Diesel Place banner

1 - 12 of 12 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter #1
I have a G3500 2001 all stock, other than having it converted to 4x4. 70,000+ miles with no problems and now when going down the road it will die. Much like turning the key off, I can restart right away and continue on. Sometimes it will die - start - die - start - run 30 seconds +/- - die - start and run for the balance of the trip. Very random, might happen after 50 miles, or right after first start of the day.

Any ideas to the probem? Took it to the GMC Truck Center in Oakland, CA., and they could not find any codes for the problem. They had it for two days and could not find anything. They did decide to replace the lift pump, but that still did not solve the problem.
 

·
Registered
Joined
·
2,991 Posts
well, the lift pump sounds like a good place to start, often they can fail or operate intermittently and cause problems like this.
If your not getting any codes tripped, sounds like very good possibility of PMD failing on you. Before you change it, try the 'wiggle' test. Remove the dog house, start the engine and wiggle the wiring harness to the PCM and to the injection pump to see if you can make it stall, if not, 99% chance you need a new PMD.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #3
Thanks. I'll try that as soon as I can and get back to the thread.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #4
I pulled the doghouse and checked all the wiring for bad connections, nothing loose or broken. Looks like I'm off to the GMC Truck Center for a new PMD.


The same thing started happening back in Sept of 2002. The Truck Center had to replace the injector pump. Would they also replace the PMD at the same time?
 

·
Registered
Joined
·
5,245 Posts
PMD is on injector pump. Stalling could be fuel supply pressure.
 

·
Registered
Joined
·
2 Posts
My 96 1 ton was doing the same thing, the dealership replaced some sensor on the turbo for about $25 and it fixed the problem.
 

·
Registered
Joined
·
5,245 Posts
The wg solenoid will help it stall but only if their's some underlyng fuel issue.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #8
OK. The van would keep stalling at odd times, normal operating temp., cold, after it set for an hour or so, fuel tank full, half full and almost empty. Gave up on the dealership finding anything, so I bought an inexpensive AutoXray scanner. The scanner came up with code P0251. Went back to the dealer and had them check it out, left it there and rented a Tahoe for a day or two.

Checked on the van three days later and found out they are going to replace the injector pump. The tech reviewed history and found DTC P0251, P1216. Found that the fuel system had metal in it.

They drained, (30gals), and removed the fuel tank and steam cleaned and dried it out, cleaned fuel lines replaced lift pump, (again), replace fuel filter. Reinstalled tank, replaced injector pump and added 5 gals of fuel. Road tested and found no codes.

The dealer had the van for 8 days, and were kind enough to pay for 3 days of the eight day rental.

Looks like every 35,000 miles or so I'll have to go through this. Both times now it took at least 3 different trips to them before they could find the problem.

Thank you guys for all the help.

Craig.
 

·
Registered
Joined
·
8,014 Posts
Ditto on the screw job Craig, I'm at work now in the thick of things I'll post more later, I suspect PMD or electrical problem. We will use this thread for the FAQS I seem to not have anything there for this problem and it is a common one.
 

·
Registered
Joined
·
595 Posts
I agree with TD and WH on ALL points mentioned.
 

·
Registered
Joined
·
8,014 Posts
Okay running through the list of what causes this problem add in if I miss one.

Many a 6.5 owner has experienced this problem most times this will Not set a code, most common culprit is a bad PMD see FAQS for Acronyms explanations, remote mounted it becomes a FSD.

The IP and it's PMD are warrantied by GM for 12yr 120K mi under special policy,

(someone please provide policy # I'm on the road away from home and don't have it with me)

if you have had this replaced by anyone other than GM you are entitled to have the repair reimbursed by them, that said you need to do any and all checks 1st to verify in fact it is PMD causing the problem.

If GM finds anything they don't like they will repair that 1st BEFORE replacing a IP/PMD combo. This is how you get 3 fuel tank drops and lift pumps swapped, GM techs aren't very up to speed on the 6.5 anymore their one or 2 "Expert Diesel Techs" if they have them are 6.6 DMAX trained now that 6.5 is out of production, a whole different animal than the 6.5.

The scenario is driving along truck misses and stumbles, cuts out may restart, or may die and restart after sitting dead on the highway. Cutting out while under load and regaining power is indicative of low fuel supply to the IP, 1st suspect for a normally operating truck is bad fuel or fuel filter, did you get some "strange" on that last fill up, could be water or a partially clogged fuel filter.

Start carrying a spare fuel filter not every parts store carries them, at 1st sign of trouble change the filter even on a "recently changed" filter I got some "strange fuel" once and within 5000 miles of the "new" filter I was having driveability problems. Use a quality fuel additive to every tank of fuel, I use FPPF total power, additives add lubricity missing in low sulphur fuel, and adds anti gel, and anti water additives.

When changing fuel filter make sure you clean debris in bottom of the fuel filter bowl (Bowl is aft center of block visible when turbo cover is removed), GM will say you have a dirty tank if the find crud or water in the bottom of the bowl, also when removing filter make sure to retain the plastic last ditch screen that sometimes sticks inside old filter, this may be missing from your truck as previous owner may have not known it is supposed to be there.

Okay now filter is clean, you have cracked the vent on top, does the lift pump come on with key or while cranking and purge air out, you should have fuel coming out the top eventually. Assuming you have power if not check for pump power (Howie E's site has some tips for regaining power http://mysite.verizon.net/vze54tx9/id13.html )

Here are some mechanical tips for testing lift pump output from another old thread. A test that works for me, is to put a long hose on the filter drain connected (Brass valve with chrome tee handle dead center front of engine) to a temporary gage in the cab and read pressure while driving, make sure to route it so hose isn't pinched which will give false readings.

At idle should have 4-6 psi on gage, on hard acceleration like in a hill climb may drop to 1-2 psi, should recover to about 4 psi during steady cruise speed, if it doesn't may have a weak lift pump. Do the power tests as Howie suggests, then do the gage check if you still are stumbling.

One last delivery test you can do, run pump with same filt bowl drain open to a collection bottle, with 3 psi minimum delivery is 15 gph, so run pump for 15 sec you should collect with a healthy pump .24 Litre or 1/2 pint. I prefer the gage method as you are checking with a real load demand of the engine and IP.

Okay we have good power, fuel delivery and a clean filter, last thing to verify before going to dealer is make sure all electrical connections and grounds on the engine are clean and solid, a loose connection to the IP PMD or remote mount FSD will also give intermittent shutdown. Crank sensor can cause stumble but generally does not shut down truck that is another post.

Check all above before going to dealer, be firm if the insist they also need to do it before warranting pump, take your reciepts to prove your point, show them you flow and gage numbers, if they insist tell them it's on them you won't pay for work you have already done, take them for a test drive with gage installed. If you still have problems gettingaction PM me and I'll tell you of another trick that sets a code they have to act on. <!-- / message --><!-- sig -->
 
1 - 12 of 12 Posts
Top