Won't start, must be out of this space in 30 minutes

[minty]

Oh my...My bus won't start and the RV park says someone needs my space in 30 minutes. This is bad.

It's a 1991 International Thomas school bus with a 7.3 (**not** turbo). The starter cranks just fine with lots of power, but it never starts. There is grayish smoke that comes out of the tailpipe during cranking. I haven't started the bus in about 2 weeks.

I'm not much of a mechanic, but different things I am reading are saying this is likely an issue with air in the fuel lines. I don't know how to bleed the fuel lines and google isn't providing much for my particular engine.

Anyone who would be willing to help would be a great help to me in this situation!

[Booyah45828]

How cold is it there? if you have gray smoke out the pipe it's getting fuel, so thats not likely to be your problem.

My guess is your glowplugs aren't working.

Bypass the relay for a few seconds and try and start it then.

[Booyah45828]

Also, on the old idi's, if you push the throttle pedal half way down while starting it will help it light off.

[minty]

Originally Posted by Booyah45828

How cold is it there? if you have gray smoke out the pipe it's getting fuel, so thats not likely to be your problem.

My guess is your glowplugs aren't working.

Bypass the relay for a few seconds and try and start it then.

It's 73F here. So the gray smoke means it's likely not air in the fuel?

Thanks for the help. The glow plugs were changed out in December by a mechanic. How do I bypass the relay?

[cadillackid]

gray smoke.. could be getting good fuel and the Fuel pump timing could be just retarded out of spec enough that it wont quite Light off.. esp if several or all of the glow plugs arent working..

I definitely find in many mechanical diesels having luck giving just a little accelerator pedal on start.. not sure why as more fuel youd think would cool the cylinder but it seems to help..

-Christopher

[Booyah45828]

Gray smoke is fuel vapor. As far as bypassing the relay, it's towards the rear of the engine by the firewall and is a pretty typical solenoid style relay. Jump accross the two big lugs.

This video shows how to do it.

https://www.youtube.com/watch?v=OJVXvLqkGKQ

You can also use a screwdriver or wrench. Since it's 73 out there you won't need to do it for the 15 seconds like they did, 5-10 should be plenty.

Odds are your controller is junk. You can replace it or bypass it like shown here 7

[minty]

Happy that it started for no apparent reason just now. I promise to come back to the thread to follow up, later today. Thank you to all!!

[EastCoastCB]

I'm so glad to hear that!
Keep us posted, and best of luck to ya!

[cowlitzcoach]

I would agree that you most likely are having an issue with your glow plug relay.

That engine will not start very well, if at all, if it is cold and the glow plugs are not working correctly. Even if the ambient temp is above 70*F it will be a hard starter if it hasn't been run recently.

On one of my buses that had a 7.3L the controller was bypassed and a simple relay was installed with a momentary switch to activate it. When you got in you turned on the key, pushed the glow plug button, and after 15-30 seconds you turned the key to the start position to energize the starter. It always started no matter how long it had sat before you tried to start it.

I am glad you got your bus started.

Keep us posted as to what you found wrong and how you fixed it.

[Rameses]

Originally Posted by cadillackid

I definitely find in many mechanical diesels having luck giving just a little accelerator pedal on start.. not sure why as more fuel youd think would cool the cylinder but it seems to help..

-Christopher

I wonder if it's possible that a little extra fuel increases the compression ratio enough to make a difference in whether or not it fires.

[Booyah45828]

Originally Posted by Rameses

I wonder if it's possible that a little extra fuel increases the compression ratio enough to make a difference in whether or not it fires.

No. It actually has to do with the internal workings of the injection pump.

It's been a few years since I went through school but if I remember correctly.

When the fuel rate is increased, timing is retarded.

So when you push down on the pedal, timing is retarded by a few degrees allowing the piston to rise slightly farther in the cylinder, building a little more pressure and heat, allowing the fuel to light off in a situation that it normally wouldn't.

It theoretically has nothing to do with the amount of fuel injected.

[minty]

Thank you so much to everyone for your help. It is much appreciated. I'm sorry I didn't keep my promise and update sooner. I think the glow plug relay seems like a plausible explanation. When I had the glow plugs replaced a couple of months ago, the mechanic told me that the dust cover for the controller/relay would not fit properly and after trying everything, he just left it off.

So that makes me wonder...I'm here on South Padre Island near the beach and nightly ocean mist...What if the dust cover being missing is causing corrosion, shorting, etc.?

On the morning this problem occurred, I finally located the relay and dug jumper cables out. I was showing my young son how to operate the ignition so that I could jump the relay, but when I wen to demonstrate, it made a sound like it might start! I then applied a little fuel pedal and it started! Now I had applied the fuel pedal before, but without success.

Does anyone have any thoughts on the missing dust cover? Also, on my dash, I have a pull lever that says "Throttle" on it, but it doesn't seem to actually do anything. Does anyone have experience with these?

[slaughridge85]

Originally Posted by minty

Does anyone have any thoughts on the missing dust cover? Also, on my dash, I have a pull lever that says "Throttle" on it, but it doesn't seem to actually do anything. Does anyone have experience with these?

Ahh south padre, I need to get back down there... As for the dust cover being MIA, I would think salt water air could wreak havoc via corrosion on an uncovered relay in short order...

I think the "Throttle" lever you see is a throttle lock. For warming up the bus at high idle for cold climates... Get it up to high idle RPM and then lock the throttle while it warms up. They replaced these locks on the newer electronic buses with a pseudo cruise control that acts the same as your throttle lock but can be programmed by the dealer to be an actual cruise control.

[Jolly Roger]

Until you can make,find or buy the cover. You can go to any auto parts store and pick up electrical connector grease. It will probably be in little packets cause most seam to be stingy with it? Can use the same same they should sell/give you? For spark plug boots.
More important is that you loosen/take apart the connections to get it onto and in between every stud,connector,washer,nut that you can.
I personally would label all the wires and a reference point somewhere and take apart and clean everything and put it back with the Grease and when all said and done if you haven't found/made a sealed cover I would use more of the same grease to cover everything left exposed. They also make it in an aerosol. It's to thick to get into the connections/threads like wd40 but it is a good final cover and if you remove and clean everything then you won't have to worry about getting back to them after coated.
I would propose Vaseline but if your there in the summer it's going to melt and run. The coating itself will still be there on the relays and stuff. The mess will depend on how much lube you use to get the job done? I don't know what tools you have to work with or your capabilities? We are here to help if we can?
Good luck

[slaughridge85]

Originally Posted by Jolly Roger

The mess will depend on how much lube you use to get the job done

Doesn't it always...