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Discussion Starter #1
Mine ran backwards this past weekend, or at least I think it did.

Happen to anyone else?
 

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had it happen on a old dd 6-71--but have never heard of it on the 7.3 pwr-----
 

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had it happen on a old dd 6-71--but have never heard of it on the 7.3 pwr-----
I don't see any reason it wouldn't. CPS can't determine rotation direction, right? It actually probably ran all right, since the computer would compensate with more fuel because of the timing issue.

Why do you think this happened?
 

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I don't see any reason it wouldn't. CPS can't determine rotation direction, right? It actually probably ran all right, since the computer would compensate with more fuel because of the timing issue.

Why do you think this happened?
Couldn't happen very long anyway. The pcm is programmed for a certain firing order, It is reversed when its "running backwords, so the injectors wouldn't fire at the right time. Only thing the cps tells the pcm s when #1 tdc is, doesn't tell it what cylinder is supposed to be firing.

Gassers and injection pumped diesels can because when they turn backwards everything does.

Sorry if spelling is off, just went to the eye doctor for laser eye surgery exam, I'm a candidate, YES!!!!, but they dilated my pupils to look at my retina and I can't see crap, including hte comp screen, just watching my fingers to type.

Bones
 

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Couldn't happen very long anyway. The pcm is programmed for a certain firing order, It is reversed when its "running backwords, so the injectors wouldn't fire at the right time. Only thing the cps tells the pcm s when #1 tdc is, doesn't tell it what cylinder is supposed to be firing.

I bet you're right. It makes me wonder why he thinks his did run backwards.
 

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Discussion Starter #6
I didn't keep the key turned when I started it. It turned over, but then kicked back and ran really wierd until I turned it off a second later.
 

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I didn't keep the key turned when I started it. It turned over, but then kicked back and ran really wierd until I turned it off a second later.

I'm thinking it didn't run backwards. It must have been running wierd forwards. Deere bones is right, the timing would be so far off it wouldn't work. Old diesels with an IP would do it because the IP would run backwards too. The PSD will follow the standard firing order.
 

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I'm thinking it didn't run backwards. It must have been running wierd forwards. Deere bones is right, the timing would be so far off it wouldn't work. Old diesels with an IP would do it because the IP would run backwards too. The PSD will follow the standard firing order.
Gentlemen: The only diesels that can run backwards are the 2 cycle engines which all detroit except the newer 60 series are 2 stroke. This includes the old 53, the 71 and the 92 series. Check with some of the older diesel heads and they can set the record straight. The 7.3 cannot run backward ! !
 

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2 strokes can run backwards, but the valve event timing would be "just a shade":jester: off if a 4 stroke were to spin backwards.

Normally you need the intake valve to open(stroke) BEFORE the exhaust(stroke) one.
 

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2 strokes can run backwards, but the valve event timing would be "just a shade":jester: off if a 4 stroke were to spin backwards.

Normally you need the intake valve to open(stroke) BEFORE the exhaust(stroke) one.

Can't the exhaust valve act like an intake valve? It just sucks in the back and blows in the front...
 

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Sometimes if you don't hold the key over long enough on the 7.3's, especially the old body styles, the engine kind of halfway fires and acts like it's running on about 3 cylinders. I bet that's what happened.

Justin
 

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Don't know how the HPOP works but the lube oil pump for sure wouldn't work properly backwards. Who wants to volunteer their stick truck for pull start in reverse.:icon_wink:

Back in high school had a friend with a 318 in a 69 Belvedere. There was an ignition problem where it wouldn't produce spark while cranking. It had to catch just as you let off the starter. Once in a while, if you had cranked enough, it would catch and run backwards for about five seconds. Obviously there was some air/fuel mix in the exhaust system that was drawn backwards and allowed combustion.

For reverse all the new two stroke snowmobiles have a feature where you press a button and the engine slows and then just as it stops a well timed ignition curve change kicks the motor into reverse rotation. Works slick. As said by others, mechanically, two strokes don't care which direction they turn.
 

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Who wants to volunteer their stick truck for pull start in reverse.
im down to give it a try in my parts truck
 

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on old 2 stroke mechanical, it will run backwards and work

with 4 stroke engine will run rough, black smoke coming from hood, rpm gauge will show nothing.

this usually happens with dump trucks and tractors, because of the PTO and stalling

but if your truck did run backwards, you would have pooped your pants in thinking that you blew up your truck

look at nascar cars, when they run backwards the engine is blown immediately.
 

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Sometimes if you don't hold the key over long enough on the 7.3's, especially the old body styles, the engine kind of halfway fires and acts like it's running on about 3 cylinders. I bet that's what happened.

Justin
I've had that happen to My truck possibly 6-8 times in the 12 yrs I've owned it. I always just thought the fire didn't light in enough holes. But I bet it was running backwards.....only lasts a second or two. Turn the key off, recycle the GP's and it always started right back up.

And I know for a fact 4-stroke mechanical pump diesels will run backwards. I drove an R-model MACK w/238 & straight 5-speed running backwards once while trying to pull a dump trailer out of a steep soggy pit after being overloaded with an endloader. It had a short stack on the air cleaner along side the passenger side of the cab I could see from the driver's seat and it was puffing black smoke for a few seconds before I shut it down. I didn't have a low enough gear to pull the load and finally had to get a pull from the endloader. Ohhh Man I hated that truck!
 

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Don't know how the HPOP works but the lube oil pump for sure wouldn't work properly backwards. Who wants to volunteer their stick truck for pull start in reverse.:icon_wink:
quote]

Better yet, pull the truck backwards while the truck is in first.:jester:
 
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