I purchased a 94 6.5 Suburban about a month ago. Started great, ran smooth, good pull with no hesitation, idle steady. The only thing that looks to be aftermarket is the PMD with heat sink that is mounted behind the front bumper, it looks like the second PMD since the original is still on the IP, and there is another one mounted to the intake. I decided to add a Heath PROM to get more drivability about a 4 days ago. I ran through the installation instructions which went well. After install it started and ran great just like with the original chip, but now with more power and response.
Fast forward 4 days, after a day of running around my wife drove the Suburban home and parked it, the next day we went out to go running with the family and it wouldn't start. I began to troubleshoot and everything seems to check out fine. I pulled the codes before clearing them and there was a DTC 25, but once cleared that didn't come back after further restart tries. The LP is pumping fuel to the T-handle behind the thermostat with good pressure, but when I crack the injector lines at the injector all I get is a drizzle of fuel. I ran through Accurate Diesel's troubleshooting guide for no start conditions and everything seems to point to the IP. I tested the PMD as directed by their instructions, is this a valid way to determine the full functionality of the PMD? Are there any other electrical sensors that will prevent starting by limiting fuel? Has anyone had a IP fail without any signs of failure? I know I am new to this forum, hopefully someone will be willing to give me a hand.

Thanks in advance
Scott

 

If your getting fuel to t handle but not out lines its your injection pump...could also b optical sensor inside the pump...but when the pmd is relocated too bumper it can still fail due too not having an adequate amount of airfow at speeds 20 mph or less especially idle heat sink or not dont matter. id relocate it in front of the radiator in grill..but by sounds of it its too late pmd fried or inj pump

 

I removed the optical sensor connector as a test for the optical sensor itself, according to Accurate this will force the computer to read the Crank Positioning Sensor as a default input. As for the PMD, is Accurate's test for the PMD correct, or has anyone ran the test to still find out the PMD was bad? Has anyone had complete IP failure with no previous signs? Are there any other electrical inputs I should check that would prevent fuel deliver from the IP?

 

bTry plugging the intake mounted PMD in and see what happens?

Should really be on the phone with Heath at this point though-new ECM is the most recent change-start there.

 

I tried the other PMD with no luck, guessing that was second on the list of PMD failures. I'll give Heath a call tomorrow to see if they have an idea as to what could cause this type of failure. I wouldn't think a PROM could cause this type of failure, but I am not sure what feeds come off that ECM that could impact fuel delivery. I did re-install my original PROM but had the same no start condition.

Thanks

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I did forget to mention it does have a Viper remote start that shuts the motor down if the brake pedal is pushed after remote start, I need to look into that as a possible culprit as well.

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Oh, and one more thing, their is white smoke coming from the tail pipe during cranking, and it smells like un-burnt fuel

 

If you get smoke it is at least trying to start.

 

That is what is kind of odd, with the smell of raw diesel and some puffs of smoke something must be working, I am wondering if the IP is producing some pressure, but not enough to start the motor.

 

is the glow circuit working? if your getting fuel and smoke i would look there.

 

I know the timer is working, but I haven't checked down to each glow plug. The temps around here have been close to 60 degrees so I figured I should get at least a stumbling start and rough idle even without glow. Could you direct me to a good thread on testing the glow circuit? I will see what I can find.

Thanks

 

Well, I finally got it figured out. I never felt like this was a mechanical issue so I was hesitant to start tearing into it, so in further testing last night I was able to get it started.

First, let me say I passed on a critical test during my troubleshooting which was assuming the glow plugs were working by the length of time the glow light was illuminated during start-up, I should have tested each plug to determine if it was working.

So here is what I did, I wanted to verify pump failure so I let the glow expire and waited a few minutes, I then shot ether into the intake to see if it would fire up. It wouldn't fire, and it was cranking real slow, so at this point I figured it may not be the pump. I decided to plug the vehicle in and warm it up to see if that would change the outcome and if I could get it to fire with or without ether. After about 3 hours of being plugged in I cranked the motor, without ether, and sure enough it fired up.

So in the end one of the easiest things to test was what it ended up being, a glow issue. Now it is time to troubleshoot the glow system.

Thanks for all the input, hopefully this will help others in the future, and I will definitely look to add to other posts when I can.

Thanks,
Scott