Archived Hard start and sputter!

[boone]

I've had an issue with hard starting over the last couple of months. Sometimes it takes two or three tries to start. When that happens I noticed that my low pressure fuel light flickers until power is applied and then goes away.

Won't come back on even at WOT.



Replaced all fuel filters and fuel in tank. Still does it. No codes but thought it was the VP44 going bad so I replaced it last weekend. Truck ran fine for a day and then coming home yesterday I got a spurt of power and then sputtering. It got so bad I barely made it the last 5 mile home.



Pulled the APPS off and checked the voltage. Sticker stated . 518 volts and I was reading . 412 volts. Removed the sensor from the mount and gently tapped it and worked it back and forth to lossen any crap that may have been shorting out the potentiometer. Recalibrated the sensor to the bracket and then recalibrated the ECM.



Seems fine until I drove it to lunch. Ran great, got there and when I went to go back to work it sputtered at idle and got so bad I barely made it back into the parking lot. #@$%!



Is it save to say that it is the APPS? I'd hate to spend another $500 just to find out that that wasn't it. :{

 

[boone]

I forgot to mention that my truck is down and out!

 

[boone]

Well, as luck would have it I spent the $500 for the APPS and that wasn't it. Installed it in the parking lot and recalibrated the ECM and it seemed to be fine. 10 miles on the hot highway and it bucked and sputtered all the way home. It starts out with a single jolt or loss of power no matter where you are on pedel and gets prgressibely worse. It got so bad I almost didn't get it off the road.



Coasted into parking lot and open the hood while all this was goin gone. Grabbed the nearest wire harness and gave it a jolt and it stopped. I was able to get her home without further issues. Thought maybe it was a short in the high idler wire harness so I bypassed it. Took it out on the road and again 10 minutes into the trip it started up again.



Can you get vapor lock on a diesel?



I don't know what to do anymore!!!!!

 

[Ruckuz]

Quit spending money until someone who can give an answer gets a chance to reply. Oo.

 

[Missouri Mule]

No diesel should not vapor lock. Vapor lock would of shut down the engine the first time.

Apps sends data to PCM so PCM can determine when the trans shifts and TC locks up. Has nothing to do with the engine running.



Air getting into system can cause hard to start situations (usually by cracked rubber fuel line).

Bad return valve can cause hard starts also ( built inside of vp 44).

Weak starter and/or batteries can cause hard starts.



Have to think on sputtering.

 

[boone]

I replaced the supply line when I upgraded the lift pump about 20K ago with the initial replacement of the VP44. However I did recheck for cracks in fuel supply line but did not find any wear marks or leaks.



Can an air leak in the return line or a bad fuel cap cause the intermitent hard start?

 

[ROADWARRIOR]

I replaced the supply line when I upgraded the lift pump about 20K ago with the initial replacement of the VP44. However I did recheck for cracks in fuel supply line but did not find any wear marks or leaks.



Can an air leak in the return line or a bad fuel cap cause the intermitent hard start?

12 valves would commonly get a hard start condition when the rubber return line failed. I'd check the banjo on the back of the head and make sure it is dry.



Dan

 

[DavidC]

If your gonna spend money, do it on some gauges such as fuel pressure,boost and egt so you actually have some numbers and not the idiot light.



Dave

 

[Dieseldemon]

Are you getting any codes from the computer? I had one do the same thing and turned out to be the inj pump.

 

[AFarmer]

As much as we hate to admit it, in most cases the VP44 is the cluprit of most of these kinds of problems. I would have to recommend getting gauges to monitor exactly what's going on. If I had to bet I would say that lift pump is getting weak. May wanna check into a FASS.

 

[boone]

I've got gauges for boost and EGT and the Bluechip warning light on the fuel system. The lift pump that I was refering to earlier is the FASS high performace pump. I too thought it might be the lift pump so I gauged it and it is putting out 15 psi (give or take) while idling.

EGT are running normal and boost has never been a problem.



I though for sure the VP44 was going so I ordered anotherone from Bluechip. The new one that I installed last Saturday is the that is misfiring and because it is not consistant and NOT throwing any codes I believe it to be an electrically related issue. Talked to Chip and he feels the same way and has provided me some dioagnostic help. I'll know more Saturday.

 

[rkressg]

I assume that the Low Fuel Pressure light is working correctly?

I had a problem similar to this. I would loose fuel pressure, and the truck would begin to buck wildly.
I have a 1/2" pickup in the tank, and I could not figure what was causing the fuel loss. It turned out my FASS sucked a rock into the pickup in the bottom of my tank, which was blocking fuel.
I would verify the fuel pressure with an actual gauge while down the road (especially when the condition occurs).
If you pull apart the tank, verify that the fuel pickup screen at the bottom of the tank is not clogged.

If you are having hard starts:
1. Check the fuel return line from the VP44. If you follow the line back towards the firewall, there is a T-Fitting with Compression Fittings. If the line was jerked when you removed the VP44, this could be leaking slightly.
2. Verify that all your Injection lines are tight, you could be leaking a insignificant amount of fuel out of the truck when parked for long periods of time (especially if it is parked facing uphill).
3. There was a TSB a few years ago (maybe someone can find and post it) for hard starting on Winterized Fuel for the 24v motors. This should not be an issue for you in Ohio, it was more for people from way north.


You could also be having an issue with a clogged/faulty/bad injector.
Are your injectors stock or aftermarket? Most stock injectors are built very well and will typically last the lifetime of the truck. There are some aftermarket injectors that are not built to this standard and can cause weird issues.

When you installed the VP44 and re-installed the fuel lines, it is possible (yet unlikely) that there is damage to the Fuel Connecting tubes in the head. If the rubber gasket on these connecting tubes is damaged or dry-rotted, Fuel could potentially leak out of this are, causing some type of drainage and rough running.

Good luck.
-Rich