I just bought a 1994 Yukon with the 6.5 in it a week ago from a lady I know. It ran when she parked it a year ago. She was scared to drive it because it would randomly die on her just down the road from her house around the same spot each time she drove it . I did some research and seen that the pmd is a big issue and can cause this so I got the relocation kit for the pmd and installed that. It will crank great but does not try to fire at all. I replaced the fuel filter I and getting fuel to the filter I know that. I took off a line to one of the injectors and it doesn’t seem I am getting fuel to the injectors. So im assuming it is some thing to do with the injection pump. I took the plunger out of the fuel shut off solenoid and put it back on with out the plunger that didn’t do any thing. I don’t really know anything about diesels I’m just going off that research I have found and now I’m stuck. Anyone have any ideas?
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Bought 6.5 will crank but won’t start
- Thread starter Glosserj
- Start date
dbrannon79
I'm getting there!
Welcome to TTS. there's lots of knowledgeable folks here to help.
I would check all your fuses, and grounds. main PCM grounds are located near the passenger side rear of the intake on a stud, there is also a small ground wire on the PMD harness mounted with a screw on the top side of the IP (injection pump). also look at connections around the optic sensor. if there is a small harness with that black box in the wires, remove it and connect the harness to the optic sensor. that tiny black box is a noise filter for the radio. they are prone to failure which will cause erratic issues.
if you have a way to read PCM codes, you might want to check that also. could be a faulty crank position sensor. it's located down at the harmonic balancer.
did the truck start before replacing the PMD? depending on where you got your extension cable or PMD. ether of those can be DOA on arrival.
I would check all your fuses, and grounds. main PCM grounds are located near the passenger side rear of the intake on a stud, there is also a small ground wire on the PMD harness mounted with a screw on the top side of the IP (injection pump). also look at connections around the optic sensor. if there is a small harness with that black box in the wires, remove it and connect the harness to the optic sensor. that tiny black box is a noise filter for the radio. they are prone to failure which will cause erratic issues.
if you have a way to read PCM codes, you might want to check that also. could be a faulty crank position sensor. it's located down at the harmonic balancer.
did the truck start before replacing the PMD? depending on where you got your extension cable or PMD. ether of those can be DOA on arrival.
Thank you I will check that stuff tomorrow when I get off. And no it would not start before I replaced it. I unplugged to new one and plugged it back into the old one just to make sure and it still wouldn’t start.
dbrannon79
I'm getting there!
Just FYI, if you didn't pull the old PMD off the IP and transfer the resistor in the plug to the new PMD, that can also be a problem. if the PCM hasn't had power in a while, it may have lost it's memory on the engine. the PCM looks for that resistor every 50 key cycles or so. when it's not there and it looks for it, I have heard of it giving a no start condition.
dbrannon79
I'm getting there!
you can also purchase a resistor pack from most of the auto parts houses. I believe three come in the package. #2, #5, and #9. I would use the #5 and see if that does it. I actually installed mine in the female side of the extension harness so I didn't have to worry about having to pull and install next time the PMD failed!
So you would recommend taking the old pmd off the injection pump?
dbrannon79
I'm getting there!
it is a PIA to remove it without removing the intake! the replacements are maybe $10 at the auto parts. I'll look up the part number and post for ya
dbrannon79
I'm getting there!
Dorman 904-107 comes with two. #5 and #9. AAP sells it for $20 and amazon shows it for $12.47. the cost is much better than a headache of pulling the intake to get to it lol
Thanks I really appreciate it I’m going to work on it a little tomorrow after work I’ll keep you updated and I could imagine it’s much easier lol
dbrannon79
I'm getting there!
correct, If you get a new resistor and install in the new PMD the old one can stay there as a decoration lol
dbrannon79
I'm getting there!
they are numbered 1-9 each one allows minuscule changes in how much fuel the IP gives. it calibrates the pump to spec when GM tested them on the assembly line.
I gotcha now I’ll just go ahead and order it and get it on its way!
dbrannon79
I'm getting there!
keep in mind, this is a possibility of the no start issue, but it can be something else. I'm sure others will chime in on things to check. if you are able to pull codes on the PCM, that might help isolate electronic issues. you can use a paperclip on the connector under the dash and count the SES light flashes. if I am not mistaken (someone correct me if I'm wrong) it's the further most right top and bottom pins in the connector. key on and the SES will start flashing stored codes
MrMarty51
Well-Known Member
Open the water drain valve located ahead of the thermostat housing/coolant cross over.
Turn the key to run position, there should be fuel blow out the exit hose attached to that valve.
Fuel should run into the jug or bucket for as long as the glow plug light is lit up.
If You get no fuel then, something is not right in the lift pump circuit.
Turn the key to run position, there should be fuel blow out the exit hose attached to that valve.
Fuel should run into the jug or bucket for as long as the glow plug light is lit up.
If You get no fuel then, something is not right in the lift pump circuit.
ak diesel driver
6.5 driver
Marty his is a 94 and the LP won't run until it sees oil pressure
dbrannon79
I'm getting there!
I forget which pin it is on the obd1 connector, but you can trigger the LP by grounding one of the pins I think. I think it goes to the relay under the hood for testing purposes.
MrMarty51
Well-Known Member
Ooooh dang. I will have to TRY and remember that.
Husker6.5
135' diagonal 16:9HD, 25KW sound!
Before firing the parts cannon at it, we need to know some things, like how many miles on the vehicle? The average life expectancy of injectors is 100K miles and an IP is 150K miles. Have you put a piece of clear hose on the IP return line to see if you're getting air into the fuel/IP (often times introduced in through the FFM when you replace the fuel filter - either the old gasket sticks inside unnoticed and when you install the new filter it 'double gaskets' and leaks air or the filter housing isn't replaced correctly and it leaks air into the fuel system) which would cause a No Start/dies after short running situation?
Do you have any previous diesel owner/driving experience? You MUST wait for the 'Wait to Start' (glowplugs) light to go out before cranking, otherwise it won't start.
Jumper the lift pump (driver's side frame under the door) to power it on and then check for sufficient fuel flow at the bleeder valve (T Valve on rubber hose near thermostat housing), should fill a pint jar in a few seconds.
A diesel only needs fuel and air to run. You need to first make sure you have an uninterrupted supply of fuel, without air in it, to the IP. After verifying that (never assume it all works and is ok), if you indeed cracked an injector line loose at an injector, cranked the motor over, and found no fuel at the injector, then the problem lies between the IP inlet and the IP's distribution head.
As mentioned above, CLEAN good grounds are critical on these 6.5s. Grounds on the back two passenger side intake manifold bolts/studs are critical both the terminal lugs and the bolts/nuts/washers must be clean and tight. Yes, pulling any codes from the OBD-I system is very helpful in diagnosing problems - either go to the help section on here or there are YouTube videos that show how to jumper the OBD-I ALDC plug under the dash and read the flashes of the Service Engine Soon (SES) light to get the code numbers - then report those numbers back to us - even if there are none.
Do you have any previous diesel owner/driving experience? You MUST wait for the 'Wait to Start' (glowplugs) light to go out before cranking, otherwise it won't start.
Jumper the lift pump (driver's side frame under the door) to power it on and then check for sufficient fuel flow at the bleeder valve (T Valve on rubber hose near thermostat housing), should fill a pint jar in a few seconds.
A diesel only needs fuel and air to run. You need to first make sure you have an uninterrupted supply of fuel, without air in it, to the IP. After verifying that (never assume it all works and is ok), if you indeed cracked an injector line loose at an injector, cranked the motor over, and found no fuel at the injector, then the problem lies between the IP inlet and the IP's distribution head.
As mentioned above, CLEAN good grounds are critical on these 6.5s. Grounds on the back two passenger side intake manifold bolts/studs are critical both the terminal lugs and the bolts/nuts/washers must be clean and tight. Yes, pulling any codes from the OBD-I system is very helpful in diagnosing problems - either go to the help section on here or there are YouTube videos that show how to jumper the OBD-I ALDC plug under the dash and read the flashes of the Service Engine Soon (SES) light to get the code numbers - then report those numbers back to us - even if there are none.
Rockabillyrat
SlIgHtLy StUpId.
OBDI is easy and hard to work on at that same time. If the CEL lights up on a bulb check then the PCM has power, ground, and is communicating. At that point you can try flash codes or if your lucky enough to have a ODB1 scanner check for codes.
The hard part about OBD1 is you can have a bad sensor and it will NOT set a code. Majority of OBD1 repairs I do on customers vehicles are a bad sensor not setting a code. That why I tell people if you don't have a scanner to read data the get ready to fire that parts cannon.
The hard part about OBD1 is you can have a bad sensor and it will NOT set a code. Majority of OBD1 repairs I do on customers vehicles are a bad sensor not setting a code. That why I tell people if you don't have a scanner to read data the get ready to fire that parts cannon.