Weird warm start issue

So, for about the last month and a half, I've been having this issue where the truck will take an extra couple seconds to start when its warm. If I cold start it, everything is fine, starts right up. But if I drive to the store or just around town and it gets up to temp and then try to restart it, say, 30 minutes later, it takes significantly longer. Anyone have any idea why this is happening?

 

Have you changed fuel filters in a while or performed any maintenance prior to this problem, or anything to associate a root cause? Or is this out of the blue?

Cheers, Ron

 

It could be injector(s) leaking by. with the expansion of metals when it gets hot your not able to make enough rail pressure. How many miles ? have you ever replaced injectors?

 

Changed fuel filters/oil about 500 miles after this started happening

Injectors were installed ~25k miles ago when the engine was rebuilt.

 

were the injectors NEW or rebuilds ? factory Bosch?

 

Rebuilds

 

Yeah that's probably your problem. Majority of rebuilds are junk. You need to find a mechanic with a DRB III tool or equivalent that can monitor rail pressure. If you can't make enough rail pressure it won't start.

 

Re-torque the connector tubes first. Free and not that hard.

 

Sag should he do it on warm motor or cold?

 

I might try that this weekend if I get some time. Checked the rail relief valve and it seemed to be working fine. I'm going to clean the grease and dirt off the engine first before I start disconnecting more fuel lines. My engine is an oily grimy mess right now so I'd rather not get a bunch of crud in my injector tubes

 

Obviously, they're done cold per the service manual, but I've done them both ways and it doesn't seem to make much difference.

 

Well, update: just got back from a 4 hour drive. Shut the truck off to pack/unpack before running some errands and the truck refused to start back up. Code reader says I'm between 1400-1800 psi at the rail when cranking which I understand is well below what it needs to be. I'm going to try and finally re-torque the injector feed tube lines sometime this week and maybe replace the rail pressure relief valve or the rail pressure sensor? I replaced the FCA with a new Bosch one (old one was an unmarked knockoff) about a month ago (after i started having this issue) so I don't think that's it. I'm kind of grasping at straws hoping its not injectors since I'm moving in a week and can't start tearing my truck apart right now

 

Which pressures do you see if it finally runs?

 

just got all tubes torqued down. one needed about 1/4 turn and the rest were to spec.

7100-7400

 

Ok, so i took it out, got it up to temp, shut it down waited a little and started it back up and then waited a little and did all that again. It still stumbles a little like it did when I first started having this problem, but at least it starts. I'm not calling it fixed just yet but it will do for now. While driving, I also monitored rail pressure via my code scanner. Maxed out at ~21,000 at redline

I also tested the resistance on the injector solenoids, all below 1 ohm.

 

21k is to low.

The problem you experience now did I have almost 2 decades ago with another vehicle with Bosch CP3, in my case it was twice the HPCR that was worn out.

Exactly the symptoms you are describing.
For me I would have a very close eye on the HPCR itself before spending money for the surrounding.
It can be bench tested, no need to buy one just on guessing.

 

So you're saying its the rail itself? A lot of what I'm seeing is leading me to believe a cracked injector since I have this window where I can't build substantial rail pressure and I'm not seeing any external leaks

 

PRV leaking/failing?

 

You could cap-off one injector after another to rules them out.

Do you run such a brutal tune? Because a stock Injector running with factory tune doesn't crack.

 

The proper test tools (Miller 9011, 9012, 9013) are WAY cheaper than guessing by throwing expensive parts at it. Diagnose it properly and repair it once.