2001 LB7 fueling problem

[MPR]

Started truck and went approx 1/2 mile and engine stopped. Dash monitor showed nothing out of ordinary. Tried priming and engine started right away. Can keep it running if I keep pumping primer. Bled system via the bleeder screw on filter. No smoke and I could not find any fuel leaks. This engine has all new injectors with approx. 4500 trouble free miles. Ideas?????

[JohnC]

Sounds like an air leak. The system is suction up to the inlet of the injection pressure pump. Did you just change the fuel filter?

[Kennedy]

All Dmax will benefit from a lift pump. When they start to act up like this it's a definite suggestion to add one.

[MPR]

No, the filter had not been changed. Truck was parked for about 3 weeks.. John, I have thought about adding a lift pump. Suggestions as to type? Would an inline type work? Was just on your web site and like your setup with the single pump. Thanks to both for your timely responses.

[Kennedy]

Cutting right to the chase most that go with the single end up adding a second. I'd suggest the twins myself. Helps get the pressure across the media as it loads.

On the other hand the single is adequate in most situations.

[UndergroundDmax]

A lift pump will help but its not fixing the issue. Your truck should run without a lift pump.

As long as you keep positive PSI on the cp3 under WOT a single pump set up is plenty.

I agree, sounds like a air leak.

[Kennedy]

It is much easier for air to get in than for fuel to get out. All Dmax trucks will essentially "make" and hold air in the filter housing. To combat this all one needs to do is place the system under pressure. This keeps the fuel liquid in the lines and filters and helps the filter(s) do a MUCH better job.

[MPR]

Further to John's advice, have installed a lift pump and put filter under positive pressure. Couple of pushes on primer pump and its hard. Truck starts with just a touch of the key. Will run for approx 30 seconds and a couple more pushes on primer will run another 30 seconds. Could do this all day. Spoke with my dealer's tech and he suggested changing filter to eliminate possible restriction in filter. Did so, but still the same problem. No fuel leaks on the tank side of filter and do not see any on outlet side. Checked primer pump hold down screws.
Must say it was a joy to change filter, turn on lift pump, open air bleed screw and have the lift pump prime the filter.
Am wondering if there could be a problem in the filter head, itself? Or possibly the seals on the primer pump under the part you push? The other possibility might be the vacum side of the engine pump?
Have done a lot of searching on internet and this seems to be an item starting to rear its ugly head.
Any more suggestions to troubleshot this will be much appreciated.

[DmaxMaverick]

The engine stalls, even with the lift pump running? Either the pressure is getting dumped after a start cycle (electronics/sensor/FRP regulator), the HP pump has failed at the suction (low pressure) pump, or you have a significant fuel flow restriction/leak.

You can produce significantly more fuel pressure with the manual primer than the [typical Diesel] lift pump(s). If the HP pump is not drawing fuel, and is restricting flow (probability), it will stall shortly after priming and running. With the engine off, pumping the primer slowly primes the HP pump, allowing enough fuel through the pump to prime it and run the engine. This could also be a fuel volume condition, which can be a kinked fuel line or significant restriction between the filter and HP pump.

You can verify fuel flow to the low pressure inlet to the HP pump. Remove the hose entering the pump and run the lift pump(s), noting the fuel flow volume (it should be similar to the flow at the filter bleed). If the flow is good, the problem is the HP pump (low side), or the high pressure management. Normally, if there is any issue on the supply side of the HP pump, or the pump is unable to maintain rail pressure, you will see (at least) a P0093 DTC. This code is also typical on 2001 models when there is a fuel filter or supply restriction, significant air leak, or FRP regulator/sensor failure. The electronics can be monitored with a scanner (Predator, Tech II, Snap-On), noting the variations between desired/actual pressures and modulations of the rail pressure and FRP. If either of these have a significant departure, it should set a DTC, but not necessarily the SES (depends on the conditions and amount of departure). The differences should be less than about 5%.

At this point, I suggest getting you hands on Kennedy's fuel system pressure gage. With this, you will see, without any doubt, the fuel system suction side pressure/vacuum while it is running, and what happens immediately prior to the stall. Any less than this could have you chasing wild geese for a long time.

One more question (too obvious to mention, really)....How much fuel in the tank? And, if the fuel level is low, how low? If below 1/4 tank (according to the gage), add 10 gallons of fuel and try again.

[MPR]

Thank you, DmaxMaverick. This sure gives me a few things to work on. Tank is 3/4 full by the way.

[Kennedy]

With the lift pump running the hand pump should be VERY firm.

I'd suggest checking the restriction/psi and see what you get. This would eliminate plugged filter, kinked or collapsed lines etc. Depending what you chose for a lift pump, you may get some high restriction
readings with the pump stopped.


http://www.kennedydiesel.com/images/Dmax-fuel-filter-rest1.gif

[madmatt]

just another pic of fuel system vac with the pump off,,, this is about 4.3 in hg just had my gauge set wrong.

[MPR]

Further to the previous threads. Problem diagnosed as suction side of injector pump. Dealer replaced pump. Now shows pressure of 23500 psi. Not a cheap fix as had a leaking a/c compresser which was changed out at same time. This truck has cost me mega dollars in repairs over its lifetime of only 177500 kms. Had an injector go and it acted like a blowtorch and ruined the original block. So all new injectors and a used engine with less mileage. This was just months after the injectors were off warranty and was on road away from home towing RV. Replaced the original Allison which had a front seal blow the year before. Alternator replaced the year before that.
Still have the original batteries and they are still good. All in all, couild have bought a new 1/2 ton. Would I buy again? Not sure. Both the new Ford and Dodge look interesting. But the 2011 GMC sure has the pulling power. And a good warranty. Give the Ford a couple more years to mature and that will be the one to beat. Enough of my ranting.
Just like to thank you guys again for your valuable insight.