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M925a2 Power Surge

74M35A2

74M35A2

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Well, the engine cranks well and ECM seems to actuate, but so far no fire. It will light off on starting fluid, but not self sustain. The engine has an electric boost pump on it, but it is inline style, and those are never lift capable, just pressure boosters once flooded with liquid. Trucks these come from still have hand prime pumps on them, I think. Right now I have 4 fuel lines in a gallon jug of diesel about a foot below the engine. It seems to be one delivery and 3 return hoses. They are all 4 below the diesel fluid level surface in the jug. But with only running the electric pump on the engine, I don't think it can lift fuel.

I cracked open one of the common rail injector feed lines, and little to no fuel came out when cranking. For something that should have nearly 20,000psi on it, I expected more than that. So far, I think it is a fuel delivery issue just with the test setup I have. I am going to add a small electric lift pump or outboard hand squeeze bulb on the inlet line, and try again. If still no fire, then will hook a diagnostic tool to it. We have Cummins diag software with the testing we do here. I think I need a manual primer pump on it to push fuel to the electric boost pump.

Engine fuel lines are 2 large ones off the back of the block labeled with one inlet and outlet arrow and then 2 small cloth braided ones coming from the high pressure common rail pump, one off the lower portion and one off the upper higher pressure part. I assume to be for cooling of the pump. Regardless, I have them all submerged in a gallon of diesel, but below the engine (can on ground, engine on trailer). So, lift or primer pump on the single larger 3/8" fuel line is the next shot.

At least mechanically she sounds and seems OK, so far. Who knows, maybe the crank sensor was bumped during removal and is wiped out, etc.... Scan tool should show this if the case, which will be next step if manual ly pressurizing fuel into the inlet line does nothing.

That's all for now, back to work, will try next step tonight after kids are in bed.
 
Another Ahab

Another Ahab

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74M35A2 said:
At least mechanically she sounds and seems OK, so far. Who knows, maybe the crank sensor was bumped during removal and is wiped out, etc.... Scan tool should show this if the case, which will be next step if manual ly pressurizing fuel into the inlet line does nothing.
Click to expand...
Are all scanners more or less "created equal"?

Or are there one or more models that are most preferred over others?
 
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74M35A2

74M35A2

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Just tried again, cracked the line from the common rail pump which feeds the common rail, and no fuel coming out. Hopefully this is just an air bound issue. I will disco the line after the boost pump and see if it will flow when the pump is on. The ECM is mounted to a plate which the diesel flows through to cool the ECM.

Just checked, no primer pump on either fuel filter which I removed from the RV. Hmmm.
 
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74M35A2

74M35A2

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Got it! Will's the man. He taught me that there should be two filters on the RV, and there was, and that fuel feed to the high pressure pump should be double filtered, and at about 70psi. This was not making sense to me, because I know the lift pump does not generate that kind of pressure. After looking at the hose type on the smaller filter housing and him saying it should have high pressure banjo fittings, I see that this filter has the same braided cotton hose on it that comes from 2 areas of my common rail pump. Well, I have both those lines stuffed into the jug, thinking they are both returns, and instead they are supposed to be joined together, with the higher pressure filter in between. So, I was simply recirculating fuel from the lift pump and low pressure pump side of the HPCR pump, and not supplying any to the upper section of the high pressure common rail fuel pump. Result? No fuel, as I was seeing.

I need to get a banjo ended test line made up for the actual start, but at least this is solved and SHOULD be the only no-start reason. As always, stay tuned...
 
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snowtrac nome

snowtrac nome

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this is an air issue just went through this with some 300 hp mrap engines, the priming pump would be a good way to get fuel to the fuel pump, which also is supposed to be your lift pump the booster just helps it along cummins uses banjo fittings with a strange metric thread on the bolts
 
74M35A2

74M35A2

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It was a mis-plumb issue in this case since everything was cut out vs disco'd. Confirmation later this evening, I need a small high pressure banjo ended hose made before she will fire, but the parts guy at the hydraulic hose store is in standby with my order, waiting to deliver it.
 
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74M35A2

74M35A2

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IT RUNS !!!!! PERFECTLY! Zero leaks, zero smoke, 400hp, ready for its next assignment. Run for your life Simp! Cats are out of the bag.

Thanks to all for the help and encouragement.
 
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T

TedCat

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VROOM VROOM VROOM VROOM... CLICK PSST... VROMMMMM VROOMMMMM VROOOOOOMMMMMMM VROMMMMMMMMMM...
(Granny plus 4 split 4 more!)
 
snowtrac nome

snowtrac nome

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same thing I had with the m rap engines I was working on we made our own fittings but had to buy the new bolts some one had discarded the bolts and fittings and tried to use brass hose nipples. insite picked it up real fast that there was air in the system.
 
74M35A2

74M35A2

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Livonia, MI
Next step is to rip this Allison off and connect the Road Ranger to it with the new clutch, may harvest the flywheel housing from my mil engine, TBD yet, based on motor mount comparison. This one has driver side starter, which may be OK, need to check clearance. Oil pan will need to flip around to front sump, will need to acquire a front sump pickup tube. Will buy new to keep my stock engine complete to sell.
 
simp5782

simp5782

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74M35A2 said:
IT RUNS !!!!! PERFECTLY! Zero leaks, zero smoke, 400hp, ready for its next assignment. Run for your life Simp! Cats are out of the bag.

Thanks to all for the help and encouragement.
Click to expand...
You think an old 855, even though its a small cam, is suppose to be scared of a tug of war vs something that powers your grandpappy's Winnebago?

Clint in winter.

https://youtu.be/9PB349Z4XEA

Sent from my SM-G935P using Tapatalk
 
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