Chevy and GMC Duramax Diesel Forum banner

1 - 14 of 14 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter #1
I have a 03 Gmc LB7 3500 duramax. 190,000 miles. Daily Driver truck.
I recently had injection pump replaced, added Fass 95 gal lift pump installed, 2 new batteries, last 30 days.
Truck is in a high humidity area, Georgia for the last 3 months.
Cranks and starts at temp of 25 degrees or above, but after running to engine temp of 150 degrees +. A short trip.
Will crank but not start.
Add ether for 1 second to air filter, and truck will start.
No smoke, no surge, truck runs fine after start. Power is good. EGT is 500 to 800 when running down road, no load just truck. Truck will go 100 mph with no load.
What could cause a warm, no start with a lift pump installed???
Computer, electrical connection, all fuses look ok. Possibly a pressure regulator, computer, electrical connection, there are many??
Does anybody have a suggestion on where to look??
Old Guy.
 

·
Premium Member
Joined
·
189 Posts
Sounds like a lack of pressure starting. The fass will get it to the filter and the pump and even cover some sucking air problems. What it you just pump the primer bulb on a hot start, wonder it its losing prime. The cold start though baffles me. I would check that dang under hood filter housing real good or rebuild/replace it if it hasnt been done. If it not loping I wouldnt think its the FPR. I have a Fass as well, my FPR went out 3 days later. Later I found out the head was sucking air probably a bad o-ring.
When you use ether your bypassing the pressure needed to start and the pump is strong enough to feed the injectors. I hate to say what I truely think, but Im leaning to Injectors leaking check your oil for fuel. They fail to hold pressure more when the engine is hot because the fuel is thinner. Codes P0087/P0093/P1093 all are usually because of injector problems.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #3
Thanks for the info.
But, under hood filter rebuilt about 9 months ago. There is no sign of fuel leak since Fass lift pump and injection pump installed. 1 shot of starting fluid, truck starts and runs fine, no smoke on startup. Scanner shows no codes. Only symptom is, crank but no start after short trip, when engine is not completely hot. Engine temp usually about 150 degrees. Truck starts fine when cold or completely warmed up. Being intermittent, it is hard to reproduce, as it does not do the same thing everytime. Hope, it is not injectors as they were replaced a little over 100,000 miles ago. (lots of money). Also, rain, and outside temp does not seem to matter. I am leaning towards an intermittent electrical issue with computer, crank sensor. It seems as if the injectors are not being pulsed when condition occur. Old Guy.
 

·
Registered
Joined
·
5 Posts
Mine was doing the same thing. This may sound dumb, but worth a shot. Battery terminal was loose on one of the batteries. Battery hold down was missing and it would loosen up again. Hope this helps
 

·
Premium Member
Joined
·
699 Posts
100,000 miles on OEM style, VCO injectors is doing well and a common problem in high mileage units is failure of the ball/seat in the internal return circuit causing an excessive return rate from one or more injectors. This issue often begins to present when the engine is hot, since as you know, diesel thins out when it warms. High return rates cause low rail pressure and your symptoms. Once the engine fires (shot of ether) it obviously seems to run normally since higher running rpm (vs cranking speed) allows the CP3 to maintain required pressure.

Search this section of the forum for “return rate test” and you will find several options, perhaps the easiest being to cut into the often rusted return line just ahead of the tank.

While “fuel in oil” is another symptom of failure in the return lines under the valve covers, the “paper towel” test will reveal that issue. Frankly, it’s not particularly common but an easy test (search).

Finally, as mentioned earlier, low rail pressure can be easily discovered with a TECH2 or similar scan tool.

Gook luck and keep us posted!
 
  • Like
Reactions: Jwaggonersr

·
Registered
Joined
·
8 Posts
My Dad had a similar issue, It turned out to be the CP3 pump. Also a 2003 duramax. Is yours original? He got a new bosh one and it runs great starts every time now. Might want to look at that.
 

·
Former GM Tech and parts
Joined
·
2,558 Posts
Sounds to me like the injectors are returning too much fuel and not allowing the rail pressure to build enough to start. Honestly, a pretty common LB7 issue. You can do a return rate test on the injectors for assurance, but with my experience with LB7s and your description with prior parts replaced, I would toss a set of injectors in it.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #9
100,000 miles on OEM style, VCO injectors is doing well and a common problem in high mileage units is failure of the ball/seat in the internal return circuit causing an excessive return rate from one or more injectors. This issue often begins to present when the engine is hot, since as you know, diesel thins out when it warms. High return rates cause low rail pressure and your symptoms. Once the engine fires (shot of ether) it obviously seems to run normally since higher running rpm (vs cranking speed) allows the CP3 to maintain required pressure.

Search this section of the forum for “return rate test” and you will find several options, perhaps the easiest being to cut into the often rusted return line just ahead of the tank.

While “fuel in oil” is another symptom of failure in the return lines under the valve covers, the “paper towel” test will reveal that issue. Frankly, it’s not particularly common but an easy test (search).

Finally, as mentioned earlier, low rail pressure can be easily discovered with a TECH2 or similar scan tool.

Gook luck and keep us posted!
Thanks for the reply.
You were right. Replace CP3 pump, added Fass lift pump and 8 injectors and high pressure lines. Hope to get the truck back this week. Poor old bank account is bone dry. Love my truck. Terry
 

·
Premium Member
Joined
·
699 Posts
What injectors did you Install?
 

·
Registered
Joined
·
18 Posts
Daily Driver-Turned 900HP Work Stock Puller

Under the hood of Jeff McCord’s ’02 Chevy Silverado 2500 HD and beneath all the polished aluminum piping, turbo, and Wagler intake, sits a balanced and blueprinted LB7 Duramax from SoCal Diesel. Installed by the truck’s previous owner and with few expenses spared.
 
1 - 14 of 14 Posts
Top