Detroit 6-71 no start after ~1 year sitting

[mmoore6856]

turbo versions did not have the issues of a runaway as it was the oil to the blower bearings that supplied the fuel for it to keep running unregulated. had to deal with 2 in my career and choking the air was the only way to stop it. there are no words that can describe the fear as you are trying to plug the intake with anything you can. at this point this happened as somebody disconnected the emergency cable cause drivers would pull it instead of the stop knob you think of some pretty interesting words to say when you speak to that moron.

[Iceni John]

Originally Posted by Booyah45828

On a detroit, they use a gear pump, and I'm not sure if one could push fuel through that, but I'm not really sure if a 12v pump would push fuel through it either. But with a 12v pump, you could leave it on while cranking, which would help immensely in bleeding air from the system.

I always liked the facet cube pumps. They were cheap, simple, took very little power, and were reliable. My local napa always had one on the shelf, maybe rebranded to echlin. With the 12v cube pump, you'd have to plumb it parallel to the fuel system with a check valve, as it won't allow near enough fuel volume to be pulled through it.

That's exactly what I've done. I have a small Facet-Purolator electronic fuel pump (for carbureted gasoline engines) in parallel with the main fuel line between the Racor 900FG primary filter and the engine's fuel pump, with a ball valve on the bypassed main fuel line that I close if running the electric pump. It pushes fuel through the engine's pump and the secondary filter while the engine is cranking, and after one or two 15-second cranks any air in the fuel gallery to the injectors is purged and the engine starts. Easy! I also have a very bright green light on the rear start panel that tells me if the electric pump is running. So far, so good.

John

[Tejon7]

Originally Posted by Iceni John

That's exactly what I've done. I have a small Facet-Purolator electronic fuel pump (for carbureted gasoline engines) in parallel with the main fuel line between the Racor 900FG primary filter and the engine's fuel pump, with a ball valve on the bypassed main fuel line that I close if running the electric pump. It pushes fuel through the engine's pump and the secondary filter while the engine is cranking, and after one or two 15-second cranks any air in the fuel gallery to the injectors is purged and the engine starts. Easy! I also have a very bright green light on the rear start panel that tells me if the electric pump is running. So far, so good.

John

Thanks for sharing this, John. This is almost exactly what I want to do. I saw a youtube video that seemed to show a 12v pump pushing fuel through the Detroit 71- and 92-series gear-driven pump, but it is good to have verification that this is not the case. I'll plan to set up a system similar to yours:

1) 12v pump installed after primary filter (in parallel with check valve)
2) Turn on 12v pump and crank engine several times for short duration
3) (hopefully) engine fires up
4) Turn off 12v pump
5) Drive fast, spew smoke, and be happy

[Booyah45828]

I never thought of using a ball valve. I'd be concerned of forgetting to open it, or it closing by accident, but that's probably just overthinking on my part.

A ball valve might be cheaper and easier to source/replace then a check valve. I know when I was looking for check valves for mine, it wasn't the easiest thing to come by, and some of them had a reliability that seemed sketchy.

[Tejon7]

I'm going to have to have to reconsider using a ball valve. For a priming pump that I hope to rarely use, the simplicity and reliability of a ball valve might be better than a check valve. My tentative plan was to use a Parker 2600 series check valve, for which I haven't found any negative reviews, but still...

[Booyah45828]

Right.

And replace-ability when it fails shouldn't be ignored either. You can get a brass ball valve at most hardware stores. I have a feeling a suitable check valve would have to be ordered and shipped.

Cost difference between the two is pretty substantial as well.

[Iceni John]

Originally Posted by Booyah45828

Right.

And replace-ability when it fails shouldn't be ignored either. You can get a brass ball valve at most hardware stores. I have a feeling a suitable check valve would have to be ordered and shipped.

Cost difference between the two is pretty substantial as well.

I was quoted an eye-watering price for a diesel-rated check valve, so I chose a less-eye-watering US-made ball valve instead. You'll quickly realize if you leave the ball valve closed when you try to drive away - the engine will bog down and splutter, just like if your fuel filters are blocked. That's why I have a bright green idiot light next to the pump's switch: "Hey John, is the valve still closed?"

John

[BFlinn181]

After sitting a year, it's likely a 6-71 has simply lost prime. I'd remove the valve cover, loosen one of the fuel lines running to an injector, and see if cranking the starter causes fuel flow at the loose connection.

Check 'Bus Grease Monkey' on YouTube for lots of videos on starting 6-71s that have been left for 20 or more years. He's the go-to guy for Detroit 2 cycle engines.

[Tejon7]

The bus is running, thanks in no small part to the ideas shared on this thread. Thank you to all for sharing your knowledge, most especially Iceni John, Booyah, and Crown Guy who's combined advice led to the priming pump setup that I now have and that works wonderfully.

I think I now have a 12v priming pump setup very similar to Iceni John's, if I understood his description correctly. Regardless, the thing works and I'm happy with it

The Facet pump sucks fuel through the primary filter and pushes towards the main gear-driven fuel pump. I initially bought a $5 ball valve to keep the fuel going in the right direction, but the spot is too tight to manipulate the valve handle. I bought a Parker Hannifin 2650 fuel line check valve instead, and later noticed that the exact same check valve was used on the input side of the primary filter. The pump is energized by a cheap lighted switch on the start panel in the engine bay on the other side of the bus.

The 12v pump can't push fuel through the gear pump, but seems to quickly prime the system. When I first turned on the 12v pump, it worked for about 15 seconds before I noticed a distinct change in it's sound. Then I cranked the engine (12v pump still running) for around 10 seconds and the engine roared to life! A tiny poof of white smoke out the tailpipe was the only evidence that it hadn't been run in over a year. Success!

[BaliMoove]

Sounds like you're having some trouble with your 1990 Detroit 6-71TA engine. Have you tried checking the fuel lines and pump to ensure you're getting fuel to the injectors? It could be a simple issue of lost prime. If all matches out and you still need help, consider getting CPL programming done, especially if you want to improve performance. Have you heard of the 14l detroit egr delete kit? It's a popular mod that can improve engine efficiency and performance and is a great way to enhance your ride before your trip to the tire shop. Hope this helps, and good luck!

[rossvtaylor]

Originally Posted by BaliMoove

Sounds like you're having some trouble with your 1990 Detroit 6-71TA engine. Have you tried checking the fuel lines and pump to ensure you're getting fuel to the injectors?

Welcome to the forum, Bali. He posted in July of last year that he got it running and what he did to resolve the issue.

[Tejon7]

Looks like our friend BaliMoove's post was immediately removed. The forum gods must have decided that they were spammers. Thanks for setting them straight anyway Ross.

Since this thread had been resurrected anyway, I'll give a slight update. I took the bus into a shop for a clutch adjustment and they happened to find a leaking/loose fitting at the fuel tank. I have only been able to drive the bus a couple times since then, but haven't lost prime again. Problem solved! Tightening one fitting would have been much cheaper and a more permanent fix than installing my 12v priming pump, but I have no regrets. That pump gives me piece of mind.

[Booyah45828]

Often times finding that leak, especially on the vacuum side of the system, isn't that easy.

That pump will make filter changes a breeze, so not all a waste

[mmoore6856]

plug your vent put 10 lbs air pressure in tank then the leaks just show up

[Tejon7]

Originally Posted by Booyah45828

That pump will make filter changes a breeze, so not all a waste

Good point!