95 GMC 6.5 runs for 10 sec. then stalls and wont start
 

My truck wiill start and run perfect for about 10 seconds then stall , and it wont start till it sits for a while. It started a couple weeks ago, it would run fine, then stall. sometimes it would run good for a couple days, then start stalling, usually it would start right back up. I changed the fuel filter, put a different (used) lift pump on, cleaned grounds, recently replaced the PMD, and relocated it to the bumper, new OPS. Injector pump is about 2 years old OEM. Batteries tested good, I can hear the lift pump running when I turn the key on, but it sounds different. I am getting fuel to the filter when cranking. Im starting to think I should do the Cummins conversion. Any and all help with this problem would be greatly appreciated. thanks in advance

You might consider the lift pump relay as part of the problem. If its coil is weak or its points burned or corroded you will get erratic operation. The relay in my '94 td is only in use during the starting cycle but I believe the relay in the '95+ is closed at all times. It's about a $20 part at O'Reilly.

first thing start with is OSP and LP test

it sound like bad PMD

you said you clean grounds was that just battery ground if so you miss alot at back right of engine their are more ground and straps make sure they are clean and good make sure the straps going from and to the firewall and to the frame and are in good shape

If you want do cummins that just wast of money going cost you you most likey fine d-max for what going cost you put cuimmins in

I cleaned the the grounds at back of intake,straps, and battery. Any others I need to be checking? How is the lp grounded? I also noticed I can hear something Buzzing in the dash, not sure that its related though.

there should be ground wire on top of the pump for the PMD

Could be bad PMD


Just because hear LP running doesn't mean it working right i would put 12v right to it and see if you get fuel out at water drain hose

If the lift pump relay coil is weak, when it tries to run the pump (which draws a lot of current) the points in the coil will open and close rapidly causing the humming sound you hear decreasing the current to the pump and decreasing, if not stopping the pump, intermitantly, decreasing the fuel flow. The relay can be tested if you don't want to replace it.

I ordered a new LP relay today, should be in tomorrow, I'll let you know how I make out.

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I installed a new LP relay today , still the same . Runs for a few seconds then shuts off and wont start for about 10-20 minutes. I have a new PMD ordered for tomorrow. Hopefully that will do it.

Sorry to hear the relay didn't solve your prob. What kind of temperatures are you having in central PA when you start your truck?

Its getting into the high teens at night. I keep my truck in a heated garage. But now that you mentioned it, I left my truck outside one night and it wouldnt start in the morning, it was a very cold morning(6degrees). I think I may have a bad GP or 2. Would this make my truck act like this?

ya it could if your glow plugs not working

no it wont it would still start but take forever check your fuel filter housing for leaks we couldnt figure out the problem on mine and put the new style filter on and there was a metal ring not letting it seal and letting air in the system it had the same symtoms as yours so check for that with a pmd relocated that shouldnt be the problem they dont go bad overnight
hope this helps you

I have a newer style filter from SSD, I did crack the bleeder today and got some air, But I just installed the filter , it only has about 30 seconds actual run time on it. I changed it as soon as It started the shutting off. I cranked the engine until I got 100% fuel out of the bleeder. I noticed the fuel doesnt come out as much when the pump is running without cranking the motor. I put the trans in drive and turned the key to start, I got fuel but only 1/2 as much as when I cranked the motor.

only thing i can think of now is is the lift pump running at full power and can you feel it running

Im gonna try the PMD when it arrives, if that doesnt work, I think I'm gonna get a new LP. I just dont like how the pump sounds. It normally wouldnt concern me but it sounds different than it did in the past.

Witemanfromhil

Did you put 12V right to the LP and check see if the truck would start i seen many pump run but fail to fuel the parts in side the pump that move the fuel falls apart and pump motor will still run

Today I removed the pump and bench tested it, pump works fine, pumps good fuel, has 12v at the plug. When I reinstalled it the pump runs much quiter than before, I can bearly hear it inside the cab. Could this be a problem?

Hi,
Did you recieve the PMD yet??If so,try it out,make sure the chip is installed in the PMD.It is located in the PMD where your harness connects into it.Use the one off the old PMD if it did not come with one.If the truck still does the same thing,I have a few tests you can do if you have a voltmeter,these tests need to be performed when the truck will not start,so you need to have meter handy.We will beable to atleast prove your control ckt from the main brain (the PCM) to the PMD which controls your injection pump.It is also helpfull if you have your fault codes read so we know what direction to start in.
Big Joe

I didnt get the PMD yet, actually they sent me the wrong part. "BIG JOE" After reading your last reply about the resistor, I checked mine and it didnt have one in it, I I got to looking and neither did the last one(pmd) I replaced. could this be part of my problem? I did order one from Walt today.

yes that could be your problem very much autozone does sell them also now for like $30.00 and it come with #er 5 and 9

If trere is no resistor in the pmd, the ecm assumes it to be the equivelent of a #1 or 5 (I don't remember which) but it doesn't affect the operation of the pmd.

some ECM will not let truck run if don't at least #er 5 in it

Let us know the results after you install the new pmd.

I finally got around to working on the truck yesterday. I installed the new PMD and the truck runs flawlessly. This is the 3rd time for the PMD, every time it acted different. Why do these keep going bad? Mine is mounted in front bumper. I hope someday someone figures out a permenant fix for these things instead of a temporary fix.

Hi Guys!
I also have a 6.5 L diesel in my '95 suburban. I got a problem with it. At a certain point, my air conditionning stop by gripping bearing and i stop the engine ( who was running perfectly until then ) so du to lack of money, i stored the vehicule for 3 years without trying to start it . Now i have replace air conditionning and also alternator but engine refuse to start. I read that the fuel manager filter could be dry, so i open the cap and fill it in fuel and after add a shot of ether in the air filter compartment and some starting, the engine start, run for few sec but stop. I try to start it again just the normal way nothing happen. When i turn the key off, i ear the electric pump running and stop after few sec. i tried, (after charging my batteries at full) to do the same method and forget the the cap open and some fuel dripped on the engine and the ground ( what tell me the pump is working :) )

So i tried that method ( with cap closed ) and the engine run well but just for few sec...What could be the problem now if everything was perfect before ???

Some use letter like PMD but as not an native english, if the right word could be place in parenteses for comprehension please, i would greatly appreciate. )


So, someone got knowledge to suggest me where is the problem to cotrrect ?

I was owner of 20 vehicules before, all gazoline, it is my first one with injection and diesel...i am lost...
I like diesel but it is quite new and apparently very easy to run ???

Thank's in advance for your guidance..

Mike

Whitemanfromhil I am sorry I couldnt get back to you sooner but it sounded like you nailed the problem!

Now lets see if we can help TOPAZJ! :humm: What I Would suggest is first make sure your fuel delivery system is working. Make sure your system is primed.sounded like your fuel system got air into it because you had to ad fuel in the fuel filter. Make sure you have good pressure on yor line comming from your fuel pump at the tank, there is a bleeding valve front and center of the motor (you will see the fuel line going to it) or disconnect fuel line,(this line goes to fuel filter) Have someone turn key,fuel pump at tank should cycle and fuel should come out about 5 or 6 PSI. If that is working,connect back up and crack the bleeder at the top of filter and turn key and wait until you get nothing but fuel commming out (no air !!) and then close the bleeder.
Now you need to find your #1 cylinder which I think is the first one on right side of engine in the front (looking at the engine) where the steel line goes into the top of the injecter, you need to get a wrench and crack that nut open. Have someone turn the engine over until you see fuel spraying out. Close, then stop turning motor over and go to the next injecter,then repeat. IF the motor wants to run and fuel is squirting out,close and move to the next injecter and repeat by cracking the nut until the engine stays running and sounds like it is firing on all cylinders. (Make sure your batteries are fully charged before you start this test!)

Let us know what you did and if it made a diferance and if not we will move foward.
Big joe

Witemanfromhil the reason your pmd keeps failing.is because when people relocate them in the bumper they dont have adequet enough cooling airflow at speeds of 20mph or less especially idle. Mounting them in the grill in front of radiator so much more open to wind and at idle your engine fan will actually draw air towards it as well. this is where mines mounted and haven had a problem with it at all:)

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Toppazj ...the last thing you wanna do is spray either in a diesel engine that uses glow plugs...unless u wanna use it for boat anchor..if u absolutely must spray something use something less comustionate such as carb cleaner did u leave a bunch of fuel in your tank without any conditioner for storing? was vehichle stored in tge winter with summer blend fuel?

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*ether

There is absolutely no problem with mounting the PMD/resistor/heatsink combo behind the bumper as long as heat transfer paste/pad is used between the PMD and the heatsink,and the PMD is torqued to 20-25" pounds to the heatsink.

Airflow is not required to remove the heat generated by the PMD when a adequately sized heatsink is used.

All PMD's fail eventually,about 2-3 years is all the average PMD tends to last.
Installation quality is a big factor in this.

I have heard that for Heath's 7 year warranty PMD combo's,he mills the PMD base and his aluminum heatsink to ensure a true flat surface at the point of contact and torques the screws to spec with the proper heat transfer medium in place?
Even then he has a warranty claims.

Racer I challenge the assertion that "all PMDs" fail 2-3 years, not berzactly :) a quality relocation is off IP out of engine bay is required for maximum life. My 2 Heath relocation one with 8 years on it now and the 2nd with 6 on it both well beyond 2-3 year point. A experiment I did a few years back led me to the Heath solution. FSD/PMD "Points to Ponder" How hot does it get

My current 8 year remoted driver is mounted inside my Buckstop bumper been there since 2005 when I added the bumper. Properly sized sink is key, airflow only critical if one uses too small a sink. I've resurrected several "bad drivers" by retorque od the transistor locknuts as well. Bill attributes longevity to his setup to flatness and torque of driver to the sink, but as you correctly state even he has to sometimes honor the warranty, as the driver itself is still made of parts that can fail.

Topaz some of the info for a basic troubleshooting checklist here :6.5 Engine Diagnostic Troubleshooting Checklist

Turbine Doc,I said all PMD's fail eventually and on average 2-3 years is the going rate of life.

Some as you well know live far beyond that even on the IP.

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Tim,what are your thoughts on anodized surfaces for heatsinks?
A great many aluminum parts are anodized to prevent oxidation and I wonder what effect that has on thermal properties?

I've been told that anodized has some insulating properties so may not be best for heat xfer properties, certainly I would not want it to be anodized from a electrical continuity perspective at point of contact, that said I have an old DSG anodized sink I carry as a spare, but that same sink when mounted under hood several locations is where I had my multi fails (some recoverable some not) of drivers.

I think Bill's method mill flat to sink & mill flat to driver is good way to go then a thermal epoxy (he has never said what brand) to seal the perifery of joint where the mating occurs

Hi Guys ( Big Joe and Detroitdiesel Idi )
Thanks for your anwers, was quite fast !, i didn't expect answers so soon !,
Sorry if i didn't come sooner, i catch a strong flu and just begin to get a little better....

So i just read that i had answer so i wanted to let you know i didnt leave, just sick, so i will read them twic to be sure to understand and will come with morew detail for your questions.... Thank's in advance guy's :jump:

Mike

I had that same problem your describing, it was one bad wire in the 5 the goto the pmd. Cleaned it up and havent had the problen since. I changed everything before I found it. Something to look into