It's a 7.3 diesel and takes many seconds of cranking to start. I've been having this problem for 4 months and just cannot find the problem, any help would be greatly appreciated.

Replaced glow plug relay and valve cover gasket and tested all 8 glow plugs.
Load tested both batteries and they were good.
Tested cranking speed which was fine.
Checked fuel pressure after the pump on the frame and it was plenty.
Oil pressure was 800 psi while cranking and 2200 psi under full load.
Oil has been freshly changed as well as fuel filter.

I'm fresh out of ideas on what it could be!

 

Also, once the truck starts it revs up to 800 rpm and then down to 450 rpm before leveling out at 600 rpm. Once it levels out it idles fine and runs great.

 

Anybody out there who could help??? still no solution

 

My truck was always a little slow starting and really slow when it was cold out after I switched to rotella t-6 full synthetic fires right up I usually forget to wait for the glow plug light. You may have a timing issue though caused by a sensor sending info to computer hopefully one of the more knowledgable members will help out soon

 

Have you checked fuel pressure at the fuel bowl? Your pump may be suffecient, but the FPR could be stuck open. Not likely, but I didn't see that checked.

When you replaced the GPR did you verify it is operating properly? Having a new GPR that doesn't turn on is pointless.

You may also have an injector o-ring that is not allowing pressure to build quickly.

 

I'm actually running T6 oil right now and it still is slow to start warm or cold

 

I did verify the GPR is working properly and the truck is the same whether warm or cold so i dont think it is in the glow plug system.

 

The next step to do is check compression. You may have low numbers and that can lead to slow/hard starts.

 

Actually the truck started fine for about 2 weeks randomly and is now back to not starting again so i don't think that it is low compression. Also i did a cylinder contribution test and came up with P0284 Cylinder 8 Contribution/Balance Fault.

 

This is common if you have the grey CPS (also referred to as the CMP).




Faulty EOT (Engine Oil Temp) sensor might cause hard starts. Use your scantool to see if it is working properly. First thing in the morning it should be close to ambient air temp, unless it was real old overnight (the oil won't warm up as fast as the air). You can compare the EOT to the MIAT (manifold intake air temp). EOT when fully warmed up should be between 195 and 205 degrees.


The EOT sensor is on the back of the HPOP reservoir.

 

I had a sticky IPR sensor causing problems. There is a procedure for removing and cleaning. My has worked great since.

 

Thats what I was going to say. I rebuilt mine a few weeks ago, and I'm good to go now-

 

EOT sensor is good as i had already checked that.


I will try the IPR Valve Cleaning tonight hopefully!

 

I got some numbers tonight in regards to the IPR and ICP sensor and i was just wondering how the numbers sound before pulling them out.

IPR % during cranking was about 60% while idling it was 12% and on the throttle hard it was also about 60%

ICP Sensor read 500 psi until starting and then it went to 600 psi idling.

How do those numbers sound?

also, i unplugged the ICP and started the truck and it was much better however was still not good.

 

Also, when i unplug the ICP sensor the truck still cranks for an excessive amount of time however once it starts it's nice and smooth but when i start it with the ICP plugged in then the truck rattles and misses for a few seconds until it levels out