Duramax Issue

[Shorty Cox]

Okay, all you Duramax guys, I need info. If you look back at my posts, you will know that Kitty purchased a new 321RSTS and we took delivery on 4-8-21. On 5-3-21 we left on its maiden voyage of 570 miles. All went well until we arrived at the campsite. We got backed into the site, lowered landing legs, pulled the hitch release, got in the truck, hit the starter. Engine spins over but will not fire. I wait several minutes and try again, same thing, engine turns over but does not start. It is too late in the day to call for service, so Kitty and I go about our stabilizing the RV and opening slides and settle in for the night.
Next morning, I try to start the truck, same thing, spins over but will not start. I call back home to the local mechanic shop talk to the tech. He informs me that it may have lost prime and to pump the hand pump on the filter housing. I do so to no avail. Same thing. As I was there to fish, I decided it would wait until after the fishing outing planned for that day. As I walked by my truck on my way to my buddy’s truck to go fishing, I said a little prayer, got in my truck and hit the starter. If fired right off and I have not had a minute’s problem to date. I have faith that the greatest mechanic ever repaired it for me.
Have you ever had a similar problem with you Duramax? Any thoughts? If so, what was the problem?

[JFlightRisk]

Just off the cuff, it sounds like it might be time to replace the filter housing o-rings, or maybe even the filter housing head assembly. Did you prime it until you felt resistance?

[Shorty Cox]

JFlightRisk, I never felt resistance when I pumped. I pumped numerous times and the last felt like the first.

[craigav]

In the future if that happens, you need to pump and pump and pump until there is resistance. Mine does that sometimes, especially if I let the engine compartment get hot (such as with prolonged idling with A/C on) and the reason is as JFlightRisk mentioned which is the o-rings allow air into the system which causes a loss of prime, especially when the temperature is high. The fact that you didn't encounter any resistance while pumping indicates a loss of prime. I have new o-rings ready to install in mine when I have a bit more time. ~CA

[Midnightmoon]

What year Duramax?

[Shorty Cox]

Midnightmoon, 2007 Classic, 85k miles.

[Midnightmoon]

This will be a good read for you.

https://www.dieselpowerproducts.com/...y-it-shouldve/

Since your truck relies on the injection pump alone to pull fuel from the tank (no lift pump), even the smallest leak in your system will cause the loss of prime that you experienced.

I'm not one to recommend parts to anyone, but do a little research on aftermarket lift pumps for the Duramax. I've had a lot of personal experience with the FASS system. But, there are other's out there. Yes, they are expensive. But, it really is the best solution for this problem long term.

[craigav]

Originally Posted by Midnightmoon

This will be a good read for you.

https://www.dieselpowerproducts.com/...y-it-shouldve/

Since your truck relies on the injection pump alone to pull fuel from the tank (no lift pump), even the smallest leak in your system will cause the loss of prime that you experienced.

I'm not one to recommend parts to anyone, but do a little research on aftermarket lift pumps for the Duramax. I've had a lot of personal experience with the FASS system. But, there are other's out there. Yes, they are expensive. But, it really is the best solution for this problem long term.

Just thinking out loud, if you did have the smallest of leaks in the fuel system, in this case the fuel filter housing pump\primer area, wouldn't it be better to have a small amount of suction on the line which would cause the loss of prime (due to air intake) vs having pressure on the system which would allow the fuel to leak? (I know sometimes things leak under suction but not under pressure, but not sure if this would be the case here). If it did leak and was under pressure at the filter\prime pump area, then the fuel would leak right above and onto the exhaust manifold which seems like a dangerous situation. I have nothing against lift pumps and more filtering, but I am not sure I would prefer to have a little leaking of fuel over sucking a little air into the fuel system. Anyway, just a thought. I plan to replace the o-rings in my filter prime pump soon in either case, first time since I bought it new in 2003, although I did have the injectors replaced about 3~4k miles ago, supposedly the newer ones are of a better design. ~CA

[Midnightmoon]

In most of the installs that I have done, the factory fuel filter is eliminated and the new fuel line is run directly to the head of the injection pump. Since the FASS has built in filtration and the capability to run very low micron filters, the factory filter housing becomes all but unnecessary. That eliminates all fittings capable of leaking except of course the input on the head of the IP, which is there already.

Again, I don't think that a FASS or similar system is for everyone and don't think that you will have any issues with your factory system if you maintain all if the o-rings and fittings as mention above. It just is a really good way to completely eliminate the possibility of this particular failure.

[CAG]

I Think that the problem is pretty well covered and I can tell you that most of use who owned Duramax will testify to the same problem happening at one time or another.

While the FASS system is fine I suggest going to Kennedy Diesel web site and looking at his lift pumps. Also the extra filtering is always good but you can change out the filter head and use CAT filters rather than the other expensive filters. Down to two microns.

Go to The Diesel Place Web site and do some reading on your particular engine and what some with a lot of Duramax experience suggest. A lift pump pumps fuel forward rather than relying on the CP3 to suck fuel from the tank which leaves the system sucking air forward with the first break in the fuel system.

And just for info, my first ORing issues left me sitting at a fuel pump in a gas station but having read enough about the fuel filter issues I knew to get out, pump the plunger and it fired right up. I added a Kennedy Lift Pump, rebuilt the filter head and added the CAT filter head. Never had a problem after and I owned two different Duramax.

[craigav]

That makes sense with bypassing the factory filter, I had thought about getting a lift pump a long time ago for it but never did. I did read a lot about the better filtration with something like the FASS setups have and how that can help the injectors to last longer. Mine is a 2003 and just over 100k, still looks and rides like new, maybe I can get another ~18 years out of it. I only use it for my farm\ranch activities now days. FYI, I have a JohnDeere tractor and had a similar issue as the OP had with losing the prime, I think my fuel gelled (this was back when Texas got the polar vortex and ~-9 temps here) although I had anti-gel in it, in any case it wouldn't start even after things warmed back up and the tractor has a similar pump on the filter head that I had to prime to get it running again. In any case, I looked at the website you shared a link to and they had an image of using the FASS system on a JohnDeere tractor, I plan to give that a bit of thought as well, maybe after the warranty on my tractor runs out. ~CA

[CAG]

Originally Posted by craigav

That makes sense with bypassing the factory filter, I had thought about getting a lift pump a long time ago for it but never did. I did read a lot about the better filtration with something like the FASS setups have and how that can help the injectors to last longer. Mine is a 2003 and just over 100k, still looks and rides like new, maybe I can get another ~18 years out of it. I only use it for my farm\ranch activities now days. FYI, I have a JohnDeere tractor and had a similar issue as the OP had with losing the prime, I think my fuel gelled (this was back when Texas got the polar vortex and ~-9 temps here) although I had anti-gel in it, in any case it wouldn't start even after things warmed back up and the tractor has a similar pump on the filter head that I had to prime to get it running again. In any case, I looked at the website you shared a link to and they had an image of using the FASS system on a JohnDeere tractor, I plan to give that a bit of thought as well, maybe after the warranty on my tractor runs out. ~CA

Your 2003 likely has the LB7 engine which is prone to injector failure. I went through three sets with my 04 in 120K miles. My grandson’s 03 went 175K before the first set gave out.

Better filtration
Lift Pump
Add lube to the fuel (Do a search on the study on the best diesel fuel lube) that may also help your gelling issue.

Those are the top items for the LB7. Later models did not have as much of an issue with the injectors but from about 13/14 on the problem became the CP4. there is currently a lawsuit over that item.

[craigav]

Originally Posted by CAG

Your 2003 likely has the LB7 engine which is prone to injector failure. I went through three sets with my 04 in 120K miles. My grandson’s 03 went 175K before the first set gave out.

Better filtration
Lift Pump
Add lube to the fuel (Do a search on the study on the best diesel fuel lube) that may also help your gelling issue.

Those are the top items for the LB7. Later models did not have as much of an issue with the injectors but from about 13/14 on the problem became the CP4. there is currently a lawsuit over that item.

Thanks CAG, I do add a little lube to the fuel, I use PowerService Diesel Kleen\lubricant in each tank full. In fact I have a mixing container in the toolbox that I use to measure how much to add, prior to pumping I fill that container with about a quart of fuel and visually inspect it prior to filling the truck's fuel tank, just to be cautious, and then if it looks good I pour it in the tank and add some diesel kleen and fill it up.

I had my injectors replaced pro-actively as I was having some other work being done at that time, the injectors likely had a lot more life in them. The new injectors though that I had installed are of the newer design and supposed to last a lot longer than the first gen injectors. ~CA

[edatlanta]

About a year ago this happened to me. I was able to pump up the system and drove to the nearest dealer. The filter housing was cracked and they replaced it. A week later it happened again so I pumped it up and back to the dealer. It seems the replacement housing had a crack in it. All better now. This all happened with a little over 200,000 on the clock. Obviously the second replacement wasn't on my nickel.

[GDGerry]

I had the same lose prime issues. Filter housing in my '06 LBZ was cracked as well. I put in a FASS 95gph filter/pump and eliminated the factory filter with fuel hose. No leaks now and never loses prime and I've put about 20K miles on since the factory filter housing delete. I'm running the CAT 1R-0750 (2M) fuel filter and the Baldwin BF7546 (10M) water separator.

[Rcemerat]

A vapor lock will do the same as lost prime occasionally

[CAG]

Originally Posted by Rcemerat

A vapor lock will do the same as lost prime occasionally

In all my years of owning diesels, I cannot recall having one, or hearing of one vapor lock. My research says they do not vapor lock. Air in the fuel line will bring things to a stop in a hurry and that is why the suggestion prior to this post.

[Rcemerat]

Well it does happen. After 4 million miles as long haul & 30yrs as a mechanic I personally have experienced only once. A bad tank vent causes it, just saying it can happen.

[mass-hole]

The symptoms sound a lot like when my Jeep Liberty CRD had a bad crank position sensor. Basically it would cold start but once the sensor was heat soaked it would start giving wacky readings and would not restart with a hot engine.

The Jeep Liberty shares a lot of the same Bosch sensors and PCM with the Duramax from that same era.

[craigav]

Whether or not it is a vapor lock, which seems possible on a stock duramax due to a vacuum being pulled on the fuel line, my duramax will sometimes lose prime when it is very hot outside and I have the engine idling with the a/c on. I have to prime it again and then it will start, I plan to put new o-rings in the filter housing soon to resolve this issue. The issue I have (and others have reported) is that when the filter prime pump area is hot that the o-rings don't seal as well and sucks in air, just like a vapor lock but perhaps a bit different seeing that it didn't use to do that. ~CA