrical lift pump which is a total dud, the ad said 15-30 psi but I never saw more tan 15 on it, mostly not even that.

But got a better video catching the bugger in the act even more explicitly

the associated sound waves look like these images:




The 1800 rpm is rough, the rpm gauge isn't reliable. Could be a camshaft rpm in the above.

Then I received the new adjustable outflow valve and what that gave me was 40-45 psi but it did not fix the problem. I will be reinstalling the old one.

The new lift pump from Dodge was quoted at $500+ cdn so THAT didn't go any further. I ordered a chinese knockoff if only for TS. When that gets here I'll try it.

Meanwhile I found a good article about the topic @

Cummins Fuel Fuel System - The Cummins Lift Pump

The Bosch P7100 is the King of Injection Pumps.

www.torkteknology.com

That's where it's at today. There may nopt be a nother snopw-removal opportunity this season.

 

[towbar]

Got the new lift pump, back to square one, This time I got a better rpm fix at 1725 and so the clicking sound comes out as being at more or less 810rpm, ballpark 1/2 crank speed i.e. most likely cam rpm and that INCLUDES the injection pump :-(



Also, while in February with -10c and -15c surging began later, now at 5c it seemed sooner but the engine warmed up sooner too. It seems like warmup rather than just time is a factor and a warmup that's a little slower than the engine block, again pointing possibly to some attached accessory like the injection pump.

Summing up there is no ice, no airlock, overflow-valve swapped out, lift-pump swapped out, all to no avail.

 

[thepumpguysc]

Do u have a mechanics stethoscope .??
Get it “clicking” and check the governor.. where it bulges out at the flyweights..
I’m thinking it might b the flyweights hitting the housing.??

 

[towbar]

I might, if not then a hose. I'll look in my boxes tomorrow. Got this engine out of a '95 dodge-25 with at the time supposedly 100K clicks on it. Rebuilt the engine but just cleaned up and installed the pump 'as was' so it might just have a used-out bushing or such in there.

 

[towbar]

No dice, what I have is a stethoscope earpiece Y with some vacuum hose attached but it doesn't do, neither does a length of 1/2 inch hose because the 1/2 crank rpm noise that the camera is picking up is not that audible to the naked ear. Today's run was at +5c outside air, the coolant temp unpegged after about 5 minutes and surging @ 1600 rpm began at about 11 minutes with coolant temperature well in the low green range. At low idle it seemed like it might not drop dead for a long time, the boost gauge is all over the place fluctuating full-scale very wildly. It looks like the snow season is done so I'm deferring the issue seeing that I have a Deutz engine and tractor to build plus a million other things to do. IF I should come across a used and cheap pump (tag) that is known to be good and can be borrowed I'll try to swap it in for TS but my plan is to get down to basics some time in the summer: valve-lash, compression, pump-timing... to see what gives before going further.

 

[towbar]

Hehe, winter ain't over just yet. We got yet another 'last snowstom' so I took the rig out this morning. Operating at 2200 (instead of the usual 1800) I did about 20-30 minutes before a die-off. Just curious, I got out at one point and looked at the fuel pressure, a steady 15psi!!! Beats the living daylight out of me, I had changed both the lift pump and the overflow valve but neither one fixed anything so I put the old ones back.