Airlocked injectors / Metal Cover over fuel injectors

[banjoron]

Hello, I've been troubleshooting an on and off will not crank problem now for a few weeks. I own a 1995 6.5 TD Silverado w/ no extras ( as of yet ) 120k miles. It acts as if it is not getting fuel to the injectors. I've replaced the fuel filter and the lift pump is working. On several occasions the truck will crank if I loosen the fuel cap which I know sounds like a bad lift pump. From all my research on the Diesel Page site it sounds as if I might have air between the IP and the injectors. I did run out of fuel 7 months ago and it restarted without having to bleed the injectors. My thoughts is that it might have then sucked air and is now 7 months later just showing up. My question is I was in the process of loosening all the injector fittings to bleed them out but can't get to the middle 2 on the passenger side because of a heat shield plate between the engine and turbo. I took the 2 little screws out of the top of it where it bolts to the engine but it won't come out or give clearance to crack the injectors. Is there an easy way to get this plate out or am I barking up the wrong tree all together? Thanks in advance for any help!!!

Banjoron

[a5150nut]

How are your batteries? These engins take 100 rpm cranking before the computer will turn on the fuel. If you were able to blead 6 of 8 injectors you would only have a miss not a no start. How is the fuel shut off solinoid? Can you hear feal it click when key is turned on/off? My $0.02

[banjoron]

Thanks for the reply... The batteries are fine and I can feel and hear the fuel shut off solenoid clicking. I have not bled the 6 lines yet for I was wondering would 6 be sufficient. I've found a few threads stating that an air locked IP could be unlocked with just a few injectors cracked and not all of them. I'll try bleeding the ones I can get to and post back and let you know if that has fixed my problem or not.

[16gaSxS]

Are you sure your lift pump is running? The OPS (oil pressure sensor) could be the culprit. Once it's running unless you have an leak in the system you don't usally need to bleed the air out it will self purge as it runs, so I doubt you have air left from 7 months ago. Did you bleed the air out from changing the filter?

[Kennedy]

Just a peeve of mine that I need to get out first. The term "crank" refers (at least to me) to the action of spinning, turning, or cranking (remember the old hand crank engines) the engine over in an attempt to start. I use the term "fire" to describe the engine's attempt to combust air/fuel mixture.


OK now that that is out of the way:

There is no need to bleed the injector lines on the GM diesel even after complete removal an drainage. If there is fuel to the IP (functional lift pump) it will push the air through by themselves unless the pump is completely shot.

Unless there is amajor leak or restriction in the system, you don't likely have an air issue. I'd lean more towards a PMD failure possibly due to lack of lift/return fuel flow.

[Turbine Doc]

Just a peeve of mine that I need to get out first. The term "crank" refers (at least to me) to the action of spinning, turning, or cranking (remember the old hand crank engines) the engine over in an attempt to start. I use the term "fire" to describe the engine's attempt to combust air/fuel mixture.


OK now that that is out of the way:

.


Amen Brother, A "it won't crank" and "it won't start/fire" are 2 different problems you ain't alone in this peeve I go round & round with the wife & In-laws over this all the time. Of course I disagree with calling engines motors, motors run off of electricity, engines need air, fuel, ignition/compression to run.


I agree with the self bleed, if IP is getting fuel and crank speed is up to par eventually injectors will purge themselves, learned the hard way not paying attention and ran out of fuel 3 yds from the pump. Also look at wiring, low volts to shutdown solenoid can cause problems, just clicking does not mean it's opening fully, had one a couple weeks ago only getting 9.6V, poor connector on power side, it clicked like it was healthy, would start then die, cleaned up connections for a full 12v and it fixed that problem.

[Bnave95]

Just a peeve of mine that I need to get out first. The term "crank" refers (at least to me) to the action of spinning, turning, or cranking (remember the old hand crank engines) the engine over in an attempt to start. I use the term "fire" to describe the engine's attempt to combust air/fuel mixture.


OK now that that is out of the way:

There is no need to bleed the injector lines on the GM diesel even after complete removal an drainage. If there is fuel to the IP (functional lift pump) it will push the air through by themselves unless the pump is completely shot.

Unless there is amajor leak or restriction in the system, you don't likely have an air issue. I'd lean more towards a PMD failure possibly due to lack of lift/return fuel flow.
John
What you doing over here :p
No body knows like, Big John:D
Also PMD. Get your self a new FSD cooler mount and put it where ever you wish.Had mine on intake with 37,600 and it still works:)
Heres a plug for JK. Myself I like the Bata cooler mounted beside the drivers side battery.
Or be brave and go with a SOL-D:eek: just kiding. I must just be one of the few that has had no trouble with the SOL-D:p

[banjoron]

Sorry I can't work on the truck until the weekend...thanks for all the input from everyone. A few things I didn't mention, I do have a FSD cooler mounted on top of the intake and I did replace the Oil Pressure Switch when all of this started. Measured pressure directly out of lift pump..6-7lbs. I plan on checking everything everyone suggested when it stops raining ( wet for 3 days now...not complaining). Thanks again

[banjoron]

O.K I've had time to look at my problem clooser. I installed a fuel guage from SS Diesel on the line from the filter to the IP to moniter fuel pressure from the lift pump. With a cold engine I had around 3.5 lbs. of pressure. Now I could begain troubleshooting. After the motor warmed up the pressure went down to 0 lbs of pressure. At this time it also stalled some. With the engine off, gear leaver in the drive position, I turned the ignition key to operate the lift pump I had 3.5 lbs. (1995 model) Started the engine and the pressure dropped to 0 lbs and most of the time the enging remains running. When I felt of the lift pump it was deffinately running. I checked the voltage to the lift pump and had 12+ volts. I even bypassed the OPS and operated the lift pump from another source...same thing. Lift pump runs, engine runs, fuel pressure at IP on the guage is nearly 0 lbs. of pressure. Once the engine is hot the fuel pressure is between 0 and 1-2 lbs. When everything is cold the pressure is at 3-4 lbs. until it gets warm then goes to back to 0 lb.

This led me to beleive that after the lift pump got warm was running but not pumping enoulgh fuel so I replaced it with a new one yesterday and had the same symptom. The only difference now is that the new lift pump is putting out 5-6 lbs of pressure. One more thing when I drove the truck onto ramps which had it at a incline to get to the lift pump easier it started stalling nearly every time. I am getting a little less than a pint of fuel in 15 sec. from the drain line with out an engine stall and the same from the fuel line at the IP with just operating the lift pump. I think I have enoulgh volumne but not enoulgh pressure. Could I be sucking air??? Anyone have any ideas???....sorry for the long post but I wanted to give all the details I could.

[rameye]

This is pretty interesting...

Why dont you run the lift pump from the battery direct via a fused pigtail, do not start the engine, and just let the lift pump only run ....let it get warm and see if the pressure drops out.....dont start the engine!

I'm hoping this will rule out a bad lift pump or faulty connection in the harness. Heat failure is common for electrical motors. They get warm they operate with way less effiency

We have to get to the basics and remove the OPS and the pCM from the equation..

lets say after 20 minutes or so of the first step

With the wiring harness, OPS and the PCM bypassed completely you start the engine and monitor the results again....

With a good solid lift pump running independently, the only cause for pressure loss would be a blockage either in the tank or somewhere up the line....

Of course if it comes to that, we can bypass the tank and fuel lines with a jug of fuel and run an independent line to your filter or IP and see if it still happens.

keep on it!!

try it out

[bdv]

I hate to bring this up but it sounds like what happened on my 94 Suburban. The DS-4 IP was shot. It was leaking internally. Hence when the engine is not running you get higher-pressure readings because the pump can build-up pressure against a closed IP. Once the engine is running the IP opens up (because it is leaking internally) back into the return line and your pressure drops again. Hence there is no leaking fuel to see because it is going back into the return and at the same time dropping the pressure. Check out this post “Can not get 4 PSI on Lift Pump. “ Good luck Brent

[rameye]

Guess we need to monitor the pressures after the pump as well!!

interesting still

[JohnC]

To beat a dead horse:

I used to get a kick out of the customers who claimed their car "cranks but won't turn over."

More to the point: Try pinching off the return line from the IP momentarily. If the pressure goes up, you've found the problem. There shouldn't be much if any pressure in the return line.

Also, verify you don't have a venting problem with the tank cap.

[banjoron]

I FIXED MY TRUCK