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Old 04-28-2022, 02:11 PM   #1
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Detroit 6-71 no start after ~1 year sitting

My bus has been trapped in it's current spot for over a year without starting. We're getting prepared for a trip to the tire shop and mechanic, so I tried to start her up yesterday. I checked that the injectors weren't stuck, made sure the airbox drains weren't clogged/closed, checked fluids, got a board ready to cover the air intake just in case, and let 'er rip! Except... no rip. The starter cranked away, but no ignition. I was nervous of the starter overheating, so I let it crank for about 20 seconds at a time. I tried about 5 times, then gave up.

I'm not in a rush, so I thought I'd sleep on it and get your opinions before breaking out the wrenches. My first assumption is that it's simply not getting fuel, because I see no reason why it wouldn't be getting air. Lost prime, perhaps? Any thoughts?

Edit: sorry, forgot to add engine specifics. It's a 1990 Detroit 6-71TA with ~140k miles and 9k hours. Prior to this, it always started instantly.

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Old 04-28-2022, 02:41 PM   #2
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DDEC? Not intimately familiar with those engines, but the troubleshooting steps vary based off ddec or not, and I don't remember when(or if) the 6-71 became electronic. I know it was around the late 80's early 90's that Detroit started converting engines to electronic control.
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Old 04-28-2022, 02:44 PM   #3
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have you tried using a starting aid like ether?
i prefer a squirt bottle with gas instead of ether.
just to see if it hits and then that would narrow it down to a fuel issue.
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Old 04-28-2022, 02:45 PM   #4
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No DDEC. It's purely mechanical from what I can tell. The only wire I've found runs to the Jake's.
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Old 04-28-2022, 02:52 PM   #5
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Quote:
Originally Posted by Jolly Roger bus 223 View Post
have you tried using a starting aid like ether?
i prefer a squirt bottle with gas instead of ether.
just to see if it hits and then that would narrow it down to a fuel issue.
I haven't tried that, partially because I'd heard some people say to never use ether, but also partially because I wouldn't know where to spray it! No carburetor to shoot it into, so I'm lost

By gas you mean gasoline, or do you mean gas as in "fuel" and I should spray diesel? And where do you spray it? Down the fuel line running from filter to engine?
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Old 04-28-2022, 02:53 PM   #6
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Well, then I'd assume it's a fuel issue as well.

When you had the valve cover off and checked to make sure the rack wasn't stuck open, it wasn't stuck shut either, right?
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Old 04-28-2022, 02:54 PM   #7
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I wouldn't think the rack would freeze after sitting for a year, but it's easy to check.

Are the filters full of fuel? Might want to fill them with some fresh stuff if they're not.
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Old 04-28-2022, 03:01 PM   #8
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The rack moved freely with a single finger. It has the "newer" spring loaded rack, but none of the springs flexed when moving the rack from open to closed.

I haven't pulled the filters off yet. That sounds like a simple check. Thanks!
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Old 04-28-2022, 03:03 PM   #9
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yes gasoline.
its alot softer on the engine than ether.
key off
open up the air intake and or spray the filter 3 or 4 good squirts and close it back up and crank it.
if it hits then you either lost prime or a bad filter or bad fuel or a combination of all of that
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Old 04-28-2022, 03:13 PM   #10
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Thanks for explaining that. I have to admit, I'm a little leery of this technique. With the turbo and blower, it seems like there's a lot of non-combusting machinery for the gas to waft through before getting to it's target. That's probably just my lack of knowledge talking.

I'll see if I have any gas in the garage. Thanks again!
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Old 04-28-2022, 04:21 PM   #11
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Spray it as close to the engine that you can, preferably into the blower itself. It's a very real fear that whatever you're spraying will accumulate somewhere, only to be sucked into the engine in one big gulp once it's running.

I'd try the filters first, and only use starting aid as a last resort. How it sits, there is something that is preventing this from starting.
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Old 04-28-2022, 05:56 PM   #12
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I left you a Voice Mail to call me regarding this and the wiper motor. Check your phone. And call me. Always something when it comes time to get them back up and running isn't it.
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Old 04-28-2022, 10:45 PM   #13
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Based on my experiences with the "old Crown" which has a Detroit 671, I would drain the fuel filter (if it has a drain) and check what comes out for water or any other nasties. Next remove it and if the inside looks OK, fill it to the top with fresh diesel. Your Crown should be like mine with a large box shaped air cleaner behind the right rear bulkhead of the engine. It would be a chore to get much into the engine through that filter. Brake cleaner is a less volatile approach than ether.
I used the fill the filter approach when I once ran out of fuel on hwy 95 in Nevada and the engine started.


Of course I would assure sufficient oil and coolant in the engine.
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Old 04-29-2022, 11:15 AM   #14
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Thanks everyone! Between the advice here and a nice long phone call with CG, I think I have a good plan moving forward. I'm no longer as nervous about spraying ether as I was, but I'm still going to approach this from the fuel delivery side first. I did try to spin off the fuel filters yesterday, but they're on so tightly that my strap wrench started mangling them pretty badly. I decided to wait until I had replacement filters before destroying the current ones. A few hours later, I discovered that I already have a new set of fuel filters in the garage, but by that point I had already formulated a new plan.

Since I am not in a rush, I'm going to take some time to incorporate a priming pump of some kind before pulling the filters off. It may turn out that there's something else going on, but I kinda wanted to do this anyway. I can't decide between a small 12v pump or changing to a new filter mount with integrated priming bulb. Booyah, you shared a link a few months ago to this Racor filter/Mounting base combo on ebay. Can a little bulb pump like that prime the entire system (eventually), or is it only capable of filling the filters after a change-out?

I'd also appreciate recommendations if anyone has a 12v priming pump that they're fond of. I have a good mounting spot adjacent to the primary filter and 12v power within a few feet.
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Old 04-29-2022, 12:52 PM   #15
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It depends on the system.

My bus uses a diaphragm fuel lift pump similar to what carb'd vehicles used years ago. Those style pumps will allow fuel to be pushed through them, and that little primer pump will push fuel through both my filters, priming the entire system.

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 filter head I linked has a plug you can remove to bleed air from the filter at the filter head, instead of pushing the air through the system. Also, the one I recieve was a genuine racor filter, but supposedly those can be faked like anything else. So use your best judgement. Also, fwiw, some people told me those primer bulbs leaked/sucked air on them. I haven't had a problem with mine, but it's something to keep in mind.
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Old 04-29-2022, 01:38 PM   #16
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Thanks for that info. I hadn't considered those little priming bulbs leaking. I was leaning towards 12v anyway, but now I'm leaning a little farther.

The Facet pumps look nice, but as you say, not enough flow to be a simple in-line solution. I vaguely remember reading that a 6-71 can have something like 80 GPH of fuel flowing through, which is well above what a Facet cube or "posi-flow" pump can handle. I'll look into plumbing one in parallel with a check valve this weekend.
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Old 04-29-2022, 03:49 PM   #17
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I don't think you'll find an inline pump that will allow enough flow pass through it for 80 gph. And I don't think I'd want to mount a primer pump that wasn't parallel to a check valve anyways.
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Old 04-29-2022, 10:15 PM   #18
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crank her and look for smoke out the tail pipe if u got no smoke its a fuel issue, you can tell alot by watching a exhaust from a pre emission diesel engine.
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Old 04-30-2022, 09:16 AM   #19
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a lot of 6-71 had a blower (supercharger) and were equipped with a red knob on the dash that looked like the shut off but said emergency on them. they tripped a trap door under the blower to shut off the air if the engine ran away. this motor was known for this issue. check its operation as it has been known to trip on its own. the other issue was they do not like to lose their prime and thats the first place i would check. as far as either put a 1 second burst directly into the manifold bypassing the air filter but no more than 1 second and if it fires and dies you know its a fuel issue
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Old 05-02-2022, 09:41 AM   #20
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My weekend did not go the way I thought it would, so no progress has been made on this. I'll post an update here when I have a chance to get back to this. Thanks again to everyone!

mmoore - thanks for the suggestion, but my bus has one of the late-model 6-71's where they apparently did away with emergency air shutoff flappers. Not sure if it was just turbo versions that didn't have it, or if it was a certain year where they stopped incorporating them, but for one reason or another I don't have one.
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