2002 GMC 2500HD - Duramax Low Fuel Pressure FIXED

[liljoe]

I have a 2002 GMC 2500HD with the 6.6 duramax. The truck is hard to start everytime. No codes, while looking at the scanner readings I noticed the FRP was only reaching 3-4MPa with a desired 34MPa. The injector pump has just been replaced with a reman unit from Pro Deisel and a lift pump installed on the frame rail.

To start I checked the fuel comong out of the bleed valve on the filter housing and it was full of air, I installed some sections of clear tubing and found that air was getting in the system at the fuel tank, fixed that problema nd figured the truck would be fixed, wrong.

Next, I hooked into the test fitting by the pass valve cover and pumped the primer, got to 14 psi with no problem, truck still had same thing going on with it. The pressure (FRP) would be real low till you spin the crap out of it. When it does start, the desired and actual FRP are right on with each other, except for the first ten to fifteen seconds, then the actual reading is considerably higher and will settle down to the desired and will match it from then on. You can shut the truck off and try to start it right back up and have the same proble, it does not have to sit for the problem to occur.

I checked the return rates of the injectors by measuring the fuel amount after 15 seconds of cranking with the PCM1 relay removed (per indentifix) and both sides were below the 12ml that is specified as max. With the truck running the balance rates of the injectors all fall between -1.3 and .9 and the customer said they were replaced at the chevy place a short time (9 months) ago. I keep coming bach to thinking I need to replace the injector pump, but I do not want to be wrong.

Any help from ya'll would be real nice......


Thanks, Liljoe.

[fortknoxx]

does this truck have a wait to start light? i know the t44e does not like it when you don't wait.

[Tim Martin]

I am tending to agree with ya, liljoe on yer diagnosis. These injector pumps can and do go bad. If there was air getting into the fuel system at the tank, all the more I would lean to a injector pump. Those pumps do not like air or water and will give trouble real fast.

[steven kiser]

yep, take that ingersol out and have at it. i've found that remans will not take any air at all. it seems to me that they are made to perform, but will not work and fail if conditions aren't perfect. burns me up when a reman fails but i bet there is scoring inside. i think i read a blurb about installing non oem lift pumps to add more pressure in line, adding to the performance.

[protraxrptr17]

Can you command fuel pressure with your scan tool? Try to ramp it all the way up. I think mine goes to 140 mpa. Watch actual and desired and balance rates. If the actual can't keep up and the balance rates stay reasonable, you have a bad cp3. Also, make sure it has a AC Delco fuel filter on it. I have had a few come in with a plain white fuel filter that only says TAIWAN. They don't seal off right. Of couse the complaint is losing prime and hard starting. One even came in on the hook last week. Died going down the road. Ol TAIWAN let him down. Theres a reason the AC filter costs twice as much.

[liljoe]

does this truck have a wait to start light? i know the t44e does not like it when you don't wait.

Yes it does, I wait till it goes out, the glow plug system is functioning as designed. The truck is hard to start even when at opperating temp, right after shut down, so the glow plugs would not be coming on.

[liljoe]

OK, here we go, I pluged the lines that go to the two fuel rails so that the pump was pumping against a closed system with the pressure sensor still installed. Spun truck over and over for 25 seconds. Pressure only got to 5MPa. Called customer and told him pump was bad. He contacted the place he got it from and they told him they would get another one ordered in and he would have to pay for it and then send the other one back for testing to verify its deffectiveness. He paid them with CC and brought the pump to me thursday evening.

I started installing it yesterday and got sidetracked on somethng else. This morning I was working on it and the pump company guy called me and asked how I determed the pump to be bad, I told him what all I had done and he said that there was something else wrong with the truck cause the pump tested on the high side of the specs. At that time I got a real sickly feeling in my stomach.

I finished putting enough things back together to be able to spin it over and watch the pressure on the scanner. In less then 15 seconds the pressure had jumped to 15 and the truck was running. Shut it off and it fired up in less then 5 seconds every time after that first time.

While I was gone to lunch, the man called back and told the secretary that he needed to speak to my supervisor, she said I don't have one, so he commenced to explain to her that the pump was good and they were not going to credit the customer for it. She said, Oh it started a truck like it was supposed to? , he told her no they bench test them. She told him the truck is fixed with the replacement pump and he told her that I had to of fixed something else on the truck to make it start.

I am sure I will be contacted by the CC company at some point reguarding the charges that he is going to dispute on his card. Not really something I want to get involved in, but life will go on......



thanks for everyone that helped out on this one!!!!!

[steven kiser]

isn't warranty issues a blast. let the customer know that if you have to go to court you expect compensation........

[brianp87]

I have a 6.6L that no starts off and on i may ask for pointers joe

[liljoe]

I don't know lots, but i will help in any way i possably can....