OK, it's 3:30 am and a 4-71 has kicked my behind.

[mitch504]

At 11 pm tonight, I stepped in a 4-71 Generator that had just had it's fuel filters changed.

An experienced marine engineer had just changed both filters on a good running genny, and couldn't restart it.

We had 80 psi on a fuel pressure gauge on the outlet of the secondary filter, just before the engine, turning on the starter, with the return orifice out of the head, and no fuel coming out. The gauge held 12-15 psi with the engine not turning. We cracked the return lines from the injectors and spun it, no fuel. We cracked the pressure line to an injector, with the engine stopped, and got a spray of fuel. We spun it with the starter and got plenty of fuel to the injectors, and nothing out of them.

As I see it, the fuel is getting to the injectors, but not through them, WHY?

By now, the Capt says he's missed the tide, forget it, and the engineer will take it all apart tomorrow.

Thanks guys, I'm getting my second bath of the evening, and going to bed now, maybe one of you will have explained it when I get up.
Mitch

 

[StanRUS]

From your description, racks are in the engine stop position?

 

[ETER]

Mitch, check your control rack like stan said and also see if your blower drive shaft is not broken...have spent a lot of time cranking and chasing fuel systems to find the blower not spinning.
Regards, Bob

 

[hetkind]

Pulling the valve cover to verify the cam is spinning might be useful...

 

[kshansen]

Just some quick thoughts. Does the fuel pump drive off the blower on this engine? If so and you have fuel pressure then that would indicate the blower is turning.

Does it do anything when cranking over, smoke out the exhaust, fire for a second then no more?

Any chance the guy who changed the fuel filters used the emergency shut down, maybe as a safety while working on engine or hit it by mistake?

How old or new is this engine? Does it have any electronic controls on it? DDEC? Can't help on those never had the "pleasure"!

Where I worked they had a 6V-53 that I heard they spent several hours trying to start and used several can of starting fluid with no luck. This was an engine that only had maybe a couple hundred hours on a complete rebuild. After all that abuse they decided to call an outside mechanic in on the job. In short order he noticed that the emergency shut down was closed. Seems this crane has two push buttons next to each other, one for shut down on the other for emergency shut down. Dash area is very dirty and in a bad location by right elbow and labels are almost gone. To make maters worse this machine is one that moves from plant to plant and they stick anyone they dig up in the seat, worst being some management types who "Think They Know Everything"!

 

[StanRUS]

Lots of 4-71s have solenoid emergency stop, could be. Fuel pumps normally drive off the blower, you've got that correct kshanssn

 

[mitch504]

I'm not sure of the exact age of this engine, but it's before 1960, nothing electric but the starter.

I couldn't see the exhaust because it was 3 decks up, but the engine would sometimes start and run for 20-30 seconds, but only maybe 3-400 rpm.

Control racks move normally, cam is moving, I was assuming fuel pressure meant blower turning, since it does drive off the blower.

I did not check the emergency flap, ointhead but why do I have 20 pounds over normal fuel pressure, with the orifice out, and no fuel at all, not a drip, from the return port in the head? And how is it keeping pressure on the inlet jumpers to the injectors, but not the outlet ones, with the engine stopped?

Thanks Guys,
Mitch

 

[walkerv]

just my 2 cents quit chasing an unknown problem and start over exactly where the problem originated (the fuel filters ) highly experienced mechanic can still have an oops here and there , pull the filters check the gaskets it sounds like it is sucking air to me , ( I just did something similar on my work service truck, parts house sent me a different brand of fuel filter and it was the wrong part number ,had a different gasket on it )

 

[willie59]

A Detroit that old, prolly has the old cannister filters, did the wrench bender possibly enter some heavy debris into the injectors after the filter change and clog the inlet inside all the injectors? Yeah, I know, never seen that happen myself, just kinda fits your problem though.

 

[mitch504]

Sucking air was my first thought, but no bubbles. I pulled and checked both canister filters, reinstalled with more new gaskets.

Debris in the injectors was the guess we parted with last night. Is there a screen at the inlets? What if we pulled both jumpers off each injector and blew shop air in the outlet?

 

[willie59]

Don't know enough about the innards of the Detroit injectors to know myself mitch, but I bet pumpguysc would.

 

[mitch504]

Yep, good thought, if he doesn't show up here tonight, I'll give him a call.

 

[walkerv]

I just asked the old mechanic here , he said there are inlet screens in the injectors , I have never messed with much 2 stroke stuff myself other them doing a pm on them

 

[StanRUS]

Did the engineer work on the unit before calling you? Could have switched lines? I found 8V92, running fuel backwards through the injectors.

Holding psi; fuel restricted by each injectors internal filter, fuel going the wrong.

 

[Shimmy1]

I hate the stuff myself, but have you tried giving it a shot of juice? Maybe it just needs a bit of convincing that the starter can't accomplish.

 

[StanRUS]

If the engine was running okay, and changing fuel filters caused the problem; human error.

Fuel filters changed because unit was running crappie, low psi causes miss firing, popping exhaust.

Check blower flap > check unit injectors filter located under the fuel inlet nut. Use torque wrench to retighten after changing filter, retorque injector hold down clamps. Use hand punp to pressure prime. Install vice grips on rack control tube in case a rack sticks open and fire the engine.

 

[RZucker]

Reading the OP, I think its plugged injector inlet filters too. Was the filter change just a normal PM, or was the engine already showing fuel problems? Did the engineer use contaminated fuel to pre-fill the secondary filter? Or was the paper in the old filter coming apart?
The proper flow through those filters is from the outside to the center, I usually pre-fill on the outside of the cartridge to prevent having unfiltered fuel enter the injectors. Worst of it is those little porous bronze filters don't clean very well once they are packed with stuff under pressure.

 

[Former Wrench]

My thought would be to replace the filters with the original AC parts. Fill the canisters. Pull a plug on the secondary filter and use a pump oil can to prime the system. It should start.

I have rebuilt hundreds of Detroits and repaired even more. I think that something simple is being overlooked. If it has fuel, air, compression, and is in time, it has to run. Go back to where you started and re-step. I think you will come up with the answer.

 

[RZucker]

My thought would be to replace the filters with the original AC parts. Fill the canisters. Pull a plug on the secondary filter and use a pump oil can to prime the system. It should start.

I have rebuilt hundreds of Detroits and repaired even more. I think that something simple is being overlooked. If it has fuel, air, compression, and is in time, it has to run. Go back to where you started and re-step. I think you will come up with the answer.

But why wont fuel flow from the inlet to the return fitting on the injector? that should be free flow regardless of the rack position. 80 lbs of fuel pressure is way to high for just cranking the engine. Should be more like 10-15lbs cranking.

 

[kshansen]

This is one of those times we all need to get more answers as it is obvious that there is something missing in the equation.

Like someone asked, what is the reason the filters were replaced? Was it routine maintenance or trying to correct a problem?

As former Wrench says if you have the three basics, fuel, air and compression and you can turn it over at a certain minimum speed a Detroit should run. Unlike too many of the "advanced engines" of today.

I know of a 4-71 that sat in the store room where I worked for maybe 15+ years hooked up a good battery and stuck fuel lines in a five gallon pail of fuel and ten seconds cranking it fired right off, another few seconds to clear it's throat and it sounded as if it had just been stopped for the night. That was over a year ago and I'd be willing to bet if the battery is still hooked up it would do the same right now!