Hi all-

Been on this forum for awhile and appreciate the help everyone gives each other. I have a recent cold start issue with my truck and am looking for some insight.

Symptoms. Had a hard/no start one morning with lots of white smoke, plenty of fuel smell. After plugged in to block heater for an hour, it fired right up. Temps around 40-50 degree.

Went to troubleshoot it the next day doing GPR testing and noticed while I cranked the motor over that white smoke was seen from the fuel bowl area. Fuel filter was at 13k, and I recently had dumped some diesel fuel in from my dozer cans (which I later found had a little junk in them), so I swapped the filter out, started fine after fuel filter replacement.

Drove it to work with no start issues, next morning leaving work it wouldn't start without the block heater pluggen in for about 30 minutes again.

Got it home and let it rest. Next day tried a cold start on a 55 degree day when the front end of the truck had been facing the south sun all day. Let the WTS light and GP's run for 1 minute 45 seconds and cranked it. Fired right over with just a little white smoke from the exhaust.

Tested the GP's at the valve harness and found them all tested as failed. (readings of either .000 or .002 on all plugs) I'm having a hard time believing all 8 GP's failed at once. Is that common? Seems to me I should be concerned with something else that failed that caused them to fail if that's the case.

Also, if the truck has been running and hasn't cooled down, it starts no problem.

Lastly, I'm not an electrician, but when I tested, I did the resistance (upside down horeshoe) set at 20.

And just today, 35 degrees, I turned to hit the glow plugs, let them sit for 1 minute 45 seconds, started truck. Ran rough for a bit, white and black smoke from the exhaust, plenty of diesel fuel smell, then cleared up and ran real smooth.

I have checked the GPR and it shows as operating per diagnostics suggested on FTE.

I have checked the GP's with resistance testing at the valve cover harness and they are all .000 or .002 readings.

Any input? Considering replacing the GP's and the GPR as preventative maintenance, but just want to make sure I'm not missing something.

Thanks!

 

I also find it difficult to believe all glow plugs are bad, but maybe improper testing or a wire issue somewhere.
Hook your multimeter to a battery and watch voltage with key in run and wts light illuminated. What voltages do you see?
If glowplugs are functioning properly and batteries are good I would expect 12.5v key off, 10.5-11v in run w/ WTS and/or Glow plugs.
If your dropping voltage at those times at least some of your glowplugs are still good, question your resistance measuring method.

Have you disconnected and tested you batteries? What is resting voltage on each?

 

Just my thoughts..... Glow plugs heat up the compression chamber... so the fuel is warmer....

The oil in your injector.... and coming from crankcase... is COLD... unless you have plugged the truck in. If it cranks faster after plugged in for an hour, that to me is an addition clue.

Do a Buzz test on a cold morning. See how they all sound cold.... later, listen to them when warm....

A complete shim kit to fix your gaps on injector solenoids is like $50.... and you don't have to pull injectors to fix the gaps. Cold oil moves really slow thru a .0001 gap, that should be .0004 (I think thats the correct numbers)

Google can tell you much more than me....

 

Your test on the glow-plugs at the harness is correct. Your interpterion is incorrect. With your meter set to resistance (Upside down horseshoe) you should read zero on the meter with one lead touching a GP pin and any metal part of the engine block. Your glow-plugs have PASSED this test. Next is the relay test. I assume you know about the two minute timed input for the GP Relay since you mentioned 1:45 minutes wait to start. So with that two minute window you should see this.

Within the two minute window of glow plug being actived....

the 12 volts DC here will go to zero volts. If it goes to anything but Zero, replace the GP Relay.

 

Have you been under the valve cover? I have seen plug-in wiring harnesses under the valve cover come unplugged to the point that the glow-plugs still made contact and the injector wiring did not. And it made white smoke under the hood. White smoke came from the passenger side, but it was the driver side harness that wasn't making full contact. If you have a injector-glow-plug pigtail connector, this test will be very simple to conduct. Almost impossible to do without pigtail and without help. Especially in the cold. I believe that is where your problem is. And due to thermo-expansion, is why the truck will start after it warms up.

 

As MoBill122 mentioned above, a buzz test early in the morning would be easiest and would reveal a connection problem with any injectors. And this would move closer to the problem. You could also conduct this test at the 42 pin connector.

Injector-glow-plug connector.

 

Thanks all for the help so far. Thanks also for the images on testing the GPR. I will try that today if I get a chance. The truck turns over steadily and easily, cold or plugged in. I will test the batteries volts before and during WTS and report back, although I vaguely remember checking those and being happy with those results. I feel like it must be the GPR and will double check my tests on that today. Thanks all!

 

Thanks for the pics. GPR front to back testing per your pics revealed 10.33 volts. Side to side testing per your pics during the 2 minutes initially revealed 0.90 volts, then after a clunk/noise from the GPR area, volts jumped up to 11.71, still within the 2 minutes. Sounding more and more like GPR? Batteries are 4 years old but a solid 12 volts sitting key off, then 10 plus volts with GP's running.

 

The front to back (10.33 volts) testing picture is the control voltage to the relay coil. Check to see if the 10.33 volts is still there after you hear the clunk noise (which is the solenoid disengaging). If it is than the coil of the relay is shorting out and not functioning properly. Your battery voltage looks a bit low too. Do have a charger and can you have them load tested? The side to side testing (Second picture) reveals the total voltage is not being allowed through the contacts of the relay. (Your voltage reading is 0.9 volts and should be zero). I think you may have found a problem right here. Keep in mind that a problem may be a part of the problem.

 

Thanks for the interpretation of the results. GPR's are cheap enough and the truck has 133k on it, so I think I will replace the GPR since it seems the most likely culprit and report back on those results.I do have a battery charger and can get the batteries checked to see how they are doing.
Thank!

 

If it's the GPR, you can short it with a screw driver for 60-120 secs and jump in the truck real quick and try and start it, or have a helper try and start it while you are shorting it. If this clears up your issue, then you know it's the GPr. If it doesn't, you have something else going on, like gaps getting too tight in the injectors, or bad GP's themselves.

 

Diesel Tech Ron had a good video as well -

 

Well, I think it was the GPR... haven’t hooked everything back up because I need some new nuts that aren’t corroded and a boot cover for the hot lead. I’ll let you all know in a day or 2 when I get it all back together.

 

Put some of this on all the terminals. We use it all over the DC plant for cell towers

 

Thanks for the tip. I’ll add it to my parts list!