67RModel Posted February 11 Share Posted February 11 Has anyone ever heard of this? I have heard some stories from people with tons more experience and years under their belt than me that this can happen. I think it would pertain to older, mechanically injected and governed diesel engines. I think the scenario I was told was that a truck was off road on a very rough construction site and was stalled and immediately was subjected to forces or momentum that forced it to move backwards I'm guessing before the driver removed his foot from the throttle? So I guess my question is can it really happen? If so is it logical to assume all the forward gears would then be reverse gears and visa versa? Would shutting off the fuel and starting it with the key as normally done return the engine to normal rotation? I guess I'm just curious if this can really happen or if it is a tall tale..... Quote Link to comment https://www.bigmacktrucks.com/topic/75151-engine-running-backwards/ Share on other sites More sharing options...
Geoff Weeks Posted February 11 Share Posted February 11 Yes, it can happen, 2 stroke Detroits were the most common to do this, because of the multiple powerstrokes/rev. Cummins with a gear fuel pump are less likely Cats and others with inline pumps can. In all cases, the oil pump is a gear pump so the engine will see no lube, and is why Cummins don't maintain pressure in the fuel system to run for very long. Most can be starved of fuel and shut off. Detroits "flapper valve" will be useless as they are now on the pressure side of the blower. Quote Link to comment https://www.bigmacktrucks.com/topic/75151-engine-running-backwards/#findComment-569054 Share on other sites More sharing options...
davehummell Posted February 11 Share Posted February 11 I had this happen to me many many years ago I came up to a red light and I can't remember what lead up to the event but I let out the clutch and it moved backwards when I had the trans in first forward the truck was a Freightliner with a 3406 engine, I think it had something to do with the jake brake I remember I shut the ignition switch off and hit the switch firing up the engine and the truck pulled away like nothing happened. Quote Link to comment https://www.bigmacktrucks.com/topic/75151-engine-running-backwards/#findComment-569055 Share on other sites More sharing options...
67RModel Posted February 11 Author Share Posted February 11 8 minutes ago, Geoff Weeks said: Yes, it can happen, 2 stroke Detroits were the most common to do this, because of the multiple powerstrokes/rev. Cummins with a gear fuel pump are less likely Cats and others with inline pumps can. In all cases, the oil pump is a gear pump so the engine will see no lube, and is why Cummins don't maintain pressure in the fuel system to run for very long. Interesting. Makes sense. 19 minutes ago, 67RModel said: is it logical to assume all the forward gears would then be reverse gears and visa versa? Quote Link to comment https://www.bigmacktrucks.com/topic/75151-engine-running-backwards/#findComment-569056 Share on other sites More sharing options...
Geoff Weeks Posted February 11 Share Posted February 11 In most cases it will not run long, or have much power. For it to run, it must have fuel pressure to the injection pump or injectors. Quote Link to comment https://www.bigmacktrucks.com/topic/75151-engine-running-backwards/#findComment-569057 Share on other sites More sharing options...
Joey Mack Posted February 11 Share Posted February 11 For what my limited knowledge offers. When in was a new guy, we had an E-6 that ran backwards for a minute, i think it had pump timing issues and when the mechanic started it, it backfired and ran backwards. Kinda like a gas engine when it diesels.. i think it was even blowing exhaust out the air cleaner.. its been a while. When I think back,, We had some rough trucks come through that shop. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75151-engine-running-backwards/#findComment-569060 Share on other sites More sharing options...
mechohaulic Posted February 11 Share Posted February 11 towed in a R-685st from a large company which ran backwards. newer truck at the time. driver was backing up to a loading ramp which was on a slight downward incline. low idle and the bump against the dock = backwards running. oil bath air cleaner -mess on right side from compression going out air cleaner; some smoke etc Mack told company brass ::: engine "blew up" . engine job done . have witnessed a Mack engine run away in a F model. didn't know to run away or assist in shutting it down. vise grip fuel line . Detroit run away another story. try climbing on top of a screaming 318 to reach emergency flapper; which was froze. engine shut itself down after all the rockers broke. Quote Link to comment https://www.bigmacktrucks.com/topic/75151-engine-running-backwards/#findComment-569062 Share on other sites More sharing options...
terry Posted February 11 Share Posted February 11 (edited) Yeah i’ve had older mack engines run backwards, just let clutch out and kill it then do a normal start up. Terry🤐 Edited February 11 by terry 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75151-engine-running-backwards/#findComment-569068 Share on other sites More sharing options...
Geoff Weeks Posted February 11 Share Posted February 11 2 stroke Detroit's were known to start on their own, spontaneously. Rack goes full fuel when stationary and if they come in from the cold, warming air in the cyl can "bump" the crank, with multiple powerstrokes, it doesn't take much to bump one in to firing then it is "off to the races. Mostly V8's but I guess some 6's would also. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75151-engine-running-backwards/#findComment-569071 Share on other sites More sharing options...
Popular Post Joey Mack Posted February 11 Popular Post Share Posted February 11 I could see where that can happen, a bit off topic, but when i lived in Maine i had snowmobiles. I had one that would start both ways, it was oull start, wrap the rope around the pulley on the fly wheel, i also think some older sleds hat ski tips on the back of the skis too, for the purpose of reversing.. off topic,i know. Just trying to sound like i know something 😉 1 2 Quote Link to comment https://www.bigmacktrucks.com/topic/75151-engine-running-backwards/#findComment-569072 Share on other sites More sharing options...
Geoff Weeks Posted February 11 Share Posted February 11 Crankcase scavenged 2 strokes (where you mix oil and gas) will run backwards for as long as you want with no damage. Spark is retarded (ATDC). In the 60's Saab made a 3 cyl 2 stroke, it would run backwards and could be driven, esp if you set the timing to close to TDC. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75151-engine-running-backwards/#findComment-569074 Share on other sites More sharing options...
Joey Mack Posted February 11 Share Posted February 11 Exactly.. I wish I had a Saab Sonnet. Dont know crap about them, but they were ugly.. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75151-engine-running-backwards/#findComment-569075 Share on other sites More sharing options...
Adkat Posted February 11 Share Posted February 11 Maybe the Saab 900 is more your style Joey 😉 Quote Link to comment https://www.bigmacktrucks.com/topic/75151-engine-running-backwards/#findComment-569076 Share on other sites More sharing options...
Joey Mack Posted February 11 Share Posted February 11 Well it is ugly.. is it yours? It looks clean. I never drove one. Quote Link to comment https://www.bigmacktrucks.com/topic/75151-engine-running-backwards/#findComment-569077 Share on other sites More sharing options...
Geoff Weeks Posted February 11 Share Posted February 11 That is a late/Euro spec. I have an '84 5 spd 16v turbo, and before someone say they didn't have the 16v in 84, yeah I know previous owner swapped it in. Scoots fast enough for me. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75151-engine-running-backwards/#findComment-569079 Share on other sites More sharing options...
tjc transport Posted February 12 Share Posted February 12 1 hour ago, terry said: Yeah i’ve had older mack engines run backwards, just let clutch out and kill it then do a normal start up. Terry🤐 same here. new 79 Mack with a 300 engine. pulled out of the loading dock into the parking lot and up a slight incline to park it to clean in front of the docks. pulled shutdown with foot on brake and trans in first gear. engine shut off and pushed shut down knob back in .let off clutch before i set parking brake and the engine fired rite up. i did not realize it was running backwards until i saw smoke coming out of the air filter hat. ran for around 30 seconds. shut it back down and it was fine after. i also had a few detriots that did the same thing, but they were much easier to get running in reverse. 1 Quote when you are up to your armpits in alligators, it is hard to remember you only came in to drain the swamp.. Link to comment https://www.bigmacktrucks.com/topic/75151-engine-running-backwards/#findComment-569082 Share on other sites More sharing options...
cruiseliner64 Posted February 12 Share Posted February 12 1 hour ago, tjc transport said: same here. new 79 Mack with a 300 engine. pulled out of the loading dock into the parking lot and up a slight incline to park it to clean in front of the docks. pulled shutdown with foot on brake and trans in first gear. engine shut off and pushed shut down knob back in .let off clutch before i set parking brake and the engine fired rite up. i did not realize it was running backwards until i saw smoke coming out of the air filter hat. ran for around 30 seconds. shut it back down and it was fine after. i also had a few detriots that did the same thing, but they were much easier to get running in reverse. Iv seen a fishing trawler with 2 8V71s one of which was set to run "backwards".It was direct drive(no gearbox) to the propellers so the reason the engines were set up this way was for counter rotation of the propellers.It was an interesting set up to say the least... Paul 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75151-engine-running-backwards/#findComment-569098 Share on other sites More sharing options...
Joey Mack Posted February 12 Share Posted February 12 Yes sir. I did a pair of engines for a small american cabin cruiser that had 2 small block chevys, and one had a reversed cam. It ran counter clockwise for the same reason you say about prop rotation.. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75151-engine-running-backwards/#findComment-569100 Share on other sites More sharing options...
tjc transport Posted February 12 Share Posted February 12 12 hours ago, cruiseliner64 said: Iv seen a fishing trawler with 2 8V71s one of which was set to run "backwards".It was direct drive(no gearbox) to the propellers so the reason the engines were set up this way was for counter rotation of the propellers.It was an interesting set up to say the least... Paul 12 hours ago, Joey Mack said: Yes sir. I did a pair of engines for a small american cabin cruiser that had 2 small block chevys, and one had a reversed cam. It ran counter clockwise for the same reason you say about prop rotation.. many years ago a friend bought a small block chevy 400 at an auction . brand new in the shipping crate. complete drop in engine. included carb, water pump, even the HEI distributor. what no one know it was a reverse rotation marine engine. put it in a 1 ton 4X4 GMC mason dump. we got it all done and went for a shake down run. put the truck in reverse and almost drove through the shop rear wall. when we realized what was up we had some fun shifting through the gears out in the parking lot doing 25mph in reverse. then pulled it back in and pulled the engine apart to put a proper cam in it. 2 Quote when you are up to your armpits in alligators, it is hard to remember you only came in to drain the swamp.. Link to comment https://www.bigmacktrucks.com/topic/75151-engine-running-backwards/#findComment-569142 Share on other sites More sharing options...
Popular Post Freightrain Posted February 12 Popular Post Share Posted February 12 Many old twin screw boats had CW and CCW engines. Funny story: motor shop I use has Dyno room. They were trying to get a 427 FE running. Just wouldn't do it. They were stumped until someone realized it was turning wrong way. Some way they got their hands on a LH starter and it was cranking it backwards. Doh. 2 1 Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/75151-engine-running-backwards/#findComment-569156 Share on other sites More sharing options...
Popular Post Geoff Weeks Posted February 12 Popular Post Share Posted February 12 Counter rotation counter acts "prop walk" where the back end of the boat will walk sideways when power is applied. With a single prop not much you can do, but with twin, each counters the other, like a twin countershaft tranmission. 3 Quote Link to comment https://www.bigmacktrucks.com/topic/75151-engine-running-backwards/#findComment-569164 Share on other sites More sharing options...
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