2003 Duramax Hard Start
#1
2003 Duramax Hard Start
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
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
Last edited by maxchevy2004; 10-29-2012 at 01:34 PM. Reason: Automerged Doublepost
#2
Join Date: Dec 2010
Location: Fool's Golden State
Posts: 1,190
Likes: 0
Received 113 Likes
on
109 Posts
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
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
#3
#4
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.
#6
#7
Join Date: Dec 2010
Location: Fool's Golden State
Posts: 1,190
Likes: 0
Received 113 Likes
on
109 Posts
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.
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.
#8
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
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
#9
Join Date: Dec 2010
Location: Fool's Golden State
Posts: 1,190
Likes: 0
Received 113 Likes
on
109 Posts
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
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
#10
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
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
Last edited by maxchevy2004; 11-01-2012 at 05:13 PM.