Cummins 8.3 not starting

Covers engines and transmissions
robertfury
Posts: 7
Joined: Sat Apr 11, 2020 5:05 pm

Cummins 8.3 not starting

Post by robertfury »

Hello All.

I finally made it to the new forum. I have an issue with my 1994 Continental with a 8.3 Cummins. I recently travelled about 1200 miles, no problems.
A couple of thousand miles ago I replaced the lift pump on the engine that picks up the diesel to send it to the injection pump.

As I said, got to my location with no problems, running great. My coach only has roughly 40k miles on it. I was here for roughly three weeks, went to start it, and nothing. Tried a week later, nothing. Turned over, built oil pressure, but didn't start or cough. I finally opened the hatch, took off the water separator and saw no fuel dripping out when I spun it off, so I decided to shoot some air into the tank to see if the problem was a loss of prime. Got diesel to come out of filter housing, let compressor rebuild air pressure, repeat several times. Same procedure as I went through when I had to replace the lift pump and lost prime. Tried to start, no smoke out the exhaust, turned over, I had it on charger overnight so it was well charged, turned over at good rpm, built oil pressure, still no start.

Under further investigation I found two wires (actually three, one was two wires spliced on one connector) that were pulled off a relay under the bed, close to the isolator. One I traced to what looks like a solenoid on the injection pump. I'm assuming this is the solenoid that turns off fuel so the motor shuts off? I was under the impression that my motor had mechanical fuel injection, no wires to the cylinders. I hooked these back off, not knowing what position they came off of relay, but looking at rust stains and absence of stains, and position of wires, I hooked them back up. Still nothing.

So my questions are

Do relays have positions where power comes in? or can all wires either be used for power signal coming in and signal going out? My understanding of 12 volt power in autos is negligible, unfortunately.

Any ideas on how to test to make sure solenoids are working?

As I said it ran fine on the way here, no starting issues. No smoke when I attempt to start, which tells me the pump isn't getting any diesel, does this sound correct? When I read the manual it says to check to make sure I'm getting pressure up to the pump. Where should I disconnect a line to make sure I'm getting pressure past the solenoid?

Any help is appreciated. Thank you in advance.

Hopefully everyone is safe and sound.

Lastly, there is a second solenoid above the water separator that is mounted on the motor, directly above the
stuplich@ymail.com
Posts: 1146
Joined: Mon Oct 28, 2019 8:51 am

Relay wiring (was: Cummins 8.3 not starting)

Post by stuplich@ymail.com »

robertfury wrote: Sat Apr 11, 2020 5:20 pm Do relays have positions where power comes in?
Image
4 TERMINAL 12V RELAY


Image
5 TERMINAL 12V RELAY
Last edited by stuplich@ymail.com on Mon Apr 13, 2020 9:13 am, edited 1 time in total.
Mel
'96 Sahara 3530, mine since '01
250 hp 3126 Cat, MD3060 Allison
Safaritoonces
Posts: 215
Joined: Sat Nov 02, 2019 9:51 am
Location: Bowen Island, BC
Contact:

Re: Cummins 8.3 not starting

Post by Safaritoonces »

My coach has a Cat 3126B so there may be some differences, but there is a description on the 12v start relays and paths that might give you some ideas in the signature link below. Follow the menu to the "fail to start" entry.

I know that on my coach the engine ECM is interlocked to the VIM module on the Allison transmission which is interlocked thru the relay system in the engine bay, the relays are activated by the ignition switch. By interlocking I mean, one device allows the next in the sequence to receive the start signal. If the conditions are not met then the signal is locked out from passing to the next device path. My guess would be you are missing an enable signal to the ECM, but as said that's a guess. You may have a fuse blown in the relay section if it is similar to mine.
Robert and Bev Lewis
2000 Safari Continental, since 2017
3126B Cat, 330hp
MD3060 Allison
Bowen Island, BC

https://safaritoonces.org/
robertfury
Posts: 7
Joined: Sat Apr 11, 2020 5:05 pm

Re: Cummins 8.3 not starting

Post by robertfury »

Thanks for the diagram. I found some last night too. I have two wires that got pulled off the relay, I think by a racoon or squirrel. And three spots on the relay. Funny thing is all the wiring diagrams I saw used 87, not 87a. One of the wires that was still connected to the relay is on 87a. So currently two are connected, two got pulled off. So I imagine then that since 87a is the normally on side, the solenoid allows fuel at the off position, because from my understanding this is what 87a does. Hope that makes sense.

I've checked all my fuses that could be related to ignition or motor, maybe there are more but if there are I don't know where they are. From my understanding there is no ECM for my motor. There is essentially two things that can go wrong for it not to start, well maybe three or four. One is starter is not working, ignition switch isn't working to run starter. My starter is working, so ignition switch is working. Motor turns over at good rpm, develops oil pressure, won't start. The second main thing is fuel is not getting to injection pump. That can be loss of prime, which I've solved, or the solenoid on the pump is not opening. As I stated after tracing one of the wires off the solenoid, it goes to the relay, and is one of the wires that got pulled off. The two wires that got pulled off include a yellow wire, and a black and a red (one from ignition switch, and one from rear starting switch is maintenance bay?). I imagine I can try the 6 different locations and see if I get it to start. I suppose if I can't, it also could be a stuck solenoid, but the odds of the solenoid failing and the wires getting pulled off the relay that goes to the solenoid at the same time seem great.

If anyone has a Safari that is close to mine year wise, I'd love to know what the wire configuration at that relay is.

Thanks Mel
TDJohn
Posts: 552
Joined: Sun Oct 27, 2019 11:34 pm

Re: Cummins 8.3 not starting

Post by TDJohn »

Robert,

Please don't start guessing with the wires. When I have time, I will try to look at my setup and see what goes where, assuming we have the same color wires. You state that two wires were disconnected and you also state 3 different colored wires. Which colors are disconnected and the third wire that is still connected, to which terminal is it connected too.
The diagram Mel posted is a general relay diagram. Your configuration is a bit different. The wire that is connected to 87A is correct as it is supposed to provide power to the shut off solenoid on the injection pump, when the ignition is on (allowing the solenoid to energize, which allows fuel to the injectors.
What this relay does when it is energized, is it cuts 12v power to the shutoff solenoid, when the stop button in the engine bay is pushed in. When that relay is energized the contact goes from 87A to 87, and since the wire is connected to 87A, energizing the relay with the stop button allows the power to be cut off, thus turning the engine off. So the 87A terminal is connected correctly (assuming that you didn't move that wire to another terminal on the relay).

As for the solenoid and the injection pump: your engine is a mechanical engine, but your engine shut off mechanism is and electro-mechanical solenoid. The reason this solenoid has three wires is because it is a dual coil solenoid. It has a high energy start coil, that pulls the solenoid in, and then it has a low energy run coil, that keeps the coil pulled in, once the engine is running. The thing to be aware of with these solenoids is the start coil generates a lot of heat, and if you crank the engine for a long time, it will overheat and burn up the start coil.
If you can, please post a photo of the relay and the wires. Please take the pictures for a distance, so I can orient on the location of the relay and the surrounding areas.

For me, it is much more practical to trouble shoot this over the phone, so if you like, send me a PM with you number and I will give you a call.
John
'95 Serengeti, Cummins C8.3-300
Allison 6spd.
robertfury
Posts: 7
Joined: Sat Apr 11, 2020 5:05 pm

Re: Cummins 8.3 not starting

Post by robertfury »

Thanks for the info John!

The wires that are disconnected are one yellow wire, and a black wire and red wire that are combined on one electrical spade connector. The two wires that are still connected to the relay are both black wires, possibly one is a double black wire to one spade connector if I am remembering correctly. I will get under there tonight and get the position of the two black wires on the relay. I have not removed any wires off the relay that weren't pulled off. So it's possible that there is one spot on the relay that won't have a wire? Because currently there are four spade connectors and 5 spots on the relay.

I didn't try starting it for long periods of time because I didn't want to harm the injector pump. Probably 10-15 second attempts, followed by long break. So the coil can go out in the shutoff solenoid? Can I pull that solenoid off and make sure it is working correctly? Obviously without the wires hooked up to the relay it won't, but obviously I need to know that it is working.

I would call, but my phone screen is cracked, no where around here to get it fixed, and my cell phone repair skills are lacking.
robertfury
Posts: 7
Joined: Sat Apr 11, 2020 5:05 pm

Re: Cummins 8.3 not starting

Post by robertfury »

There is a black wire going to position 30 and a black wire going to position 87a. The other three positions are open. Two spade connectors, one with one yellow wire and one with one black and one red are the ones that got pulled off the relay.
TDJohn
Posts: 552
Joined: Sun Oct 27, 2019 11:34 pm

Re: Cummins 8.3 not starting

Post by TDJohn »

robertfury wrote: Wed Apr 15, 2020 6:01 pm There is a black wire going to position 30 and a black wire going to position 87a. The other three positions are open. Two spade connectors, one with one yellow wire and one with one black and one red are the ones that got pulled off the relay.
Robert,

The internal coil that opens/closes the relay is by-directional, so it does not matter which side you hook the yellow wire and the black and red wire. So, connect the yellow wire to either terminal 85 or 86, and the black and red wire to the opposite terminal (86 or 85).

Have you tried starting the engine using the remote start button in the service bay? The ignition switch needs to be turned on to start the engine using the remote start button. Also when you activate the starter, you should be able to see the fuel shut of solenoid energize and pull in.
John
'95 Serengeti, Cummins C8.3-300
Allison 6spd.
robertfury
Posts: 7
Joined: Sat Apr 11, 2020 5:05 pm

Re: Cummins 8.3 not starting

Post by robertfury »

I have tried starting in service bay, but same no start. Hmmmmmm, how does one tell that the solenoid is working, short of unbolting? Which I guess is my next course of action. Two disconnected wires are hooked back up on 85 and 86. I'm going to reprime today and try starting again, if no go I'm going to pull solenoid and check to make sure that is working, unless you have another idea. I suppose I can run a test light to circuit to see if it is energizing, but that doesn't really tell me if solenoid is working. Maybe I'm missing something, I will go take a look at that solenoid again and see if I see something I'm missing.

Thanks again for your help John!
TDJohn
Posts: 552
Joined: Sun Oct 27, 2019 11:34 pm

Re: Cummins 8.3 not starting

Post by TDJohn »

Robert,

Have a friend help you engage the starter, while you watch for the solenoid movement. It should briskly move to the open position as soon as the starter is engaged. If it does not move, check for power at at the solenoid. One wire should be energized when the ignition is on, and the other, when the starter is engaged. The third wire is the ground...
John
'95 Serengeti, Cummins C8.3-300
Allison 6spd.
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