start and die

[c_hasbeen]

1995 thomas re with a 8.3 cummins engine, I crank the engine over and she fires off imediatly, let go of the key and she dies. hold the key and she stays running until I let off the key.

It is dark out now so I have to get a closer look tomorrow after work, but to me this sounds like maybe a fuel shut off solenoid/ or a relay? breaker? fuse?
I tried to use the rear start button and it did not work, but I have never tried it before so I am not sure if that is related.

Tomorrow I may try and get someone to turn the key over while I watch the pump solenoid.

any ideas anyone?
thanks
Cliff

[milkmania]

Originally Posted by c_hasbeen

1995 thomas re with a 8.3 cummins engine, I crank the engine over and she fires off imediatly, let go of the key and she dies. hold the key and she stays running until I let off the key.

It is dark out now so I have to get a closer look tomorrow after work, but to me this sounds like maybe a fuel shut off solenoid/ or a relay? breaker? fuse?
I tried to use the rear start button and it did not work, but I have never tried it before so I am not sure if that is related.

Tomorrow I may try and get someone to turn the key over while I watch the pump solenoid.

any ideas anyone?
thanks
Cliff

I had something similarly quirky happen on a 1996 lincoln town car limousine.
Start the car normally, everything worked!
Turn off ignition and all electrical shut off, but engine kept running...
it would not die until I pulled the "drivetrain" fuse under the hood...

But get this, you could leave the fuse out, and car would start and have all electrical. But it would die at the most inopportune moment.

Electrical engineer wired a relay to the "normal on" wire under dash out to solenoid on fender under hood.

Chased that gremlin for months!

with you having the key twisted to the furthest right, you are closing contacts.... release the key and you are opening contacts.

[opus]

Unhook the fuel shut off solenoid and see what happens. You can of course manually throw the lever to shut it off.

[nat_ster]

Your lift pump on the side of the engine block has failed.

When you hold the key on, you activate the small electric primer pump T'ed off the fuel intake line to the injection pump.

To verify this, disconnect power to the small electric primer pump. The engine will not start at all.

OR

Install a fuel pressure gauge in the same line the small electric primer pump is in using another T. Google what pressure you should have for that engine. Have someone stand there and watch it as you crank and start the bus.

Hope this helps.

Nat

[c_hasbeen]

at lunch I put a piece of wood under the fuel shut off solenoid to hold it in the up position, started the engine from the front and she fired up immediately and idled just fine, however I did not have any dash gauges and the low air buzzer was not buzzing.
pilled the block of wood out and the engine died.

I will dig deeper after work if I get the lawn mowed in time

[nat_ster]

Is your fuel shutoff solenoid air powered on your bus, or electric?

Glad you got her to idle.

Nat

[c_hasbeen]

Originally Posted by nat_ster

Is your fuel shutoff solenoid air powered on your bus, or electric?

Glad you got her to idle.

Nat

Nat, it is an electric solenoid.

[nat_ster]

Originally Posted by c_hasbeen

Nat, it is an electric solenoid.

Ah good.

Should just be a simple two wire connection. Simple to figure out if it's the wiring failing, or the solenoid it's self.

Nat

[c_hasbeen]

Originally Posted by nat_ster

Ah good.

Should just be a simple two wire connection. Simple to figure out if it's the wiring failing, or the solenoid it's self.

Nat

yea, it actually has three wires, I turned on the ignition to the run position and tested all three wires with a test light but no voltage present, I may talk the wife into turning the key to the start position tonight to see which wire is going hot when the crank over starts.
It should be a simple fix once I get to chasing down wires

thanks
Cliff

[Booyah45828]

Originally Posted by c_hasbeen

at lunch I put a piece of wood under the fuel shut off solenoid to hold it in the up position, started the engine from the front and she fired up immediately and idled just fine, however I did not have any dash gauges and the low air buzzer was not buzzing.
pilled the block of wood out and the engine died.

I will dig deeper after work if I get the lawn mowed in time

Did you check the ignition switch at all? Seems odd that the engine doesn't run and none of the gauges or buzzers work in the on position. It could just be as simple as that contact in the switch is bad.

[c_hasbeen]

Originally Posted by Booyah45828

Did you check the ignition switch at all? Seems odd that the engine doesn't run and none of the gauges or buzzers work in the on position. It could just be as simple as that contact in the switch is bad.

good point, I will check
thanks
Cliff

[c_hasbeen]

I got it figured out, I took the advice to look at the ignition switch, it was working properly, I then found those wires inside the access panel and figured out that the body relay was not working, I was able to jump it across with a #10 wire. Once I jumpered it the low air buzzer came on, I started her up and she ran and my gauges all started working except my tach, and my alternator did not start charging.

I let the air build up and noticed my air throttle was not working, I went to the back and throttled up the engine a couple of times.
my throttle started working like it should and my alternator was charging.

No clue as to what that was all about.

I need to find me a service manual so I can fix these things easier than chasing wires

this has two identical relays, the diagram on the door calls one a chassis relay, the other is a body relay.
I am going to order two relays, take the known working relay as a spare, then take the one which has failed apart just to see if it is contacts that are bad.

anyway thanks for all the ideas everyone!

[c_hasbeen]

Parts arrived today, when I was looking closer at the old relay I noticed that someone had scrapped off some of the paint where the relay spacers come up against the mounting surface, it appears that there were ground issues at one time, I put a jumper on to give it a good ground but no good.
I replaced the relay with the new one and reattached the ground jumper I made up to the ground terminal right next to it just to give it a good ground.

All works like it should, I have all gauges and starts and runs like a real champ.


I think it may be possible that the relay failed due to excessive heat from having a poor ground, but I do not know.

here is the ground strap I added to ensure a ground going forward.

[nat_ster]

Thanks for the update.

I love it when things get worked out.

Nat