Hi l have a 2003 Duramax it is very hard to start when cold my friend has a tech 2 all test done at ideal It does not blow any smoke nor seems to have power lose and there is no codes It does seem to be using alot of fuel Please help
Actual Fuel Rail Presure 6078psi
Diesired Fuel Rail Presure 6090psi

Balance Rates 1 -6.1
2 -1.9
3-1.4
4 2.4
5-1.2
6 4.0
7 -2.1
8 6.8

---AutoMerged DoublePost---

I sure could use some help please l am on a tight budget these days thank

---AutoMerged DoublePost---

I noticed also the prime does not stay hard after shutting down engine l srayed soapy water on it after priming it hard and there is no visable leaks l am wondering if there is a bad injectors causing this issues also or if they are all related

 

how cold is cold?

could be a bad injector(s). number 1, 6 & 8 our out of spec if the engine was warm

what are the numbers in drive with foot on break idling?

you need to fix the priming issue first before anything else. air in the lines can cause all sorts of issues with starting. balance rates could be affected too.

the filter housing and all lines up to the CP3 are under negative pressure and wont make the soap bubble. you would have to pressurize the fuel tank to make it bubble.

the bleeder screw is the first suspect, then the primer bulb seals and cracked filter housing. the rubber lines could also develop leaks too.

have your friend command, with the tech 2, max fuel Mpa while idling and see what pressure you get. also log the pressure while cranking. should be 10 Mpa or more for it to start

 

Thanks 2004 LB7
-Temp out side is 50 F
-numbers in drive with foot on break idling
1 -4.1
2 -1.2
3-2.2
4 2.0
5 -3.2
6 4.3
7 -1.7
8 5.4
- with the tech 2, max fuel Mpa
Actual 5644.8 psi
Disired 5655.0 psi

 

Looks like injectors to me, mine was doing same thing, but you need to take care of the air in the system first. Like said above check the bleeder screw. I did my injectors my self with the help of a thread here and merchant automotive. Ordered everything from them and took a whole weekend and it was done.

 

well non of the numbers are above 6 so they "should" be fine. But this doesn't tell us the return rates which is where the majority of the injector problems lie.

you need to command max fuel and see what the CP3 can do

 

I just compared the prime bush button to my friends and it seems to be fine same amount of presure How do you check return rates? Thank You
Just did Max Fuel with Tech2
Actual 23015 psi
Desired 23200 psi

 

CP3 seems to be fine.

the primer bulb should stay hard or get hard after a few pushes. the bulb has a spring under it so the pressure should be the same as your friends until it builds fuel pressure. what happens is that sometimes the seals around the bulb leak and the fuel pump sucks air into the filter housing and into the fuel lines. this will cause it to loose prime and not start. depending on where the leak is fuel can drain back into the fuel tank and fill the lines full of air

try pressurizing the tank with a rag and air hose till about 5 PSI, check for leaks and try starting it while still under pressure.

 

Ok primer bulb is hard went over all lines and bulb for leaks non using preasure at tank
Went to start truck this morning same crank crank for about 10 seconds then fires up this happens only when it is sitting a long time and worse it gets longer it sits
did Max Fuel with Tech2
Actual 23015 psi
Desired 23200 psi
Just did a log at start up
230psi key on
start cranking 663psi 1450psi 1699pso to 6072psi

Balance Rates
1) -5.2
2) -1.3
3) 3.3
4) 7.5
5) -2.1
6) -1.4
7) -0.4
8) 6.7

 

Any injectors more then +-4 in neutral and +-6 in drive are considered bad. now remember this is just showing how much the ECM is adding or subtracting fuel to make the engine run smoothly. it wont show the return rates which if high can cause the engine not to start of hard to start

return rates are a bit difficult to test on the LB7 engine. basically you test each bank at a time and the side with the higher flow gets its valve cover removed and then each injector tested. dont remember what the flow rate is for a good injector but google should know.

as a rule of thumb, when replacing injectors on the LB7, you should at least replace all the injectors on the bank if not all 8 injectors. if not you are likely to be back in there replacing the others in a short time

 

Thanks 2004LB7 I Guess eveything is pointing to injectors couple questions
1)How hard should the pime bulb be mine is fairley stiff
2) I always thought when there is bad injectors l would have white smoke but my balance rates show otherwise