Cummins 8.3, Won’t Start

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Cummins 8.3, Won’t Start

June 15, 2023, 04:40:13 pm

Pulled into our campsite yesterday (no issues during our 1 hr drive) and decided to reposition a few hours later and rig won't start. Until now it always started immediately. Engine turns, but does not start.

1. Checked the batteries: Load test good and good charge
2. Looked at the fuel filter with the clear bottom and it appears to have diesel and is not leaking
3. No leaks at the second filter
4. Pumped the rubber primer and messed with the throttle, then she started with me pumping the throttle petal.
5. Ran her for 20min, shut her off, restarted and she cranked up normally.
6. Tried to start her again after 2 hours... NOPE. Not even with pumping on the rubber primer.

What now?

We are at a campground in Morgan Hill, CA for just under 2 weeks before we've gotta get moving again.

On a side note: We found a broken spring (see picture). Assuming it is the throttle return spring?? Will try to get one to replace it at the hardware store. Unsure if this is part of the problem.

Re: Cummins 8.3, Won’t Start

Reply #1 – June 15, 2023, 05:12:06 pm

I have no experience with the 8.3 but diesels don't have the equivalent of an accelerator pump so if pumping the throttle had anything to do with your problem the spring could also be involved. replace it first.

Re: Cummins 8.3, Won’t Start

Reply #2 – June 15, 2023, 05:28:53 pm

Might want to check to see if your fuel shut off solenoid is operating properly.

Re: Cummins 8.3, Won’t Start

Reply #3 – June 15, 2023, 05:30:51 pm

That is thr throttle return spring,you have 2,research here or send me your number I can call you and talk you thru.

Re: Cummins 8.3, Won’t Start

Reply #4 – June 15, 2023, 07:14:53 pm

The broken spring won't have anything to do with not starting. It's probably the fuel solenoid. Lift up the
bed and on the right side of the coach and the left side of the engine you will see the solenoid. Have some
one turn the engine over and you should see it move if it doesn't you can tie it up with wire. If it doesn't
start then I would change the fuel filters.

Re: Cummins 8.3, Won’t Start

Reply #5 – June 15, 2023, 07:30:50 pm

Adding to the advice above, in your photo (below) I have marked the fuel shutoff solenoid with a yellow arrow.

When you turn the ignition key to start, the rod hanging out of the solenoid should pull up into the solenoid. As it does, it lifts the fuel shutoff lever on the injection pump. If this does not happen, then your engine will not start. Second photo shows the old OEM solenoid from our 8.3 along with the new replacement.

Re: Cummins 8.3, Won’t Start

Reply #6 – June 15, 2023, 08:16:49 pm

You can disconnect wiring to fuel shut off solenoid. If you connect ohm meter between red and black wires of solenoid and it is an open load or very high resistance then you have found your problem. When you turn key to start you should see the lever pull up, when you release starter it should stay up until ignition key is turned off. It does not pull up until you try to crank the engine. As others have said, it can be zip tied open, must lift bed and cut zip tie to turn off.

Here is an explanation
https://youtu.be/G4mJ6_-lmTU

Re: Cummins 8.3, Won’t Start

Reply #7 – June 15, 2023, 08:41:13 pm

Quote from: Chuck & Jeannie – June 15, 2023, 07:30:50 pm

Adding to the advice above, in your photo (below) I have marked the fuel shutoff solenoid with a yellow arrow.

When you turn the ignition key to start, the rod hanging out of the solenoid should pull up into the solenoid. As it does, it lifts the fuel shutoff lever on the injection pump. If this does not happen, then your engine will not start. Second photo shows the old OEM solenoid from our 8.3 along with the new replacement.

The rod does pull up. Looks kinda raggedy, but is functioning as described. The yellow arrow was SUPER helpful!
Guess we will try to change the filters tomorrow... should be fun.

Re: Cummins 8.3, Won’t Start

Reply #8 – June 15, 2023, 09:52:20 pm

Quote from: Realmccoy – June 15, 2023, 08:16:49 pm

You can disconnect wiring to fuel shut off solenoid. If you connect ohm meter between red and black wires of solenoid and it is an open load or very high resistance then you have found your problem. When you turn key to start you should see the lever pull up, when you release starter it should stay up until ignition key is turned off. It does not pull up until you try to crank the engine. As others have said, it can be zip tied open, must lift bed and cut zip tie to turn off.

Here is an explanation
https://youtu.be/G4mJ6_-lmTU

Unsure what high resistance would be. We got 36 OHMs with the tester. He used the plug that has P E D and measured between P & E and P & D. Both sides were 36 OHMs.

Re: Cummins 8.3, Won’t Start

Reply #9 – June 15, 2023, 10:17:48 pm

I have an 8.3 but later vintage than yours so cant quite advise on your particular setup...My vintage had CAPS injection and a common issues with lift pumps, yours I dont think has the same, rather you have a mechanical pump and also has a fuel cut solenoid, and a fuel return solenoid...however, here is an article on everything foretravel that is about a 96 with very similar issues. Might point you in a direction.

Engine: Cummins 300hp 8.3 Fuel System Overview - All Things Foretravel

Re: Cummins 8.3, Won’t Start

Reply #10 – June 15, 2023, 10:57:45 pm

I have a 1996 u295 with the 8.3 for the last 12 years. A question is does/did it crank over faster than normal when it doesn't want to start?
When they starve for fuel, ( like losing prime, bad fuel filters, or fuel shut off solenoid not opening) they will crank over faster.

Re: Cummins 8.3, Won’t Start

Reply #11 – June 16, 2023, 09:34:49 am

So it wont start, you used primer then it did start. Upon restart it wouldnt. Sounds like fuel air leak or fuel valve not opening.
Air leaks could be lines, filter, primer pump. Everything is in a vacuum till it reaches the pump. Air will get drawn in and diesel engine dont play well with air in the fuel. Fuel will not pressurize to hi enough pressures to function correct. Once started rotational speed May be hi enough to overcome the air leak.allowing it to continue to run
Scott

Re: Cummins 8.3, Won’t Start

Reply #12 – June 16, 2023, 09:37:24 am

One of my previous coaches had same engine. Your description of issue matches others advice. fuel shut off solenoid

On my previous coach there was also a constant duty solonoid that fed the power to the fuel shut off solonoid. Both should be checked as part of the issue. Low voltage can also cause the same problem.

As someone mentioned, you can tie or strap the fuel cut off solonoid open to run the coach, then release when you arrive at destination.

Re: Cummins 8.3, Won’t Start

Reply #13 – June 16, 2023, 09:44:08 am

Quote from: Ahb867 – June 15, 2023, 10:57:45 pm

I have a 1996 u295 with the 8.3 for the last 12 years. A question is does/did it crank over faster than normal when it doesn't want to start?
When they starve for fuel, ( like losing prime, bad fuel filters, or fuel shut off solenoid not opening) they will crank over faster.

If anything it seems a bit slower than normal.

Re: Cummins 8.3, Won’t Start

Reply #14 – June 16, 2023, 09:52:44 am

Quote from: AC7880 – June 16, 2023, 09:37:24 am

One of my previous coaches had same engine. Your description of issue matches others advice. fuel shut off solenoid

On my previous coach there was also a constant duty solonoid that fed the power to the fuel shut off solonoid. Both should be checked as part of the issue. Low voltage can also cause the same problem.

As someone mentioned, you can tie or strap the fuel cut off solonoid open to run the coach, then release when you arrive at destination.

Can you point us towards the constant duty solenoid? Shut off solenoid seems to be functioning... pulls up when we crank.

Re: Cummins 8.3, Won’t Start

Reply #15 – June 16, 2023, 09:56:07 am

Quote from: dsd – June 16, 2023, 09:34:49 am

So it wont start, you used primer then it did start. Upon restart it wouldnt. Sounds like fuel air leak or fuel valve not opening.
Air leaks could be lines, filter, primer pump. Everything is in a vacuum till it reaches the pump. Air will get drawn in and diesel engine dont play well with air in the fuel. Fuel will not pressurize to hi enough pressures to function correct. Once started rotational speed May be hi enough to overcome the air leak.allowing it to continue to run
Scott

Primer sound like its moving air to me, but we don't know what it should sound like.

Re: Cummins 8.3, Won’t Start

Reply #16 – June 16, 2023, 10:11:30 am

Quote from: Chuck & Jeannie – June 15, 2023, 07:30:50 pm

Adding to the advice above, in your photo (below) I have marked the fuel shutoff solenoid with a yellow arrow.

When you turn the ignition key to start, the rod hanging out of the solenoid should pull up into the solenoid. As it does, it lifts the fuel shutoff lever on the injection pump. If this does not happen, then your engine will not start. Second photo shows the old OEM solenoid from our 8.3 along with the new replacement.

Chuck, do you have the part number for this solenoid? Ours is missing the rubber cover and wed like to go ahead and replace.

Re: Cummins 8.3, Won’t Start

Reply #17 – June 16, 2023, 10:13:36 am

Quote from: mkc1962 – June 15, 2023, 10:17:48 pm

I have an 8.3 but later vintage than yours so cant quite advise on your particular setup...My vintage had CAPS injection and a common issues with lift pumps, yours I dont think has the same, rather you have a mechanical pump and also has a fuel cut solenoid, and a fuel return solenoid...however, here is an article on everything foretravel that is about a 96 with very similar issues. Might point you in a direction.

Engine: Cummins 300hp 8.3 Fuel System Overview - All Things Foretravel

First paragraph sound exactly like our situation. Do you know where the pictures would be? They are not clickable, but look like they would be very helpful if we could just see them!

Re: Cummins 8.3, Won’t Start

Reply #18 – June 16, 2023, 10:52:28 am

Give Larry B's a call for your fuel shut off solenoid and maybe a few other parts.
May want to replace the fuel overflow valve also.

Shop online for Dodge 12 valve fuel solenoids, starter parts and more! -...

Re: Cummins 8.3, Won’t Start

Reply #19 – June 16, 2023, 11:03:28 am

Quote from: Doug W. – June 16, 2023, 10:52:28 am

Give Larry B's I call for your fuel shut off solenoid

X2 on LarryB's. If not sure which one to order call and ask. They are good folks at fostertruck.com

Re: Cummins 8.3, Won’t Start

Reply #20 – June 16, 2023, 11:16:07 am

Quote from: Vossx2 – June 16, 2023, 09:56:07 am

Primer sound like its moving air to me, but we don't know what it should sound like.

When you pump the hand primer it should push in fairly easy at first, then get progressively harder as the pressure increases. When you have achieved max pressure you should be able to hear the overflow valve make a "squeaking" noise. This means it is opening to allow the excess fuel to go down the return line to the fuel tank. The overflow valve is located on the top of the injection pump, right under the air conditioner compressor on my coach.

When the overflow valve squeaks, the hand pump has done all it can do.

Re: Cummins 8.3, Won’t Start

Reply #21 – June 16, 2023, 11:33:14 am

I'm not sure what you mean about a rubber primer. The only primer I know about would be the
one in the Winn fuel filter and there is a button called air purge at the back of the coach that operates
it. If you haven't pressed it you should. You can hear the pump running and while it is running try and
start it from the rear of the coach. If it doesn't start loosen the fitting on the Winns filter going to the
engine, press the air purge and see it you have fuel coming out.

Re: Cummins 8.3, Won’t Start

Reply #22 – June 16, 2023, 12:01:26 pm

So a few years back, I got tired of my 8.3 not starting and being reliable after setting for a week or more due to losing prime. I even replaced the check valve oring in the pump several times and my fuel return line with no luck. How to get it started is I would take an extra fuel cap drill a hole in it, stick an air fitting in it and glue it to seal it. Then I would lightly pressurize the fuel tank to get the fuel back up to the engine. This is how I determined that I was losing prime. Manually pumping the rubber plunger on the fuel pump is insane if you have to bring the fuel all the way from the tank. So when I travel with my foretravels, which I have a 99 as well with a M11 engine, I always travel with a 2000 watt Honda generator and battery charger, and a Milwaukee battery operated air compressor just for these insane moments when we are let down.
Oh, so after determining what was causing the issue, I installed a fass fuel system and never again had a starting problem due to the lack of fuel, except for one time when I didn't replace the main filter fuel on the engine block. Alway replace this fuel filter every year due to diesel fuel can build up debris inside the filter.

I just bought a 99, u320 with a M 11 engine and when I got home I started having starting problems so I took out the old transfer pump and filter system and installed a fass fuel system as well and it has been much more reliable

As far as your engine cranking a little slower may be due to your starter batteries wearing down. I always found that when the engine cranked over quickly with good solid batteries, it was due to a lack of fuel getting to the engine. I tested this theory multiple times and found it to be accurate on my 8.3.

Also make sure your fuel shut off mentioned above is engaging. you can have your wife turn the key to try to start it with your hand on the fuel shut off/on solenoid, making sure that it's engaging.

Re: Cummins 8.3, Won’t Start

Reply #23 – June 16, 2023, 01:03:25 pm

Careful here. We are now discussing what are likely very different fuel systems here (Cummins C mechanical vs M with Winn filter system with electric fuel pump vs FASS aftermarket pump/filter)

Re: Cummins 8.3, Won’t Start

Reply #24 – June 16, 2023, 02:38:15 pm

Chuck's description of priming the mechanical C8.3 is spot on. When I had my fuel lines replaced this spring at Foretravel I walked by as they were trying to start my coach. They had a young guy with a slightly cut down broom handle reaching through the start battery compartment to push the black rubber primer button on the fuel pump. I've used the handle of a screwdriver while hanging into engine bay from bedroom- not the most comfortable position. Others use a hammer handle. It's awkward and not fun. Fill the fuel filters with fuel prior to priming.

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