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hesitates under heavy load

haggus

haggus

Member
Messages
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5
Location
Sooke BC
I have noticed something new, under heavy acceleration above 2200 rpm the engine seems to be missing. It only does it if I step on the pedal hard otherwise all is normal. I have GMTDScanTech, but I haven't looked for codes yet I guess I will do that first. Just wondering if anyone out there has had a similar symptom and what may have caused it.

Thanks
 
So I'm sitting my truck right now playing with GMCTD Scan tech there are there are no current DTC but historic has 78 wastegate solenoid 93 #6 cyl imbalance still checking the timing to see what it's set at rigt now.
 
I just recently changed both my Fuel filters and the problem seems to be gone. I still need to scan it again but I'm busy with work lately so it will wait until I'm back.
 
Fuel pressure gauge installed on the dash or shop tool used to test lift pump pressure is almost required with a 6.5. If you clog a tank sock, fuel filter, or the lift pump goes T.U. they run bad from fuel starvation. I test mine every 3K or every oil changer whatever is sooner.

The computer will not pick this up unless you really start to miss before you walk.

There is a reason I use Walbro fuel pumps and that is the short life of the stock lift pumps.
 
WarWagon said:
Fuel pressure gauge installed on the dash or shop tool used to test lift pump pressure is almost required with a 6.5. If you clog a tank sock, fuel filter, or the lift pump goes T.U. they run bad from fuel starvation. I test mine every 3K or every oil changer whatever is sooner.

The computer will not pick this up unless you really start to miss before you walk.

There is a reason I use Walbro fuel pumps and that is the short life of the stock lift pumps.
Click to expand...


Yeah the FFM flter was really dirty. It was really my fault I procrastinated far too long on this one. I am glad it wasn't a serious problem. I still have more stuff to do on the truck but what I'm really lacking is the amount of time too get it done. I would like a pressure gauge for the fuel but that probably won't get done real soon.
 
Hey Guys

Looking for some help and search is not turning up the answer if it is I am missing it. Anyway I got my new WP,fan, and clutch. truck seemed to run fine. Last couple runs it almost stalled no power it is a definitely not getting fuel. I don't see any leaks LP test passed no air in FFM one thing I noticed is the Oil press when cold its steady at 250Kpa but as the truck warms up if I take my foot off or stop at a light it falls to 125Kpa I don't remember this happening before.

I have received a new walbro and OPS hose it was in the plan already. I'm not sure but I was thinking OPS switch maybe. I don't have a fuel pressure tester right now. The truck seems to idle and run fine until it is warm. I checked the oil level is good and it was changed about 200Km ago. Some minor oil leaks are on the engine but nothing major. I used rotella T 15W 40.

Any help is appreciated
 
Your going to need to give a little more data here...

  • How many miles on the truck?
  • With the truck running, how many volts are you getting to the lift pump at the connector on the frame?
  • What is your fuel pressure at idle and WOT (this can be done by hooking up a cheap 0-15psi guage to the drain line comning off the T-handle fitting bolted to the water inlet, than opening the T-handle)
  • Age of Injection Pump?
  • Age of PMD?
  • Age of Lift Pump?

I see you mentioned this only happens after the truck has had time to warm up. Roughly how long does it take before it will start to run rough and "hickup"?
 
It is definitely leaking fuel and it is coming from above the starter. I have a feeling I am not going to enjoy this.
 
BigBlueChevy said:
Your going to need to give a little more data here...

  • How many miles on the truck?
  • With the truck running, how many volts are you getting to the lift pump at the connector on the frame?
  • What is your fuel pressure at idle and WOT (this can be done by hooking up a cheap 0-15psi guage to the drain line comning off the T-handle fitting bolted to the water inlet, than opening the T-handle)
  • Age of Injection Pump?
  • Age of PMD?
  • Age of Lift Pump?

I see you mentioned this only happens after the truck has had time to warm up. Roughly how long does it take before it will start to run rough and "hickup"?
Click to expand...

*275K Km
*fuel press no gauge as mentioned
*PMD 3yrs located in front bumper
*about 20 mins until it gets bad
*have not checked the voltage at LP harness connector yet.
*Injection pump age unknown
 
Your first priority,..fix leaking hose at the FM or firewall.
Your second priority,..INSTALL IN CAB FUEL PRESSURE GAUGE,all other mods you are planning are useless if you have fuel issues.
 
As far as leak go's, Sounds like a return hose or the cap on rear injector (pretty common)
 
Burning oil said:
As far as leak go's, Sounds like a return hose or the cap on rear injector (pretty common)
Click to expand...

It looks like I start today finding the leak and adding those parts from you. Since I'm working on the fuel system whether I like it or not. I think when I lifted the t off the Tstat I pulled something on that line but I will check that injector first.
 
I found the leak it is at the fitting below the tee just enough leakage to give the truck the stumbling I guess as it heats up it leaks more. I took the upper intake off it is a F intake. Sprayed my intake bolts because it looks as though it needs to come off to get at the hose. I don't even know what the part number would be.

Just wondering if anyone has taken one of these out before? Looks like I'll get to work on the OPS mod while I am in there and get the walbro pump in place since I already have the fuel system apart might just get the injectors done while in there.

Next stop is KMS or Princess auto to get a fuel gauge and also a vac tester hopefully just cheap ones as I doubt very much these are tools I would use often. I wish we had AZ like the US loan a tool would be a nice option I think Can Tire does it but wuld not be very sure of the range of available tools.
 
The OPS mod you want to do is actually the relay mod? The 95 OPS is NOT under the intake.
It is still hard to take out but if you do the relay mod, you hardly ever change the OPS anymore.

Just a suggestion.
 
JMJNet said:
The OPS mod you want to do is actually the relay mod? The 95 OPS is NOT under the intake.
It is still hard to take out but if you do the relay mod, you hardly ever change the OPS anymore.

Just a suggestion.
Click to expand...

Yes I am adding the relay to the OPS harness I had a look at the sticky from Schwind. I see it back there by the GP controller. I am removing the FFM because the water drain line is leaking. I am pretty sure I could put the new hose without removing the intake but I figure one thing I have learned removal of interference items often speeds up the job. This way I am not fishing through the fuel lines.

I am adding the ops extension hose from pmd cable probably going to do injectors and valve cover gaskets as well lots of removing to do to get at everything. I will probably end up pulling the turbo to do injectors oh well there goes a bunch of hours but what the heck it gives me something to do.
 
Well I have good news the walbro, OPS realy, PMDcable OPS extension, ACDelco OPS, and Walking J stainless FTB. So it's been 8 days since I started this. I thought had it all done got the truck running fuel pressure gauge was reading close to 14 psi and then I start doing leak checks up top looks good go underneath and it is still leaking from the same area right above the starter.

Only now with the walbro it is really dripping fast out with the light look around the injectors, FFM and supply line at the firewall still can't see it but I know it is there. So I get to continue ripping apart my fuel system I get the feeling I will have changed more than I planned. Well off to read more about the 6.5 Turbo diesel fuel system.
 
ak diesel driver said:
check the orings on the FFM
Click to expand...

I thought I did but apparently I wasn't wearing my glasses. The filter air bleed o-ring was caught between cap and the thread. I may get lucky. I haven't started it up to verify if it's the cause but I will try it tomorrow.

Thanks
 
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