8V92 Coughs but Won't Start (SOLVED!)

[matt2491]

(See post #73 for solution)

All of a sudden my M978 HEMTT w/ 8V92 diesel won't start. It cranks over fine and on the first turn it will sort of cough or sputter a little like it wants to go, but then it just goes cold. If I wait a minute and try again, I get the same result - a tiny sign of life but then nothing.

Tank is 1/3rd full, and temps have been in the 30s on average. Not cold enough to gel the fuel I wouldn't think. It's in the low 40s today and still doing the same thing. Tried a little starter fluid, didn't really help.

Any ideas?

 

[NDT]

Blower drive snapped off?

 

[87cr250r]

The batteries sound a bit weak. What voltage is it maintaining while cranking?


Any white smoke?

 

[wrenchturner6238]

Has it set for a while since starting last time? if you are not getting any smoke. First thing If no smoke I would check to make sure you kill is in the run position. If you get little or no smoke I would make sure you are your fuel is primed and make sure you get fuel PSI

 

[matt2491]

It has not been sitting. I drove it 3 days prior. Ran fine then.

It does smoke quite a bit while cranking. Didn't really pay attention to the color. Sort of grey, maybe a little blue? I'll check again tomorrow; I'll take a video.

Matt

 

[wrenchturner6238]

it is possible that low fuel psi will give you enough fuel to smoke good but not enough to start

 

[87cr250r]

I ask about the smoke because that means it's getting fuel. Without smoke I would be looking at the shutdown solenoid.

Anyways, a Detroit that won't run on starting fluid? Maybe NDT is on to something with the blower drive shaft. NDT, have you heard of this happening? I used to run a lot of 71 series engines and can tell you that nobody knows how to assemble blowers correctly. All of the ones I have opened have the rotor clearances set incorrectly, they all touch when spun backwards. This could break the quill shaft.

Do these engines have the shutdown air damper? That always got our tugboat crews.

 

[KN6KXR]

Beat me to it I was going to say check the shutdown damper as well. I worked with a bunch of 71's in the marine biz this got guys all the time.

 

[davidb56]

Beat me to it I was going to say check the shutdown damper as well. I worked with a bunch of 71's in the marine biz this got guys all the time.

yea.got me too once.

 

[87cr250r]

I always built my 71 series engines with spring return racks which let me eliminate the shutdown air damper. Saved me many midnight phone calls.

 

[matt2491]

View of the exhaust on today's attempt. 43°F today. Once again, you can hear it want to catch, but then doesn't. I guess it's getting fuel since we see smoke.

Those talking about the shutdown air damper - what & where is that?

Thanks everyone.

 

[87cr250r]

White smoke like that means the engine is fueling.

IF you have a shutdown damper it's in the blower inlet duct. You can see the shaft in this picture from eBay



This link has the rest of the pictures that show the shaft, damper flap, and catch mechanism.

Detroit Diesel 8V92 Engine Air Intake Assembly 8926708 / 5134835, 5100893 OEM | eBay

Find many great new & used options and get the best deals for Detroit Diesel 8V92 Engine Air Intake Assembly 8926708 / 5134835, 5100893 OEM at the best online prices at eBay! Free shipping for many products!

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Also, 43F is right at the minimum starting temp so don't be afraid to feed it some ether.

 

[US6x4]

Replace with 16V92 ?

 

[matt2491]

The factory ether shot device doesn't work but I will try spraying some regular starter fluid into the intake.

I'll check for the shutdown damper too. Is that what is being activated when I press the 'engine off' toggle switch? It just blocks air flow to the engine?

 

[87cr250r]

The shutdown air damper does not close during a normal shutdown. It's usually connected to an overspeed trip or emergency shutdown.

 

[KN6KXR]

Overspeed trip. They had a nasty habit of eating their own sump, running away, going KABLOOEY. It's a Detroit thing....

 

[chucky]

Its been so long ago but there was something up around the blower that if it tripped you had to manually recock this little arm and you were back in business on 6v and 8v if my memory serves me !

 

[87cr250r]

Overspeed trip. They had a nasty habit of eating their own sump, running away, going KABLOOEY. It's a Detroit thing....

The engines had a fixed fuel rack so if you got a stuck injector because of water in the fuel the governor couldn't bring the injectors back to the shutdown position. The remaining injectors would be stuck at that power setting. If you removed the load or declutched the engine would overspeed and the shutdown damper would bring everything to a halt. The spring return fuel racks eliminate the stuck rack if a single injector seized. I have never had a Detroit pull oil from it's pan. I did build my own blowers.

 

[davidb56]

The factory ether shot device doesn't work but I will try spraying some regular starter fluid into the intake.

I'll check for the shutdown damper too. Is that what is being activated when I press the 'engine off' toggle switch? It just blocks air flow to the engine?

ether won't do squat if the damper is closed. it cant get into the intake. check it first like many have stated.

 

[KN6KXR]

The engines had a fixed fuel rack so if you got a stuck injector because of water in the fuel the governor couldn't bring the injectors back to the shutdown position. The remaining injectors would be stuck at that power setting. If you removed the load or declutched the engine would overspeed and the shutdown damper would bring everything to a halt. The spring return fuel racks eliminate the stuck rack if a single injector seized. I have never had a Detroit pull oil from it's pan. I did build my own blowers.

I believe you. I was told this in regard to the many 4, 6, 8 and 12-71 series we ran. The explanation was the blowers lost the seals. But we didn't build our own blowers we swapped them. I never saw it happen. Cracked liners IIRC the most common problem. Probably got told some marine folklore there was a lot of that....