7.3 cranking but won't start… is it the CPS or something else?

I’ve been dealing with some annoying starting problems. At first, I had to crank it twice, and then it would shut down after a few seconds. It got better for a week, but now it’s back. Today, I couldn’t even get the truck to turn over after several tries, so I picked up a new CPS from AutoZone (only had the Duralast one).

After installing it, I can get the truck to crank, but now it runs for about 4 seconds, sputters a couple of times, and shuts off again. Could it be the CPS, or should I check something else?

When did you last change the fuel filters? I had similar issues, and mine were way overdue.

Ocean said:
When did you last change the fuel filters? I had similar issues, and mine were way overdue.

Good point. I haven’t changed them since I’ve owned it—been about 4 years and 10k miles. I’ll check that out.

When this happened to you, were you still able to drive it once it started? Mine was tough to start, but once running, it would go anywhere until now.

@Harley
Yeah, it would start rough and sometimes act like it wanted to die on turns. After I replaced the filters, I drove it for about 45 minutes. It took 20 minutes for it to settle in, but no issues afterward.

One time, my truck completely died—crank but no start. Turned out to be a $2 spring in the fuel system, but I wasted $600 on diagnostics and other fixes before figuring it out.

Edit: Filters are cheap, so I’d just swap them now. Four years is a long time for debris and gunk to build up. Are you treating your fuel? If not, start doing that too.

@Ocean
Thanks for the advice. I’m grabbing a new filter tomorrow. I’ve heard the CPS can cause random shut-offs, but my issue is only with starting.

I just started treating the fuel with this last tank. That CPS swap was a pain! My arms are too big to make that angle easy, and it was worse than replacing the starter. Annoyed it didn’t fix the problem.

@Harley
I hear you. Once they’re sorted out, these trucks are great, but they don’t like short trips. Mine had turbo issues, then fuel problems, but it’s been solid since fixing those.

If you’re only doing short runs to Lowe’s or the dump, it’s worth driving it on the highway for at least 30 minutes weekly. These engines need to heat up fully to keep running well.

@Ocean
Wow, my fuel filter was nasty. The outer layer was nearly black, and the inner part wasn’t much better. Unfortunately, I mostly use the truck for short trips to haul stuff, so it rarely gets a good run.

@Harley
Glad you found the issue. Even with short trips, try to take it on longer drives occasionally. Maybe a weekly outing across town. These engines need to heat up fully to keep things running properly.

@Ocean
I’ve heard non-DEF diesels don’t have as many problems with short trips, but I agree I need to drive it more. I don’t go far often—I only fill up every few months. But I’ve been starting it at least once a week to keep it from sitting too long.

@Harley
It’s not just starting it—it’s about getting the engine fully warmed up. Diesel engines need that heat to function properly, like big generators warming up before running power. If you’re not heating the system fully, it’s not running at its best.

@Ocean
Unfortunately, I had no luck after changing the fuel filter. I let the fuel pump prime twice and made sure the bowl was full before trying to start it. Cranked for 5 seconds, and nothing. Now my batteries are pretty much drained.

The bowl seemed pressurized when I opened it. Should I just try again tomorrow with fresh batteries, or is there something else to check?

@Harley
You could try checking the FPR screen and making sure the oil level in the HPOP reservoir is good. Low oil can also cause problems like this.

If it’s not the CPS, check your fuel system. Could be a bad fuel filter, low pressure, or cracks in the fuel bowl. I had similar problems, and it turned out my fuel bowl drain gaskets were leaking and losing pressure.

@Lex
I checked the fuel bowl after priming, and it’s filling up and seems pressurized. I’m letting my batteries charge now since cranking drained them.

Harley said:
@Lex
I checked the fuel bowl after priming, and it’s filling up and seems pressurized. I’m letting my batteries charge now since cranking drained them.

Check your battery terminals too. I had a loose one once, and it caused weird issues. Tightened it up and added a new ground cable, and it was fine.

@Lex
I had a melted terminal connector on the passenger side once. It was loose for weeks before it finally melted, and I had trouble starting. Fixed it with new ends, and it cranked great after that. Fun fact: you can start these trucks on one battery in the summer.

@Harley
These trucks always have something going on. I just replaced my water pump, hoses, and thermostat after a belt change. Recently rebuilt the fuel bowl, and next up are valve cover gaskets and glow plugs. But hey, mine’s never left me stranded yet!

Lots of good tips here already. Check out this flow chart. Hopefully, it’s just the filter, and fresh batteries will get you going.

@Drue
Thanks for sharing. I gave it a good 10-second crank, but it didn’t catch. The tach moved to around 200 RPM, but nothing from the exhaust. Fresh filter, fuel in the bowl, but I’m not sure fuel is making it further. I’ll look up the FPR screen and top off my oil since it’s a little low.

@Harley
The FPR screen is on the driver’s side of the fuel bowl. Also, check the HPOP reservoir—oil should be within an inch of the top. Cranking with the ICP unplugged might help too.