01 Duramax / Allison, 37k miles. Started it up last night after sitting for a day or so outside, temperature about 30 deg. F; started up just fine and ran for only a few seconds then quit. No signs of life since then. Cranks fine at about 120 RPM as indicated by scan tool, no DTC's set; fuel rail pressure is low at about 126 psi and does not seem to change when cranking or not. I think the factory manual says this pressure should be above 10 mPa (1450 psi) but does not do a great job of saying what the potential problem could be. Any ideas out there?

Stan

try priming the fuel filter and maybe replacing it.

The next morning - still cold and 14 F overnight, opened prime vent valve and it sounded like air went in not out - no fuel out the vent at all, manually pumped prime pump until there was a fairly steady fuel stream out, closed the vent valve. Scan tool indicated about 155 psi on the fuel rail (zero offset?) before cranking and pressure started up after a few seconds. One thing I noticed last night when looking at the fuel rail pressure was that it started at about 155 psi after the engine had been sitting for a while and the indication went down to about 126 psi as the engine was cranked. Is it possible that a decreasing fuel rail pressure when cranking could be used as a diagnostic to show that the thing just needs to be primed not all the diagnostics in the factory manual?

Does this fuel system just lose prime out of the blue like this often or am I just unusually lucky?

Stan

not often. but every once in awhile someone may come up with similar issues. These usually have something to do with the filter. Maybe replacing the filter may fix it. Or try tightening the filter. There may be an issue with one of your rubber gaskets that come with the filter. Might be causing air in the system.

Do you have winter fuel? Do you run an additive? Sounds like(you said that it sucked air when you opened the bleed screw)might be something clogging the pickup screen. Maybe ice crystals or bio-slime? Change fuel filter and cut open the old one and disect it.

After getting the truck going by priming the other day, it did not start as easily as it always had in the past. Crank times were 3 to 10 times longer than usually required (maybe 10 seconds at most). Replaced the fuel filter yesterday and noticed fuel dripping from the drain valve at the bottom of the WIF sensor assembly after removing the filter. Inspecting more closely, it was leaking from pinholes in the filter shell just above the threaded boss where the WIF goes. I figure this must have been the reason for the repeated loss of prime and hard starting. Prolem solved hopefully.

Stan

Glad you found the problem. Who makes the filter? I would go back to them for a faulty filter and maybe you can get a new one or more for free due to your troubles.

After getting the truck going by priming the other day, it did not start as easily as it always had in the past. Crank times were 3 to 10 times longer than usually required (maybe 10 seconds at most). Replaced the fuel filter yesterday and noticed fuel dripping from the drain valve at the bottom of the WIF sensor assembly after removing the filter. Inspecting more closely, it was leaking from pinholes in the filter shell just above the threaded boss where the WIF goes. I figure this must have been the reason for the repeated loss of prime and hard starting. Prolem solved hopefully.

StanStan, if you can cut the filter open and see if there was any water/rust in the bottom. If the filter was on the truck for a while, and the filter held a little water, it might have rusted thru the filter causing the pin hole. probibly not, but you never know. And if possible post pics of the filter with details. ie: how many miles, amount of time fitler was on truck, do you use additives, and where you are located(warm vs. cold climate) Info like this helps us all.

wow that would be a lot of rust.. if you don't drive it many miles it might help to service the fuel filter a bit more often based on time instaed of mileage alone..

Hey guys

I have a 02 duramax cc and i have the same problem every day if i leave the truck sit for more than 8 hours there is no hope unless i prime the filter!! what i have been noticing is mine looks like it is leaking out of the bleed screw. so of course gm doesn't have any stock and they are like 40 bucks for a new one i will try the new one tuesday and let you guys know if it works.

Greg sells an excellent stainless steel replacement bleed screw...

http://www.lubricationspecialistllc.com/product_info.php?cPath=14&products_id=113

http://www.lubricationspecialistllc.com/graphics/products/bleeder.jpg

i second what hoot said...

I have seen the filter housings leak and allow air into the system without seeing any external fuel leaks somewhat regularly. If the water in fuel sensor is overtight you can also damage it during removal resulting in a leak that looks to be coming from the drain valve. the sensor is available by itself. You can tell if there is a problem with the sensor by priming the system and looking for a leak. If there is no leak, but you continue to loose prime it is probably the entire filter / primer housing assembly. It is covered by the diesel 5yr / 100k warranty. Hope this helps.:D

Mine started to slowly take longer since about October usually only when sitting for a day or so, just noticable enough to start to irritate me. So I took it in to a dealer in a couple months ago in case it was warranty work and they told me it was the batteries which was incorrect because I had proved it before I brought it in and had told them so...so I happened to have two brand new ones in my 95 then brought it back. Then said it was fuel filter swapped it out and improved start time but not to standard start times for a DMAX. I had them check all the injectors and they were fine...made them eat the cost on that because they kept me coming back and not listening to me. Anybody know a great DMAX mechanic in Boise? The last month or so it had gotten steadily worse from only happening occasionally when cold to every start. I tried getting back in but I dont trust the dealer I had been in and I guess I'll have to hunt down someone because this morning I turned over the DMAX enough that my garage stunk like a Flying J and had to put the battery charger on new Interstates...cuz it aint starting. Any ideas before I get stuck with towing charges and whatever else isnt gonna be covered by warranty?